CPS implementation of throw and rethrow.

pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
index a0fb612a58386c835b435fd0df6fdb595739bdaa..9985c94238817fc53740c5e4128d485febf25762 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
@@ -1764,13 +1764,15 @@ abstract class IrBuilder {
       LocalVariableElement exceptionVariable =
           catchClauseInfo.exceptionVariable;
       ir.Parameter exceptionParameter = new ir.Parameter(exceptionVariable);
-      catchBuilder.environment.extend(exceptionVariable, exceptionParameter);
+      catchBuilder.declareLocalVariable(exceptionVariable,

[Kevin Millikin (Google), 2015/04/17 09:52:10]

It is necessary to 'declare' these parameters in case they are captured by a
closure.  This helper function will emit the backend-specific boxing code in
case they are captured.

+                                        initialValue: exceptionParameter);
       ir.Parameter traceParameter;
       LocalVariableElement stackTraceVariable =
           catchClauseInfo.stackTraceVariable;
       if (stackTraceVariable != null) {
         traceParameter = new ir.Parameter(stackTraceVariable);
-        catchBuilder.environment.extend(stackTraceVariable, traceParameter);
+        catchBuilder.declareLocalVariable(stackTraceVariable,
+                                          initialValue: traceParameter);
       } else {
         // Use a dummy continuation parameter for the stack trace parameter.
         // This will ensure that all handlers have two parameters and so they
@@ -1881,6 +1883,23 @@ abstract class IrBuilder {
     return false;
   }
 
+  void buildThrow(ir.Primitive value) {
+    assert(isOpen);
+    add(new ir.Throw(value));
+    _current = null;
+  }
+
+  ir.Primitive buildNonTailThrow(ir.Primitive value) {
+    assert(isOpen);
+    return addPrimitive(new ir.NonTailThrow(value));
+  }
+
+  void buildRethrow() {
+    assert(isOpen);
+    add(new ir.Rethrow());

[asgerf, 2015/04/17 10:33:01]

I would imagine this needs a reference to the exception variable in JS.

[Kevin Millikin (Google), 2015/04/17 11:17:07]

It will be translated by the unsugar pass to 'throw e' where e is that variable.

+    _current = null;
+  }
+
   /// Create a negation of [condition].
   ir.Primitive buildNegation(ir.Primitive condition) {
     // ! e is translated as e ? false : true