Infer Null for return type of functions with empty returns.

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';
@@ skipping 21 matching lines @@
 /**
  * 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> _isFutureOfNull;
   Asserter<InterfaceType> _isFutureOrOfInt;
   Asserter<DartType> _isInt;
+  Asserter<DartType> _isNull;
   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;
+      _isNull = _assertions.isNull;
       _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]);
+      _isFutureOfNull = _isFutureOf([_isNull]);
       _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
@@ skipping 1011 matching lines @@
   test_futureOr_methods4() async {
     // Test that FutureOr<dynamic> does not have all methods
     MethodInvocation invoke = await _testFutureOr(
         r'''
     dynamic test(FutureOr<dynamic> x) => x.abs();
     ''',
         errors: [StaticTypeWarningCode.UNDEFINED_METHOD]);
     _isDynamic(invoke.staticType);
   }
 
+  test_futureOr_no_return() async {
+    MethodInvocation invoke = await _testFutureOr(r'''
+    FutureOr<T> mk<T>(Future<T> x) => x;
+    Future<int> f;
+    test() => f.then((int x) {});
+    ''');
+    _isFunction2Of(_isInt, _isNull)(
+        invoke.argumentList.arguments[0].staticType);
+    _isFutureOfDynamic(invoke.staticType);
+  }
+
+  test_futureOr_no_return_value() async {
+    MethodInvocation invoke = await _testFutureOr(r'''
+    FutureOr<T> mk<T>(Future<T> x) => x;
+    Future<int> f;
+    test() => f.then((int x) {return;});
+    ''');
+    _isFunction2Of(_isInt, _isNull)(
+        invoke.argumentList.arguments[0].staticType);
+    _isFutureOfDynamic(invoke.staticType);
+  }
+
+  test_futureOr_return_null() async {
+    MethodInvocation invoke = await _testFutureOr(r'''
+    FutureOr<T> mk<T>(Future<T> x) => x;
+    Future<int> f;
+    test() => f.then((int x) {});
+    ''');
+    _isFunction2Of(_isInt, _isNull)(
+        invoke.argumentList.arguments[0].staticType);
+    _isFutureOfDynamic(invoke.staticType);
+  }
+
   test_futureOr_upwards1() async {
     // Test that upwards inference correctly prefers to instantiate type
     // variables with the "smaller" solution when both are possible.
     MethodInvocation invoke = await _testFutureOr(r'''
     Future<T> mk<T>(FutureOr<T> x) => null;
     dynamic test() => mk(new Future<int>.value(42));
     ''');
     _isFutureOfInt(invoke.staticType);
   }
 
   test_futureOr_upwards2() async {
     // Test that upwards inference fails when the solution doesn't
     // match the bound.
     MethodInvocation invoke = await _testFutureOr(
         r'''
     Future<T> mk<T extends Future<Object>>(FutureOr<T> x) => null;
     dynamic test() => mk(new Future<int>.value(42));
     ''',
         errors: [StrongModeCode.COULD_NOT_INFER]);
     _isFutureOf([_isObject])(invoke.staticType);
   }
 
+  test_futureOrNill_no_return_value() async {

[Brian Wilkerson, 2017/02/03 14:41:45]

"Nill" --> "Null"

[Leaf, 2017/02/06 18:27:15]

Done.

+    MethodInvocation invoke = await _testFutureOr(r'''
+    FutureOr<T> mk<T>(Future<T> x) => x;
+    Future<int> f;
+    test() => f.then<Null>((int x) {return;});
+    ''');
+    _isFunction2Of(_isInt, _isNull)(
+        invoke.argumentList.arguments[0].staticType);
+    _isFutureOfNull(invoke.staticType);
+  }
+
+  test_futureOrNull_no_return() async {
+    MethodInvocation invoke = await _testFutureOr(r'''
+    FutureOr<T> mk<T>(Future<T> x) => x;
+    Future<int> f;
+    test() => f.then<Null>((int x) {});
+    ''');
+    _isFunction2Of(_isInt, _isNull)(
+        invoke.argumentList.arguments[0].staticType);
+    _isFutureOfNull(invoke.staticType);
+  }
+
+  test_futureOrNull_return_null() async {
+    MethodInvocation invoke = await _testFutureOr(r'''
+    FutureOr<T> mk<T>(Future<T> x) => x;
+    Future<int> f;
+    test() => f.then<Null>((int x) {});
+    ''');
+    _isFunction2Of(_isInt, _isNull)(
+        invoke.argumentList.arguments[0].staticType);
+    _isFutureOfNull(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 2321 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);
   }
 }