Fix horizontal inference logic for extension method invocations.

The front end desugars extension methods by inserting a synthetic
`this` argument before all other arguments.  But this synthetic
argument isn't included in the `formalTypes` and `actualTypes` arrays.
So when recording a value into
`_DeferredParamInfo.evaluationOrderIndex` we may need to subtract 1 in
order to ensure that later logic will find the correct argument.

Fixes a corner case of https://github.com/dart-lang/language/issues/731.

Change-Id: Idbf136195e40555199f7c5b61a575a430f6ec6bd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/243854
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

@@ -128,6 +128,8 @@ List<_ParamInfo> _computeUndeferredParamInfo(List<DartType> formalTypes,
     for (_DeferredParamInfo functionLiteral in deferredFunctionLiterals)
       functionLiteral.evaluationOrderIndex
   };
+  assert(evaluationOrderIndicesAlreadyCovered
+      .every((i) => 0 <= i && i < formalTypes.length));
   return [
     for (int i = 0; i < formalTypes.length; i++)
       if (!evaluationOrderIndicesAlreadyCovered.contains(i))
@@ -2527,7 +2529,9 @@ class TypeInferrerImpl implements TypeInferrer {
             argumentExpression: argumentExpression,
             unparenthesizedExpression: unparenthesizedExpression,
             isNamed: !isExpression,
-            evaluationOrderIndex: evaluationOrderIndex,
+            evaluationOrderIndex: isImplicitExtensionMember
+                ? evaluationOrderIndex - 1
+                : evaluationOrderIndex,
             index: index));
         // We don't have `identical` info yet, so fill it in with `null` for
         // now.  Later, when we visit the function literal, we'll replace it.

pkg/front_end/testcases/inference_update_1/horizontal_inference_extension_method.dart

@@ -0,0 +1,173 @@
+// Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Tests that horizontal inference works properly when the invocation is an
+// extension member.  This is an important corner case because the front end
+// adds an implicit `this` argument to extension members as part of the lowering
+// process.  We need to make sure that the dependency tracking logic properly
+// accounts for this extra argument.
+
+// SharedOptions=--enable-experiment=inference-update-1
+
+testLaterUnnamedParameter(int i) {
+  i._laterUnnamedParameter(0, (x) {
+    x;
+  });
+}
+
+/// This special case verifies that the implementations correctly associate the
+/// zeroth positional parameter with the corresponding argument (even if that
+/// argument isn't in the zeroth position at the call site).
+testLaterUnnamedParameterDependsOnNamedParameter(int i) {
+  i._laterUnnamedParameterDependsOnNamedParameter(a: 0, (x) {
+    x;
+  });
+}
+
+testEarlierUnnamedParameter(int i) {
+  i._earlierUnnamedParameter((x) {
+    x;
+  }, 0);
+}
+
+testLaterNamedParameter(int i) {
+  i._laterNamedParameter(
+      a: 0,
+      b: (x) {
+        x;
+      });
+}
+
+testEarlierNamedParameter(int i) {
+  i._earlierNamedParameter(
+      a: (x) {
+        x;
+      },
+      b: 0);
+}
+
+/// This special case verifies that the implementations correctly associate the
+/// zeroth positional parameter with the corresponding argument (even if that
+/// argument isn't in the zeroth position at the call site).
+testEarlierNamedParameterDependsOnUnnamedParameter(int i) {
+  i._earlierNamedParameterDependsOnUnnamedParameter(a: (x) {
+    x;
+  }, 0);
+}
+
+testPropagateToReturnType(int i) {
+  i._propagateToReturnType(0, (x) => [x]);
+}
+
+// The test cases below exercise situations where there are multiple closures in
+// the invocation, and they need to be inferred in the right order.
+
+testClosureAsParameterType(int i) {
+  i._closureAsParameterType(() => 0, (h) => [h()])
+      ;
+}
+
+testPropagateToEarlierClosure(int i) {
+  i._propagateToEarlierClosure((x) => [x], () => 0)
+      ;
+}
+
+testPropagateToLaterClosure(int i) {
+  i._propagateToLaterClosure(() => 0, (x) => [x])
+      ;
+}
+
+testLongDependencyChain(int i) {
+  i._longDependencyChain(() => [0], (x) => x.single,
+          (y) => {y})
+      ;
+}
+
+testDependencyCycle(int i) {
+  i._dependencyCycle((x) => [x],
+          (y) => {y})
+      ;
+}
+
+testPropagateFromContravariantReturnType(int i) {
+  i._propagateFromContravariantReturnType(() => (int i) {}, (x) => [x])
+      ;
+}
+
+testPropagateToContravariantParameterType(int i) {
+  i._propagateToContravariantParameterType(() => 0, (x) => [x])
+      ;
+}
+
+testReturnTypeRefersToMultipleTypeVars(int i) {
+  i._returnTypeRefersToMultipleTypeVars(() => {0: ''}, (k) {
+    k;
+  }, (v) {
+    v;
+  });
+}
+
+testUnnecessaryDueToNoDependency(int i) {
+  i._unnecessaryDueToNoDependency(() => 0, null);
+}
+
+testUnnecessaryDueToExplicitParameterTypeNamed(int i) {
+  var a = i._unnecessaryDueToExplicitParameterTypeNamed(null, ({int? x, required y}) => (x ?? 0) + y);
+  a;
+}
+
+testParenthesized(int i) {
+  i._parenthesized(0, ((x) {
+    x;
+  }));
+}
+
+testParenthesizedNamed(int i) {
+  i._parenthesizedNamed(
+      a: 0,
+      b: ((x) {
+        x;
+      }));
+}
+
+testParenthesizedTwice(int i) {
+  i._parenthesizedTwice(0, (((x) {
+    x;
+  })));
+}
+
+testParenthesizedTwiceNamed(int i) {
+  i._parenthesizedTwiceNamed(
+      a: 0,
+      b: (((x) {
+        x;
+      })));
+}
+
+extension on int {
+  T _laterUnnamedParameter<T>(T x, void Function(T) y) => throw '';
+  void _laterUnnamedParameterDependsOnNamedParameter<T>(void Function(T) x, {required T a}) => throw '';
+  void _earlierUnnamedParameter<T>(void Function(T) x, T y) => throw '';
+  void _laterNamedParameter<T>({required T a, required void Function(T) b}) => throw '';
+  void _earlierNamedParameter<T>({required void Function(T) a, required T b}) => throw '';
+  void _earlierNamedParameterDependsOnUnnamedParameter<T>(T b, {required void Function(T) a}) => throw '';
+  U _propagateToReturnType<T, U>(T x, U Function(T) y) => throw '';
+  U _closureAsParameterType<T, U>(T x, U Function(T) y) => throw '';
+  U _propagateToEarlierClosure<T, U>(U Function(T) x, T Function() y) => throw '';
+  U _propagateToLaterClosure<T, U>(T Function() x, U Function(T) y) => throw '';
+  V _longDependencyChain<T, U, V>(T Function() x, U Function(T) y, V Function(U) z) => throw '';
+  Map<T, U> _dependencyCycle<T, U>(T Function(U) x, U Function(T) y) => throw '';
+  U _propagateFromContravariantReturnType<T, U>(void Function(T) Function() x, U Function(T) y) => throw '';
+  U _propagateToContravariantParameterType<T, U>(T Function() x, U Function(void Function(T)) y) => throw '';
+  void _returnTypeRefersToMultipleTypeVars<T, U>(
+            Map<T, U> Function() x, void Function(T) y, void Function(U) z) => throw '';
+  T _unnecessaryDueToNoDependency<T>(T Function() x, T y) => throw '';
+  T _unnecessaryDueToExplicitParameterTypeNamed<T>(T x, T Function({required T x, required int y}) y) => throw '';
+  void _parenthesized<T>(T x, void Function(T) y) => throw '';
+  void _parenthesizedNamed<T>({required T a, required void Function(T) b}) => throw '';
+  void _parenthesizedTwice<T>(T x, void Function(T) y) => throw '';
+  void _parenthesizedTwiceNamed<T>({required T a, required void Function(T) b}) => throw '';
+}
+
+main() {}

pkg/front_end/testcases/inference_update_1/horizontal_inference_extension_method.dart.textual_outline.expect

@@ -0,0 +1,68 @@
+testLaterUnnamedParameter(int i) {}
+testLaterUnnamedParameterDependsOnNamedParameter(int i) {}
+testEarlierUnnamedParameter(int i) {}
+testLaterNamedParameter(int i) {}
+testEarlierNamedParameter(int i) {}
+testEarlierNamedParameterDependsOnUnnamedParameter(int i) {}
+testPropagateToReturnType(int i) {}
+testClosureAsParameterType(int i) {}
+testPropagateToEarlierClosure(int i) {}
+testPropagateToLaterClosure(int i) {}
+testLongDependencyChain(int i) {}
+testDependencyCycle(int i) {}
+testPropagateFromContravariantReturnType(int i) {}
+testPropagateToContravariantParameterType(int i) {}
+testReturnTypeRefersToMultipleTypeVars(int i) {}
+testUnnecessaryDueToNoDependency(int i) {}
+testUnnecessaryDueToExplicitParameterTypeNamed(int i) {}
+testParenthesized(int i) {}
+testParenthesizedNamed(int i) {}
+testParenthesizedTwice(int i) {}
+testParenthesizedTwiceNamed(int i) {}
+
+extension on int {
+  T _laterUnnamedParameter<T>(T x, void Function(T) y) => throw '';
+  void _laterUnnamedParameterDependsOnNamedParameter<T>(void Function(T) x,
+          {required T a}) =>
+      throw '';
+  void _earlierUnnamedParameter<T>(void Function(T) x, T y) => throw '';
+  void _laterNamedParameter<T>({required T a, required void Function(T) b}) =>
+      throw '';
+  void _earlierNamedParameter<T>({required void Function(T) a, required T b}) =>
+      throw '';
+  void _earlierNamedParameterDependsOnUnnamedParameter<T>(T b,
+          {required void Function(T) a}) =>
+      throw '';
+  U _propagateToReturnType<T, U>(T x, U Function(T) y) => throw '';
+  U _closureAsParameterType<T, U>(T x, U Function(T) y) => throw '';
+  U _propagateToEarlierClosure<T, U>(U Function(T) x, T Function() y) =>
+      throw '';
+  U _propagateToLaterClosure<T, U>(T Function() x, U Function(T) y) => throw '';
+  V _longDependencyChain<T, U, V>(
+          T Function() x, U Function(T) y, V Function(U) z) =>
+      throw '';
+  Map<T, U> _dependencyCycle<T, U>(T Function(U) x, U Function(T) y) =>
+      throw '';
+  U _propagateFromContravariantReturnType<T, U>(
+          void Function(T) Function() x, U Function(T) y) =>
+      throw '';
+  U _propagateToContravariantParameterType<T, U>(
+          T Function() x, U Function(void Function(T)) y) =>
+      throw '';
+  void _returnTypeRefersToMultipleTypeVars<T, U>(
+          Map<T, U> Function() x, void Function(T) y, void Function(U) z) =>
+      throw '';
+  T _unnecessaryDueToNoDependency<T>(T Function() x, T y) => throw '';
+  T _unnecessaryDueToExplicitParameterTypeNamed<T>(
+          T x, T Function({required T x, required int y}) y) =>
+      throw '';
+  void _parenthesized<T>(T x, void Function(T) y) => throw '';
+  void _parenthesizedNamed<T>({required T a, required void Function(T) b}) =>
+      throw '';
+  void _parenthesizedTwice<T>(T x, void Function(T) y) => throw '';
+  void _parenthesizedTwiceNamed<T>(
+          {required T a, required void Function(T) b}) =>
+      throw '';
+}
+
+main() {}

pkg/front_end/testcases/inference_update_1/horizontal_inference_extension_method.dart.textual_outline_modelled.expect

@@ -0,0 +1,67 @@
+extension on int {
+  Map<T, U> _dependencyCycle<T, U>(T Function(U) x, U Function(T) y) =>
+      throw '';
+  T _laterUnnamedParameter<T>(T x, void Function(T) y) => throw '';
+  T _unnecessaryDueToExplicitParameterTypeNamed<T>(
+          T x, T Function({required T x, required int y}) y) =>
+      throw '';
+  T _unnecessaryDueToNoDependency<T>(T Function() x, T y) => throw '';
+  U _closureAsParameterType<T, U>(T x, U Function(T) y) => throw '';
+  U _propagateFromContravariantReturnType<T, U>(
+          void Function(T) Function() x, U Function(T) y) =>
+      throw '';
+  U _propagateToContravariantParameterType<T, U>(
+          T Function() x, U Function(void Function(T)) y) =>
+      throw '';
+  U _propagateToEarlierClosure<T, U>(U Function(T) x, T Function() y) =>
+      throw '';
+  U _propagateToLaterClosure<T, U>(T Function() x, U Function(T) y) => throw '';
+  U _propagateToReturnType<T, U>(T x, U Function(T) y) => throw '';
+  V _longDependencyChain<T, U, V>(
+          T Function() x, U Function(T) y, V Function(U) z) =>
+      throw '';
+  void _earlierNamedParameter<T>({required void Function(T) a, required T b}) =>
+      throw '';
+  void _earlierNamedParameterDependsOnUnnamedParameter<T>(T b,
+          {required void Function(T) a}) =>
+      throw '';
+  void _earlierUnnamedParameter<T>(void Function(T) x, T y) => throw '';
+  void _laterNamedParameter<T>({required T a, required void Function(T) b}) =>
+      throw '';
+  void _laterUnnamedParameterDependsOnNamedParameter<T>(void Function(T) x,
+          {required T a}) =>
+      throw '';
+  void _parenthesized<T>(T x, void Function(T) y) => throw '';
+  void _parenthesizedNamed<T>({required T a, required void Function(T) b}) =>
+      throw '';
+  void _parenthesizedTwice<T>(T x, void Function(T) y) => throw '';
+  void _parenthesizedTwiceNamed<T>(
+          {required T a, required void Function(T) b}) =>
+      throw '';
+  void _returnTypeRefersToMultipleTypeVars<T, U>(
+          Map<T, U> Function() x, void Function(T) y, void Function(U) z) =>
+      throw '';
+}
+
+main() {}
+testClosureAsParameterType(int i) {}
+testDependencyCycle(int i) {}
+testEarlierNamedParameter(int i) {}
+testEarlierNamedParameterDependsOnUnnamedParameter(int i) {}
+testEarlierUnnamedParameter(int i) {}
+testLaterNamedParameter(int i) {}
+testLaterUnnamedParameter(int i) {}
+testLaterUnnamedParameterDependsOnNamedParameter(int i) {}
+testLongDependencyChain(int i) {}
+testParenthesized(int i) {}
+testParenthesizedNamed(int i) {}
+testParenthesizedTwice(int i) {}
+testParenthesizedTwiceNamed(int i) {}
+testPropagateFromContravariantReturnType(int i) {}
+testPropagateToContravariantParameterType(int i) {}
+testPropagateToEarlierClosure(int i) {}
+testPropagateToLaterClosure(int i) {}
+testPropagateToReturnType(int i) {}
+testReturnTypeRefersToMultipleTypeVars(int i) {}
+testUnnecessaryDueToExplicitParameterTypeNamed(int i) {}
+testUnnecessaryDueToNoDependency(int i) {}

pkg/front_end/testcases/inference_update_1/horizontal_inference_extension_method.dart.weak.expect

@@ -0,0 +1,232 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "dart:collection" as col;
+
+extension _extension#0 on core::int {
+  method _laterUnnamedParameter = self::_extension#0|_laterUnnamedParameter;
+  tearoff _laterUnnamedParameter = self::_extension#0|get#_laterUnnamedParameter;
+  method _laterUnnamedParameterDependsOnNamedParameter = self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter;
+  tearoff _laterUnnamedParameterDependsOnNamedParameter = self::_extension#0|get#_laterUnnamedParameterDependsOnNamedParameter;
+  method _earlierUnnamedParameter = self::_extension#0|_earlierUnnamedParameter;
+  tearoff _earlierUnnamedParameter = self::_extension#0|get#_earlierUnnamedParameter;
+  method _laterNamedParameter = self::_extension#0|_laterNamedParameter;
+  tearoff _laterNamedParameter = self::_extension#0|get#_laterNamedParameter;
+  method _earlierNamedParameter = self::_extension#0|_earlierNamedParameter;
+  tearoff _earlierNamedParameter = self::_extension#0|get#_earlierNamedParameter;
+  method _earlierNamedParameterDependsOnUnnamedParameter = self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter;
+  tearoff _earlierNamedParameterDependsOnUnnamedParameter = self::_extension#0|get#_earlierNamedParameterDependsOnUnnamedParameter;
+  method _propagateToReturnType = self::_extension#0|_propagateToReturnType;
+  tearoff _propagateToReturnType = self::_extension#0|get#_propagateToReturnType;
+  method _closureAsParameterType = self::_extension#0|_closureAsParameterType;
+  tearoff _closureAsParameterType = self::_extension#0|get#_closureAsParameterType;
+  method _propagateToEarlierClosure = self::_extension#0|_propagateToEarlierClosure;
+  tearoff _propagateToEarlierClosure = self::_extension#0|get#_propagateToEarlierClosure;
+  method _propagateToLaterClosure = self::_extension#0|_propagateToLaterClosure;
+  tearoff _propagateToLaterClosure = self::_extension#0|get#_propagateToLaterClosure;
+  method _longDependencyChain = self::_extension#0|_longDependencyChain;
+  tearoff _longDependencyChain = self::_extension#0|get#_longDependencyChain;
+  method _dependencyCycle = self::_extension#0|_dependencyCycle;
+  tearoff _dependencyCycle = self::_extension#0|get#_dependencyCycle;
+  method _propagateFromContravariantReturnType = self::_extension#0|_propagateFromContravariantReturnType;
+  tearoff _propagateFromContravariantReturnType = self::_extension#0|get#_propagateFromContravariantReturnType;
+  method _propagateToContravariantParameterType = self::_extension#0|_propagateToContravariantParameterType;
+  tearoff _propagateToContravariantParameterType = self::_extension#0|get#_propagateToContravariantParameterType;
+  method _returnTypeRefersToMultipleTypeVars = self::_extension#0|_returnTypeRefersToMultipleTypeVars;
+  tearoff _returnTypeRefersToMultipleTypeVars = self::_extension#0|get#_returnTypeRefersToMultipleTypeVars;
+  method _unnecessaryDueToNoDependency = self::_extension#0|_unnecessaryDueToNoDependency;
+  tearoff _unnecessaryDueToNoDependency = self::_extension#0|get#_unnecessaryDueToNoDependency;
+  method _unnecessaryDueToExplicitParameterTypeNamed = self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed;
+  tearoff _unnecessaryDueToExplicitParameterTypeNamed = self::_extension#0|get#_unnecessaryDueToExplicitParameterTypeNamed;
+  method _parenthesized = self::_extension#0|_parenthesized;
+  tearoff _parenthesized = self::_extension#0|get#_parenthesized;
+  method _parenthesizedNamed = self::_extension#0|_parenthesizedNamed;
+  tearoff _parenthesizedNamed = self::_extension#0|get#_parenthesizedNamed;
+  method _parenthesizedTwice = self::_extension#0|_parenthesizedTwice;
+  tearoff _parenthesizedTwice = self::_extension#0|get#_parenthesizedTwice;
+  method _parenthesizedTwiceNamed = self::_extension#0|_parenthesizedTwiceNamed;
+  tearoff _parenthesizedTwiceNamed = self::_extension#0|get#_parenthesizedTwiceNamed;
+}
+static method testLaterUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterUnnamedParameter<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testLaterUnnamedParameterDependsOnNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter<core::int>(i, (core::int x) → void {
+    x;
+  }, a: 0);
+}
+static method testEarlierUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierUnnamedParameter<core::int>(i, (core::int x) → void {
+    x;
+  }, 0);
+}
+static method testLaterNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterNamedParameter<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method testEarlierNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierNamedParameter<core::int>(i, a: (core::int x) → void {
+    x;
+  }, b: 0);
+}
+static method testEarlierNamedParameterDependsOnUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter<core::int>(i, 0, a: (core::int x) → void {
+    x;
+  });
+}
+static method testPropagateToReturnType(core::int i) → dynamic {
+  self::_extension#0|_propagateToReturnType<core::int, core::List<core::int>>(i, 0, (core::int x) → core::List<core::int> => <core::int>[x]);
+}
+static method testClosureAsParameterType(core::int i) → dynamic {
+  self::_extension#0|_closureAsParameterType<() → core::int, core::List<core::int>>(i, () → core::int => 0, (() → core::int h) → core::List<core::int> => <core::int>[h(){() → core::int}]);
+}
+static method testPropagateToEarlierClosure(core::int i) → dynamic {
+  self::_extension#0|_propagateToEarlierClosure<core::int, core::List<core::int>>(i, (core::int x) → core::List<core::int> => <core::int>[x], () → core::int => 0);
+}
+static method testPropagateToLaterClosure(core::int i) → dynamic {
+  self::_extension#0|_propagateToLaterClosure<core::int, core::List<core::int>>(i, () → core::int => 0, (core::int x) → core::List<core::int> => <core::int>[x]);
+}
+static method testLongDependencyChain(core::int i) → dynamic {
+  self::_extension#0|_longDependencyChain<core::List<core::int>, core::int, core::Set<core::int>>(i, () → core::List<core::int> => <core::int>[0], (core::List<core::int> x) → core::int => x.{core::Iterable::single}{core::int}, (core::int y) → core::Set<core::int> => block {
+    final core::Set<core::int> #t1 = col::LinkedHashSet::•<core::int>();
+    #t1.{core::Set::add}{Invariant}(y){(core::int) → core::bool};
+  } =>#t1);
+}
+static method testDependencyCycle(core::int i) → dynamic {
+  self::_extension#0|_dependencyCycle<core::List<core::Object?>, core::Set<core::Object?>>(i, (core::Object? x) → core::List<core::Object?> => <core::Object?>[x], (core::Object? y) → core::Set<core::Object?> => block {
+    final core::Set<core::Object?> #t2 = col::LinkedHashSet::•<core::Object?>();
+    #t2.{core::Set::add}{Invariant}(y){(core::Object?) → core::bool};
+  } =>#t2);
+}
+static method testPropagateFromContravariantReturnType(core::int i) → dynamic {
+  self::_extension#0|_propagateFromContravariantReturnType<core::int, core::List<core::int>>(i, () → (core::int) → void => (core::int i) → void {}, (core::int x) → core::List<core::int> => <core::int>[x]);
+}
+static method testPropagateToContravariantParameterType(core::int i) → dynamic {
+  self::_extension#0|_propagateToContravariantParameterType<core::int, core::List<(core::int) → void>>(i, () → core::int => 0, ((core::int) → void x) → core::List<(core::int) → void> => <(core::int) → void>[x]);
+}
+static method testReturnTypeRefersToMultipleTypeVars(core::int i) → dynamic {
+  self::_extension#0|_returnTypeRefersToMultipleTypeVars<core::int, core::String>(i, () → core::Map<core::int, core::String> => <core::int, core::String>{0: ""}, (core::int k) → void {
+    k;
+  }, (core::String v) → void {
+    v;
+  });
+}
+static method testUnnecessaryDueToNoDependency(core::int i) → dynamic {
+  self::_extension#0|_unnecessaryDueToNoDependency<core::int?>(i, () → core::int => 0, null);
+}
+static method testUnnecessaryDueToExplicitParameterTypeNamed(core::int i) → dynamic {
+  core::int? a = self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed<core::int?>(i, null, ({core::int? x = #C1, required core::int y = #C1}) → core::int => (let final core::int? #t3 = x in #t3 == null ?{core::int} 0 : #t3{core::int}).{core::num::+}(y){(core::num) → core::int});
+  a;
+}
+static method testParenthesized(core::int i) → dynamic {
+  self::_extension#0|_parenthesized<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedNamed(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedNamed<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedTwice(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedTwice<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedTwiceNamed(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedTwiceNamed<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method _extension#0|_laterUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_laterUnnamedParameter::T% x, (self::_extension#0|_laterUnnamedParameter::T%) → void y) → self::_extension#0|_laterUnnamedParameter::T%
+  return throw "";
+static method _extension#0|get#_laterUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → T%
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → T% => self::_extension#0|_laterUnnamedParameter<T%>(#this, x, y);
+static method _extension#0|_laterUnnamedParameterDependsOnNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter::T%) → void x, {required self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter::T% a = #C1}) → void
+  return throw "";
+static method _extension#0|get#_laterUnnamedParameterDependsOnNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>((T%) → void, {a: T%}) → void
+  return <T extends core::Object? = dynamic>((T%) → void x, {T% a = #C1}) → void => self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter<T%>(#this, x, a: a);
+static method _extension#0|_earlierUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_earlierUnnamedParameter::T%) → void x, self::_extension#0|_earlierUnnamedParameter::T% y) → void
+  return throw "";
+static method _extension#0|get#_earlierUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>((T%) → void, T%) → void
+  return <T extends core::Object? = dynamic>((T%) → void x, T% y) → void => self::_extension#0|_earlierUnnamedParameter<T%>(#this, x, y);
+static method _extension#0|_laterNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_laterNamedParameter::T% a = #C1, required (self::_extension#0|_laterNamedParameter::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_laterNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_laterNamedParameter<T%>(#this, a: a, b: b);
+static method _extension#0|_earlierNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, {required (self::_extension#0|_earlierNamedParameter::T%) → void a = #C1, required self::_extension#0|_earlierNamedParameter::T% b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_earlierNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: (T%) → void, b: T%}) → void
+  return <T extends core::Object? = dynamic>({(T%) → void a = #C1, T% b = #C1}) → void => self::_extension#0|_earlierNamedParameter<T%>(#this, a: a, b: b);
+static method _extension#0|_earlierNamedParameterDependsOnUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter::T% b, {required (self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter::T%) → void a = #C1}) → void
+  return throw "";
+static method _extension#0|get#_earlierNamedParameterDependsOnUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, {a: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>(T% b, {(T%) → void a = #C1}) → void => self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter<T%>(#this, b, a: a);
+static method _extension#0|_propagateToReturnType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_propagateToReturnType::T% x, (self::_extension#0|_propagateToReturnType::T%) → self::_extension#0|_propagateToReturnType::U% y) → self::_extension#0|_propagateToReturnType::U%
+  return throw "";
+static method _extension#0|get#_propagateToReturnType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T% x, (T%) → U% y) → U% => self::_extension#0|_propagateToReturnType<T%, U%>(#this, x, y);
+static method _extension#0|_closureAsParameterType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_closureAsParameterType::T% x, (self::_extension#0|_closureAsParameterType::T%) → self::_extension#0|_closureAsParameterType::U% y) → self::_extension#0|_closureAsParameterType::U%
+  return throw "";
+static method _extension#0|get#_closureAsParameterType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T% x, (T%) → U% y) → U% => self::_extension#0|_closureAsParameterType<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToEarlierClosure<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_propagateToEarlierClosure::T%) → self::_extension#0|_propagateToEarlierClosure::U% x, () → self::_extension#0|_propagateToEarlierClosure::T% y) → self::_extension#0|_propagateToEarlierClosure::U%
+  return throw "";
+static method _extension#0|get#_propagateToEarlierClosure(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((T%) → U%, () → T%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((T%) → U% x, () → T% y) → U% => self::_extension#0|_propagateToEarlierClosure<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToLaterClosure<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_propagateToLaterClosure::T% x, (self::_extension#0|_propagateToLaterClosure::T%) → self::_extension#0|_propagateToLaterClosure::U% y) → self::_extension#0|_propagateToLaterClosure::U%
+  return throw "";
+static method _extension#0|get#_propagateToLaterClosure(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T% x, (T%) → U% y) → U% => self::_extension#0|_propagateToLaterClosure<T%, U%>(#this, x, y);
+static method _extension#0|get#_longDependencyChain(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(() → T%, (T%) → U%, (U%) → V%) → V%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(() → T% x, (T%) → U% y, (U%) → V% z) → V% => self::_extension#0|_longDependencyChain<T%, U%, V%>(#this, x, y, z);
+static method _extension#0|_longDependencyChain<T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_longDependencyChain::T% x, (self::_extension#0|_longDependencyChain::T%) → self::_extension#0|_longDependencyChain::U% y, (self::_extension#0|_longDependencyChain::U%) → self::_extension#0|_longDependencyChain::V% z) → self::_extension#0|_longDependencyChain::V%
+  return throw "";
+static method _extension#0|_dependencyCycle<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_dependencyCycle::U%) → self::_extension#0|_dependencyCycle::T% x, (self::_extension#0|_dependencyCycle::T%) → self::_extension#0|_dependencyCycle::U% y) → core::Map<self::_extension#0|_dependencyCycle::T%, self::_extension#0|_dependencyCycle::U%>
+  return throw "";
+static method _extension#0|get#_dependencyCycle(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((U%) → T%, (T%) → U%) → core::Map<T%, U%>
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((U%) → T% x, (T%) → U% y) → core::Map<T%, U%> => self::_extension#0|_dependencyCycle<T%, U%>(#this, x, y);
+static method _extension#0|_propagateFromContravariantReturnType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → (self::_extension#0|_propagateFromContravariantReturnType::T%) → void x, (self::_extension#0|_propagateFromContravariantReturnType::T%) → self::_extension#0|_propagateFromContravariantReturnType::U% y) → self::_extension#0|_propagateFromContravariantReturnType::U%
+  return throw "";
+static method _extension#0|get#_propagateFromContravariantReturnType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → (T%) → void, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → (T%) → void x, (T%) → U% y) → U% => self::_extension#0|_propagateFromContravariantReturnType<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToContravariantParameterType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_propagateToContravariantParameterType::T% x, ((self::_extension#0|_propagateToContravariantParameterType::T%) → void) → self::_extension#0|_propagateToContravariantParameterType::U% y) → self::_extension#0|_propagateToContravariantParameterType::U%
+  return throw "";
+static method _extension#0|get#_propagateToContravariantParameterType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T%, ((T%) → void) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T% x, ((T%) → void) → U% y) → U% => self::_extension#0|_propagateToContravariantParameterType<T%, U%>(#this, x, y);
+static method _extension#0|_returnTypeRefersToMultipleTypeVars<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → core::Map<self::_extension#0|_returnTypeRefersToMultipleTypeVars::T%, self::_extension#0|_returnTypeRefersToMultipleTypeVars::U%> x, (self::_extension#0|_returnTypeRefersToMultipleTypeVars::T%) → void y, (self::_extension#0|_returnTypeRefersToMultipleTypeVars::U%) → void z) → void
+  return throw "";
+static method _extension#0|get#_returnTypeRefersToMultipleTypeVars(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → core::Map<T%, U%>, (T%) → void, (U%) → void) → void
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → core::Map<T%, U%> x, (T%) → void y, (U%) → void z) → void => self::_extension#0|_returnTypeRefersToMultipleTypeVars<T%, U%>(#this, x, y, z);
+static method _extension#0|_unnecessaryDueToNoDependency<T extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_unnecessaryDueToNoDependency::T% x, self::_extension#0|_unnecessaryDueToNoDependency::T% y) → self::_extension#0|_unnecessaryDueToNoDependency::T%
+  return throw "";
+static method _extension#0|get#_unnecessaryDueToNoDependency(lowered final core::int #this) → <T extends core::Object? = dynamic>(() → T%, T%) → T%
+  return <T extends core::Object? = dynamic>(() → T% x, T% y) → T% => self::_extension#0|_unnecessaryDueToNoDependency<T%>(#this, x, y);
+static method _extension#0|_unnecessaryDueToExplicitParameterTypeNamed<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T% x, ({required x: self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T%, required y: core::int}) → self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T% y) → self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T%
+  return throw "";
+static method _extension#0|get#_unnecessaryDueToExplicitParameterTypeNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, ({required x: T%, required y: core::int}) → T%) → T%
+  return <T extends core::Object? = dynamic>(T% x, ({required x: T%, required y: core::int}) → T% y) → T% => self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed<T%>(#this, x, y);
+static method _extension#0|_parenthesized<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_parenthesized::T% x, (self::_extension#0|_parenthesized::T%) → void y) → void
+  return throw "";
+static method _extension#0|get#_parenthesized(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → void
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → void => self::_extension#0|_parenthesized<T%>(#this, x, y);
+static method _extension#0|_parenthesizedNamed<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_parenthesizedNamed::T% a = #C1, required (self::_extension#0|_parenthesizedNamed::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_parenthesizedNamed<T%>(#this, a: a, b: b);
+static method _extension#0|_parenthesizedTwice<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_parenthesizedTwice::T% x, (self::_extension#0|_parenthesizedTwice::T%) → void y) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedTwice(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → void
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → void => self::_extension#0|_parenthesizedTwice<T%>(#this, x, y);
+static method _extension#0|_parenthesizedTwiceNamed<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_parenthesizedTwiceNamed::T% a = #C1, required (self::_extension#0|_parenthesizedTwiceNamed::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedTwiceNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_parenthesizedTwiceNamed<T%>(#this, a: a, b: b);
+static method main() → dynamic {}
+
+constants  {
+  #C1 = null
+}

pkg/front_end/testcases/inference_update_1/horizontal_inference_extension_method.dart.weak.modular.expect

@@ -0,0 +1,232 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "dart:collection" as col;
+
+extension _extension#0 on core::int {
+  method _laterUnnamedParameter = self::_extension#0|_laterUnnamedParameter;
+  tearoff _laterUnnamedParameter = self::_extension#0|get#_laterUnnamedParameter;
+  method _laterUnnamedParameterDependsOnNamedParameter = self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter;
+  tearoff _laterUnnamedParameterDependsOnNamedParameter = self::_extension#0|get#_laterUnnamedParameterDependsOnNamedParameter;
+  method _earlierUnnamedParameter = self::_extension#0|_earlierUnnamedParameter;
+  tearoff _earlierUnnamedParameter = self::_extension#0|get#_earlierUnnamedParameter;
+  method _laterNamedParameter = self::_extension#0|_laterNamedParameter;
+  tearoff _laterNamedParameter = self::_extension#0|get#_laterNamedParameter;
+  method _earlierNamedParameter = self::_extension#0|_earlierNamedParameter;
+  tearoff _earlierNamedParameter = self::_extension#0|get#_earlierNamedParameter;
+  method _earlierNamedParameterDependsOnUnnamedParameter = self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter;
+  tearoff _earlierNamedParameterDependsOnUnnamedParameter = self::_extension#0|get#_earlierNamedParameterDependsOnUnnamedParameter;
+  method _propagateToReturnType = self::_extension#0|_propagateToReturnType;
+  tearoff _propagateToReturnType = self::_extension#0|get#_propagateToReturnType;
+  method _closureAsParameterType = self::_extension#0|_closureAsParameterType;
+  tearoff _closureAsParameterType = self::_extension#0|get#_closureAsParameterType;
+  method _propagateToEarlierClosure = self::_extension#0|_propagateToEarlierClosure;
+  tearoff _propagateToEarlierClosure = self::_extension#0|get#_propagateToEarlierClosure;
+  method _propagateToLaterClosure = self::_extension#0|_propagateToLaterClosure;
+  tearoff _propagateToLaterClosure = self::_extension#0|get#_propagateToLaterClosure;
+  method _longDependencyChain = self::_extension#0|_longDependencyChain;
+  tearoff _longDependencyChain = self::_extension#0|get#_longDependencyChain;
+  method _dependencyCycle = self::_extension#0|_dependencyCycle;
+  tearoff _dependencyCycle = self::_extension#0|get#_dependencyCycle;
+  method _propagateFromContravariantReturnType = self::_extension#0|_propagateFromContravariantReturnType;
+  tearoff _propagateFromContravariantReturnType = self::_extension#0|get#_propagateFromContravariantReturnType;
+  method _propagateToContravariantParameterType = self::_extension#0|_propagateToContravariantParameterType;
+  tearoff _propagateToContravariantParameterType = self::_extension#0|get#_propagateToContravariantParameterType;
+  method _returnTypeRefersToMultipleTypeVars = self::_extension#0|_returnTypeRefersToMultipleTypeVars;
+  tearoff _returnTypeRefersToMultipleTypeVars = self::_extension#0|get#_returnTypeRefersToMultipleTypeVars;
+  method _unnecessaryDueToNoDependency = self::_extension#0|_unnecessaryDueToNoDependency;
+  tearoff _unnecessaryDueToNoDependency = self::_extension#0|get#_unnecessaryDueToNoDependency;
+  method _unnecessaryDueToExplicitParameterTypeNamed = self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed;
+  tearoff _unnecessaryDueToExplicitParameterTypeNamed = self::_extension#0|get#_unnecessaryDueToExplicitParameterTypeNamed;
+  method _parenthesized = self::_extension#0|_parenthesized;
+  tearoff _parenthesized = self::_extension#0|get#_parenthesized;
+  method _parenthesizedNamed = self::_extension#0|_parenthesizedNamed;
+  tearoff _parenthesizedNamed = self::_extension#0|get#_parenthesizedNamed;
+  method _parenthesizedTwice = self::_extension#0|_parenthesizedTwice;
+  tearoff _parenthesizedTwice = self::_extension#0|get#_parenthesizedTwice;
+  method _parenthesizedTwiceNamed = self::_extension#0|_parenthesizedTwiceNamed;
+  tearoff _parenthesizedTwiceNamed = self::_extension#0|get#_parenthesizedTwiceNamed;
+}
+static method testLaterUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterUnnamedParameter<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testLaterUnnamedParameterDependsOnNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter<core::int>(i, (core::int x) → void {
+    x;
+  }, a: 0);
+}
+static method testEarlierUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierUnnamedParameter<core::int>(i, (core::int x) → void {
+    x;
+  }, 0);
+}
+static method testLaterNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterNamedParameter<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method testEarlierNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierNamedParameter<core::int>(i, a: (core::int x) → void {
+    x;
+  }, b: 0);
+}
+static method testEarlierNamedParameterDependsOnUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter<core::int>(i, 0, a: (core::int x) → void {
+    x;
+  });
+}
+static method testPropagateToReturnType(core::int i) → dynamic {
+  self::_extension#0|_propagateToReturnType<core::int, core::List<core::int>>(i, 0, (core::int x) → core::List<core::int> => <core::int>[x]);
+}
+static method testClosureAsParameterType(core::int i) → dynamic {
+  self::_extension#0|_closureAsParameterType<() → core::int, core::List<core::int>>(i, () → core::int => 0, (() → core::int h) → core::List<core::int> => <core::int>[h(){() → core::int}]);
+}
+static method testPropagateToEarlierClosure(core::int i) → dynamic {
+  self::_extension#0|_propagateToEarlierClosure<core::int, core::List<core::int>>(i, (core::int x) → core::List<core::int> => <core::int>[x], () → core::int => 0);
+}
+static method testPropagateToLaterClosure(core::int i) → dynamic {
+  self::_extension#0|_propagateToLaterClosure<core::int, core::List<core::int>>(i, () → core::int => 0, (core::int x) → core::List<core::int> => <core::int>[x]);
+}
+static method testLongDependencyChain(core::int i) → dynamic {
+  self::_extension#0|_longDependencyChain<core::List<core::int>, core::int, core::Set<core::int>>(i, () → core::List<core::int> => <core::int>[0], (core::List<core::int> x) → core::int => x.{core::Iterable::single}{core::int}, (core::int y) → core::Set<core::int> => block {
+    final core::Set<core::int> #t1 = col::LinkedHashSet::•<core::int>();
+    #t1.{core::Set::add}{Invariant}(y){(core::int) → core::bool};
+  } =>#t1);
+}
+static method testDependencyCycle(core::int i) → dynamic {
+  self::_extension#0|_dependencyCycle<core::List<core::Object?>, core::Set<core::Object?>>(i, (core::Object? x) → core::List<core::Object?> => <core::Object?>[x], (core::Object? y) → core::Set<core::Object?> => block {
+    final core::Set<core::Object?> #t2 = col::LinkedHashSet::•<core::Object?>();
+    #t2.{core::Set::add}{Invariant}(y){(core::Object?) → core::bool};
+  } =>#t2);
+}
+static method testPropagateFromContravariantReturnType(core::int i) → dynamic {
+  self::_extension#0|_propagateFromContravariantReturnType<core::int, core::List<core::int>>(i, () → (core::int) → void => (core::int i) → void {}, (core::int x) → core::List<core::int> => <core::int>[x]);
+}
+static method testPropagateToContravariantParameterType(core::int i) → dynamic {
+  self::_extension#0|_propagateToContravariantParameterType<core::int, core::List<(core::int) → void>>(i, () → core::int => 0, ((core::int) → void x) → core::List<(core::int) → void> => <(core::int) → void>[x]);
+}
+static method testReturnTypeRefersToMultipleTypeVars(core::int i) → dynamic {
+  self::_extension#0|_returnTypeRefersToMultipleTypeVars<core::int, core::String>(i, () → core::Map<core::int, core::String> => <core::int, core::String>{0: ""}, (core::int k) → void {
+    k;
+  }, (core::String v) → void {
+    v;
+  });
+}
+static method testUnnecessaryDueToNoDependency(core::int i) → dynamic {
+  self::_extension#0|_unnecessaryDueToNoDependency<core::int?>(i, () → core::int => 0, null);
+}
+static method testUnnecessaryDueToExplicitParameterTypeNamed(core::int i) → dynamic {
+  core::int? a = self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed<core::int?>(i, null, ({core::int? x = #C1, required core::int y = #C1}) → core::int => (let final core::int? #t3 = x in #t3 == null ?{core::int} 0 : #t3{core::int}).{core::num::+}(y){(core::num) → core::int});
+  a;
+}
+static method testParenthesized(core::int i) → dynamic {
+  self::_extension#0|_parenthesized<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedNamed(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedNamed<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedTwice(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedTwice<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedTwiceNamed(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedTwiceNamed<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method _extension#0|_laterUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_laterUnnamedParameter::T% x, (self::_extension#0|_laterUnnamedParameter::T%) → void y) → self::_extension#0|_laterUnnamedParameter::T%
+  return throw "";
+static method _extension#0|get#_laterUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → T%
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → T% => self::_extension#0|_laterUnnamedParameter<T%>(#this, x, y);
+static method _extension#0|_laterUnnamedParameterDependsOnNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter::T%) → void x, {required self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter::T% a = #C1}) → void
+  return throw "";
+static method _extension#0|get#_laterUnnamedParameterDependsOnNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>((T%) → void, {a: T%}) → void
+  return <T extends core::Object? = dynamic>((T%) → void x, {T% a = #C1}) → void => self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter<T%>(#this, x, a: a);
+static method _extension#0|_earlierUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_earlierUnnamedParameter::T%) → void x, self::_extension#0|_earlierUnnamedParameter::T% y) → void
+  return throw "";
+static method _extension#0|get#_earlierUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>((T%) → void, T%) → void
+  return <T extends core::Object? = dynamic>((T%) → void x, T% y) → void => self::_extension#0|_earlierUnnamedParameter<T%>(#this, x, y);
+static method _extension#0|_laterNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_laterNamedParameter::T% a = #C1, required (self::_extension#0|_laterNamedParameter::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_laterNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_laterNamedParameter<T%>(#this, a: a, b: b);
+static method _extension#0|_earlierNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, {required (self::_extension#0|_earlierNamedParameter::T%) → void a = #C1, required self::_extension#0|_earlierNamedParameter::T% b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_earlierNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: (T%) → void, b: T%}) → void
+  return <T extends core::Object? = dynamic>({(T%) → void a = #C1, T% b = #C1}) → void => self::_extension#0|_earlierNamedParameter<T%>(#this, a: a, b: b);
+static method _extension#0|_earlierNamedParameterDependsOnUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter::T% b, {required (self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter::T%) → void a = #C1}) → void
+  return throw "";
+static method _extension#0|get#_earlierNamedParameterDependsOnUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, {a: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>(T% b, {(T%) → void a = #C1}) → void => self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter<T%>(#this, b, a: a);
+static method _extension#0|_propagateToReturnType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_propagateToReturnType::T% x, (self::_extension#0|_propagateToReturnType::T%) → self::_extension#0|_propagateToReturnType::U% y) → self::_extension#0|_propagateToReturnType::U%
+  return throw "";
+static method _extension#0|get#_propagateToReturnType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T% x, (T%) → U% y) → U% => self::_extension#0|_propagateToReturnType<T%, U%>(#this, x, y);
+static method _extension#0|_closureAsParameterType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_closureAsParameterType::T% x, (self::_extension#0|_closureAsParameterType::T%) → self::_extension#0|_closureAsParameterType::U% y) → self::_extension#0|_closureAsParameterType::U%
+  return throw "";
+static method _extension#0|get#_closureAsParameterType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T% x, (T%) → U% y) → U% => self::_extension#0|_closureAsParameterType<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToEarlierClosure<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_propagateToEarlierClosure::T%) → self::_extension#0|_propagateToEarlierClosure::U% x, () → self::_extension#0|_propagateToEarlierClosure::T% y) → self::_extension#0|_propagateToEarlierClosure::U%
+  return throw "";
+static method _extension#0|get#_propagateToEarlierClosure(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((T%) → U%, () → T%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((T%) → U% x, () → T% y) → U% => self::_extension#0|_propagateToEarlierClosure<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToLaterClosure<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_propagateToLaterClosure::T% x, (self::_extension#0|_propagateToLaterClosure::T%) → self::_extension#0|_propagateToLaterClosure::U% y) → self::_extension#0|_propagateToLaterClosure::U%
+  return throw "";
+static method _extension#0|get#_propagateToLaterClosure(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T% x, (T%) → U% y) → U% => self::_extension#0|_propagateToLaterClosure<T%, U%>(#this, x, y);
+static method _extension#0|get#_longDependencyChain(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(() → T%, (T%) → U%, (U%) → V%) → V%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(() → T% x, (T%) → U% y, (U%) → V% z) → V% => self::_extension#0|_longDependencyChain<T%, U%, V%>(#this, x, y, z);
+static method _extension#0|_longDependencyChain<T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_longDependencyChain::T% x, (self::_extension#0|_longDependencyChain::T%) → self::_extension#0|_longDependencyChain::U% y, (self::_extension#0|_longDependencyChain::U%) → self::_extension#0|_longDependencyChain::V% z) → self::_extension#0|_longDependencyChain::V%
+  return throw "";
+static method _extension#0|_dependencyCycle<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_dependencyCycle::U%) → self::_extension#0|_dependencyCycle::T% x, (self::_extension#0|_dependencyCycle::T%) → self::_extension#0|_dependencyCycle::U% y) → core::Map<self::_extension#0|_dependencyCycle::T%, self::_extension#0|_dependencyCycle::U%>
+  return throw "";
+static method _extension#0|get#_dependencyCycle(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((U%) → T%, (T%) → U%) → core::Map<T%, U%>
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((U%) → T% x, (T%) → U% y) → core::Map<T%, U%> => self::_extension#0|_dependencyCycle<T%, U%>(#this, x, y);
+static method _extension#0|_propagateFromContravariantReturnType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → (self::_extension#0|_propagateFromContravariantReturnType::T%) → void x, (self::_extension#0|_propagateFromContravariantReturnType::T%) → self::_extension#0|_propagateFromContravariantReturnType::U% y) → self::_extension#0|_propagateFromContravariantReturnType::U%
+  return throw "";
+static method _extension#0|get#_propagateFromContravariantReturnType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → (T%) → void, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → (T%) → void x, (T%) → U% y) → U% => self::_extension#0|_propagateFromContravariantReturnType<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToContravariantParameterType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_propagateToContravariantParameterType::T% x, ((self::_extension#0|_propagateToContravariantParameterType::T%) → void) → self::_extension#0|_propagateToContravariantParameterType::U% y) → self::_extension#0|_propagateToContravariantParameterType::U%
+  return throw "";
+static method _extension#0|get#_propagateToContravariantParameterType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T%, ((T%) → void) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T% x, ((T%) → void) → U% y) → U% => self::_extension#0|_propagateToContravariantParameterType<T%, U%>(#this, x, y);
+static method _extension#0|_returnTypeRefersToMultipleTypeVars<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → core::Map<self::_extension#0|_returnTypeRefersToMultipleTypeVars::T%, self::_extension#0|_returnTypeRefersToMultipleTypeVars::U%> x, (self::_extension#0|_returnTypeRefersToMultipleTypeVars::T%) → void y, (self::_extension#0|_returnTypeRefersToMultipleTypeVars::U%) → void z) → void
+  return throw "";
+static method _extension#0|get#_returnTypeRefersToMultipleTypeVars(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → core::Map<T%, U%>, (T%) → void, (U%) → void) → void
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → core::Map<T%, U%> x, (T%) → void y, (U%) → void z) → void => self::_extension#0|_returnTypeRefersToMultipleTypeVars<T%, U%>(#this, x, y, z);
+static method _extension#0|_unnecessaryDueToNoDependency<T extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_unnecessaryDueToNoDependency::T% x, self::_extension#0|_unnecessaryDueToNoDependency::T% y) → self::_extension#0|_unnecessaryDueToNoDependency::T%
+  return throw "";
+static method _extension#0|get#_unnecessaryDueToNoDependency(lowered final core::int #this) → <T extends core::Object? = dynamic>(() → T%, T%) → T%
+  return <T extends core::Object? = dynamic>(() → T% x, T% y) → T% => self::_extension#0|_unnecessaryDueToNoDependency<T%>(#this, x, y);
+static method _extension#0|_unnecessaryDueToExplicitParameterTypeNamed<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T% x, ({required x: self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T%, required y: core::int}) → self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T% y) → self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T%
+  return throw "";
+static method _extension#0|get#_unnecessaryDueToExplicitParameterTypeNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, ({required x: T%, required y: core::int}) → T%) → T%
+  return <T extends core::Object? = dynamic>(T% x, ({required x: T%, required y: core::int}) → T% y) → T% => self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed<T%>(#this, x, y);
+static method _extension#0|_parenthesized<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_parenthesized::T% x, (self::_extension#0|_parenthesized::T%) → void y) → void
+  return throw "";
+static method _extension#0|get#_parenthesized(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → void
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → void => self::_extension#0|_parenthesized<T%>(#this, x, y);
+static method _extension#0|_parenthesizedNamed<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_parenthesizedNamed::T% a = #C1, required (self::_extension#0|_parenthesizedNamed::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_parenthesizedNamed<T%>(#this, a: a, b: b);
+static method _extension#0|_parenthesizedTwice<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_parenthesizedTwice::T% x, (self::_extension#0|_parenthesizedTwice::T%) → void y) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedTwice(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → void
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → void => self::_extension#0|_parenthesizedTwice<T%>(#this, x, y);
+static method _extension#0|_parenthesizedTwiceNamed<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_parenthesizedTwiceNamed::T% a = #C1, required (self::_extension#0|_parenthesizedTwiceNamed::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedTwiceNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_parenthesizedTwiceNamed<T%>(#this, a: a, b: b);
+static method main() → dynamic {}
+
+constants  {
+  #C1 = null
+}

pkg/front_end/testcases/inference_update_1/horizontal_inference_extension_method.dart.weak.outline.expect

@@ -0,0 +1,176 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+extension _extension#0 on core::int {
+  method _laterUnnamedParameter = self::_extension#0|_laterUnnamedParameter;
+  tearoff _laterUnnamedParameter = self::_extension#0|get#_laterUnnamedParameter;
+  method _laterUnnamedParameterDependsOnNamedParameter = self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter;
+  tearoff _laterUnnamedParameterDependsOnNamedParameter = self::_extension#0|get#_laterUnnamedParameterDependsOnNamedParameter;
+  method _earlierUnnamedParameter = self::_extension#0|_earlierUnnamedParameter;
+  tearoff _earlierUnnamedParameter = self::_extension#0|get#_earlierUnnamedParameter;
+  method _laterNamedParameter = self::_extension#0|_laterNamedParameter;
+  tearoff _laterNamedParameter = self::_extension#0|get#_laterNamedParameter;
+  method _earlierNamedParameter = self::_extension#0|_earlierNamedParameter;
+  tearoff _earlierNamedParameter = self::_extension#0|get#_earlierNamedParameter;
+  method _earlierNamedParameterDependsOnUnnamedParameter = self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter;
+  tearoff _earlierNamedParameterDependsOnUnnamedParameter = self::_extension#0|get#_earlierNamedParameterDependsOnUnnamedParameter;
+  method _propagateToReturnType = self::_extension#0|_propagateToReturnType;
+  tearoff _propagateToReturnType = self::_extension#0|get#_propagateToReturnType;
+  method _closureAsParameterType = self::_extension#0|_closureAsParameterType;
+  tearoff _closureAsParameterType = self::_extension#0|get#_closureAsParameterType;
+  method _propagateToEarlierClosure = self::_extension#0|_propagateToEarlierClosure;
+  tearoff _propagateToEarlierClosure = self::_extension#0|get#_propagateToEarlierClosure;
+  method _propagateToLaterClosure = self::_extension#0|_propagateToLaterClosure;
+  tearoff _propagateToLaterClosure = self::_extension#0|get#_propagateToLaterClosure;
+  method _longDependencyChain = self::_extension#0|_longDependencyChain;
+  tearoff _longDependencyChain = self::_extension#0|get#_longDependencyChain;
+  method _dependencyCycle = self::_extension#0|_dependencyCycle;
+  tearoff _dependencyCycle = self::_extension#0|get#_dependencyCycle;
+  method _propagateFromContravariantReturnType = self::_extension#0|_propagateFromContravariantReturnType;
+  tearoff _propagateFromContravariantReturnType = self::_extension#0|get#_propagateFromContravariantReturnType;
+  method _propagateToContravariantParameterType = self::_extension#0|_propagateToContravariantParameterType;
+  tearoff _propagateToContravariantParameterType = self::_extension#0|get#_propagateToContravariantParameterType;
+  method _returnTypeRefersToMultipleTypeVars = self::_extension#0|_returnTypeRefersToMultipleTypeVars;
+  tearoff _returnTypeRefersToMultipleTypeVars = self::_extension#0|get#_returnTypeRefersToMultipleTypeVars;
+  method _unnecessaryDueToNoDependency = self::_extension#0|_unnecessaryDueToNoDependency;
+  tearoff _unnecessaryDueToNoDependency = self::_extension#0|get#_unnecessaryDueToNoDependency;
+  method _unnecessaryDueToExplicitParameterTypeNamed = self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed;
+  tearoff _unnecessaryDueToExplicitParameterTypeNamed = self::_extension#0|get#_unnecessaryDueToExplicitParameterTypeNamed;
+  method _parenthesized = self::_extension#0|_parenthesized;
+  tearoff _parenthesized = self::_extension#0|get#_parenthesized;
+  method _parenthesizedNamed = self::_extension#0|_parenthesizedNamed;
+  tearoff _parenthesizedNamed = self::_extension#0|get#_parenthesizedNamed;
+  method _parenthesizedTwice = self::_extension#0|_parenthesizedTwice;
+  tearoff _parenthesizedTwice = self::_extension#0|get#_parenthesizedTwice;
+  method _parenthesizedTwiceNamed = self::_extension#0|_parenthesizedTwiceNamed;
+  tearoff _parenthesizedTwiceNamed = self::_extension#0|get#_parenthesizedTwiceNamed;
+}
+static method testLaterUnnamedParameter(core::int i) → dynamic
+  ;
+static method testLaterUnnamedParameterDependsOnNamedParameter(core::int i) → dynamic
+  ;
+static method testEarlierUnnamedParameter(core::int i) → dynamic
+  ;
+static method testLaterNamedParameter(core::int i) → dynamic
+  ;
+static method testEarlierNamedParameter(core::int i) → dynamic
+  ;
+static method testEarlierNamedParameterDependsOnUnnamedParameter(core::int i) → dynamic
+  ;
+static method testPropagateToReturnType(core::int i) → dynamic
+  ;
+static method testClosureAsParameterType(core::int i) → dynamic
+  ;
+static method testPropagateToEarlierClosure(core::int i) → dynamic
+  ;
+static method testPropagateToLaterClosure(core::int i) → dynamic
+  ;
+static method testLongDependencyChain(core::int i) → dynamic
+  ;
+static method testDependencyCycle(core::int i) → dynamic
+  ;
+static method testPropagateFromContravariantReturnType(core::int i) → dynamic
+  ;
+static method testPropagateToContravariantParameterType(core::int i) → dynamic
+  ;
+static method testReturnTypeRefersToMultipleTypeVars(core::int i) → dynamic
+  ;
+static method testUnnecessaryDueToNoDependency(core::int i) → dynamic
+  ;
+static method testUnnecessaryDueToExplicitParameterTypeNamed(core::int i) → dynamic
+  ;
+static method testParenthesized(core::int i) → dynamic
+  ;
+static method testParenthesizedNamed(core::int i) → dynamic
+  ;
+static method testParenthesizedTwice(core::int i) → dynamic
+  ;
+static method testParenthesizedTwiceNamed(core::int i) → dynamic
+  ;
+static method _extension#0|_laterUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_laterUnnamedParameter::T% x, (self::_extension#0|_laterUnnamedParameter::T%) → void y) → self::_extension#0|_laterUnnamedParameter::T%
+  ;
+static method _extension#0|get#_laterUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → T%
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → T% => self::_extension#0|_laterUnnamedParameter<T%>(#this, x, y);
+static method _extension#0|_laterUnnamedParameterDependsOnNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter::T%) → void x, {required self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter::T% a}) → void
+  ;
+static method _extension#0|get#_laterUnnamedParameterDependsOnNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>((T%) → void, {a: T%}) → void
+  return <T extends core::Object? = dynamic>((T%) → void x, {T% a}) → void => self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter<T%>(#this, x, a: a);
+static method _extension#0|_earlierUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_earlierUnnamedParameter::T%) → void x, self::_extension#0|_earlierUnnamedParameter::T% y) → void
+  ;
+static method _extension#0|get#_earlierUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>((T%) → void, T%) → void
+  return <T extends core::Object? = dynamic>((T%) → void x, T% y) → void => self::_extension#0|_earlierUnnamedParameter<T%>(#this, x, y);
+static method _extension#0|_laterNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_laterNamedParameter::T% a, required (self::_extension#0|_laterNamedParameter::T%) → void b}) → void
+  ;
+static method _extension#0|get#_laterNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a, (T%) → void b}) → void => self::_extension#0|_laterNamedParameter<T%>(#this, a: a, b: b);
+static method _extension#0|_earlierNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, {required (self::_extension#0|_earlierNamedParameter::T%) → void a, required self::_extension#0|_earlierNamedParameter::T% b}) → void
+  ;
+static method _extension#0|get#_earlierNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: (T%) → void, b: T%}) → void
+  return <T extends core::Object? = dynamic>({(T%) → void a, T% b}) → void => self::_extension#0|_earlierNamedParameter<T%>(#this, a: a, b: b);
+static method _extension#0|_earlierNamedParameterDependsOnUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter::T% b, {required (self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter::T%) → void a}) → void
+  ;
+static method _extension#0|get#_earlierNamedParameterDependsOnUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, {a: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>(T% b, {(T%) → void a}) → void => self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter<T%>(#this, b, a: a);
+static method _extension#0|_propagateToReturnType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_propagateToReturnType::T% x, (self::_extension#0|_propagateToReturnType::T%) → self::_extension#0|_propagateToReturnType::U% y) → self::_extension#0|_propagateToReturnType::U%
+  ;
+static method _extension#0|get#_propagateToReturnType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T% x, (T%) → U% y) → U% => self::_extension#0|_propagateToReturnType<T%, U%>(#this, x, y);
+static method _extension#0|_closureAsParameterType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_closureAsParameterType::T% x, (self::_extension#0|_closureAsParameterType::T%) → self::_extension#0|_closureAsParameterType::U% y) → self::_extension#0|_closureAsParameterType::U%
+  ;
+static method _extension#0|get#_closureAsParameterType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T% x, (T%) → U% y) → U% => self::_extension#0|_closureAsParameterType<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToEarlierClosure<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_propagateToEarlierClosure::T%) → self::_extension#0|_propagateToEarlierClosure::U% x, () → self::_extension#0|_propagateToEarlierClosure::T% y) → self::_extension#0|_propagateToEarlierClosure::U%
+  ;
+static method _extension#0|get#_propagateToEarlierClosure(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((T%) → U%, () → T%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((T%) → U% x, () → T% y) → U% => self::_extension#0|_propagateToEarlierClosure<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToLaterClosure<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_propagateToLaterClosure::T% x, (self::_extension#0|_propagateToLaterClosure::T%) → self::_extension#0|_propagateToLaterClosure::U% y) → self::_extension#0|_propagateToLaterClosure::U%
+  ;
+static method _extension#0|get#_propagateToLaterClosure(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T% x, (T%) → U% y) → U% => self::_extension#0|_propagateToLaterClosure<T%, U%>(#this, x, y);
+static method _extension#0|get#_longDependencyChain(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(() → T%, (T%) → U%, (U%) → V%) → V%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(() → T% x, (T%) → U% y, (U%) → V% z) → V% => self::_extension#0|_longDependencyChain<T%, U%, V%>(#this, x, y, z);
+static method _extension#0|_longDependencyChain<T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_longDependencyChain::T% x, (self::_extension#0|_longDependencyChain::T%) → self::_extension#0|_longDependencyChain::U% y, (self::_extension#0|_longDependencyChain::U%) → self::_extension#0|_longDependencyChain::V% z) → self::_extension#0|_longDependencyChain::V%
+  ;
+static method _extension#0|_dependencyCycle<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_dependencyCycle::U%) → self::_extension#0|_dependencyCycle::T% x, (self::_extension#0|_dependencyCycle::T%) → self::_extension#0|_dependencyCycle::U% y) → core::Map<self::_extension#0|_dependencyCycle::T%, self::_extension#0|_dependencyCycle::U%>
+  ;
+static method _extension#0|get#_dependencyCycle(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((U%) → T%, (T%) → U%) → core::Map<T%, U%>
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((U%) → T% x, (T%) → U% y) → core::Map<T%, U%> => self::_extension#0|_dependencyCycle<T%, U%>(#this, x, y);
+static method _extension#0|_propagateFromContravariantReturnType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → (self::_extension#0|_propagateFromContravariantReturnType::T%) → void x, (self::_extension#0|_propagateFromContravariantReturnType::T%) → self::_extension#0|_propagateFromContravariantReturnType::U% y) → self::_extension#0|_propagateFromContravariantReturnType::U%
+  ;
+static method _extension#0|get#_propagateFromContravariantReturnType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → (T%) → void, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → (T%) → void x, (T%) → U% y) → U% => self::_extension#0|_propagateFromContravariantReturnType<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToContravariantParameterType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_propagateToContravariantParameterType::T% x, ((self::_extension#0|_propagateToContravariantParameterType::T%) → void) → self::_extension#0|_propagateToContravariantParameterType::U% y) → self::_extension#0|_propagateToContravariantParameterType::U%
+  ;
+static method _extension#0|get#_propagateToContravariantParameterType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T%, ((T%) → void) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T% x, ((T%) → void) → U% y) → U% => self::_extension#0|_propagateToContravariantParameterType<T%, U%>(#this, x, y);
+static method _extension#0|_returnTypeRefersToMultipleTypeVars<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → core::Map<self::_extension#0|_returnTypeRefersToMultipleTypeVars::T%, self::_extension#0|_returnTypeRefersToMultipleTypeVars::U%> x, (self::_extension#0|_returnTypeRefersToMultipleTypeVars::T%) → void y, (self::_extension#0|_returnTypeRefersToMultipleTypeVars::U%) → void z) → void
+  ;
+static method _extension#0|get#_returnTypeRefersToMultipleTypeVars(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → core::Map<T%, U%>, (T%) → void, (U%) → void) → void
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → core::Map<T%, U%> x, (T%) → void y, (U%) → void z) → void => self::_extension#0|_returnTypeRefersToMultipleTypeVars<T%, U%>(#this, x, y, z);
+static method _extension#0|_unnecessaryDueToNoDependency<T extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_unnecessaryDueToNoDependency::T% x, self::_extension#0|_unnecessaryDueToNoDependency::T% y) → self::_extension#0|_unnecessaryDueToNoDependency::T%
+  ;
+static method _extension#0|get#_unnecessaryDueToNoDependency(lowered final core::int #this) → <T extends core::Object? = dynamic>(() → T%, T%) → T%
+  return <T extends core::Object? = dynamic>(() → T% x, T% y) → T% => self::_extension#0|_unnecessaryDueToNoDependency<T%>(#this, x, y);
+static method _extension#0|_unnecessaryDueToExplicitParameterTypeNamed<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T% x, ({required x: self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T%, required y: core::int}) → self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T% y) → self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T%
+  ;
+static method _extension#0|get#_unnecessaryDueToExplicitParameterTypeNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, ({required x: T%, required y: core::int}) → T%) → T%
+  return <T extends core::Object? = dynamic>(T% x, ({required x: T%, required y: core::int}) → T% y) → T% => self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed<T%>(#this, x, y);
+static method _extension#0|_parenthesized<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_parenthesized::T% x, (self::_extension#0|_parenthesized::T%) → void y) → void
+  ;
+static method _extension#0|get#_parenthesized(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → void
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → void => self::_extension#0|_parenthesized<T%>(#this, x, y);
+static method _extension#0|_parenthesizedNamed<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_parenthesizedNamed::T% a, required (self::_extension#0|_parenthesizedNamed::T%) → void b}) → void
+  ;
+static method _extension#0|get#_parenthesizedNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a, (T%) → void b}) → void => self::_extension#0|_parenthesizedNamed<T%>(#this, a: a, b: b);
+static method _extension#0|_parenthesizedTwice<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_parenthesizedTwice::T% x, (self::_extension#0|_parenthesizedTwice::T%) → void y) → void
+  ;
+static method _extension#0|get#_parenthesizedTwice(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → void
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → void => self::_extension#0|_parenthesizedTwice<T%>(#this, x, y);
+static method _extension#0|_parenthesizedTwiceNamed<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_parenthesizedTwiceNamed::T% a, required (self::_extension#0|_parenthesizedTwiceNamed::T%) → void b}) → void
+  ;
+static method _extension#0|get#_parenthesizedTwiceNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a, (T%) → void b}) → void => self::_extension#0|_parenthesizedTwiceNamed<T%>(#this, a: a, b: b);
+static method main() → dynamic
+  ;

pkg/front_end/testcases/inference_update_1/horizontal_inference_extension_method.dart.weak.transformed.expect

@@ -0,0 +1,232 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "dart:collection" as col;
+
+extension _extension#0 on core::int {
+  method _laterUnnamedParameter = self::_extension#0|_laterUnnamedParameter;
+  tearoff _laterUnnamedParameter = self::_extension#0|get#_laterUnnamedParameter;
+  method _laterUnnamedParameterDependsOnNamedParameter = self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter;
+  tearoff _laterUnnamedParameterDependsOnNamedParameter = self::_extension#0|get#_laterUnnamedParameterDependsOnNamedParameter;
+  method _earlierUnnamedParameter = self::_extension#0|_earlierUnnamedParameter;
+  tearoff _earlierUnnamedParameter = self::_extension#0|get#_earlierUnnamedParameter;
+  method _laterNamedParameter = self::_extension#0|_laterNamedParameter;
+  tearoff _laterNamedParameter = self::_extension#0|get#_laterNamedParameter;
+  method _earlierNamedParameter = self::_extension#0|_earlierNamedParameter;
+  tearoff _earlierNamedParameter = self::_extension#0|get#_earlierNamedParameter;
+  method _earlierNamedParameterDependsOnUnnamedParameter = self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter;
+  tearoff _earlierNamedParameterDependsOnUnnamedParameter = self::_extension#0|get#_earlierNamedParameterDependsOnUnnamedParameter;
+  method _propagateToReturnType = self::_extension#0|_propagateToReturnType;
+  tearoff _propagateToReturnType = self::_extension#0|get#_propagateToReturnType;
+  method _closureAsParameterType = self::_extension#0|_closureAsParameterType;
+  tearoff _closureAsParameterType = self::_extension#0|get#_closureAsParameterType;
+  method _propagateToEarlierClosure = self::_extension#0|_propagateToEarlierClosure;
+  tearoff _propagateToEarlierClosure = self::_extension#0|get#_propagateToEarlierClosure;
+  method _propagateToLaterClosure = self::_extension#0|_propagateToLaterClosure;
+  tearoff _propagateToLaterClosure = self::_extension#0|get#_propagateToLaterClosure;
+  method _longDependencyChain = self::_extension#0|_longDependencyChain;
+  tearoff _longDependencyChain = self::_extension#0|get#_longDependencyChain;
+  method _dependencyCycle = self::_extension#0|_dependencyCycle;
+  tearoff _dependencyCycle = self::_extension#0|get#_dependencyCycle;
+  method _propagateFromContravariantReturnType = self::_extension#0|_propagateFromContravariantReturnType;
+  tearoff _propagateFromContravariantReturnType = self::_extension#0|get#_propagateFromContravariantReturnType;
+  method _propagateToContravariantParameterType = self::_extension#0|_propagateToContravariantParameterType;
+  tearoff _propagateToContravariantParameterType = self::_extension#0|get#_propagateToContravariantParameterType;
+  method _returnTypeRefersToMultipleTypeVars = self::_extension#0|_returnTypeRefersToMultipleTypeVars;
+  tearoff _returnTypeRefersToMultipleTypeVars = self::_extension#0|get#_returnTypeRefersToMultipleTypeVars;
+  method _unnecessaryDueToNoDependency = self::_extension#0|_unnecessaryDueToNoDependency;
+  tearoff _unnecessaryDueToNoDependency = self::_extension#0|get#_unnecessaryDueToNoDependency;
+  method _unnecessaryDueToExplicitParameterTypeNamed = self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed;
+  tearoff _unnecessaryDueToExplicitParameterTypeNamed = self::_extension#0|get#_unnecessaryDueToExplicitParameterTypeNamed;
+  method _parenthesized = self::_extension#0|_parenthesized;
+  tearoff _parenthesized = self::_extension#0|get#_parenthesized;
+  method _parenthesizedNamed = self::_extension#0|_parenthesizedNamed;
+  tearoff _parenthesizedNamed = self::_extension#0|get#_parenthesizedNamed;
+  method _parenthesizedTwice = self::_extension#0|_parenthesizedTwice;
+  tearoff _parenthesizedTwice = self::_extension#0|get#_parenthesizedTwice;
+  method _parenthesizedTwiceNamed = self::_extension#0|_parenthesizedTwiceNamed;
+  tearoff _parenthesizedTwiceNamed = self::_extension#0|get#_parenthesizedTwiceNamed;
+}
+static method testLaterUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterUnnamedParameter<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testLaterUnnamedParameterDependsOnNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter<core::int>(i, (core::int x) → void {
+    x;
+  }, a: 0);
+}
+static method testEarlierUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierUnnamedParameter<core::int>(i, (core::int x) → void {
+    x;
+  }, 0);
+}
+static method testLaterNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_laterNamedParameter<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method testEarlierNamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierNamedParameter<core::int>(i, a: (core::int x) → void {
+    x;
+  }, b: 0);
+}
+static method testEarlierNamedParameterDependsOnUnnamedParameter(core::int i) → dynamic {
+  self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter<core::int>(i, 0, a: (core::int x) → void {
+    x;
+  });
+}
+static method testPropagateToReturnType(core::int i) → dynamic {
+  self::_extension#0|_propagateToReturnType<core::int, core::List<core::int>>(i, 0, (core::int x) → core::List<core::int> => core::_GrowableList::_literal1<core::int>(x));
+}
+static method testClosureAsParameterType(core::int i) → dynamic {
+  self::_extension#0|_closureAsParameterType<() → core::int, core::List<core::int>>(i, () → core::int => 0, (() → core::int h) → core::List<core::int> => core::_GrowableList::_literal1<core::int>(h(){() → core::int}));
+}
+static method testPropagateToEarlierClosure(core::int i) → dynamic {
+  self::_extension#0|_propagateToEarlierClosure<core::int, core::List<core::int>>(i, (core::int x) → core::List<core::int> => core::_GrowableList::_literal1<core::int>(x), () → core::int => 0);
+}
+static method testPropagateToLaterClosure(core::int i) → dynamic {
+  self::_extension#0|_propagateToLaterClosure<core::int, core::List<core::int>>(i, () → core::int => 0, (core::int x) → core::List<core::int> => core::_GrowableList::_literal1<core::int>(x));
+}
+static method testLongDependencyChain(core::int i) → dynamic {
+  self::_extension#0|_longDependencyChain<core::List<core::int>, core::int, core::Set<core::int>>(i, () → core::List<core::int> => core::_GrowableList::_literal1<core::int>(0), (core::List<core::int> x) → core::int => x.{core::Iterable::single}{core::int}, (core::int y) → core::Set<core::int> => block {
+    final core::Set<core::int> #t1 = new col::_CompactLinkedHashSet::•<core::int>();
+    #t1.{core::Set::add}{Invariant}(y){(core::int) → core::bool};
+  } =>#t1);
+}
+static method testDependencyCycle(core::int i) → dynamic {
+  self::_extension#0|_dependencyCycle<core::List<core::Object?>, core::Set<core::Object?>>(i, (core::Object? x) → core::List<core::Object?> => core::_GrowableList::_literal1<core::Object?>(x), (core::Object? y) → core::Set<core::Object?> => block {
+    final core::Set<core::Object?> #t2 = new col::_CompactLinkedHashSet::•<core::Object?>();
+    #t2.{core::Set::add}{Invariant}(y){(core::Object?) → core::bool};
+  } =>#t2);
+}
+static method testPropagateFromContravariantReturnType(core::int i) → dynamic {
+  self::_extension#0|_propagateFromContravariantReturnType<core::int, core::List<core::int>>(i, () → (core::int) → void => (core::int i) → void {}, (core::int x) → core::List<core::int> => core::_GrowableList::_literal1<core::int>(x));
+}
+static method testPropagateToContravariantParameterType(core::int i) → dynamic {
+  self::_extension#0|_propagateToContravariantParameterType<core::int, core::List<(core::int) → void>>(i, () → core::int => 0, ((core::int) → void x) → core::List<(core::int) → void> => core::_GrowableList::_literal1<(core::int) → void>(x));
+}
+static method testReturnTypeRefersToMultipleTypeVars(core::int i) → dynamic {
+  self::_extension#0|_returnTypeRefersToMultipleTypeVars<core::int, core::String>(i, () → core::Map<core::int, core::String> => <core::int, core::String>{0: ""}, (core::int k) → void {
+    k;
+  }, (core::String v) → void {
+    v;
+  });
+}
+static method testUnnecessaryDueToNoDependency(core::int i) → dynamic {
+  self::_extension#0|_unnecessaryDueToNoDependency<core::int?>(i, () → core::int => 0, null);
+}
+static method testUnnecessaryDueToExplicitParameterTypeNamed(core::int i) → dynamic {
+  core::int? a = self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed<core::int?>(i, null, ({core::int? x = #C1, required core::int y = #C1}) → core::int => (let final core::int? #t3 = x in #t3 == null ?{core::int} 0 : #t3{core::int}).{core::num::+}(y){(core::num) → core::int});
+  a;
+}
+static method testParenthesized(core::int i) → dynamic {
+  self::_extension#0|_parenthesized<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedNamed(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedNamed<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedTwice(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedTwice<core::int>(i, 0, (core::int x) → void {
+    x;
+  });
+}
+static method testParenthesizedTwiceNamed(core::int i) → dynamic {
+  self::_extension#0|_parenthesizedTwiceNamed<core::int>(i, a: 0, b: (core::int x) → void {
+    x;
+  });
+}
+static method _extension#0|_laterUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_laterUnnamedParameter::T% x, (self::_extension#0|_laterUnnamedParameter::T%) → void y) → self::_extension#0|_laterUnnamedParameter::T%
+  return throw "";
+static method _extension#0|get#_laterUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → T%
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → T% => self::_extension#0|_laterUnnamedParameter<T%>(#this, x, y);
+static method _extension#0|_laterUnnamedParameterDependsOnNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter::T%) → void x, {required self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter::T% a = #C1}) → void
+  return throw "";
+static method _extension#0|get#_laterUnnamedParameterDependsOnNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>((T%) → void, {a: T%}) → void
+  return <T extends core::Object? = dynamic>((T%) → void x, {T% a = #C1}) → void => self::_extension#0|_laterUnnamedParameterDependsOnNamedParameter<T%>(#this, x, a: a);
+static method _extension#0|_earlierUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_earlierUnnamedParameter::T%) → void x, self::_extension#0|_earlierUnnamedParameter::T% y) → void
+  return throw "";
+static method _extension#0|get#_earlierUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>((T%) → void, T%) → void
+  return <T extends core::Object? = dynamic>((T%) → void x, T% y) → void => self::_extension#0|_earlierUnnamedParameter<T%>(#this, x, y);
+static method _extension#0|_laterNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_laterNamedParameter::T% a = #C1, required (self::_extension#0|_laterNamedParameter::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_laterNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_laterNamedParameter<T%>(#this, a: a, b: b);
+static method _extension#0|_earlierNamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, {required (self::_extension#0|_earlierNamedParameter::T%) → void a = #C1, required self::_extension#0|_earlierNamedParameter::T% b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_earlierNamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: (T%) → void, b: T%}) → void
+  return <T extends core::Object? = dynamic>({(T%) → void a = #C1, T% b = #C1}) → void => self::_extension#0|_earlierNamedParameter<T%>(#this, a: a, b: b);
+static method _extension#0|_earlierNamedParameterDependsOnUnnamedParameter<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter::T% b, {required (self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter::T%) → void a = #C1}) → void
+  return throw "";
+static method _extension#0|get#_earlierNamedParameterDependsOnUnnamedParameter(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, {a: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>(T% b, {(T%) → void a = #C1}) → void => self::_extension#0|_earlierNamedParameterDependsOnUnnamedParameter<T%>(#this, b, a: a);
+static method _extension#0|_propagateToReturnType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_propagateToReturnType::T% x, (self::_extension#0|_propagateToReturnType::T%) → self::_extension#0|_propagateToReturnType::U% y) → self::_extension#0|_propagateToReturnType::U%
+  return throw "";
+static method _extension#0|get#_propagateToReturnType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T% x, (T%) → U% y) → U% => self::_extension#0|_propagateToReturnType<T%, U%>(#this, x, y);
+static method _extension#0|_closureAsParameterType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_closureAsParameterType::T% x, (self::_extension#0|_closureAsParameterType::T%) → self::_extension#0|_closureAsParameterType::U% y) → self::_extension#0|_closureAsParameterType::U%
+  return throw "";
+static method _extension#0|get#_closureAsParameterType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(T% x, (T%) → U% y) → U% => self::_extension#0|_closureAsParameterType<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToEarlierClosure<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_propagateToEarlierClosure::T%) → self::_extension#0|_propagateToEarlierClosure::U% x, () → self::_extension#0|_propagateToEarlierClosure::T% y) → self::_extension#0|_propagateToEarlierClosure::U%
+  return throw "";
+static method _extension#0|get#_propagateToEarlierClosure(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((T%) → U%, () → T%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((T%) → U% x, () → T% y) → U% => self::_extension#0|_propagateToEarlierClosure<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToLaterClosure<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_propagateToLaterClosure::T% x, (self::_extension#0|_propagateToLaterClosure::T%) → self::_extension#0|_propagateToLaterClosure::U% y) → self::_extension#0|_propagateToLaterClosure::U%
+  return throw "";
+static method _extension#0|get#_propagateToLaterClosure(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T%, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T% x, (T%) → U% y) → U% => self::_extension#0|_propagateToLaterClosure<T%, U%>(#this, x, y);
+static method _extension#0|get#_longDependencyChain(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(() → T%, (T%) → U%, (U%) → V%) → V%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(() → T% x, (T%) → U% y, (U%) → V% z) → V% => self::_extension#0|_longDependencyChain<T%, U%, V%>(#this, x, y, z);
+static method _extension#0|_longDependencyChain<T extends core::Object? = dynamic, U extends core::Object? = dynamic, V extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_longDependencyChain::T% x, (self::_extension#0|_longDependencyChain::T%) → self::_extension#0|_longDependencyChain::U% y, (self::_extension#0|_longDependencyChain::U%) → self::_extension#0|_longDependencyChain::V% z) → self::_extension#0|_longDependencyChain::V%
+  return throw "";
+static method _extension#0|_dependencyCycle<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, (self::_extension#0|_dependencyCycle::U%) → self::_extension#0|_dependencyCycle::T% x, (self::_extension#0|_dependencyCycle::T%) → self::_extension#0|_dependencyCycle::U% y) → core::Map<self::_extension#0|_dependencyCycle::T%, self::_extension#0|_dependencyCycle::U%>
+  return throw "";
+static method _extension#0|get#_dependencyCycle(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((U%) → T%, (T%) → U%) → core::Map<T%, U%>
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>((U%) → T% x, (T%) → U% y) → core::Map<T%, U%> => self::_extension#0|_dependencyCycle<T%, U%>(#this, x, y);
+static method _extension#0|_propagateFromContravariantReturnType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → (self::_extension#0|_propagateFromContravariantReturnType::T%) → void x, (self::_extension#0|_propagateFromContravariantReturnType::T%) → self::_extension#0|_propagateFromContravariantReturnType::U% y) → self::_extension#0|_propagateFromContravariantReturnType::U%
+  return throw "";
+static method _extension#0|get#_propagateFromContravariantReturnType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → (T%) → void, (T%) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → (T%) → void x, (T%) → U% y) → U% => self::_extension#0|_propagateFromContravariantReturnType<T%, U%>(#this, x, y);
+static method _extension#0|_propagateToContravariantParameterType<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_propagateToContravariantParameterType::T% x, ((self::_extension#0|_propagateToContravariantParameterType::T%) → void) → self::_extension#0|_propagateToContravariantParameterType::U% y) → self::_extension#0|_propagateToContravariantParameterType::U%
+  return throw "";
+static method _extension#0|get#_propagateToContravariantParameterType(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T%, ((T%) → void) → U%) → U%
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → T% x, ((T%) → void) → U% y) → U% => self::_extension#0|_propagateToContravariantParameterType<T%, U%>(#this, x, y);
+static method _extension#0|_returnTypeRefersToMultipleTypeVars<T extends core::Object? = dynamic, U extends core::Object? = dynamic>(lowered final core::int #this, () → core::Map<self::_extension#0|_returnTypeRefersToMultipleTypeVars::T%, self::_extension#0|_returnTypeRefersToMultipleTypeVars::U%> x, (self::_extension#0|_returnTypeRefersToMultipleTypeVars::T%) → void y, (self::_extension#0|_returnTypeRefersToMultipleTypeVars::U%) → void z) → void
+  return throw "";
+static method _extension#0|get#_returnTypeRefersToMultipleTypeVars(lowered final core::int #this) → <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → core::Map<T%, U%>, (T%) → void, (U%) → void) → void
+  return <T extends core::Object? = dynamic, U extends core::Object? = dynamic>(() → core::Map<T%, U%> x, (T%) → void y, (U%) → void z) → void => self::_extension#0|_returnTypeRefersToMultipleTypeVars<T%, U%>(#this, x, y, z);
+static method _extension#0|_unnecessaryDueToNoDependency<T extends core::Object? = dynamic>(lowered final core::int #this, () → self::_extension#0|_unnecessaryDueToNoDependency::T% x, self::_extension#0|_unnecessaryDueToNoDependency::T% y) → self::_extension#0|_unnecessaryDueToNoDependency::T%
+  return throw "";
+static method _extension#0|get#_unnecessaryDueToNoDependency(lowered final core::int #this) → <T extends core::Object? = dynamic>(() → T%, T%) → T%
+  return <T extends core::Object? = dynamic>(() → T% x, T% y) → T% => self::_extension#0|_unnecessaryDueToNoDependency<T%>(#this, x, y);
+static method _extension#0|_unnecessaryDueToExplicitParameterTypeNamed<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T% x, ({required x: self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T%, required y: core::int}) → self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T% y) → self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed::T%
+  return throw "";
+static method _extension#0|get#_unnecessaryDueToExplicitParameterTypeNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, ({required x: T%, required y: core::int}) → T%) → T%
+  return <T extends core::Object? = dynamic>(T% x, ({required x: T%, required y: core::int}) → T% y) → T% => self::_extension#0|_unnecessaryDueToExplicitParameterTypeNamed<T%>(#this, x, y);
+static method _extension#0|_parenthesized<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_parenthesized::T% x, (self::_extension#0|_parenthesized::T%) → void y) → void
+  return throw "";
+static method _extension#0|get#_parenthesized(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → void
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → void => self::_extension#0|_parenthesized<T%>(#this, x, y);
+static method _extension#0|_parenthesizedNamed<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_parenthesizedNamed::T% a = #C1, required (self::_extension#0|_parenthesizedNamed::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_parenthesizedNamed<T%>(#this, a: a, b: b);
+static method _extension#0|_parenthesizedTwice<T extends core::Object? = dynamic>(lowered final core::int #this, self::_extension#0|_parenthesizedTwice::T% x, (self::_extension#0|_parenthesizedTwice::T%) → void y) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedTwice(lowered final core::int #this) → <T extends core::Object? = dynamic>(T%, (T%) → void) → void
+  return <T extends core::Object? = dynamic>(T% x, (T%) → void y) → void => self::_extension#0|_parenthesizedTwice<T%>(#this, x, y);
+static method _extension#0|_parenthesizedTwiceNamed<T extends core::Object? = dynamic>(lowered final core::int #this, {required self::_extension#0|_parenthesizedTwiceNamed::T% a = #C1, required (self::_extension#0|_parenthesizedTwiceNamed::T%) → void b = #C1}) → void
+  return throw "";
+static method _extension#0|get#_parenthesizedTwiceNamed(lowered final core::int #this) → <T extends core::Object? = dynamic>({a: T%, b: (T%) → void}) → void
+  return <T extends core::Object? = dynamic>({T% a = #C1, (T%) → void b = #C1}) → void => self::_extension#0|_parenthesizedTwiceNamed<T%>(#this, a: a, b: b);
+static method main() → dynamic {}
+
+constants  {
+  #C1 = null
+}

tests/language/inference_update_1/horizontal_inference_extension_method_test.dart

@@ -0,0 +1,214 @@
+// Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Tests that horizontal inference works properly when the invocation is an
+// extension member.  This is an important corner case because the front end
+// adds an implicit `this` argument to extension members as part of the lowering
+// process.  We need to make sure that the dependency tracking logic properly
+// accounts for this extra argument.
+
+// SharedOptions=--enable-experiment=inference-update-1
+
+import '../static_type_helper.dart';
+
+testLaterUnnamedParameter(int i) {
+  i._laterUnnamedParameter(0, (x) {
+    x.expectStaticType<Exactly<int>>();
+  });
+}
+
+/// This special case verifies that the implementations correctly associate the
+/// zeroth positional parameter with the corresponding argument (even if that
+/// argument isn't in the zeroth position at the call site).
+testLaterUnnamedParameterDependsOnNamedParameter(int i) {
+  i._laterUnnamedParameterDependsOnNamedParameter(a: 0, (x) {
+    x.expectStaticType<Exactly<int>>();
+  });
+}
+
+testEarlierUnnamedParameter(int i) {
+  i._earlierUnnamedParameter((x) {
+    x.expectStaticType<Exactly<int>>();
+  }, 0);
+}
+
+testLaterNamedParameter(int i) {
+  i._laterNamedParameter(
+      a: 0,
+      b: (x) {
+        x.expectStaticType<Exactly<int>>();
+      });
+}
+
+testEarlierNamedParameter(int i) {
+  i._earlierNamedParameter(
+      a: (x) {
+        x.expectStaticType<Exactly<int>>();
+      },
+      b: 0);
+}
+
+/// This special case verifies that the implementations correctly associate the
+/// zeroth positional parameter with the corresponding argument (even if that
+/// argument isn't in the zeroth position at the call site).
+testEarlierNamedParameterDependsOnUnnamedParameter(int i) {
+  i._earlierNamedParameterDependsOnUnnamedParameter(a: (x) {
+    x.expectStaticType<Exactly<int>>();
+  }, 0);
+}
+
+testPropagateToReturnType(int i) {
+  i
+      ._propagateToReturnType(0, (x) => [x])
+      .expectStaticType<Exactly<List<int>>>();
+}
+
+// The test cases below exercise situations where there are multiple closures in
+// the invocation, and they need to be inferred in the right order.
+
+testClosureAsParameterType(int i) {
+  i
+      ._closureAsParameterType(
+          () => 0, (h) => [h()]..expectStaticType<Exactly<List<int>>>())
+      .expectStaticType<Exactly<List<int>>>();
+}
+
+testPropagateToEarlierClosure(int i) {
+  i
+      ._propagateToEarlierClosure(
+          (x) => [x]..expectStaticType<Exactly<List<int>>>(), () => 0)
+      .expectStaticType<Exactly<List<int>>>();
+}
+
+testPropagateToLaterClosure(int i) {
+  i
+      ._propagateToLaterClosure(
+          () => 0, (x) => [x]..expectStaticType<Exactly<List<int>>>())
+      .expectStaticType<Exactly<List<int>>>();
+}
+
+testLongDependencyChain(int i) {
+  i
+      ._longDependencyChain(
+          () => [0],
+          (x) => x.single..expectStaticType<Exactly<int>>(),
+          (y) => {y}..expectStaticType<Exactly<Set<int>>>())
+      .expectStaticType<Exactly<Set<int>>>();
+}
+
+testDependencyCycle(int i) {
+  i
+      ._dependencyCycle((x) => [x]..expectStaticType<Exactly<List<Object?>>>(),
+          (y) => {y}..expectStaticType<Exactly<Set<Object?>>>())
+      .expectStaticType<Exactly<Map<List<Object?>, Set<Object?>>>>();
+}
+
+testPropagateFromContravariantReturnType(int i) {
+  i
+      ._propagateFromContravariantReturnType(
+          () => (int i) {}, (x) => [x]..expectStaticType<Exactly<List<int>>>())
+      .expectStaticType<Exactly<List<int>>>();
+}
+
+testPropagateToContravariantParameterType(int i) {
+  i
+      ._propagateToContravariantParameterType(() => 0,
+          (x) => [x]..expectStaticType<Exactly<List<void Function(int)>>>())
+      .expectStaticType<Exactly<List<void Function(int)>>>();
+}
+
+testReturnTypeRefersToMultipleTypeVars(int i) {
+  i._returnTypeRefersToMultipleTypeVars(() => {0: ''}, (k) {
+    k.expectStaticType<Exactly<int>>();
+  }, (v) {
+    v.expectStaticType<Exactly<String>>();
+  });
+}
+
+testUnnecessaryDueToNoDependency(int i) {
+  i
+      ._unnecessaryDueToNoDependency(() => 0, null)
+      .expectStaticType<Exactly<int?>>();
+}
+
+testUnnecessaryDueToExplicitParameterTypeNamed(int i) {
+  var a = i._unnecessaryDueToExplicitParameterTypeNamed(
+      null, ({int? x, required y}) => (x ?? 0) + y);
+  a.expectStaticType<Exactly<int?>>();
+}
+
+testParenthesized(int i) {
+  i._parenthesized(0, ((x) {
+    x.expectStaticType<Exactly<int>>();
+  }));
+}
+
+testParenthesizedNamed(int i) {
+  i._parenthesizedNamed(
+      a: 0,
+      b: ((x) {
+        x.expectStaticType<Exactly<int>>();
+      }));
+}
+
+testParenthesizedTwice(int i) {
+  i._parenthesizedTwice(0, (((x) {
+    x.expectStaticType<Exactly<int>>();
+  })));
+}
+
+testParenthesizedTwiceNamed(int i) {
+  i._parenthesizedTwiceNamed(
+      a: 0,
+      b: (((x) {
+        x.expectStaticType<Exactly<int>>();
+      })));
+}
+
+extension on int {
+  T _laterUnnamedParameter<T>(T x, void Function(T) y) => throw '';
+  void _laterUnnamedParameterDependsOnNamedParameter<T>(void Function(T) x,
+          {required T a}) =>
+      throw '';
+  void _earlierUnnamedParameter<T>(void Function(T) x, T y) => throw '';
+  void _laterNamedParameter<T>({required T a, required void Function(T) b}) =>
+      throw '';
+  void _earlierNamedParameter<T>({required void Function(T) a, required T b}) =>
+      throw '';
+  void _earlierNamedParameterDependsOnUnnamedParameter<T>(T b,
+          {required void Function(T) a}) =>
+      throw '';
+  U _propagateToReturnType<T, U>(T x, U Function(T) y) => throw '';
+  U _closureAsParameterType<T, U>(T x, U Function(T) y) => throw '';
+  U _propagateToEarlierClosure<T, U>(U Function(T) x, T Function() y) =>
+      throw '';
+  U _propagateToLaterClosure<T, U>(T Function() x, U Function(T) y) => throw '';
+  V _longDependencyChain<T, U, V>(
+          T Function() x, U Function(T) y, V Function(U) z) =>
+      throw '';
+  Map<T, U> _dependencyCycle<T, U>(T Function(U) x, U Function(T) y) =>
+      throw '';
+  U _propagateFromContravariantReturnType<T, U>(
+          void Function(T) Function() x, U Function(T) y) =>
+      throw '';
+  U _propagateToContravariantParameterType<T, U>(
+          T Function() x, U Function(void Function(T)) y) =>
+      throw '';
+  void _returnTypeRefersToMultipleTypeVars<T, U>(
+          Map<T, U> Function() x, void Function(T) y, void Function(U) z) =>
+      throw '';
+  T _unnecessaryDueToNoDependency<T>(T Function() x, T y) => throw '';
+  T _unnecessaryDueToExplicitParameterTypeNamed<T>(
+          T x, T Function({required T x, required int y}) y) =>
+      throw '';
+  void _parenthesized<T>(T x, void Function(T) y) => throw '';
+  void _parenthesizedNamed<T>({required T a, required void Function(T) b}) =>
+      throw '';
+  void _parenthesizedTwice<T>(T x, void Function(T) y) => throw '';
+  void _parenthesizedTwiceNamed<T>(
+          {required T a, required void Function(T) b}) =>
+      throw '';
+}
+
+main() {}