Avoid using Invalid{Statement,Expression,Initializer}.

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

Index: pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart b/pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart
index 336169c7bd4e5ff37ff22b0703bbad5ef5ff702f..f84ddd683b63fbc9e1c56a07cf04a5c8e0ec3ce0 100644
--- a/pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart
@@ -21,10 +21,12 @@ import 'package:front_end/src/scanner/token.dart' show Token;
 import 'package:front_end/src/fasta/kernel/fasta_accessors.dart'
     show BuilderHelper;
 
-import 'package:kernel/ast.dart' hide MethodInvocation;
+import 'package:kernel/ast.dart' hide MethodInvocation, InvalidExpression;
 
 import '../names.dart' show equalsName, indexGetName, indexSetName;
 
+import '../errors.dart' show internalError;
+
 /// An [Accessor] represents a subexpression for which we can't yet build a
 /// kernel [Expression] because we don't yet know the context in which it is
 /// used.
@@ -136,13 +138,19 @@ abstract class Accessor {
   /// Returns an [Expression] representing a compile-time error.
   ///
   /// At runtime, an exception will be thrown.
-  makeInvalidRead() => new InvalidExpression();
+  makeInvalidRead() {
+    return internalError(
+        "Unhandled compile-time error.", null, offsetForToken(token));
+  }
 
   /// Returns an [Expression] representing a compile-time error wrapping
   /// [value].
   ///
   /// At runtime, [value] will be evaluated before throwing an exception.
-  makeInvalidWrite(Expression value) => wrapInvalid(value);
+  makeInvalidWrite(Expression value) {
+    return internalError(
+        "Unhandled compile-time error.", null, offsetForToken(token));
+  }
 }
 
 abstract class VariableAccessor extends Accessor {
@@ -530,7 +538,3 @@ VariableDeclaration makeOrReuseVariable(Expression value) {
   // or is fresh (hence needs a let binding).
   return new VariableDeclaration.forValue(value);
 }
-
-Expression wrapInvalid(Expression e) {
-  return new Let(new VariableDeclaration.forValue(e), new InvalidExpression());
-}