Avoid using Invalid{Statement,Expression,Initializer}.

pkg/front_end/lib/src/fasta/kernel/frontend_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.
 
 /// A library to help transform compounds and null-aware accessors into
 /// let expressions.
 
 import 'package:front_end/src/fasta/kernel/kernel_shadow_ast.dart'
     show
         KernelArguments,
         KernelMethodInvocation,
         KernelPropertyGet,
         KernelPropertySet,
         KernelVariableGet,
         KernelVariableSet;
 
 import 'package:front_end/src/fasta/kernel/utils.dart' show offsetForToken;
 
 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.
 ///
 /// Once the context is known, an [Accessor] can be converted into an
 /// [Expression] by calling a "build" method.
 ///
 /// For example, when building a kernel representation for `a[x] = b`, after
 /// parsing `a[x]` but before parsing `= b`, we don't yet know whether to
 /// generate an invocation of `operator[]` or `operator[]=`, so we generate an
@@ skipping 91 matching lines @@
 
   Expression _makeRead();
 
   Expression _makeWrite(Expression value, bool voidContext);
 
   Expression _finish(Expression body) => body;
 
   /// 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 {
   VariableDeclaration variable;
   DartType promotedType;
 
   VariableAccessor(
       BuilderHelper helper, this.variable, this.promotedType, Token token)
       : super(helper, token);
 
@@ skipping 367 matching lines @@
 
 Expression buildIsNull(Expression value, {int offset: TreeNode.noOffset}) {
   return makeBinary(value, equalsName, null, new NullLiteral(), offset: offset);
 }
 
 VariableDeclaration makeOrReuseVariable(Expression value) {
   // TODO: Devise a way to remember if a variable declaration was reused
   // 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());
-}