dart2js: Smaller async error sequence when only one handler

tests/compiler/dart2js/async_await_js_transform_test.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.
 
 import "package:expect/expect.dart";
 import "package:compiler/src/js/js.dart";
 import "package:compiler/src/js/rewrite_async.dart";
 import "package:compiler/src/js_backend/js_backend.dart" show StringBackedName;
 
 void testTransform(String source, String expected, AsyncRewriterBase rewriter) {
@@ skipping 46 matching lines @@
   var closures = [new A.main_closure()], v0 = await closures, v1 = 0, v2, v3;
   if (v1 < 0 || v1 >= v0.length)
     H.ioore(v0, v1);
   v2 = 4;
   v3 = 2;
   P.print(v0[v1].call$2(v2, v3));
 }""",
 
           /// 01: ok
           r"""function() {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError, closures, v0, v1, v2, v3;
+  var __goto = 0, __completer = NewCompleter(), closures, v0, v1, v2, v3;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
           closures = [new A.main_closure()];
           __goto = 2;
           return awaitHelper(closures, body);
         case 2:
           // returning from await.
           v0 = __result;
           v1 = 0;
           if (v1 < 0 || v1 >= v0.length)
             H.ioore(v0, v1);
           v2 = 4;
           v3 = 2;
           P.print(v0[v1].call$2(v2, v3));
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""")
 
       /// 01: ok
       ;
 
   testAsyncTransform(
       """
 function(a) async {
   print(this.x); // Ensure `this` is translated in the helper function.
   await foo();
 }""",
       """
 function(a) {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError, __self = this;
+  var __goto = 0, __completer = NewCompleter(), __self = this;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
           print(__self.x);
           __goto = 2;
           return awaitHelper(foo(), body);
         case 2:
           // returning from await.
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
   function(b) async {
     try {
       __outer: while (true) { // Overlapping label name.
@@ skipping 124 matching lines @@
   var a, b, c, d, e, f;
   a = b++; // post- and preincrements.
   b = --b;
   c = (await foo()).a++;
   d = ++(await foo()).a;
   e = foo1()[await foo2()]--;
   f = --foo1()[await foo2()];
 }""",
       """
 function(c) {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError, a, b, c, d, e, f, __temp1;
+  var __goto = 0, __completer = NewCompleter(), a, b, c, d, e, f, __temp1;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
           a = b++;
           b = --b;
           __goto = 2;
           return awaitHelper(foo(), body);
         case 2:
           // returning from await.
@@ skipping 10 matching lines @@
           // returning from await.
           e = __temp1[__result]--;
           __temp1 = foo1();
           __goto = 5;
           return awaitHelper(foo2(), body);
         case 5:
           // returning from await.
           f = --__temp1[__result];
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
   function(d2) async {
     var a, b, c, d, e, f, g, h; // empty initializer
     a = foo1() || await foo2(); // short circuiting operators
     b = await foo1() || foo2();
     c = await foo1() || foo3(await foo2());
     d = foo1() || foo2();
     e = foo1() && await foo2();
     f = await foo1() && foo2();
     g = await foo1() && await foo2();
     h = foo1() && foo2();
   }""",
       """
 function(d2) {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError, a, b, c, d, e, f, g, h, __temp1;
+  var __goto = 0, __completer = NewCompleter(), a, b, c, d, e, f, g, h, __temp1;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
           __temp1 = foo1();
           if (__temp1)
             __result = __temp1;
           else {
             // goto then
             __goto = 2;
@@ skipping 86 matching lines @@
           __goto = 17;
           return awaitHelper(foo2(), body);
         case 17:
           // returning from await.
         case 15:
           // join
           g = __result;
           h = foo1() && foo2();
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
 function(x, y) async {
   while (true) {
     switch(y) { // Switch with no awaits in case key expressions
       case 0:
       case 1: 
         await foo();
         continue; // Continue the loop, not the switch
       case 1: // Duplicate case
         await foo();
         break; // Break the switch
       case 2:
         foo(); // No default
     }
   }
 }""",
       """
 function(x, y) {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError;
+  var __goto = 0, __completer = NewCompleter();
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
         case 2:
           // while condition
         case 4:
           // switch
           switch (y) {
             case 0:
@@ skipping 43 matching lines @@
           foo();
         case 5:
           // after switch
           // goto while condition
           __goto = 2;
           break;
         case 3:
           // after while
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
   function(f) async {
     do {
       var a = await foo();
       if (a) // If with no awaits in body
         break;
       else
         continue;
     } while (await foo());
   }
   """,
       """
 function(f) {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError, a;
+  var __goto = 0, __completer = NewCompleter(), a;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
         case 2:
           // do body
           __goto = 5;
           return awaitHelper(foo(), body);
         case 5:
           // returning from await.
@@ skipping 15 matching lines @@
           // returning from await.
           if (__result) {
             // goto do body
             __goto = 2;
             break;
           }
         case 4:
           // after do
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
 function(g) async {
   for (var i = 0; i < await foo1(); i += await foo2()) {
     if (foo(i))
       continue;
     else
       break;
     if (!foo(i)) { // If with no else and await in body.
       await foo();
       return;
     }
     print(await(foo(i)));
   } 
 }
 """,
       """
 function(g) {
-  var __goto = 0, __completer = NewCompleter(), __returnValue, __handler = 2, __currentError, i, __temp1;
+  var __goto = 0, __completer = NewCompleter(), __returnValue, i, __temp1;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
           i = 0;
         case 3:
           // for condition
           __temp1 = i;
           __goto = 6;
           return awaitHelper(foo1(), body);
@@ skipping 40 matching lines @@
           // returning from await.
           i += __result;
           // goto for condition
           __goto = 3;
           break;
         case 5:
           // after for
         case 1:
           // return
           return returnHelper(__returnValue, __completer);
-        case 2:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
   function(a, h) async {
     var x = {"a": foo1(), "b": await foo2(), "c": foo3()};
     x["a"] = 2; // Different assignments
     (await foo()).a = 3;
     x[await foo()] = 4;
     x[(await foo1()).a = await foo2()] = 5;
     (await foo1())[await foo2()] = await foo3(6);
   }
   """,
       """
 function(a, h) {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError, x, __temp1, __temp2;
+  var __goto = 0, __completer = NewCompleter(), x, __temp1, __temp2;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
           __temp1 = foo1();
           __goto = 2;
           return awaitHelper(foo2(), body);
         case 2:
           // returning from await.
           x = {a: __temp1, b: __result, c: foo3()};
@@ skipping 30 matching lines @@
         case 8:
           // returning from await.
           __temp2 = __result;
           __goto = 9;
           return awaitHelper(foo3(6), body);
         case 9:
           // returning from await.
           __temp1[__temp2] = __result;
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
 function(c, i) async {
   try {
     var x = c ? await foo() : foo(); // conditional
@@ skipping 116 matching lines @@
   function(x, y, j) async {
     print(await(foo(x))); // calls
     (await print)(foo(x));
     print(foo(await x));
     await (print(foo(await x)));
     print(foo(x, await y, z));
   }
   """,
       """
 function(x, y, j) {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError, __temp1, __temp2, __temp3;
+  var __goto = 0, __completer = NewCompleter(), __temp1, __temp2, __temp3;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
           __temp1 = print;
           __goto = 2;
           return awaitHelper(foo(x), body);
         case 2:
           // returning from await.
           __temp1(__result);
@@ skipping 22 matching lines @@
           __temp1 = print;
           __temp2 = foo;
           __temp3 = x;
           __goto = 7;
           return awaitHelper(y, body);
         case 7:
           // returning from await.
           __temp1(__temp2(__temp3, __result, z));
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
 function(x, y, k) async {
   while (await(foo())) {
     lab: { // labelled statement
@@ skipping 14 matching lines @@
         }
       default: // default case
         break lab; // break to label
       }
       foo();
     }
   }
 }""",
       """
 function(x, y, k) {
-  var __goto = 0, __completer = NewCompleter(), __returnValue, __handler = 2, __currentError, __temp1;
+  var __goto = 0, __completer = NewCompleter(), __returnValue, __temp1;
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
         case 3:
           // while condition
           __goto = 5;
           return awaitHelper(foo(), body);
         case 5:
           // returning from await.
@@ skipping 79 matching lines @@
         case 6:
           // break lab
           // goto while condition
           __goto = 3;
           break;
         case 4:
           // after while
         case 1:
           // return
           return returnHelper(__returnValue, __completer);
-        case 2:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
   function(l) async {
     switch(await l) {
       case 1:
         print(1);
         break;
       case 2:
         print(1);
         // Fallthrough
       default:
         print(2);
         break;
     }
   }""",
       """
 function(l) {
-  var __goto = 0, __completer = NewCompleter(), __handler = 1, __currentError;
+  var __goto = 0, __completer = NewCompleter();
   var body = _wrapJsFunctionForAsync(function(__errorCode, __result) {
-    if (__errorCode === 1) {
-      __currentError = __result;
-      __goto = __handler;
-    }
+    if (__errorCode === 1)
+      return rethrowHelper(__result, __completer);
     while (true)
       switch (__goto) {
         case 0:
           // Function start
           __goto = 2;
           return awaitHelper(l, body);
         case 2:
           // returning from await.
           switch (__result) {
             case 1:
               print(1);
               break;
             case 2:
               print(1);
             default:
               print(2);
               break;
           }
           // implicit return
           return returnHelper(null, __completer);
-        case 1:
-          // rethrow
-          return rethrowHelper(__currentError, __completer);
       }
   });
   return startHelper(body, __completer);
 }""");
 
   testAsyncTransform(
       """
   function(m) async {
     var exception = 1;
     try {
@@ skipping 102 matching lines @@
             // return
             return endOfIteration();
           case 2:
             // rethrow
             return uncaughtError(__currentError);
         }
     };
   });
 }""");
 }