[cfe] Update messages for invalid returns

Closes #42527

Change-Id: Ic240dd7a8822c85c550941923bf9ce3b5cfe0dba
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153348
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Erik Ernst <eernst@google.com>

pkg/front_end/lib/src/fasta/fasta_codes_cfe_generated.dart

@@ -2040,6 +2040,84 @@ Message _withArgumentsInvalidCastTopLevelFunction(
       arguments: {'type': _type, 'type2': _type2});
 }
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<
+    Message Function(
+        DartType _type,
+        DartType _type2,
+        bool
+            isNonNullableByDefault)> templateInvalidReturn = const Template<
+        Message Function(
+            DartType _type, DartType _type2, bool isNonNullableByDefault)>(
+    messageTemplate:
+        r"""A value of type '#type' can't be returned from a function with return type '#type2'.""",
+    withArguments: _withArgumentsInvalidReturn);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<
+        Message Function(
+            DartType _type, DartType _type2, bool isNonNullableByDefault)>
+    codeInvalidReturn = const Code<
+        Message Function(
+            DartType _type, DartType _type2, bool isNonNullableByDefault)>(
+  "InvalidReturn",
+  templateInvalidReturn,
+);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsInvalidReturn(
+    DartType _type, DartType _type2, bool isNonNullableByDefault) {
+  TypeLabeler labeler = new TypeLabeler(isNonNullableByDefault);
+  List<Object> typeParts = labeler.labelType(_type);
+  List<Object> type2Parts = labeler.labelType(_type2);
+  String type = typeParts.join();
+  String type2 = type2Parts.join();
+  return new Message(codeInvalidReturn,
+      message:
+          """A value of type '${type}' can't be returned from a function with return type '${type2}'.""" +
+              labeler.originMessages,
+      arguments: {'type': _type, 'type2': _type2});
+}
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<
+    Message Function(
+        DartType _type,
+        DartType _type2,
+        bool
+            isNonNullableByDefault)> templateInvalidReturnAsync = const Template<
+        Message Function(
+            DartType _type, DartType _type2, bool isNonNullableByDefault)>(
+    messageTemplate:
+        r"""A value of type '#type' can't be returned from an async function with return type '#type2'.""",
+    withArguments: _withArgumentsInvalidReturnAsync);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<
+        Message Function(
+            DartType _type, DartType _type2, bool isNonNullableByDefault)>
+    codeInvalidReturnAsync = const Code<
+        Message Function(
+            DartType _type, DartType _type2, bool isNonNullableByDefault)>(
+  "InvalidReturnAsync",
+  templateInvalidReturnAsync,
+);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsInvalidReturnAsync(
+    DartType _type, DartType _type2, bool isNonNullableByDefault) {
+  TypeLabeler labeler = new TypeLabeler(isNonNullableByDefault);
+  List<Object> typeParts = labeler.labelType(_type);
+  List<Object> type2Parts = labeler.labelType(_type2);
+  String type = typeParts.join();
+  String type2 = type2Parts.join();
+  return new Message(codeInvalidReturnAsync,
+      message:
+          """A value of type '${type}' can't be returned from an async function with return type '${type2}'.""" +
+              labeler.originMessages,
+      arguments: {'type': _type, 'type2': _type2});
+}
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<
         Message Function(DartType _type, DartType _type2, DartType _type3,

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

@@ -195,7 +195,8 @@ class _SyncClosureContext implements ClosureContext {
           // nor dynamic, and S is void.
           statement.expression = inferrer.helper.wrapInProblem(
               statement.expression,
-              messageVoidExpression,
+              templateInvalidReturn.withArguments(expressionType,
+                  _declaredReturnType, inferrer.isNonNullableByDefault),
               statement.expression.fileOffset,
               noLength)
             ..parent = statement;
@@ -204,7 +205,9 @@ class _SyncClosureContext implements ClosureContext {
           // S is not assignable to T.
           Expression expression = inferrer.ensureAssignable(
               _returnContext, expressionType, statement.expression,
-              fileOffset: statement.expression.fileOffset, isVoidAllowed: true);
+              fileOffset: statement.expression.fileOffset,
+              isVoidAllowed: true,
+              errorTemplate: templateInvalidReturn);
           statement.expression = expression..parent = statement;
         }
       }
@@ -481,7 +484,8 @@ class _AsyncClosureContext implements ClosureContext {
           // flatten(S) is neither void, dynamic, Null.
           statement.expression = inferrer.helper.wrapInProblem(
               new NullLiteral()..fileOffset = statement.fileOffset,
-              messageReturnFromVoidFunction,
+              templateInvalidReturnAsync.withArguments(expressionType,
+                  _declaredReturnType, inferrer.isNonNullableByDefault),
               statement.expression.fileOffset,
               noLength)
             ..parent = statement;
@@ -492,25 +496,11 @@ class _AsyncClosureContext implements ClosureContext {
           // nor dynamic, and flatten(S) is void.
           statement.expression = inferrer.helper.wrapInProblem(
               new NullLiteral()..fileOffset = statement.fileOffset,
-              messageVoidExpression,
+              templateInvalidReturnAsync.withArguments(expressionType,
+                  _declaredReturnType, inferrer.isNonNullableByDefault),
               statement.expression.fileOffset,
               noLength)
             ..parent = statement;
-/*        } else if (flattenedExpressionType is! VoidType &&
-            !inferrer.isAssignable(futureValueType, expressionType) &&
-            !inferrer.typeSchemaEnvironment
-                .performNullabilityAwareSubtypeCheck(
-                    flattenedExpressionType, futureValueType)
-                .isSubtypeWhenUsingNullabilities()) {
-          // It is a compile-time error if s is `return e;`, flatten(S) is not
-          // void, S is not assignable to T_v, and flatten(S) is not a subtype
-          // of T_v.
-          statement.expression = inferrer.helper.wrapInProblem(
-              new NullLiteral()..fileOffset = statement.fileOffset,
-              messageReturnWithoutExpressionAsync,
-              statement.expression.fileOffset,
-              noLength)
-            ..parent = statement;*/
         } else if (flattenedExpressionType is! VoidType &&
             !inferrer.typeSchemaEnvironment
                 .performNullabilityAwareSubtypeCheck(
@@ -523,7 +513,9 @@ class _AsyncClosureContext implements ClosureContext {
               futureValueType, expressionType, statement.expression,
               fileOffset: statement.expression.fileOffset,
               runtimeCheckedType: _returnContext,
-              isVoidAllowed: false)
+              declaredContextType: _declaredReturnType,
+              isVoidAllowed: false,
+              errorTemplate: templateInvalidReturnAsync)
             ..parent = statement;
         }
       }

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

@@ -387,6 +387,13 @@ class TypeInferrerImpl implements TypeInferrer {
   /// [contextType], and inserts an implicit downcast, inserts a tear-off, or
   /// reports an error if appropriate.
   ///
+  /// If [declaredContextType] is provided, this is used instead of
+  /// [contextType] for reporting the type against which [expressionType] isn't
+  /// assignable. This is used when checking the assignability of return
+  /// statements in async functions in which the assignability is checked
+  /// against the future value type but the reporting should refer to the
+  /// declared return type.
+  ///
   /// If [runtimeCheckedType] is provided, this is used for the implicit cast,
   /// otherwise [contextType] is used. This is used for return from async
   /// where the returned expression is wrapped in a `Future`, if necessary,
@@ -395,6 +402,7 @@ class TypeInferrerImpl implements TypeInferrer {
   Expression ensureAssignable(
       DartType contextType, DartType expressionType, Expression expression,
       {int fileOffset,
+      DartType declaredContextType,
       DartType runtimeCheckedType,
       bool isVoidAllowed: false,
       Template<Message Function(DartType, DartType, bool)> errorTemplate}) {
@@ -444,8 +452,8 @@ class TypeInferrerImpl implements TypeInferrer {
         break;
       case AssignabilityKind.unassignable:
         // Error: not assignable.  Perform error recovery.
-        result = _wrapUnassignableExpression(
-            expression, expressionType, contextType, errorTemplate);
+        result = _wrapUnassignableExpression(expression, expressionType,
+            contextType, declaredContextType, errorTemplate);
         break;
       case AssignabilityKind.unassignableVoid:
         // Error: not assignable.  Perform error recovery.
@@ -465,8 +473,12 @@ class TypeInferrerImpl implements TypeInferrer {
       case AssignabilityKind.unassignableTearoff:
         TypedTearoff typedTearoff =
             _tearOffCall(expression, expressionType, fileOffset);
-        result = _wrapUnassignableExpression(typedTearoff.tearoff,
-            typedTearoff.tearoffType, contextType, errorTemplate);
+        result = _wrapUnassignableExpression(
+            typedTearoff.tearoff,
+            typedTearoff.tearoffType,
+            contextType,
+            declaredContextType,
+            errorTemplate);
         break;
       case AssignabilityKind.unassignableCantTearoff:
         result = _wrapTearoffErrorExpression(
@@ -505,6 +517,7 @@ class TypeInferrerImpl implements TypeInferrer {
       Expression expression,
       DartType expressionType,
       DartType contextType,
+      DartType declaredContextType,
       Template<Message Function(DartType, DartType, bool)> template) {
     Expression errorNode = new AsExpression(
         expression,
@@ -520,7 +533,9 @@ class TypeInferrerImpl implements TypeInferrer {
       errorNode = helper.wrapInProblem(
           errorNode,
           (template ?? templateInvalidAssignmentError).withArguments(
-              expressionType, contextType, isNonNullableByDefault),
+              expressionType,
+              declaredContextType ?? contextType,
+              isNonNullableByDefault),
           errorNode.fileOffset,
           noLength);
     }

pkg/front_end/messages.status

@@ -415,6 +415,8 @@ InvalidContinueTarget/example: Fail
 InvalidInitializer/example: Fail
 InvalidPackageUri/analyzerCode: Fail
 InvalidPackageUri/example: Fail
+InvalidReturn/analyzerCode: Fail
+InvalidReturnAsync/analyzerCode: Fail
 InvalidSuperInInitializer/example: Fail
 InvalidThisInInitializer/example: Fail
 InvalidTypeVariableInSupertype/analyzerCode: Fail

pkg/front_end/messages.yaml

@@ -3413,6 +3413,16 @@ ReturnWithoutExpressionAsync:
   configuration: nnbd-strong
   declaration: "Future<int> foo() async { return; }"
 
+InvalidReturn:
+  template: "A value of type '#type' can't be returned from a function with return type '#type2'."
+  configuration: nnbd-strong
+  declaration: "int foo() { return true; }"
+
+InvalidReturnAsync:
+  template: "A value of type '#type' can't be returned from an async function with return type '#type2'."
+  configuration: nnbd-strong
+  declaration: "Future<int> foo() async { return true; }"
+
 ImplicitReturnNull:
   template: "A non-null value must be returned since the return type '#type' doesn't allow null."
   configuration: nnbd-strong

pkg/front_end/testcases/nnbd/dynamic_object_call.dart.textual_outline.expect

@@ -0,0 +1,9 @@
+class Class {
+  @override
+  noSuchMethod(Object o, {String foo = ''}) => 42;
+  @override
+  toString({String foo = ''}) => 'foo';
+}
+
+main() {}
+test() {}

pkg/front_end/testcases/nnbd/dynamic_object_call.dart.textual_outline_modelled.expect

@@ -0,0 +1,9 @@
+class Class {
+  @override
+  noSuchMethod(Object o, {String foo = ''}) => 42;
+  @override
+  toString({String foo = ''}) => 'foo';
+}
+
+main() {}
+test() {}

pkg/front_end/testcases/nnbd/issue41386.dart.textual_outline.expect

@@ -0,0 +1,3 @@
+bool Function(T) predicate<T>(bool Function(T) fn) => (T val) => fn(val);
+void test() {}
+void main() {}

pkg/front_end/testcases/nnbd/issue41386.dart.textual_outline_modelled.expect

@@ -0,0 +1,3 @@
+bool Function(T) predicate<T>(bool Function(T) fn) => (T val) => fn(val);
+void main() {}
+void test() {}

pkg/front_end/testcases/nnbd/issue41386b.dart.textual_outline.expect

@@ -0,0 +1,2 @@
+void test() {}
+main() {}

pkg/front_end/testcases/nnbd/issue41386b.dart.textual_outline_modelled.expect

@@ -0,0 +1,2 @@
+main() {}
+void test() {}

pkg/front_end/testcases/nnbd/issue41437a.dart.strong.expect

@@ -2,12 +2,12 @@ library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+// pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
 //  - 'Future' is from 'dart:async'.
 // Future<bool> test5() => getFutureNull(); // error
 //                         ^
 //
-// pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+// pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
 //  - 'Future' is from 'dart:async'.
 //   Future<bool> test5() => getFutureNull(); // error
 //                           ^
@@ -48,7 +48,7 @@ static method test3() → core::bool
 static method test4() → asy::Future<core::bool> async 
   return await self::getFutureNull() as{TypeError,ForDynamic,ForNonNullableByDefault} FutureOr<core::bool>;
 static method test5() → asy::Future<core::bool>
-  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
  - 'Future' is from 'dart:async'.
 Future<bool> test5() => getFutureNull(); // error
                         ^" in self::getFutureNull() as{TypeError,ForNonNullableByDefault} asy::Future<core::bool>;
@@ -66,7 +66,7 @@ static method test() → dynamic async {
   function test4() → asy::Future<core::bool> async 
     return await self::getFutureNull() as{TypeError,ForDynamic,ForNonNullableByDefault} FutureOr<core::bool>;
   function test5() → asy::Future<core::bool>
-    return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+    return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
  - 'Future' is from 'dart:async'.
   Future<bool> test5() => getFutureNull(); // error
                           ^" in self::getFutureNull() as{TypeError,ForNonNullableByDefault} asy::Future<core::bool>;

pkg/front_end/testcases/nnbd/issue41437a.dart.strong.transformed.expect

@@ -2,12 +2,12 @@ library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+// pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
 //  - 'Future' is from 'dart:async'.
 // Future<bool> test5() => getFutureNull(); // error
 //                         ^
 //
-// pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+// pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
 //  - 'Future' is from 'dart:async'.
 //   Future<bool> test5() => getFutureNull(); // error
 //                           ^
@@ -150,7 +150,7 @@ static method test4() → asy::Future<core::bool> /* originally async */ {
   return :async_completer.{asy::Completer::future};
 }
 static method test5() → asy::Future<core::bool>
-  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
  - 'Future' is from 'dart:async'.
 Future<bool> test5() => getFutureNull(); // error
                         ^" in self::getFutureNull() as{TypeError,ForNonNullableByDefault} asy::Future<core::bool>;
@@ -258,7 +258,7 @@ static method test() → dynamic /* originally async */ {
           return :async_completer.{asy::Completer::future};
         }
         function test5() → asy::Future<core::bool>
-          return let final<BottomType> #t6 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+          return let final<BottomType> #t6 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
  - 'Future' is from 'dart:async'.
   Future<bool> test5() => getFutureNull(); // error
                           ^" in self::getFutureNull() as{TypeError,ForNonNullableByDefault} asy::Future<core::bool>;

pkg/front_end/testcases/nnbd/issue41437a.dart.weak.expect

@@ -2,12 +2,12 @@ library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+// pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
 //  - 'Future' is from 'dart:async'.
 // Future<bool> test5() => getFutureNull(); // error
 //                         ^
 //
-// pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+// pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
 //  - 'Future' is from 'dart:async'.
 //   Future<bool> test5() => getFutureNull(); // error
 //                           ^
@@ -48,7 +48,7 @@ static method test3() → core::bool
 static method test4() → asy::Future<core::bool> async 
   return await self::getFutureNull() as{TypeError,ForDynamic,ForNonNullableByDefault} FutureOr<core::bool>;
 static method test5() → asy::Future<core::bool>
-  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:18:25: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
  - 'Future' is from 'dart:async'.
 Future<bool> test5() => getFutureNull(); // error
                         ^" in self::getFutureNull() as{TypeError,ForNonNullableByDefault} asy::Future<core::bool>;
@@ -66,7 +66,7 @@ static method test() → dynamic async {
   function test4() → asy::Future<core::bool> async 
     return await self::getFutureNull() as{TypeError,ForDynamic,ForNonNullableByDefault} FutureOr<core::bool>;
   function test5() → asy::Future<core::bool>
-    return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be assigned to a variable of type 'Future<bool>'.
+    return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue41437a.dart:27:27: Error: A value of type 'Future<dynamic>' can't be returned from a function with return type 'Future<bool>'.
  - 'Future' is from 'dart:async'.
   Future<bool> test5() => getFutureNull(); // error
                           ^" in self::getFutureNull() as{TypeError,ForNonNullableByDefault} asy::Future<core::bool>;