Reapply "Distinguish between actual closure scopes and non-closure scopes."

pkg/compiler/lib/src/js_model/closure_visitors.dart

 // Copyright (c) 2017, 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.
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../closure.dart';
 import '../elements/entities.dart';
 import '../kernel/element_map.dart';
 import 'closure.dart';
 
 /// This builder walks the code to determine what variables are captured/free at
 /// various points to build ClosureScope that can respond to queries
 /// about how a particular variable is being used at any point in the code.
 class ClosureScopeBuilder extends ir.Visitor {
   /// A map of each visited call node with the associated information about what
   /// variables are captured/used. Each ir.Node key corresponds to a scope that
   /// was encountered while visiting a closure (initially called through
   /// [translateLazyIntializer] or [translateConstructorOrProcedure]).
-  Map<ir.Node, ClosureScope> _closureInfoMap = <ir.Node, ClosureScope>{};
+  final Map<ir.Node, ClosureScope> _scopesCapturedInClosureMap;
+
+  /// Map entities to their corresponding scope information (such as what
+  /// variables are captured/used).
+  final Map<Entity, ScopeInfo> _scopeInfoMap;
 
   /// A map of the nodes that we have flagged as necessary to generate closure
   /// classes for in a later stage. We map that node to information ascertained
   /// about variable usage in the surrounding scope.
-  Map<ir.TreeNode /* ir.Field | ir.FunctionNode */, ScopeInfo>
-      _closuresToGenerate = <ir.TreeNode, ScopeInfo>{};
+  final Map<ir.TreeNode /* ir.Field | ir.FunctionNode */, ScopeInfo>
+      _closuresToGenerate;
 
   /// The local variables that have been declared in the current scope.
   List<ir.VariableDeclaration> _scopeVariables;
 
   /// Pointer to the context in which this closure is executed.
   /// For example, in the expression `var foo = () => 3 + i;`, the executable
   /// context as we walk the nodes in that expression is the ir.Field `foo`.
   ir.Node _executableContext;
 
   /// A flag to indicate if we are currently inside a closure.
@@ skipping 17 matching lines @@
   bool _inTry = false;
 
   /// Lookup the local entity that corresponds to a kernel variable declaration.
   final KernelToLocalsMap _localsMap;
 
   /// The current scope we are in.
   KernelScopeInfo _currentScopeInfo;
 
   final KernelToElementMap _kernelToElementMap;
 
-  ClosureScopeBuilder(this._closureInfoMap, this._closuresToGenerate,
-      this._localsMap, this._kernelToElementMap);
+  /// The original entity from which we start the tree-walk to find closure and
+  /// scope information.
+  final Entity _originalEntity;
+
+  ClosureScopeBuilder(
+      this._scopesCapturedInClosureMap,
+      this._scopeInfoMap,
+      this._originalEntity,
+      this._closuresToGenerate,
+      this._localsMap,
+      this._kernelToElementMap);
 
   /// Update the [ClosureScope] object corresponding to
   /// this node if any variables are captured.
   void attachCapturedScopeVariables(ir.Node node) {
     Set<Local> capturedVariablesForScope = new Set<Local>();
 
     for (ir.VariableDeclaration variable in _scopeVariables) {
       // No need to box non-assignable elements.
       if (variable.isFinal || variable.isConst) continue;
       if (!_mutatedVariables.contains(variable)) continue;
       if (_capturedVariables.contains(variable)) {
         capturedVariablesForScope.add(_localsMap.getLocal(variable));
       }
     }
     if (!capturedVariablesForScope.isEmpty) {
       ThisLocal thisLocal = null;
       if (node is ir.Member && node.isInstanceMember) {
         if (node is ir.Procedure) {
           thisLocal = new ThisLocal(_kernelToElementMap.getMethod(node));
         } else if (node is ir.Field) {
           thisLocal = new ThisLocal(_kernelToElementMap.getField(node));
         }
       } else if (node is ir.Constructor) {
         thisLocal = new ThisLocal(_kernelToElementMap.getConstructor(node));
       }
 
-      Entity context;
-      if (_executableContext is ir.Member) {
-        context = _kernelToElementMap.getMember(_executableContext);
-      } else {
-        context = _kernelToElementMap.getLocalFunction(_executableContext);
-      }
-      _closureInfoMap[node] =
-          new KernelClosureScope(capturedVariablesForScope, context, thisLocal);
+      assert(_scopeInfoMap[_nodeToEntity(node)] != null);
+      _scopesCapturedInClosureMap[node] = new KernelClosureScope(
+          capturedVariablesForScope,
+          _nodeToEntity(_executableContext),
+          thisLocal);
     }
   }
 
+  Entity _nodeToEntity(ir.Node node) {
+    if (node is ir.Member) {
+      return _kernelToElementMap.getMember(node);
+    } else {
+      return _kernelToElementMap.getLocalFunction(node);
+    }
+  }
+
   /// Perform book-keeping with the current set of local variables that have
   /// been seen thus far before entering this new scope.
   void enterNewScope(ir.Node node, Function visitNewScope) {
     List<ir.VariableDeclaration> oldScopeVariables = _scopeVariables;
     _scopeVariables = <ir.VariableDeclaration>[];
     visitNewScope();
     attachCapturedScopeVariables(node);
     _mutatedVariables.removeAll(_scopeVariables);
     _scopeVariables = oldScopeVariables;
   }
@@ skipping 77 matching lines @@
       // See if we have declared loop variables that need to be boxed.
       for (ir.VariableDeclaration variable in node.variables) {
         // Non-mutated variables should not be boxed.  The _mutatedVariables set
         // gets cleared when `enterNewScope` returns, so check it here.
         if (_capturedVariables.contains(variable) &&
             _mutatedVariables.contains(variable)) {
           boxedLoopVariables.add(_localsMap.getLocal(variable));
         }
       }
     });
-    KernelClosureScope scope = _closureInfoMap[node];
+    KernelClosureScope scope = _scopesCapturedInClosureMap[node];
     if (scope == null) return;
-    _closureInfoMap[node] = new KernelLoopClosureScope(scope.boxedVariables,
-        boxedLoopVariables, scope.context, scope.thisLocal);
+    _scopesCapturedInClosureMap[node] = new KernelLoopClosureScope(
+        scope.boxedVariables,
+        boxedLoopVariables,
+        scope.context,
+        scope.thisLocal);
   }
 
   void visitInvokable(ir.TreeNode node) {
     bool oldIsInsideClosure = _isInsideClosure;
     ir.Node oldExecutableContext = _executableContext;
     KernelScopeInfo oldScopeInfo = _currentScopeInfo;
 
     // _outermostNode is only null the first time we enter the body of the
     // field, constructor, or method that is being analyzed.
     _isInsideClosure = _outermostNode != null;
     _executableContext = node;
-    if (!_isInsideClosure) {
+    _currentScopeInfo = new KernelScopeInfo(_nodeToThisLocal(node));
+    if (_isInsideClosure) {
+      _closuresToGenerate[node] = _currentScopeInfo;
+    } else {
       _outermostNode = node;
+      _scopeInfoMap[_originalEntity] = _currentScopeInfo;
     }
-    _currentScopeInfo = new KernelScopeInfo(_nodeToThisLocal(node));
-    _closuresToGenerate[node] = _currentScopeInfo;
 
     enterNewScope(node, () {
       node.visitChildren(this);
     });
 
     KernelScopeInfo savedScopeInfo = _currentScopeInfo;
     bool savedIsInsideClosure = _isInsideClosure;
 
     // Restore old values.
     _isInsideClosure = oldIsInsideClosure;
@@ skipping 55 matching lines @@
               nodeToConvert.isInstanceMember)) {
         return new ThisLocal(_kernelToElementMap.getConstructor(nodeToConvert));
       } else if (nodeToConvert is ir.Procedure &&
           nodeToConvert.isInstanceMember) {
         return new ThisLocal(_kernelToElementMap.getMethod(nodeToConvert));
       }
     }
     return null;
   }
 }