Prepare for improved error recovery from compile-time errors.

pkg/kernel/lib/target/targets.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 kernel.target.targets;
 
 import '../ast.dart';
 import '../class_hierarchy.dart';
 import '../core_types.dart';
 import '../transformations/treeshaker.dart' show ProgramRoot;
 import 'flutter.dart' show FlutterTarget;
@@ skipping 112 matching lines @@
       bool isGetter: false,
       bool isSetter: false,
       bool isField: false,
       bool isLocalVariable: false,
       bool isDynamic: false,
       bool isSuper: false,
       bool isStatic: false,
       bool isConstructor: false,
       bool isTopLevel: false});
 
+  /// Builds an expression that throws [error] as compile-time error. The
+  /// target must be able to handle this expression in a constant expression.
+  Expression throwCompileConstantError(CoreTypes coreTypes, Expression error) {
+    // This method returns `const _ConstantExpressionError()._throw(error)`.
+    int offset = error.fileOffset;
+    var receiver = new ConstructorInvocation(
+        coreTypes.constantExpressionErrorDefaultConstructor,
+        new Arguments.empty()..fileOffset = offset,
+        isConst: true)
+      ..fileOffset = offset;
+    return new MethodInvocation(
+        receiver,
+        new Name("_throw", coreTypes.coreLibrary),
+        new Arguments(<Expression>[error])..fileOffset = error.fileOffset)
+      ..fileOffset = offset;
+  }
+
+  /// Builds an expression that represents a compile-time error which is
+  /// suitable for being passed to [throwCompileConstantError].
+  Expression buildCompileTimeError(
+      CoreTypes coreTypes, String message, int offset) {
+    return new ConstructorInvocation(
+        coreTypes.compileTimeErrorDefaultConstructor,
+        new Arguments(<Expression>[new StringLiteral(message)])
+          ..fileOffset = offset)
+      ..fileOffset = offset;
+  }
+
   String toString() => 'Target($name)';
 }
 
 class NoneTarget extends Target {
   final TargetFlags flags;
 
   NoneTarget(this.flags);
 
   bool get strongMode => flags.strongMode;
   String get name => 'none';
@@ skipping 19 matching lines @@
       bool isField: false,
       bool isLocalVariable: false,
       bool isDynamic: false,
       bool isSuper: false,
       bool isStatic: false,
       bool isConstructor: false,
       bool isTopLevel: false}) {
     return new InvalidExpression();
   }
 }