Implementation of async-await transformation on js ast.

pkg/compiler/lib/src/ssa/nodes.dart

Index: pkg/compiler/lib/src/ssa/nodes.dart
diff --git a/pkg/compiler/lib/src/ssa/nodes.dart b/pkg/compiler/lib/src/ssa/nodes.dart
index 7337b7b14c7a41568c706f8ce58ad313f60a836d..6a643ed8890b5526c8ec9788af3505b9505b56d8 100644
--- a/pkg/compiler/lib/src/ssa/nodes.dart
+++ b/pkg/compiler/lib/src/ssa/nodes.dart
@@ -6,6 +6,7 @@ part of ssa;
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
+  R visitAwait(HAwait node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
@@ -71,6 +72,7 @@ abstract class HVisitor<R> {
   R visitTry(HTry node);
   R visitTypeConversion(HTypeConversion node);
   R visitTypeKnown(HTypeKnown node);
+  R visitYield(HYield node);
   R visitReadTypeVariable(HReadTypeVariable node);
   R visitFunctionType(HFunctionType node);
   R visitVoidType(HVoidType node);
@@ -354,6 +356,8 @@ class HBaseVisitor extends HGraphVisitor implements HVisitor {
   visitVoidType(HVoidType node) => visitInstruction(node);
   visitInterfaceType(HInterfaceType node) => visitInstruction(node);
   visitDynamicType(HDynamicType node) => visitInstruction(node);
+  visitAwait(HAwait node) => visitInstruction(node);
+  visitYield(HYield node) => visitInstruction(node);
 }
 
 class SubGraph {
@@ -2234,6 +2238,25 @@ class HThrowExpression extends HInstruction {
   bool canThrow() => true;
 }
 
+class HAwait extends HInstruction {
+  HAwait(HInstruction value, TypeMask type)
+      : super(<HInstruction>[value], type);
+  toString() => 'await';
+  accept(HVisitor visitor) => visitor.visitAwait(this);
+  bool canThrow() => inputs[0].canThrow(); // TODO is this true?

[floitsch, 2015/02/02 22:00:11]

I don't think that's correct.

I believe an await can throw, if the future is not "correct".

var myFakeFuture = new BadFuture();  // (throwing for `then`);
await myFakeFuture; // BOOM.

[sigurdm, 2015/02/03 16:59:32]

Thanks

+  SideEffects sideEffects = new SideEffects();
+}
+
+class HYield extends HInstruction {
+  HYield(HInstruction value, this.hasStar)
+      : super(<HInstruction>[value], const TypeMask.nonNullEmpty());
+  bool hasStar;
+  toString() => 'yield';
+  accept(HVisitor visitor) => visitor.visitYield(this);
+  bool canThrow() => inputs[0].canThrow(); // TODO is this true?

[floitsch, 2015/02/02 22:00:11]

ditto. I don't think this is correct.
This should only be true, if yield(x) can throw for any evaluated x. That is, if
the following can throw: var t = x; yield(t);

[sigurdm, 2015/02/03 16:59:32]

Done.

+  SideEffects sideEffects = new SideEffects();
+}
+
 class HThrow extends HControlFlow {
   final bool isRethrow;
   HThrow(value, {this.isRethrow: false}) : super(<HInstruction>[value]);