Handle bad rethrows.

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 '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
@@ skipping 67 matching lines @@
 
   @override
   final Uri uri;
 
   Scope formalParameterScope;
 
   bool inInitializer = false;
 
   bool inCatchClause = false;
 
+  bool inCatchBlock = false;
+
   int functionNestingLevel = 0;
 
   Statement compileTimeErrorInTry;
 
   Statement compileTimeErrorInLoopOrSwitch;
 
   Scope switchScope;
 
   CloneVisitor cloner;
 
@@ skipping 1413 matching lines @@
   @override
   void beginCatchClause(Token token) {
     debugEvent("beginCatchClause");
     inCatchClause = true;
   }
 
   @override
   void endCatchClause(Token token) {
     debugEvent("CatchClause");
     inCatchClause = false;
+    push(inCatchBlock);
+    inCatchBlock = true;
   }
 
   @override
   void handleCatchBlock(Token onKeyword, Token catchKeyword) {
     debugEvent("CatchBlock");
     Block body = pop();
+    inCatchBlock = pop();
     if (catchKeyword != null) {
       exitLocalScope();
     }
     FormalParameters catchParameters = popIfNotNull(catchKeyword);
     DartType type = popIfNotNull(onKeyword) ?? const DynamicType();
     VariableDeclaration exception;
     VariableDeclaration stackTrace;
     if (catchParameters != null) {
       if (catchParameters.required.length > 0) {
         exception = catchParameters.required[0];
@@ skipping 366 matching lines @@
     scope[variable.name] = new KernelVariableBuilder(
         variable, member ?? classBuilder ?? library, uri);
     enterLocalScope();
   }
 
   void enterFunction() {
     debugEvent("enterFunction");
     functionNestingLevel++;
     push(switchScope ?? NullValue.SwitchScope);
     switchScope = null;
+    push(inCatchBlock);
+    inCatchBlock = false;
   }
 
   void exitFunction() {
     debugEvent("exitFunction");
     functionNestingLevel--;
+    inCatchBlock = pop();
     switchScope = pop();
   }
 
   @override
   void beginFunction(Token token) {
     debugEvent("beginFunction");
     enterFunction();
   }
 
   @override
@@ skipping 165 matching lines @@
         statement = new LabeledStatement(statement);
       }
       target.continueTarget.resolveContinues(statement);
     }
     push(statement);
   }
 
   @override
   void endRethrowStatement(Token throwToken, Token endToken) {
     debugEvent("RethrowStatement");
-    push(new ExpressionStatement(
-        new Rethrow()..fileOffset = throwToken.charOffset));
+    if (inCatchBlock) {
+      push(new ExpressionStatement(
+          new Rethrow()..fileOffset = throwToken.charOffset));
+    } else {
+      push(buildCompileTimeErrorStatement(
+          "'rethrow' can only be used in catch clauses.",
+          throwToken.charOffset));
+    }
   }
 
   @override
   void handleFinallyBlock(Token finallyKeyword) {
     debugEvent("FinallyBlock");
     // Do nothing, handled by [endTryStatement].
   }
 
   @override
   void endWhileStatement(Token whileKeyword, Token endToken) {
@@ skipping 825 matching lines @@
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisAccessor) {
     return node.isSuper ? "super" : "this";
   } else if (node is FastaAccessor) {
     return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }