Added for-loop variable tracking and regular closures/initializers captured variable tracking.

pkg/compiler/lib/src/ssa/locals_handler.dart

Index: pkg/compiler/lib/src/ssa/locals_handler.dart
diff --git a/pkg/compiler/lib/src/ssa/locals_handler.dart b/pkg/compiler/lib/src/ssa/locals_handler.dart
index 6c3bb870d8e88a70c69e9b2b79279e12bae32148..3c3ad5dca5a5949d786aeb105f6d6c0d2de5d2f2 100644
--- a/pkg/compiler/lib/src/ssa/locals_handler.dart
+++ b/pkg/compiler/lib/src/ssa/locals_handler.dart
@@ -178,21 +178,20 @@ class LocalsHandler {
 
   /// Replaces the current box with a new box and copies over the given list
   /// of elements from the old box into the new box.
-  void updateCaptureBox(LoopClosureScope loopInfo) {
-    Local boxElement = loopInfo.context;
+  void updateCaptureBox(Local context, List<Local> toBeCopiedElements) {

[Siggi Cherem (dart-lang), 2017/06/30 22:02:10]

nit: maybe rename context or update the comment to undersdtand the connection
here. For example `context` => `currentBox`?

[Emily Fortuna, 2017/06/30 23:48:10]

Done.

     // Create a new box and copy over the values from the old box into the
     // new one.
-    HInstruction oldBox = readLocal(boxElement);
+    HInstruction oldBox = readLocal(context);
     HInstruction newBox = createBox();
-    loopInfo.forEachBoxedVariable((Local boxedVariable, _) {
-      // [readLocal] uses the [boxElement] to find its box. By replacing it
+    for (Local boxedVariable in toBeCopiedElements) {
+      // [readLocal] uses the [context] to find its box. By replacing it
       // behind its back we can still get to the old values.
-      updateLocal(boxElement, oldBox);
+      updateLocal(context, oldBox);
       HInstruction oldValue = readLocal(boxedVariable);
-      updateLocal(boxElement, newBox);
+      updateLocal(context, newBox);
       updateLocal(boxedVariable, oldValue);
-    });
-    updateLocal(boxElement, newBox);
+    }
+    updateLocal(context, newBox);
   }
 
   /// Documentation wanted -- johnniwinther
@@ -478,7 +477,7 @@ class LocalsHandler {
   ///    goto loop-entry;
   ///  loop-exit:
   void startLoop(LoopClosureScope loopInfo) {
-    if (loopInfo.hasBoxedVariables) {
+    if (loopInfo.hasBoxedLoopVariables) {
       // If there are boxed loop variables then we set up the box and
       // redirections already now. This way the initializer can write its
       // values into the box.
@@ -513,7 +512,7 @@ class LocalsHandler {
   void enterLoopBody(LoopClosureScope loopInfo) {
     // If there are no declared boxed loop variables then we did not create the
     // box before the initializer and we have to create the box now.
-    if (!loopInfo.hasBoxedVariables) {
+    if (!loopInfo.hasBoxedLoopVariables) {
       enterScope(loopInfo);
     }
   }
@@ -524,8 +523,8 @@ class LocalsHandler {
     // updates.
     // In all other cases a new box will be created when entering the body of
     // the next iteration.
-    if (loopInfo.hasBoxedVariables) {
-      updateCaptureBox(loopInfo);
+    if (loopInfo.hasBoxedLoopVariables) {
+      updateCaptureBox(loopInfo.context, loopInfo.boxedLoopVariables);
     }
   }