Preserve type variables in closure conversion.

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

 // Copyright (c) 2016, 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.
 
 library kernel.transformations.closure.info;
 
 import '../../ast.dart'
     show
         Class,
         Constructor,
@@ skipping 12 matching lines @@
 
 import '../../visitor.dart' show RecursiveVisitor;
 
 class ClosureInfo extends RecursiveVisitor {
   FunctionNode currentFunction;
   final Map<VariableDeclaration, FunctionNode> function =
       <VariableDeclaration, FunctionNode>{};
 
   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>>{};
 
   /// Map from members to synthetic variables for accessing `this` in a local
   /// function.
   final Map<FunctionNode, VariableDeclaration> thisAccess =
       <FunctionNode, VariableDeclaration>{};
 
   final Set<String> currentMemberLocalNames = new Set<String>();
 
@@ skipping 116 matching lines @@
     saveCurrentFunction(() {
       currentFunction = node;
       node.visitChildren(this);
     });
 
     Set<TypeParameter> capturedTypeVariables = typeVariables[node];
     if (capturedTypeVariables != null && !isOuterMostContext) {
       // 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.

     }
   }
 
   visitVariableDeclaration(VariableDeclaration node) {
     function[node] = currentFunction;
     node.visitChildren(this);
   }
 
   visitVariableGet(VariableGet node) {
     if (function[node.variable] != currentFunction) {
       variables.add(node.variable);
     }
     node.visitChildren(this);
   }
 
   visitVariableSet(VariableSet node) {
     if (function[node.variable] != currentFunction) {
       variables.add(node.variable);
     }
     node.visitChildren(this);
   }
 
   visitTypeParameterType(TypeParameterType node) {
-    if (!isOuterMostContext) {
+    if (!isOuterMostContext && node.parameter.parent != currentFunction) {
       typeVariables
           .putIfAbsent(currentFunction, () => new Set<TypeParameter>())
           .add(node.parameter);
     }
   }
 
   visitThisExpression(ThisExpression node) {
     if (!isOuterMostContext) {
       thisAccess.putIfAbsent(
           currentMemberFunction, () => new VariableDeclaration("#self"));
     }
   }
 
   saveCurrentFunction(void f()) {
     var saved = currentFunction;
     try {
       f();
     } finally {
       currentFunction = saved;
     }
   }
 }