- Parse the return type of JS during resolution to know what can be instantiated there.

sdk/lib/_internal/compiler/implementation/ssa/nodes.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/nodes.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/ssa/nodes.dart	(revision 15453)
+++ sdk/lib/_internal/compiler/implementation/ssa/nodes.dart	(working copy)
@@ -1509,7 +1509,7 @@
     if (declaredType.slowToString() == 'double') return HType.DOUBLE;
     if (declaredType.slowToString() == 'num') return HType.NUMBER;
     if (declaredType.slowToString() == 'String') return HType.STRING;
-    if (declaredType.slowToString() == 'JSArray') return HType.READABLE_ARRAY;
+    if (declaredType.slowToString() == '=List') return HType.READABLE_ARRAY;

[sra1, 2012/11/29 00:12:51]

I have not figured out how to do it yet, but we should use the typesReturned set
from NativeBehavior.
We would need to compute a least upper bound here since HType does not do big
unions.

Using the NativeBehavior allows us to in future mark JS-calls and DOM methods
with the effects that they cause and are sensitive to.

Also, we might want to extend the annotation and JS-call type with nullability
annotations - I saw elsewhere that you desire the distinction between '=List'
and '=List|Null'.

[ngeoffray, 2012/11/29 11:10:44]

Agree. The current JS form is pretty limited and w'ere trying to do more and
more things with it. We should add more variants to it.

     return HType.UNKNOWN;
   }