[kernel] Position on switch expression

pkg/front_end/lib/src/fasta/kernel/body_builder.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.body_builder;
 
 import 'package:kernel/ast.dart'
     hide InvalidExpression, InvalidInitializer, InvalidStatement;
 
 import 'package:kernel/class_hierarchy.dart' show ClassHierarchy;
@@ skipping 2844 matching lines @@
     push(labels);
   }
 
   @override
   void endSwitchStatement(Token switchKeyword, Token endToken) {
     debugEvent("SwitchStatement");
     // Do nothing. Handled by [endSwitchBlock].
   }
 
   @override
-  void endSwitchBlock(int caseCount, Token beginToken, Token endToken) {
+  void endSwitchBlock(
+      int caseCount, Token beginToken, Token endToken, Token switchKeyword) {
     debugEvent("SwitchBlock");
     List<SwitchCase> cases =
         new List<SwitchCase>.filled(caseCount, null, growable: true);
     for (int i = caseCount - 1; i >= 0; i--) {
       List<Label> labels = pop();
       SwitchCase current = cases[i] = pop();
       for (Label label in labels) {
         JumpTarget target = switchScope.lookupLabel(label.name);
         if (target != null) {
           target.resolveGotos(current);
@@ skipping 30 matching lines @@
           lastNode is! ReturnStatement &&
           lastNode is! Throw) {
         block.addStatement(
             new ExpressionStatement(buildFallThroughError(current.fileOffset)));
       }
     }
     JumpTarget target = exitBreakTarget();
     exitSwitchScope();
     exitLocalScope();
     Expression expression = popForValue();
-    Statement result = new KernelSwitchStatement(expression, cases);
+    Statement result = new KernelSwitchStatement(expression, cases)
+      ..fileOffset = switchKeyword.charOffset;
     if (target.hasUsers) {
       result = new KernelLabeledStatement(result);
       target.resolveBreaks(result);
     }
     exitLoopOrSwitch(result);
   }
 
   @override
   void handleCaseMatch(Token caseKeyword, Token colon) {
     debugEvent("CaseMatch");
@@ skipping 891 matching lines @@
       return AsyncMarker.Async;
     } else {
       assert(identical(starToken.stringValue, "*"));
       return AsyncMarker.AsyncStar;
     }
   } else {
     return unhandled(asyncToken.lexeme, "asyncMarkerFromTokens",
         asyncToken.charOffset, null);
   }
 }