Add a language test to check expressions for which implicit call tearoff should occur.

Currently, all the language tests that exercise implicit call tearoff
do so using expressions that are either instance creation expressions
(e.g. `new C()`, where `C` is a class containing a `.call` method) or
simple identifiers.

This test exercises all of the syntactic constructs which are capable
of undergoing implicit call tearoff.

This will help ensure that some upcoming analyzer changes don't break
implicit call tearoff support.

Change-Id: I3e6471a3ba22fb3e3be38f2721db549da631668a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/232920
Reviewed-by: Lasse Nielsen <lrn@google.com>
Reviewed-by: Erik Ernst <eernst@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>

tests/language/call/implicit_tearoff_test.dart

@@ -0,0 +1,177 @@
+// 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.
+
+// This test exercises all the grammar constructs for which implicit tear-off of
+// `call` methods should occur.
+
+// NOTICE: This test checks the currently implemented behavior, even though the
+// implemented behavior does not match the language specification.  Until an
+// official decision has been made about whether to change the implementation to
+// match the specification, or vice versa, this regression test is intended to
+// protect against inadvertent implementation changes.
+
+import '../static_type_helper.dart';
+
+class B {}
+
+class C extends B {
+  void call() {}
+  void m() {}
+  void testThisExpression() {
+    context<void Function()>(this);
+  }
+}
+
+class D {
+  C operator +(other) => C();
+  C operator -() => C();
+  C instanceMethod() => C();
+  static C staticMethod() => C();
+  C get instanceGetter => C();
+}
+
+C topLevelMethod() => C();
+
+// These are top level getters rather than local variables to avoid triggering
+// flow analysis.
+bool get bTrue => true;
+bool get bFalse => false;
+
+void testAsExpression() {
+  dynamic d = C();
+  context<void Function()>(d as C);
+}
+
+void testAssignmentExpression() {
+  B b = B(); // ignore: unused_local_variable
+  context<void Function()>(b = C());
+}
+
+Future<void> testAwaitExpression() async {
+  Future<C> fc = Future.value(C());
+  context<void Function()>(await fc);
+}
+
+void testBinaryExpression() {
+  D d = D();
+  context<void Function()>(d + d);
+}
+
+void testCascadeExpression() {
+  // Note: we don't apply implicit `.call` tear-offs to the *target* of a
+  // cascade, but we do apply them to the cascade expression as a whole, so
+  // `c..m()` is equivalent to `(c..m()).call`.
+  C c = C();
+  context<void Function()>(c..m());
+}
+
+void testConditionalExpression() {
+  // Note: we know from `implicit_tearoff_exceptions_test.dart` that the two
+  // branches of the conditional expression are *not* subject to implicit
+  // `.call` tearoff, so the `.call` tearoff in this case is applied to the
+  // whole conditional expression.  In other words, `b ? c : c` desugars to
+  // `(b ? c : c).call` rather than `(b ? c.call : c.call)`.
+  C c = C();
+  context<void Function()>(bFalse ? c : c);
+  context<void Function()>(bTrue ? c : c);
+}
+
+void testFunctionExpressionInvocation() {
+  C c = C();
+  context<void Function()>((() => c)());
+}
+
+void testFunctionInvocationLocal() {
+  C localFunction() => C();
+  context<void Function()>(localFunction());
+}
+
+void testFunctionInvocationStatic() {
+  context<void Function()>(D.staticMethod());
+}
+
+void testFunctionInvocationTopLevel() {
+  context<void Function()>(topLevelMethod());
+}
+
+void testIfNullExpression() {
+  C? c1 = bTrue ? C() : null;
+  C c2 = C();
+  context<void Function()>(c1 ?? c2);
+  c1 = null;
+  context<void Function()>(c1 ?? c2);
+}
+
+void testIndexExpression() {
+  List<C> l = [C()];
+  context<void Function()>(l[0]);
+}
+
+void testInstanceCreationExpressionExplicit() {
+  context<void Function()>(new C());
+}
+
+void testInstanceCreationExpressionImplicit() {
+  context<void Function()>(C());
+}
+
+void testInstanceGetGeneral() {
+  D Function() dFunction = () => D();
+  context<void Function()>(dFunction().instanceGetter);
+}
+
+void testInstanceGetViaPrefixedIdentifier() {
+  D d = D();
+  context<void Function()>(d.instanceGetter);
+}
+
+void testMethodInvocation() {
+  context<void Function()>(D().instanceMethod());
+}
+
+void testNullCheckExpression() {
+  C? c = bTrue ? C() : null;
+  context<void Function()>(c!);
+}
+
+void testParenthesizedExpression() {
+  C c = C();
+  context<void Function()>((c));
+}
+
+void testUnaryMinusExpression() {
+  D d = D();
+  context<void Function()>(-d);
+}
+
+extension on C {
+  void testThisExpressionExtension() {
+    context<void Function()>(this);
+  }
+}
+
+main() async {
+  testAsExpression();
+  testAssignmentExpression();
+  await testAwaitExpression();
+  testBinaryExpression();
+  testCascadeExpression();
+  testConditionalExpression();
+  testFunctionExpressionInvocation();
+  testFunctionInvocationLocal();
+  testFunctionInvocationStatic();
+  testFunctionInvocationTopLevel();
+  testIfNullExpression();
+  testIndexExpression();
+  testInstanceCreationExpressionExplicit();
+  testInstanceCreationExpressionImplicit();
+  testInstanceGetGeneral();
+  testInstanceGetViaPrefixedIdentifier();
+  testMethodInvocation();
+  testNullCheckExpression();
+  testParenthesizedExpression();
+  testUnaryMinusExpression();
+  C().testThisExpression();
+  C().testThisExpressionExtension();
+}

tests/language_2/call/implicit_tearoff_test.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.
+
+// This test exercises all the grammar constructs for which implicit tear-off of
+// `call` methods should occur.
+
+// NOTICE: This test checks the currently implemented behavior, even though the
+// implemented behavior does not match the language specification.  Until an
+// official decision has been made about whether to change the implementation to
+// match the specification, or vice versa, this regression test is intended to
+// protect against inadvertent implementation changes.
+
+// @dart = 2.9
+
+import '../static_type_helper.dart';
+
+class B {}
+
+class C extends B {
+  void call() {}
+  void m() {}
+  void testThisExpression() {
+    context<void Function()>(this);
+  }
+}
+
+class D {
+  C operator +(other) => C();
+  C operator -() => C();
+  C instanceMethod() => C();
+  static C staticMethod() => C();
+  C get instanceGetter => C();
+}
+
+C topLevelMethod() => C();
+
+// These are top level getters rather than local variables to avoid triggering
+// flow analysis.
+bool get bTrue => true;
+bool get bFalse => false;
+
+void testAsExpression() {
+  dynamic d = C();
+  context<void Function()>(d as C);
+}
+
+void testAssignmentExpression() {
+  B b = B(); // ignore: unused_local_variable
+  context<void Function()>(b = C());
+}
+
+Future<void> testAwaitExpression() async {
+  Future<C> fc = Future.value(C());
+  context<void Function()>(await fc);
+}
+
+void testBinaryExpression() {
+  D d = D();
+  context<void Function()>(d + d);
+}
+
+void testCascadeExpression() {
+  // Note: we don't apply implicit `.call` tear-offs to the *target* of a
+  // cascade, but we do apply them to the cascade expression as a whole, so
+  // `c..m()` is equivalent to `(c..m()).call`.
+  C c = C();
+  context<void Function()>(c..m());
+}
+
+void testConditionalExpression() {
+  // Note: we know from `implicit_tearoff_exceptions_test.dart` that the two
+  // branches of the conditional expression are *not* subject to implicit
+  // `.call` tearoff, so the `.call` tearoff in this case is applied to the
+  // whole conditional expression.  In other words, `b ? c : c` desugars to
+  // `(b ? c : c).call` rather than `(b ? c.call : c.call)`.
+  C c = C();
+  context<void Function()>(bFalse ? c : c);
+  context<void Function()>(bTrue ? c : c);
+}
+
+void testFunctionExpressionInvocation() {
+  C c = C();
+  context<void Function()>((() => c)());
+}
+
+void testFunctionInvocationLocal() {
+  C localFunction() => C();
+  context<void Function()>(localFunction());
+}
+
+void testFunctionInvocationStatic() {
+  context<void Function()>(D.staticMethod());
+}
+
+void testFunctionInvocationTopLevel() {
+  context<void Function()>(topLevelMethod());
+}
+
+void testIfNullExpression() {
+  C c1 = bTrue ? C() : null;
+  C c2 = C();
+  context<void Function()>(c1 ?? c2);
+  c1 = null;
+  context<void Function()>(c1 ?? c2);
+}
+
+void testIndexExpression() {
+  List<C> l = [C()];
+  context<void Function()>(l[0]);
+}
+
+void testInstanceCreationExpressionExplicit() {
+  context<void Function()>(new C());
+}
+
+void testInstanceCreationExpressionImplicit() {
+  context<void Function()>(C());
+}
+
+void testInstanceGetGeneral() {
+  D Function() dFunction = () => D();
+  context<void Function()>(dFunction().instanceGetter);
+}
+
+void testInstanceGetViaPrefixedIdentifier() {
+  D d = D();
+  context<void Function()>(d.instanceGetter);
+}
+
+void testMethodInvocation() {
+  context<void Function()>(D().instanceMethod());
+}
+
+void testParenthesizedExpression() {
+  C c = C();
+  context<void Function()>((c));
+}
+
+void testUnaryMinusExpression() {
+  D d = D();
+  context<void Function()>(-d);
+}
+
+extension on C {
+  void testThisExpressionExtension() {
+    context<void Function()>(this);
+  }
+}
+
+main() async {
+  testAsExpression();
+  testAssignmentExpression();
+  await testAwaitExpression();
+  testBinaryExpression();
+  testCascadeExpression();
+  testConditionalExpression();
+  testFunctionExpressionInvocation();
+  testFunctionInvocationLocal();
+  testFunctionInvocationStatic();
+  testFunctionInvocationTopLevel();
+  testIfNullExpression();
+  testIndexExpression();
+  testInstanceCreationExpressionExplicit();
+  testInstanceCreationExpressionImplicit();
+  testInstanceGetGeneral();
+  testInstanceGetViaPrefixedIdentifier();
+  testMethodInvocation();
+  testParenthesizedExpression();
+  testUnaryMinusExpression();
+  C().testThisExpression();
+  C().testThisExpressionExtension();
+}