[cfe] Infer loadLibrary return a non-nullable future

Closes #41122

Change-Id: I1ca82e27cc73900e19369d152cec4f7a7621777b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/140400
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>

pkg/front_end/lib/src/fasta/kernel/inference_visitor.dart

@@ -5684,7 +5684,7 @@ class InferenceVisitor
   ExpressionInferenceResult visitLoadLibrary(
       covariant LoadLibraryImpl node, DartType typeContext) {
     DartType inferredType = inferrer.typeSchemaEnvironment
-        .futureType(const DynamicType(), inferrer.library.nullable);
+        .futureType(const DynamicType(), inferrer.library.nonNullable);
     if (node.arguments != null) {
       FunctionType calleeType =
           new FunctionType([], inferredType, inferrer.library.nonNullable);
@@ -5699,7 +5699,7 @@ class InferenceVisitor
     DartType inferredType = new FunctionType(
         [],
         inferrer.typeSchemaEnvironment
-            .futureType(const DynamicType(), inferrer.library.nullable),
+            .futureType(const DynamicType(), inferrer.library.nonNullable),
         inferrer.library.nonNullable);
     Expression replacement = new StaticGet(node.target)
       ..fileOffset = node.fileOffset;

pkg/front_end/testcases/nnbd/load_library.dart

@@ -0,0 +1,12 @@
+// Copyright (c) 2020, 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.
+
+import "dart:math" deferred as math;
+
+main() {
+  var v1 = math.loadLibrary();
+  v1.then((_) {});
+  var v2 = math.loadLibrary;
+  v2().then((_) {});
+}

pkg/front_end/testcases/nnbd/load_library.dart.outline.expect

@@ -0,0 +1,7 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+
+import "dart:math" deferred as math;
+
+static method main() → dynamic
+  ;

pkg/front_end/testcases/nnbd/load_library.dart.strong.expect

@@ -0,0 +1,19 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:math" deferred as math;
+
+static method main() → dynamic {
+  asy::Future<dynamic> v1 = LoadLibrary(math);
+  v1.{asy::Future::then}<core::Null?>((dynamic _) → core::Null? {});
+  () → asy::Future<dynamic> v2 = #C1;
+  v2.call().{asy::Future::then}<core::Null?>((dynamic _) → core::Null? {});
+}
+static method _#loadLibrary_math() → asy::Future<dynamic>
+  return LoadLibrary(math);
+
+constants  {
+  #C1 = tearoff self::_#loadLibrary_math
+}

pkg/front_end/testcases/nnbd/load_library.dart.strong.transformed.expect

@@ -0,0 +1,19 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:math" deferred as math;
+
+static method main() → dynamic {
+  asy::Future<dynamic> v1 = LoadLibrary(math);
+  v1.{asy::Future::then}<core::Null?>((dynamic _) → core::Null? {});
+  () → asy::Future<dynamic> v2 = #C1;
+  v2.call().{asy::Future::then}<core::Null?>((dynamic _) → core::Null? {});
+}
+static method _#loadLibrary_math() → asy::Future<dynamic>
+  return LoadLibrary(math);
+
+constants  {
+  #C1 = tearoff self::_#loadLibrary_math
+}

pkg/front_end/testcases/nnbd/load_library.dart.weak.expect

@@ -0,0 +1,19 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:math" deferred as math;
+
+static method main() → dynamic {
+  asy::Future<dynamic> v1 = LoadLibrary(math);
+  v1.{asy::Future::then}<core::Null?>((dynamic _) → core::Null? {});
+  () → asy::Future<dynamic> v2 = #C1;
+  v2.call().{asy::Future::then}<core::Null?>((dynamic _) → core::Null? {});
+}
+static method _#loadLibrary_math() → asy::Future<dynamic>
+  return LoadLibrary(math);
+
+constants  {
+  #C1 = tearoff self::_#loadLibrary_math
+}

pkg/front_end/testcases/nnbd/load_library.dart.weak.transformed.expect

@@ -0,0 +1,19 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:async" as asy;
+import "dart:core" as core;
+
+import "dart:math" deferred as math;
+
+static method main() → dynamic {
+  asy::Future<dynamic> v1 = LoadLibrary(math);
+  v1.{asy::Future::then}<core::Null?>((dynamic _) → core::Null? {});
+  () → asy::Future<dynamic> v2 = #C1;
+  v2.call().{asy::Future::then}<core::Null?>((dynamic _) → core::Null? {});
+}
+static method _#loadLibrary_math() → asy::Future<dynamic>
+  return LoadLibrary(math);
+
+constants  {
+  #C1 = tearoff self::_#loadLibrary_math
+}

pkg/front_end/testcases/text_serialization.status

@@ -1301,6 +1301,7 @@ nnbd/later: TextSerializationFailure
 nnbd/lhs_of_if_null: TextSerializationFailure
 nnbd/list_constructor: TextSerializationFailure
 nnbd/literal_from_opt_in: TextSerializationFailure
+nnbd/load_library: TextSerializationFailure
 nnbd/member_inheritance_from_opt_in: TextSerializationFailure
 nnbd/member_inheritance_from_opt_out: TextSerializationFailure
 nnbd/messages_with_types_opt_in: TypeCheckError