implement rethrow

lib/src/codegen/js_codegen.dart

 // Copyright (c) 2015, 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 ddc.src.codegen.js_codegen;
 
 import 'dart:io' show Directory, File;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/src/generated/ast.dart' hide ConstantEvaluator;
@@ skipping 19 matching lines @@
 
 // This must match the optional parameter name used in runtime.js
 const String _jsNamedParameterName = r'opt$';
 
 class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
   final LibraryInfo libraryInfo;
   final TypeRules rules;
 
   /// The variable for the target of the current `..` cascade expression.
   SimpleIdentifier _cascadeTarget;
+  /// The variable for the current catch clause
+  String _catchParameter;
 
   ClassDeclaration currentClass;
   ConstantEvaluator _constEvaluator;
 
   final _exports = <String>[];
   final _lazyFields = <VariableDeclaration>[];
   final _properties = <FunctionDeclaration>[];
 
   JSCodegenVisitor(LibraryInfo libraryInfo, TypeRules rules)
       : libraryInfo = libraryInfo,
@@ skipping 1230 matching lines @@
   visitThrowExpression(ThrowExpression node) {
     var expr = _visit(node.expression);
     if (node.parent is ExpressionStatement) {
       return js.statement('throw #;', expr);
     } else {
       return js.call('dart.throw_(#)', expr);
     }
   }
 
   @override
+  visitRethrowExpression(RethrowExpression node){
+    if (node.parent is ExpressionStatement) {
+      return js.statement('throw #;', _catchParameter);
+    } else {
+      return js.call('dart.throw_(#)', _catchParameter);
+    }
+  }
+
+  @override
   JS.If visitIfStatement(IfStatement node) {
     return new JS.If(_visit(node.condition), _visit(node.thenStatement),
         _visitOrEmpty(node.elseStatement));
   }
 
   @override
   JS.For visitForStatement(ForStatement node) {
     var init = _visit(node.initialization);
     if (init == null) init = _visit(node.variables);
     return new JS.For(init, _visit(node.condition),
@@ skipping 35 matching lines @@
   visitTryStatement(TryStatement node) {
     return new JS.Try(_visit(node.body), _visitCatch(node.catchClauses),
         _visit(node.finallyBlock));
   }
 
   _visitCatch(NodeList<CatchClause> clauses) {
     if (clauses == null || clauses.isEmpty) return null;
 
     // TODO(jmesserly): need a better way to get a temporary variable.
     // This could incorrectly shadow a user's name.
-    var name = '\$e';
+    var savedCatch = _catchParameter;
+    _catchParameter = '\$e';
 
     if (clauses.length == 1) {
       // Special case for a single catch.
       var clause = clauses.single;
       if (clause.exceptionParameter != null) {
-        name = clause.exceptionParameter.name;
+        _catchParameter = clause.exceptionParameter.name;
       }
     }
 
-    var catchBody = _statement(clauses.map((c) => _visitCatchClause(c, name)));
+    var catchVarDecl = new JS.VariableDeclaration(_catchParameter);
+    var catchBody = _statement(_visitList(clauses));
+    _catchParameter = savedCatch;
 
-    return new JS.Catch(new JS.VariableDeclaration(name), catchBody);
+    return new JS.Catch(catchVarDecl, catchBody);
   }
 
   JS.Statement _statement(Iterable stmts) {
     var s = stmts is List ? stmts : new List<JS.Statement>.from(stmts);
     // TODO(jmesserly): empty block singleton?
     if (s.length == 0) return new JS.Block([]);
     if (s.length == 1) return s[0];
     return new JS.Block(s);
   }
 
-  JS.Statement _visitCatchClause(CatchClause node, String varName) {
+  @override
+  JS.Statement visitCatchClause(CatchClause node) {
     var body = [];
+
+    var savedCatch = _catchParameter;
     if (node.catchKeyword != null) {
       var name = node.exceptionParameter;
-      if (name != null && name.name != varName) {
-        body.add(js.statement('let # = #;', [_visit(name), varName]));
+      if (name != null && name.name != _catchParameter) {
+        body.add(js.statement('let # = #;', [_visit(name), _catchParameter]));
+        _catchParameter = name.name;
       }
       if (node.stackTraceParameter != null) {
         var stackVar = node.stackTraceParameter.name;
         body.add(js.statement(
             'let # = dart.stackTrace(#);', [stackVar, _visit(name)]));
       }
     }
 
     body.add(_visit(node.body));
+    _catchParameter = savedCatch;
 
     if (node.exceptionType != null) {
       return js.statement('if (dart.is(#, #)) #;', [
-        varName,
+        _catchParameter,
         _emitTypeName(node.exceptionType.type),
         _statement(body)
       ]);
     }
+
     return _statement(body);
   }
 
   @override
   JS.Case visitSwitchCase(SwitchCase node) {
     var expr = _visit(node.expression);
     var body = _visitList(node.statements);
     if (node.labels.isNotEmpty) {
       body.insert(0, js.comment('Unimplemented case labels: ${node.labels}'));
     }
@@ skipping 431 matching lines @@
 
     // TODO(jmesserly): in many cases marking the end will be unncessary.
     printer.mark(_location(node.end));
   }
 
   String _getIdentifier(AstNode node) {
     if (node is SimpleIdentifier) return node.name;
     return null;
   }
 }