Implementation of async-await transformation on js ast.

pkg/compiler/lib/src/closure.dart

Index: pkg/compiler/lib/src/closure.dart
diff --git a/pkg/compiler/lib/src/closure.dart b/pkg/compiler/lib/src/closure.dart
index 93e7bb2c2b87e60d99bc6d8ac0dcad80f3a7c8c9..b72f6a8e3df831d5ec5cf34b1d76342128af3cab 100644
--- a/pkg/compiler/lib/src/closure.dart
+++ b/pkg/compiler/lib/src/closure.dart
@@ -272,6 +272,7 @@ class SynthesizedCallMethodElementX extends BaseFunctionElementX {
                                 ClosureClassElement enclosing)
       : expression = other,
         super(name, other.kind, other.modifiers, enclosing, false) {
+    asyncMarker = other.asyncMarker;
     functionSignatureCache = other.functionSignature;
   }
 
@@ -347,7 +348,7 @@ class ClosureClassMap {
   // contain any nested closure.
   final Map<Node, ClosureScope> capturingScopes = new Map<Node, ClosureScope>();
 
-  final Set<Local> usedVariablesInTry = new Set<Local>();
+  final Set<Local> variablesUsedInTryOrGenerator = new Set<Local>();

[floitsch, 2015/02/02 22:00:06]

Add comment.
Not every variable in a generator is in this set.

[sigurdm, 2015/02/03 16:59:27]

Done.

 
   ClosureClassMap(this.closureElement,
                   this.closureClassElement,
@@ -427,6 +428,7 @@ class ClosureTranslator extends Visitor {
   int closureFieldCounter = 0;
   int boxedFieldCounter = 0;
   bool inTryStatement = false;
+
   final Map<Node, ClosureClassMap> closureMappingCache;
 
   // Map of captured variables. Initially they will map to `null`. If
@@ -589,8 +591,14 @@ class ClosureTranslator extends Visitor {
       if (variable != closureData.thisLocal &&
           variable != closureData.closureElement) {
         // TODO(ngeoffray): only do this if the variable is mutated.

[floitsch, 2015/02/02 22:00:06]

We should have an "isEffectivelyFinal" getter on variables.
Johnni already talked about it some time ago.

Merge the TODOs (here and in line 600) and ask Johnni if we can put his ldap
into the TODO.

[sigurdm, 2015/02/03 16:59:27]

Done.

-        closureData.usedVariablesInTry.add(variable);
+        closureData.variablesUsedInTryOrGenerator.add(variable);
       }
+    } else if (variable is LocalParameterElement &&
+        variable.functionDeclaration.asyncMarker == AsyncMarker.SYNC_STAR) {
+      // Parameters in a sync* function are shared between each Iterator created
+      // by the Iterable returned by the function, therefore they must be boxed.
+      // TODO(sigurdm): only do this if the variable is mutated.
+      closureData.variablesUsedInTryOrGenerator.add(variable);
     }
   }