Add boxed fields in closure classes.

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

Index: pkg/compiler/lib/src/js_model/closure_visitors.dart
diff --git a/pkg/compiler/lib/src/js_model/closure_visitors.dart b/pkg/compiler/lib/src/js_model/closure_visitors.dart
index d5e291b10098c7d615295ecf0268fa994d9a02c3..0447a7d07b7f25d339f87ecc57fe5b639148bc2f 100644
--- a/pkg/compiler/lib/src/js_model/closure_visitors.dart
+++ b/pkg/compiler/lib/src/js_model/closure_visitors.dart
@@ -34,7 +34,7 @@ class CapturedScopeBuilder extends ir.Visitor {
   /// 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;
+  ir.TreeNode _executableContext;
 
   /// A flag to indicate if we are currently inside a closure.
   bool _isInsideClosure = false;
@@ -61,6 +61,10 @@ class CapturedScopeBuilder extends ir.Visitor {
 
   final bool _hasThisLocal;
 
+  /// Keeps track of the number of boxes that we've created so that they each
+  /// have unique names.
+  int _boxCounter = 0;
+
   CapturedScopeBuilder(this._model, {bool hasThisLocal})
       : this._hasThisLocal = hasThisLocal;
 
@@ -84,6 +88,8 @@ class CapturedScopeBuilder extends ir.Visitor {
       KernelScopeInfo from = _model.scopeInfo;
       _scopesCapturedInClosureMap[node] = new KernelCapturedScope(
           capturedVariablesForScope,
+          new NodeBox(getBoxName(), _executableContext,
+              _getMemberContext(_executableContext)),

[Johnni Winther, 2017/08/01 09:09:10]

The member context is not needed. See comment in [_constructClosureFields].

[Emily Fortuna, 2017/08/01 19:30:06]

got it.

           _currentLocalFunction,
           from.localsUsedInTryOrSync,
           from.freeVariables,
@@ -91,6 +97,35 @@ class CapturedScopeBuilder extends ir.Visitor {
     }
   }
 
+  /// Look up the outermost member that contains this node.
+  ///
+  /// For top level, static or instance members, the member context is the
+  /// node itself. For parameters, local variables and nested closures, the
+  /// member context is the top level, static or instance member in which it is
+  /// defined.
+  ir.Member _getMemberContext(ir.TreeNode startNode) {
+    ir.TreeNode node = startNode;
+    while (node is! ir.Member && node != _outermostNode) {
+      node = node.parent;
+    }
+    assert(node is ir.Member);
+    return node;
+  }
+
+  /// Generate a unique name for the [_boxCounter]th box field.
+  ///
+  /// The result is used as the name of [NodeBox]s and [BoxLocal]s, and must
+  /// therefore be unique to avoid breaking an invariant in the element model
+  /// (classes cannot declare multiple fields with the same name).
+  ///
+  /// Also, the names should be distinct from real field names to prevent
+  /// clashes with selectors for those fields.
+  ///
+  /// These names are not used in generated code, just as element name.
+  String getBoxName() {
+    return "_box_${_boxCounter++}";
+  }
+
   /// 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, void visitNewScope()) {
@@ -192,6 +227,7 @@ class CapturedScopeBuilder extends ir.Visitor {
     if (scope == null) return;
     _scopesCapturedInClosureMap[node] = new KernelCapturedLoopScope(
         scope.boxedVariables,
+        scope.capturedVariablesAccessor,
         boxedLoopVariables,
         scope.context,
         scope.localsUsedInTryOrSync,
@@ -201,7 +237,7 @@ class CapturedScopeBuilder extends ir.Visitor {
 
   void visitInvokable(ir.TreeNode node) {
     bool oldIsInsideClosure = _isInsideClosure;
-    ir.Node oldExecutableContext = _executableContext;
+    ir.TreeNode oldExecutableContext = _executableContext;
     KernelScopeInfo oldScopeInfo = _currentScopeInfo;
     ir.TreeNode oldLocalFunction = _currentLocalFunction;