Fix renaming of exception variables on left-hand-sides.

Also fix compound assignments.

BUG=
R=floitsch@google.com

Review URL: https://codereview.chromium.org//1012783002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@44558 260f80e4-7a28-3924-810f-c04153c831b5

pkg/compiler/lib/src/js/rewrite_async.dart

@@ -749,7 +749,12 @@ abstract class AsyncRewriterBase extends js.NodeVisitor {
     js.Expression leftHandSide = node.leftHandSide;
     if (leftHandSide is js.VariableUse) {
       return withExpression(node.value, (js.Expression value) {
-        return new js.Assignment(leftHandSide, value);
+        // A non-compound [js.Assignment] has `op==null`. So it works out to
+        // use [js.Assignment.compound] for all cases.
+        // Visit the [js.VariableUse] to ensure renaming is done correctly.
+        return new js.Assignment.compound(visitExpression(leftHandSide),
+                                          node.op,
+                                          value);
       }, store: false);
     } else if (leftHandSide is js.PropertyAccess) {
       return withExpressions([
@@ -1211,7 +1216,7 @@ abstract class AsyncRewriterBase extends js.NodeVisitor {
     if (node.op == "++" || node.op == "--") {
       js.Expression argument = node.argument;
       if (argument is js.VariableUse) {
-        return new js.Postfix(node.op, argument);
+        return new js.Postfix(node.op, visitExpression(argument));
       } else if (argument is js.PropertyAccess) {
         return withExpression2(argument.receiver, argument.selector,
             (receiver, selector) {
@@ -1233,7 +1238,7 @@ abstract class AsyncRewriterBase extends js.NodeVisitor {
     if (node.op == "++" || node.op == "--") {
       js.Expression argument = node.argument;
       if (argument is js.VariableUse) {
-        return new js.Prefix(node.op, argument);
+        return new js.Prefix(node.op, visitExpression(argument));
       } else if (argument is js.PropertyAccess) {
         return withExpression2(argument.receiver, argument.selector,
             (receiver, selector) {
@@ -1528,7 +1533,7 @@ abstract class AsyncRewriterBase extends js.NodeVisitor {
 
   @override
   js.Expression visitVariableDeclarationList(js.VariableDeclarationList node) {
-    List<js.Assignment> initializations = new List<js.Assignment>();
+    List<js.Expression> initializations = new List<js.Expression>();
 
     // Declaration of local variables is hoisted outside the helper but the
     // initialization is done here.

pkg/js_ast/lib/src/nodes.dart

@@ -611,6 +611,7 @@ class Assignment extends Expression {
 
   Assignment(leftHandSide, value)
       : this.compound(leftHandSide, null, value);
+  // If `this.op == null` this will be a non-compound assignment.
   Assignment.compound(this.leftHandSide, this.op, this.value);
 
   int get precedenceLevel => ASSIGNMENT;

tests/compiler/dart2js/async_await_js_transform_test.dart

@@ -597,7 +597,7 @@ function(g) {
           return thenHelper(foo2(), __body, __completer);
         case 11:
           // returning from await.
-          i = __result;
+          i += __result;
           // goto for condition
           __goto = 3;
           break;
@@ -1059,4 +1059,83 @@ function(l) {
   }
   return thenHelper(null, __body, __completer, null);
 }""");
+
+  testTransform("""
+  function(m) async {
+    var exception = 1;
+    try {
+      await 42;
+      throw 42;
+    } catch (exception) {
+      exception = await 10;
+      exception += await 10;
+      exception++;
+      exception--;
+      ++exception;
+      --exception;
+      exception += 10;
+    }
+    print(exception);
+  }""", """
+function(m) {
+  var __goto = 0, __completer = new Completer(), __handler = 1, __currentError, __next = [], exception, __exception;
+  function __body(__errorCode, __result) {
+    if (__errorCode === 1) {
+      __currentError = __result;
+      __goto = __handler;
+    }
+    while (true)
+      switch (__goto) {
+        case 0:
+          // Function start
+          exception = 1;
+          __handler = 3;
+          __goto = 6;
+          return thenHelper(42, __body, __completer);
+        case 6:
+          // returning from await.
+          throw 42;
+          __handler = 1;
+          // goto after finally
+          __goto = 5;
+          break;
+        case 3:
+          // catch
+          __handler = 2;
+          __exception = __currentError;
+          __goto = 7;
+          return thenHelper(10, __body, __completer);
+        case 7:
+          // returning from await.
+          __exception = __result;
+          __goto = 8;
+          return thenHelper(10, __body, __completer);
+        case 8:
+          // returning from await.
+          __exception += __result;
+          __exception++;
+          __exception--;
+          ++__exception;
+          --__exception;
+          __exception += 10;
+          // goto after finally
+          __goto = 5;
+          break;
+        case 2:
+          // uncaught
+          // goto rethrow
+          __goto = 1;
+          break;
+        case 5:
+          // after finally
+          print(exception);
+          // implicit return
+          return thenHelper(null, 0, __completer, null);
+        case 1:
+          // rethrow
+          return thenHelper(__currentError, 1, __completer);
+      }
+  }
+  return thenHelper(null, __body, __completer, null);
+}""");
 }

tests/language/async_await_catch_regression_test.dart

@@ -0,0 +1,26 @@
+// 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.
+
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+foo() async {
+  throw 42;
+}
+
+test() async {
+  var exception;
+  try {
+    await foo();
+  } catch (e) {
+    print(await(e));
+    await (exception = await e);
+  }
+  Expect.equals(42, exception);
+}
+
+main() {
+  asyncStart();
+  test().then((_) => asyncEnd());
+}