Complain about assignments to parenthesized expressions.

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

Index: pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart b/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
index 90151e15b3b193c45ea305d7d0cfb90d80750fec..98a30e47396b1bb3ac7aad6c3dc6a47b9d227acb 100644
--- a/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
@@ -20,6 +20,7 @@ import 'package:kernel/frontend/accessors.dart' as kernel
         IndexAccessor,
         NullAwarePropertyAccessor,
         PropertyAccessor,
+        ReadOnlyAccessor,
         StaticAccessor,
         SuperIndexAccessor,
         SuperPropertyAccessor,
@@ -775,6 +776,32 @@ class VariableAccessor extends kernel.VariableAccessor with FastaAccessor {
   toString() => "VariableAccessor()";
 }
 
+class ReadOnlyAccessor extends kernel.ReadOnlyAccessor with FastaAccessor {
+  final BuilderHelper helper;
+
+  final String plainNameForRead;
+
+  ReadOnlyAccessor(
+      this.helper, Expression expression, this.plainNameForRead, int offset)
+      : super(expression, offset);
+
+  Expression doInvocation(int offset, Arguments arguments) {
+    return buildMethodInvocation(
+        buildSimpleRead(), callName, arguments, offset);
+  }
+}
+
+class ParenthesizedExpression extends ReadOnlyAccessor {
+  ParenthesizedExpression(
+      BuilderHelper helper, Expression expression, int offset)
+      : super(helper, expression, "<a parenthesized expression>", offset);
+
+  Expression makeInvalidWrite(Expression value) {
+    return helper.buildCompileTimeError(
+        "Can't assign to a parenthesized expression.", offset);
+  }
+}
+
 bool isFieldOrGetter(Member member) {
   return member is Field || (member is Procedure && member.isGetter);
 }