fix #28526 and fix #28527 FutureOr<T> in await and subtype

pkg/analyzer/test/generated/strong_mode_test.dart

 // Copyright (c) 2016, 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.
 
 library analyzer.test.generated.strong_mode_test;
 
 import 'dart:async';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/standard_resolution_map.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source_io.dart';
+import 'package:front_end/src/base/errors.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../utils.dart';
 import 'resolver_test_case.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(StrongModeLocalInferenceTest);
     defineReflectiveTests(StrongModeStaticTypeAnalyzer2Test);
     defineReflectiveTests(StrongModeTypePropagationTest);
   });
 }
 
 /**
  * Strong mode static analyzer local type inference tests
  */
 @reflectiveTest
 class StrongModeLocalInferenceTest extends ResolverTestCase {
   TypeAssertions _assertions;
 
   Asserter<DartType> _isDynamic;
   Asserter<InterfaceType> _isFutureOfDynamic;
   Asserter<InterfaceType> _isFutureOfInt;
+  Asserter<InterfaceType> _isFutureOrOfInt;
   Asserter<DartType> _isInt;
   Asserter<DartType> _isNum;
   Asserter<DartType> _isObject;
   Asserter<DartType> _isString;
 
   AsserterBuilder2<Asserter<DartType>, Asserter<DartType>, DartType>
       _isFunction2Of;
   AsserterBuilder<List<Asserter<DartType>>, InterfaceType> _isFutureOf;
+  AsserterBuilder<List<Asserter<DartType>>, InterfaceType> _isFutureOrOf;
   AsserterBuilderBuilder<Asserter<DartType>, List<Asserter<DartType>>, DartType>
       _isInstantiationOf;
   AsserterBuilder<Asserter<DartType>, InterfaceType> _isListOf;
   AsserterBuilder2<Asserter<DartType>, Asserter<DartType>, InterfaceType>
       _isMapOf;
   AsserterBuilder<List<Asserter<DartType>>, InterfaceType> _isStreamOf;
   AsserterBuilder<DartType, DartType> _isType;
 
   AsserterBuilder<Element, DartType> _hasElement;
   AsserterBuilder<DartType, DartType> _hasElementOf;
 
   @override
   Future<TestAnalysisResult> computeAnalysisResult(Source source) async {
     TestAnalysisResult result = await super.computeAnalysisResult(source);
     if (_assertions == null) {
       _assertions = new TypeAssertions(typeProvider);
       _isType = _assertions.isType;
       _hasElement = _assertions.hasElement;
       _isInstantiationOf = _assertions.isInstantiationOf;
       _isInt = _assertions.isInt;
       _isNum = _assertions.isNum;
       _isObject = _assertions.isObject;
       _isString = _assertions.isString;
       _isDynamic = _assertions.isDynamic;
       _isListOf = _assertions.isListOf;
       _isMapOf = _assertions.isMapOf;
       _isFunction2Of = _assertions.isFunction2Of;
       _hasElementOf = _assertions.hasElementOf;
       _isFutureOf = _isInstantiationOf(_hasElementOf(typeProvider.futureType));
+      _isFutureOrOf =
+          _isInstantiationOf(_hasElementOf(typeProvider.futureOrType));
       _isFutureOfDynamic = _isFutureOf([_isDynamic]);
       _isFutureOfInt = _isFutureOf([_isInt]);
+      _isFutureOrOfInt = _isFutureOrOf([_isInt]);
       _isStreamOf = _isInstantiationOf(_hasElementOf(typeProvider.streamType));
     }
     return result;
   }
 
   fail_constrainedByBounds3() async {
     // Test that upwards inference with two type variables does
     // not propogate from the constrained variable to the unconstrained
     // variable if they are ordered right to left, and that if the result
     // is not a valid instantiation an error is issued
@@ skipping 38 matching lines @@
     VariableDeclaration decl = stmt.variables.variables[0];
     Expression call = decl.initializer;
     _isInt(call.staticType);
   }
 
   fail_futureOr_downwards7() async {
     // Test that downwards inference incorporates bounds correctly
     // when instantiating type variables.
     // TODO(leafp): I think this should pass once the inference changes
     // that jmesserly is adding are landed.
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     T mk<T extends int>(T x) => null;
     FutureOr<int> test() => mk(new Future.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOfInt(invoke.staticType);
     _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
   }
 
   fail_futureOr_downwards8() async {
     // Test that downwards inference incorporates bounds correctly
     // when instantiating type variables.
     // TODO(leafp): I think this should pass once the inference changes
     // that jmesserly is adding are landed.
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     T mk<T extends Future<Object>>(T x) => null;
     FutureOr<int> test() => mk(new Future.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOfInt(invoke.staticType);
     _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
   }
 
   fail_pinning_multipleConstraints1() async {
     // Test that downwards inference with two different downwards covariant
     // constraints on the same parameter correctly fails to infer when
     // the types do not share a common subtype
     String code = r'''
     class A<S, T> {
@@ skipping 780 matching lines @@
     expect(functionReturnValue(0).staticType, typeProvider.intType);
     expect(functionReturnValue(1).staticType, typeProvider.intType);
     expect(functionReturnValue(2).staticType, typeProvider.intType);
     expect(functionReturnValue(3).staticType, typeProvider.dynamicType);
     expect(functionReturnValue(4).staticType, typeProvider.stringType);
   }
 
   test_futureOr_downwards1() async {
     // Test that downwards inference interacts correctly with FutureOr
     // parameters.
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     Future<T> mk<T>(FutureOr<T> x) => null;
     Future<int> test() => mk(new Future<int>.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOfInt(invoke.staticType);
   }
 
   test_futureOr_downwards2() async {
     // Test that downwards inference interacts correctly with FutureOr
     // parameters when the downwards context is FutureOr
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     Future<T> mk<T>(FutureOr<T> x) => null;
     FutureOr<int> test() => mk(new Future<int>.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOfInt(invoke.staticType);
   }
 
   test_futureOr_downwards3() async {
     // Test that downwards inference correctly propogates into
     // arguments.
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     Future<T> mk<T>(FutureOr<T> x) => null;
     Future<int> test() => mk(new Future.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOfInt(invoke.staticType);
     _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
   }
 
   test_futureOr_downwards4() async {
     // Test that downwards inference interacts correctly with FutureOr
     // parameters when the downwards context is FutureOr
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     Future<T> mk<T>(FutureOr<T> x) => null;
     FutureOr<int> test() => mk(new Future.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOfInt(invoke.staticType);
     _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
   }
 
   test_futureOr_downwards5() async {
     // Test that downwards inference correctly pins the type when it
     // comes from a FutureOr
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     Future<T> mk<T>(FutureOr<T> x) => null;
     FutureOr<num> test() => mk(new Future.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOf([_isNum])(invoke.staticType);
     _isFutureOf([_isNum])(invoke.argumentList.arguments[0].staticType);
   }
 
   test_futureOr_downwards6() async {
     // Test that downwards inference doesn't decompose FutureOr
     // when instantiating type variables.
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     T mk<T>(T x) => null;
     FutureOr<int> test() => mk(new Future.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOfInt(invoke.staticType);
     _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
   }
 
   test_futureOr_downwards9() async {
     // Test that downwards inference decomposes correctly with
     // other composite types
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     List<T> mk<T>(T x) => null;
     FutureOr<List<int>> test() => mk(3);
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isListOf(_isInt)(invoke.staticType);
     _isInt(invoke.argumentList.arguments[0].staticType);
   }
 
   test_futureOr_methods1() async {
     // Test that FutureOr has the Object methods
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     dynamic test(FutureOr<int> x) => x.toString();
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isString(invoke.staticType);
   }
 
   test_futureOr_methods2() async {
     // Test that FutureOr does not have the constituent type methods
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(
+        r'''
     dynamic test(FutureOr<int> x) => x.abs();
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertErrors(source, [StaticTypeWarningCode.UNDEFINED_METHOD]);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''',
+        errors: [StaticTypeWarningCode.UNDEFINED_METHOD]);
     _isDynamic(invoke.staticType);
   }
 
   test_futureOr_methods3() async {
     // Test that FutureOr does not have the Future type methods
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(
+        r'''
     dynamic test(FutureOr<int> x) => x.then((x) => x);
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertErrors(source, [StaticTypeWarningCode.UNDEFINED_METHOD]);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''',
+        errors: [StaticTypeWarningCode.UNDEFINED_METHOD]);
     _isDynamic(invoke.staticType);
   }
 
   test_futureOr_methods4() async {
     // Test that FutureOr<dynamic> does not have all methods
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(
+        r'''
     dynamic test(FutureOr<dynamic> x) => x.abs();
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertErrors(source, [StaticTypeWarningCode.UNDEFINED_METHOD]);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''',
+        errors: [StaticTypeWarningCode.UNDEFINED_METHOD]);
     _isDynamic(invoke.staticType);
   }
 
   test_futureOr_upwards1() async {
     // Test that upwards inference correctly prefers to instantiate type
     // variables with the "smaller" solution when both are possible.
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(r'''
     Future<T> mk<T>(FutureOr<T> x) => null;
     dynamic test() => mk(new Future<int>.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertNoErrors(source);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''');
     _isFutureOfInt(invoke.staticType);
   }
 
   test_futureOr_upwards2() async {
     // Test that upwards inference fails when the solution doesn't
     // match the bound.
-    String code = r'''
-    import "dart:async";
+    MethodInvocation invoke = await _testFutureOr(
+        r'''
     Future<T> mk<T extends Future<Object>>(FutureOr<T> x) => null;
     dynamic test() => mk(new Future<int>.value(42));
-   ''';
-    Source source = addSource(code);
-    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
-    assertErrors(source, [StrongModeCode.COULD_NOT_INFER]);
-    verify([source]);
-    CompilationUnit unit = analysisResult.unit;
-    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
-    ExpressionFunctionBody body = test.functionExpression.body;
-    MethodInvocation invoke = body.expression;
+    ''',
+        errors: [StrongModeCode.COULD_NOT_INFER]);
     _isFutureOf([_isObject])(invoke.staticType);
   }
 
+  test_futureOr_assignFromValue() async {
+    // Test a T can be assigned to FutureOr<T>.
+    MethodInvocation invoke = await _testFutureOr(r'''
+    FutureOr<T> mk<T>(T x) => x;
+    test() => mk(42);
+    ''');
+    _isFutureOrOfInt(invoke.staticType);
+  }
+
+  test_futureOr_assignFromFuture() async {
+    // Test a Future<T> can be assigned to FutureOr<T>.
+    MethodInvocation invoke = await _testFutureOr(r'''
+    FutureOr<T> mk<T>(Future<T> x) => x;
+    test() => mk(new Future<int>.value(42));
+    ''');
+    _isFutureOrOfInt(invoke.staticType);
+  }
+
+  test_futureOr_await() async {
+    // Test a FutureOr<T> can be awaited.
+    MethodInvocation invoke = await _testFutureOr(r'''
+    Future<T> mk<T>(FutureOr<T> x) async => await x;
+    test() => mk(42);
+    ''');
+    _isFutureOfInt(invoke.staticType);
+  }
+
+  test_futureOr_asyncExpressionBody() async {
+    // A FutureOr<T> can be used as the expression body for an async function
+    MethodInvocation invoke = await _testFutureOr(r'''
+    Future<T> mk<T>(FutureOr<T> x) async => x;
+    test() => mk(42);
+    ''');
+    _isFutureOfInt(invoke.staticType);
+  }
+
+  test_futureOr_asyncReturn() async {
+    // A FutureOr<T> can be used as the return value for an async function
+    MethodInvocation invoke = await _testFutureOr(r'''
+    Future<T> mk<T>(FutureOr<T> x) async { return x; }
+    test() => mk(42);
+    ''');
+    _isFutureOfInt(invoke.staticType);
+  }
+
   test_inference_hints() async {
     Source source = addSource(r'''
       void main () {
         var x = 3;
         List<int> l0 = [];
      }
    ''');
     await computeAnalysisResult(source);
     assertNoErrors(source);
     verify([source]);
@@ skipping 842 matching lines @@
       Expression exp = stmt.expression;
       typeTest(exp.staticType);
     }
 
     check("f0", _isListOf(_isDynamic));
     check("f1", _isListOf(_isDynamic));
 
     check("f2", _isListOf(_isInt));
     check("f3", _isListOf((DartType type) => _isListOf(_isInt)(type)));
   }
+
+  /// Helper method for testing `FutureOr<T>`.
+  ///
+  /// Validates that [code] produces [errors]. It should define a function
+  /// "test", whose body is an expression that invokes a method. Returns that
+  /// invocation.
+  Future<MethodInvocation> _testFutureOr(String code,
+      {List<ErrorCode> errors}) async {
+    Source source = addSource("""
+    import "dart:async";
+    $code""");
+    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
+
+    if (errors == null) {
+      assertNoErrors(source);
+    } else {
+      assertErrors(source, errors);
+    }
+    verify([source]);
+    FunctionDeclaration test =
+        AstFinder.getTopLevelFunction(analysisResult.unit, "test");
+    ExpressionFunctionBody body = test.functionExpression.body;
+    return body.expression;
+  }
 }
 
 /**
  * Strong mode static analyzer end to end tests
  */
 @reflectiveTest
 class StrongModeStaticTypeAnalyzer2Test extends StaticTypeAnalyzer2TestShared {
   void expectStaticInvokeType(String search, String type) {
     var invocation = findIdentifier(search).parent as MethodInvocation;
     expect(invocation.staticInvokeType.toString(), type);
@@ skipping 1328 matching lines @@
   var v = x;
   v; // marker
 }
 int x = 3;
 ''';
     CompilationUnit unit = await resolveSource(code);
     assertPropagatedAssignedType(code, unit, typeProvider.intType, null);
     assertTypeOfMarkedExpression(code, unit, typeProvider.intType, null);
   }
 }