Compile-time errors instead of internal errors.

pkg/front_end/lib/src/fasta/kernel/builder_accessors.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 fasta.builder_accessors;
 
 export 'frontend_accessors.dart' show wrapInvalid;
 
 import 'frontend_accessors.dart' show Accessor;
 
@@ skipping 39 matching lines @@
 
   Expression buildCompileTimeError(error, [int charOffset]);
 
   Initializer buildCompileTimeErrorIntializer(error, [int charOffset]);
 
   Expression buildStaticInvocation(Procedure target, Arguments arguments);
 
   Expression buildProblemExpression(Builder builder, String name);
 }
 
 abstract class BuilderAccessor implements Accessor {

[karlklose, 2017/03/09 10:48:26]

Please add a TODO to document this hierarchy.

[ahe, 2017/03/09 13:03:10]

I created this bug instead: https://github.com/dart-lang/sdk/issues/28999

   BuilderHelper get helper;
 
   int get charOffset;
 
   String get plainNameForRead;
 
   Uri get uri => helper.uri;
 
   CoreTypes get coreTypes => helper.coreTypes;
 
@@ skipping 172 matching lines @@
               isSuper: isSuper)));
     } else if (isSuper) {
       result = new SuperInitializer(constructor, arguments);
     } else {
       result = new RedirectingInitializer(constructor, arguments);
     }
     return result..fileOffset = charOffset;
   }
 
   Expression buildAssignment(Expression value, {bool voidContext: false}) {
-    return internalError("");
+    return buildAssignmentError();
   }
 
   Expression buildNullAwareAssignment(Expression value, DartType type,
       {bool voidContext: false}) {
-    return internalError("");
+    return buildAssignmentError();
   }
 
   Expression buildCompoundAssignment(Name binaryOperator, Expression value,
       {bool voidContext: false, Procedure interfaceTarget}) {
-    return internalError("");
+    return buildAssignmentError();
   }
 
   Expression buildPrefixIncrement(Name binaryOperator,
       {bool voidContext: false, Procedure interfaceTarget}) {
-    return internalError("");
+    return buildAssignmentError();
   }
 
   Expression buildPostfixIncrement(Name binaryOperator,
       {bool voidContext: false, Procedure interfaceTarget}) {
-    return internalError("");
+    return buildAssignmentError();
+  }
+
+  Expression buildAssignmentError() {
+    String message =
+        isSuper ? "Can't assign to 'super'." : "Can't assign to 'this'.";
+    return helper.buildCompileTimeError(message, charOffset);
   }
 
   toString() => "ThisAccessor($charOffset${isSuper ? ', super' : ''})";
 }
 
 abstract class IncompleteSend extends BuilderAccessor {
   final BuilderHelper helper;
 
   final int charOffset;
 
@@ skipping 73 matching lines @@
     } else {
       result = buildMethodInvocation(
           helper.toValue(receiver), name, arguments, charOffset,
           isNullAware: isNullAware);
     }
     return result..fileOffset = charOffset;
   }
 
   Expression buildNullAwareAssignment(Expression value, DartType type,
       {bool voidContext: false}) {
-    return internalError("");
+    return internalError("Unhandled");
   }
 
   Expression buildCompoundAssignment(Name binaryOperator, Expression value,
       {bool voidContext: false, Procedure interfaceTarget}) {
-    return internalError("");
+    return internalError("Unhandled");
   }
 
   Expression buildPrefixIncrement(Name binaryOperator,
       {bool voidContext: false, Procedure interfaceTarget}) {
     return internalError("Unhandled");
   }
 
   Expression buildPostfixIncrement(Name binaryOperator,
       {bool voidContext: false, Procedure interfaceTarget}) {
     return internalError("Unhandled");
@@ skipping 366 matching lines @@
             buildIsNull(new VariableGet(variable)),
             new NullLiteral(),
             new MethodInvocation(new VariableGet(variable), name, arguments)
               ..fileOffset = charOffset,
             const DynamicType()));
   } else {
     return new MethodInvocation(receiver, name, arguments)
       ..fileOffset = charOffset;
   }
 }