[cfe] Use original name in extension method errors.

Previously the errors were reported using the synthesized name, like
`Extension|method` instead of `method`.

+ Report errors on invalid uses of explicit extension application as
an expression or lvalue.

Change-Id: I6d85430be4ab3966ee94131b37aa365265c07eac
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/118383
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Jens Johansen <jensj@google.com>

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

@@ -3317,6 +3317,26 @@ const MessageCode messageExplicitExtensionArgumentMismatch = const MessageCode(
     message:
         r"""Explicit extension application requires exactly 1 positional argument.""");
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeExplicitExtensionAsExpression =
+    messageExplicitExtensionAsExpression;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageExplicitExtensionAsExpression = const MessageCode(
+    "ExplicitExtensionAsExpression",
+    message:
+        r"""Explicit extension application cannot be used as an expression.""");
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeExplicitExtensionAsLvalue =
+    messageExplicitExtensionAsLvalue;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageExplicitExtensionAsLvalue = const MessageCode(
+    "ExplicitExtensionAsLvalue",
+    message:
+        r"""Explicit extension application cannot be a target for assignment.""");
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<
     Message Function(

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

@@ -1859,11 +1859,12 @@ class BodyBuilder extends ScopeListener<JumpTarget>
       Builder setter =
           _getCorrespondingSetterBuilder(scope, declaration, name, charOffset);
       // TODO(johnniwinther): Check for constantContext like below?
-      return new ExtensionInstanceAccessGenerator.fromBuilder(this,
+      return new ExtensionInstanceAccessGenerator.fromBuilder(this, name,
           extensionThis, extensionTypeParameters, declaration, token, setter);
     } else if (declaration.isRegularMethod) {
       assert(declaration.isStatic || declaration.isTopLevel);
-      return new StaticAccessGenerator(this, token, declaration.target, null);
+      return new StaticAccessGenerator(
+          this, token, name, declaration.target, null);
     } else if (declaration is PrefixBuilder) {
       assert(prefix == null);
       return new PrefixUseGenerator(this, token, declaration);
@@ -1875,7 +1876,7 @@ class BodyBuilder extends ScopeListener<JumpTarget>
       Builder setter =
           _getCorrespondingSetterBuilder(scope, declaration, name, charOffset);
       StaticAccessGenerator generator = new StaticAccessGenerator.fromBuilder(
-          this, declaration, token, setter);
+          this, name, declaration, token, setter);
       if (constantContext != ConstantContext.none) {
         Member readTarget = generator.readTarget;
         if (!(readTarget is Field && readTarget.isConst ||

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

@@ -1367,6 +1367,9 @@ class SuperIndexedAccessGenerator extends Generator {
 ///   }
 ///
 class StaticAccessGenerator extends Generator {
+  /// The name of the original target;
+  final String targetName;
+
   /// The static [Member] used for performing a read or invocation on this
   /// subexpression.
   ///
@@ -1383,12 +1386,17 @@ class StaticAccessGenerator extends Generator {
   final Member writeTarget;
 
   StaticAccessGenerator(ExpressionGeneratorHelper helper, Token token,
-      this.readTarget, this.writeTarget)
-      : assert(readTarget != null || writeTarget != null),
+      this.targetName, this.readTarget, this.writeTarget)
+      : assert(targetName != null),
+        assert(readTarget != null || writeTarget != null),
         super(helper, token);
 
-  factory StaticAccessGenerator.fromBuilder(ExpressionGeneratorHelper helper,
-      Builder declaration, Token token, Builder builderSetter) {
+  factory StaticAccessGenerator.fromBuilder(
+      ExpressionGeneratorHelper helper,
+      String targetName,
+      Builder declaration,
+      Token token,
+      Builder builderSetter) {
     if (declaration is AccessErrorBuilder) {
       AccessErrorBuilder error = declaration;
       declaration = error.builder;
@@ -1409,14 +1417,14 @@ class StaticAccessGenerator extends Generator {
         setter = builderSetter.target;
       }
     }
-    return new StaticAccessGenerator(helper, token, getter, setter);
+    return new StaticAccessGenerator(helper, token, targetName, getter, setter);
   }
 
   @override
   String get _debugName => "StaticAccessGenerator";
 
   @override
-  String get _plainNameForRead => (readTarget ?? writeTarget).name.name;
+  String get _plainNameForRead => targetName;
 
   @override
   Expression buildSimpleRead() {
@@ -1524,6 +1532,8 @@ class StaticAccessGenerator extends Generator {
   @override
   void printOn(StringSink sink) {
     NameSystem syntheticNames = new NameSystem();
+    sink.write(", targetName: ");
+    sink.write(targetName);
     sink.write(", readTarget: ");
     printQualifiedNameOn(readTarget, sink, syntheticNames: syntheticNames);
     sink.write(", writeTarget: ");
@@ -1550,6 +1560,9 @@ class StaticAccessGenerator extends Generator {
 ///
 /// These can only occur within an extension instance member.
 class ExtensionInstanceAccessGenerator extends Generator {
+  /// The original name of the target.
+  final String targetName;
+
   /// The static [Member] generated for an instance extension member which is
   /// used for performing a read on this subexpression.
   ///
@@ -1586,17 +1599,20 @@ class ExtensionInstanceAccessGenerator extends Generator {
   ExtensionInstanceAccessGenerator(
       ExpressionGeneratorHelper helper,
       Token token,
+      this.targetName,
       this.readTarget,
       this.invokeTarget,
       this.writeTarget,
       this.extensionThis,
       this.extensionTypeParameters)
-      : assert(readTarget != null || writeTarget != null),
+      : assert(targetName != null),
+        assert(readTarget != null || writeTarget != null),
         assert(extensionThis != null),
         super(helper, token);
 
   factory ExtensionInstanceAccessGenerator.fromBuilder(
       ExpressionGeneratorHelper helper,
+      String targetName,
       VariableDeclaration extensionThis,
       List<TypeParameter> extensionTypeParameters,
       Builder declaration,
@@ -1628,15 +1644,22 @@ class ExtensionInstanceAccessGenerator extends Generator {
     if (builderSetter != null && builderSetter.isSetter) {
       writeTarget = builderSetter.target;
     }
-    return new ExtensionInstanceAccessGenerator(helper, token, readTarget,
-        invokeTarget, writeTarget, extensionThis, extensionTypeParameters);
+    return new ExtensionInstanceAccessGenerator(
+        helper,
+        token,
+        targetName,
+        readTarget,
+        invokeTarget,
+        writeTarget,
+        extensionThis,
+        extensionTypeParameters);
   }
 
   @override
   String get _debugName => "InstanceExtensionAccessGenerator";
 
   @override
-  String get _plainNameForRead => (readTarget ?? writeTarget).name.name;
+  String get _plainNameForRead => targetName;
 
   int get _extensionTypeParameterCount => extensionTypeParameters?.length ?? 0;
 
@@ -1785,6 +1808,8 @@ class ExtensionInstanceAccessGenerator extends Generator {
   @override
   void printOn(StringSink sink) {
     NameSystem syntheticNames = new NameSystem();
+    sink.write(", targetName: ");
+    sink.write(targetName);
     sink.write(", readTarget: ");
     printQualifiedNameOn(readTarget, sink, syntheticNames: syntheticNames);
     sink.write(", writeTarget: ");
@@ -1814,6 +1839,9 @@ class ExtensionInstanceAccessGenerator extends Generator {
 ///   }
 ///
 class ExplicitExtensionInstanceAccessGenerator extends Generator {
+  /// The name of the original target;
+  final String targetName;
+
   /// The static [Member] generated for an instance extension member which is
   /// used for performing a read on this subexpression.
   ///
@@ -1850,13 +1878,15 @@ class ExplicitExtensionInstanceAccessGenerator extends Generator {
   ExplicitExtensionInstanceAccessGenerator(
       ExpressionGeneratorHelper helper,
       Token token,
+      this.targetName,
       this.readTarget,
       this.invokeTarget,
       this.writeTarget,
       this.receiver,
       this.explicitTypeArguments,
       this.extensionTypeParameterCount)
-      : assert(readTarget != null || writeTarget != null),
+      : assert(targetName != null),
+        assert(readTarget != null || writeTarget != null),
         assert(receiver != null),
         super(helper, token);
 
@@ -1868,6 +1898,7 @@ class ExplicitExtensionInstanceAccessGenerator extends Generator {
       Expression receiver,
       List<DartType> explicitTypeArguments,
       int extensionTypeParameterCount) {
+    String targetName;
     Procedure readTarget;
     Procedure invokeTarget;
     if (getterBuilder != null) {
@@ -1878,11 +1909,14 @@ class ExplicitExtensionInstanceAccessGenerator extends Generator {
         // when not explicitly looking for a setter.
         assert(getterBuilder.isSetter);
       } else if (getterBuilder.isGetter) {
-        readTarget = getterBuilder.target;
+        MemberBuilder memberBuilder = getterBuilder;
+        readTarget = memberBuilder.member;
+        targetName = memberBuilder.name;
       } else if (getterBuilder.isRegularMethod) {
         MemberBuilder procedureBuilder = getterBuilder;
         readTarget = procedureBuilder.extensionTearOff;
         invokeTarget = procedureBuilder.procedure;
+        targetName = procedureBuilder.name;
       } else {
         return unhandled(
             "${getterBuilder.runtimeType}",
@@ -1892,12 +1926,17 @@ class ExplicitExtensionInstanceAccessGenerator extends Generator {
       }
     }
     Procedure writeTarget;
-    if (setterBuilder != null && setterBuilder.isSetter) {
-      writeTarget = setterBuilder.target;
+    if (setterBuilder is AccessErrorBuilder) {
+      targetName ??= setterBuilder.name;
+    } else if (setterBuilder != null && setterBuilder.isSetter) {
+      MemberBuilder memberBuilder = setterBuilder;
+      writeTarget = memberBuilder.member;
+      targetName ??= memberBuilder.name;
     }
     return new ExplicitExtensionInstanceAccessGenerator(
         helper,
         token,
+        targetName,
         readTarget,
         invokeTarget,
         writeTarget,
@@ -1910,7 +1949,7 @@ class ExplicitExtensionInstanceAccessGenerator extends Generator {
   String get _debugName => "InstanceExtensionAccessGenerator";
 
   @override
-  String get _plainNameForRead => (readTarget ?? writeTarget).name.name;
+  String get _plainNameForRead => targetName;
 
   List<DartType> _createExtensionTypeArguments() {
     return explicitTypeArguments ?? const <DartType>[];
@@ -2065,6 +2104,8 @@ class ExplicitExtensionInstanceAccessGenerator extends Generator {
   @override
   void printOn(StringSink sink) {
     NameSystem syntheticNames = new NameSystem();
+    sink.write(", targetName: ");
+    sink.write(targetName);
     sink.write(", readTarget: ");
     printQualifiedNameOn(readTarget, sink, syntheticNames: syntheticNames);
     sink.write(", writeTarget: ");
@@ -2183,6 +2224,18 @@ class ExplicitExtensionAccessGenerator extends Generator {
         "ExplicitExtensionAccessGenerator.doInvocation", fileOffset, _uri);
   }
 
+  @override
+  Expression _makeInvalidRead() {
+    return _helper.buildProblem(messageExplicitExtensionAsExpression,
+        fileOffset, lengthForToken(token));
+  }
+
+  @override
+  Expression _makeInvalidWrite(Expression value) {
+    return _helper.buildProblem(
+        messageExplicitExtensionAsLvalue, fileOffset, lengthForToken(token));
+  }
+
   @override
   void printOn(StringSink sink) {
     sink.write(", extensionBuilder: ");
@@ -2445,8 +2498,8 @@ class TypeUseGenerator extends ReadOnlyAccessGenerator {
   final TypeDeclarationBuilder declaration;
 
   TypeUseGenerator(ExpressionGeneratorHelper helper, Token token,
-      this.declaration, String plainNameForRead)
-      : super(helper, token, null, plainNameForRead);
+      this.declaration, String targetName)
+      : super(helper, token, null, targetName);
 
   @override
   String get _debugName => "TypeUseGenerator";
@@ -2489,7 +2542,7 @@ class TypeUseGenerator extends ReadOnlyAccessGenerator {
       }
     }
     return new NamedTypeBuilder(
-        _plainNameForRead, nullabilityBuilder, argumentBuilders)
+        targetName, nullabilityBuilder, argumentBuilders)
       ..bind(declaration);
   }
 
@@ -2542,16 +2595,6 @@ class TypeUseGenerator extends ReadOnlyAccessGenerator {
     return super.expression;
   }
 
-  @override
-  Expression _makeInvalidWrite(Expression value) {
-    return _helper.throwNoSuchMethodError(
-        _forest.createNullLiteral(fileOffset),
-        _plainNameForRead,
-        _forest.createArguments(fileOffset, <Expression>[value]),
-        fileOffset,
-        isSetter: true);
-  }
-
   @override
   buildPropertyAccess(
       IncompleteSendGenerator send, int operatorOffset, bool isNullAware) {
@@ -2604,7 +2647,7 @@ class TypeUseGenerator extends ReadOnlyAccessGenerator {
           }
         }
         generator = new StaticAccessGenerator.fromBuilder(
-            _helper, member, send.token, setter);
+            _helper, name.name, member, send.token, setter);
       }
 
       return arguments == null
@@ -2673,20 +2716,22 @@ class TypeUseGenerator extends ReadOnlyAccessGenerator {
 ///   }
 ///
 class ReadOnlyAccessGenerator extends Generator {
-  @override
-  final String _plainNameForRead;
+  final String targetName;
 
   Expression expression;
 
   VariableDeclaration value;
 
   ReadOnlyAccessGenerator(ExpressionGeneratorHelper helper, Token token,
-      this.expression, this._plainNameForRead)
+      this.expression, this.targetName)
       : super(helper, token);
 
   @override
   String get _debugName => "ReadOnlyAccessGenerator";
 
+  @override
+  String get _plainNameForRead => targetName;
+
   @override
   Expression buildSimpleRead() => expression;
 
@@ -2736,7 +2781,7 @@ class ReadOnlyAccessGenerator extends Generator {
   @override
   doInvocation(int offset, Arguments arguments) {
     return _helper.buildMethodInvocation(buildSimpleRead(), callName, arguments,
-        adjustForImplicitCall(_plainNameForRead, offset),
+        adjustForImplicitCall(targetName, offset),
         isImplicitCall: true);
   }
 
@@ -2746,7 +2791,7 @@ class ReadOnlyAccessGenerator extends Generator {
     sink.write(", expression: ");
     printNodeOn(expression, sink, syntheticNames: syntheticNames);
     sink.write(", plainNameForRead: ");
-    sink.write(_plainNameForRead);
+    sink.write(targetName);
     sink.write(", value: ");
     printNodeOn(value, sink, syntheticNames: syntheticNames);
   }
@@ -3380,9 +3425,8 @@ class UnexpectedQualifiedUseGenerator extends Generator {
       : super(helper, token);
 
   @override
-  String get _plainNameForRead {
-    return "${prefixGenerator._plainNameForRead}.${token.lexeme}";
-  }
+  String get _plainNameForRead =>
+      "${prefixGenerator._plainNameForRead}.${token.lexeme}";
 
   @override
   String get _debugName => "UnexpectedQualifiedUseGenerator";

pkg/front_end/messages.status

@@ -197,6 +197,10 @@ ExplicitExtensionArgumentMismatch/analyzerCode: Fail
 ExplicitExtensionArgumentMismatch/example: Fail
 ExplicitExtensionTypeArgumentMismatch/analyzerCode: Fail
 ExplicitExtensionTypeArgumentMismatch/example: Fail
+ExplicitExtensionAsExpression/analyzerCode: Fail
+ExplicitExtensionAsExpression/example: Fail
+ExplicitExtensionAsLvalue/analyzerCode: Fail
+ExplicitExtensionAsLvalue/example: Fail
 ExportAfterPart/part_wrapped_script1: Fail
 ExportAfterPart/script1: Fail
 ExpressionNotMetadata/analyzerCode: Fail

pkg/front_end/messages.yaml

@@ -3706,3 +3706,9 @@ ExplicitExtensionArgumentMismatch:
 
 ExplicitExtensionTypeArgumentMismatch:
   template: "Explicit extension application of extension '#name' takes '#count' type argument(s)."
+
+ExplicitExtensionAsExpression:
+  template: "Explicit extension application cannot be used as an expression."
+
+ExplicitExtensionAsLvalue:
+  template: "Explicit extension application cannot be a target for assignment."

pkg/front_end/test/fasta/generator_to_string_test.dart

@@ -161,9 +161,10 @@ main() {
         " getter: $uri::myGetter, setter: $uri::mySetter)",
         new SuperIndexedAccessGenerator(helper, token, index, getter, setter));
     check(
-        "StaticAccessGenerator(offset: 4, readTarget: $uri::myGetter,"
+        "StaticAccessGenerator(offset: 4, targetName: foo,"
+        " readTarget: $uri::myGetter,"
         " writeTarget: $uri::mySetter)",
-        new StaticAccessGenerator(helper, token, getter, setter));
+        new StaticAccessGenerator(helper, token, 'foo', getter, setter));
     check(
         "LoadLibraryGenerator(offset: 4,"
         " builder: Instance of 'LoadLibraryBuilder')",

pkg/front_end/testcases/extensions/explicit_invalid_access.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2019, 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.
+
+class Class {}
+
+extension Extension on Class {}
+
+errors(Class c) {
+  Extension(c);
+  Extension(c) = 42;
+  Extension(c) += 42;
+  Extension(c)++;
+  ++Extension(c);
+}
+
+main() {
+}

pkg/front_end/testcases/extensions/explicit_invalid_access.dart.outline.expect

@@ -0,0 +1,14 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    ;
+}
+extension Extension on self::Class* {
+}
+static method errors(self::Class* c) → dynamic
+  ;
+static method main() → dynamic
+  ;

pkg/front_end/testcases/extensions/explicit_invalid_access.dart.strong.expect

@@ -0,0 +1,52 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:10:3: Error: Explicit extension application cannot be used as an expression.
+//   Extension(c);
+//   ^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:11:3: Error: Explicit extension application cannot be a target for assignment.
+//   Extension(c) = 42;
+//   ^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:12:3: Error: Explicit extension application cannot be used as an expression.
+//   Extension(c) += 42;
+//   ^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:13:3: Error: Explicit extension application cannot be used as an expression.
+//   Extension(c)++;
+//   ^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:14:5: Error: Explicit extension application cannot be used as an expression.
+//   ++Extension(c);
+//     ^^^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    : super core::Object::•()
+    ;
+}
+extension Extension on self::Class* {
+}
+static method errors(self::Class* c) → dynamic {
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:10:3: Error: Explicit extension application cannot be used as an expression.
+  Extension(c);
+  ^^^^^^^^^";
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:11:3: Error: Explicit extension application cannot be a target for assignment.
+  Extension(c) = 42;
+  ^^^^^^^^^";
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:12:3: Error: Explicit extension application cannot be used as an expression.
+  Extension(c) += 42;
+  ^^^^^^^^^";
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:13:3: Error: Explicit extension application cannot be used as an expression.
+  Extension(c)++;
+  ^^^^^^^^^";
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:14:5: Error: Explicit extension application cannot be used as an expression.
+  ++Extension(c);
+    ^^^^^^^^^";
+}
+static method main() → dynamic {}

pkg/front_end/testcases/extensions/explicit_invalid_access.dart.strong.transformed.expect

@@ -0,0 +1,52 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:10:3: Error: Explicit extension application cannot be used as an expression.
+//   Extension(c);
+//   ^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:11:3: Error: Explicit extension application cannot be a target for assignment.
+//   Extension(c) = 42;
+//   ^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:12:3: Error: Explicit extension application cannot be used as an expression.
+//   Extension(c) += 42;
+//   ^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:13:3: Error: Explicit extension application cannot be used as an expression.
+//   Extension(c)++;
+//   ^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/explicit_invalid_access.dart:14:5: Error: Explicit extension application cannot be used as an expression.
+//   ++Extension(c);
+//     ^^^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    : super core::Object::•()
+    ;
+}
+extension Extension on self::Class* {
+}
+static method errors(self::Class* c) → dynamic {
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:10:3: Error: Explicit extension application cannot be used as an expression.
+  Extension(c);
+  ^^^^^^^^^";
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:11:3: Error: Explicit extension application cannot be a target for assignment.
+  Extension(c) = 42;
+  ^^^^^^^^^";
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:12:3: Error: Explicit extension application cannot be used as an expression.
+  Extension(c) += 42;
+  ^^^^^^^^^";
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:13:3: Error: Explicit extension application cannot be used as an expression.
+  Extension(c)++;
+  ^^^^^^^^^";
+  invalid-expression "pkg/front_end/testcases/extensions/explicit_invalid_access.dart:14:5: Error: Explicit extension application cannot be used as an expression.
+  ++Extension(c);
+    ^^^^^^^^^";
+}
+static method main() → dynamic {}

pkg/front_end/testcases/text_serialization.status

@@ -18,6 +18,7 @@ extensions/dynamic_invoke: TextSerializationFailure
 extensions/explicit_extension_access: TextSerializationFailure
 extensions/explicit_extension_inference: TextSerializationFailure
 extensions/explicit_generic_extension_access: TextSerializationFailure
+extensions/explicit_invalid_access: TextSerializationFailure
 extensions/explicit_this: TextSerializationFailure
 extensions/extension_methods: TextSerializationFailure
 extensions/extension_setter: TextSerializationFailure