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

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

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
@@ skipping 1491 matching lines @@
         _isStatement = true,
         super(inputs);
   accept(HVisitor visitor) => visitor.visitForeign(this);
 
   static HType computeTypeFromDeclaredType(DartString declaredType) {
     if (declaredType.slowToString() == 'bool') return HType.BOOLEAN;
     if (declaredType.slowToString() == 'int') return HType.INTEGER;
     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;
   }
 
   HType get guaranteedType => foreignType;
 
   bool isJsStatement(HTypeMap types) => _isStatement;
 }
 
 class HForeignNew extends HForeign {
   ClassElement element;
@@ skipping 1417 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty);
     return statements.last.end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }