Preserve type variables in closure conversion.

pkg/kernel/lib/transformations/closure/info.dart

Index: pkg/kernel/lib/transformations/closure/info.dart
diff --git a/pkg/kernel/lib/transformations/closure/info.dart b/pkg/kernel/lib/transformations/closure/info.dart
index 68b82c1dc5e51e0c5fd4393e813aafc780f3a49d..082209aeca85e1da8a789d85dcff7d8c313e2460 100644
--- a/pkg/kernel/lib/transformations/closure/info.dart
+++ b/pkg/kernel/lib/transformations/closure/info.dart
@@ -30,6 +30,8 @@ class ClosureInfo extends RecursiveVisitor {
 
   final Set<VariableDeclaration> variables = new Set<VariableDeclaration>();
 
+  /// Map from functions to set of type variables captured within them.
+  ///

[karlklose, 2017/07/25 09:38:23]

Remove empty comment line.

[sjindel, 2017/07/25 13:11:48]

Done.

   final Map<FunctionNode, Set<TypeParameter>> typeVariables =
       <FunctionNode, Set<TypeParameter>>{};
 
@@ -166,7 +168,8 @@ class ClosureInfo extends RecursiveVisitor {
       // Propagate captured type variables to enclosing function.
       typeVariables
           .putIfAbsent(currentFunction, () => new Set<TypeParameter>())
-          .addAll(capturedTypeVariables);
+          .addAll(
+              capturedTypeVariables.where((t) => t.parent != currentFunction));

[karlklose, 2017/07/25 09:38:23]

Consider adding a comment here to explain when 't.parent == currentFunction'
(also below).

[sjindel, 2017/07/25 13:11:48]

Done.

[Dmitry Stefantsov, 2017/07/26 09:12:09]

Karl may correct me, but I think using square brackets in comments in situations
like this won't produce the intended result.  I think, only identifiers can be
put into square brackets to be later turned into hyperlinks in the extracted
documentation.  I use backticks for fragments of code like this one.

[karlklose, 2017/07/26 10:36:30]

Yes, you should use `` for code fragments. Note that they will not be analyzed
by tools when they appear in normal (//) comments, but we still use them for
uniformity.

     }
   }
 
@@ -190,7 +193,7 @@ class ClosureInfo extends RecursiveVisitor {
   }
 
   visitTypeParameterType(TypeParameterType node) {
-    if (!isOuterMostContext) {
+    if (!isOuterMostContext && node.parameter.parent != currentFunction) {
       typeVariables
           .putIfAbsent(currentFunction, () => new Set<TypeParameter>())
           .add(node.parameter);