Implement cycle-checking and code generation for redirecting constructors.

frog/leg/ssa/builder.dart

Index: frog/leg/ssa/builder.dart
diff --git a/frog/leg/ssa/builder.dart b/frog/leg/ssa/builder.dart
index 20007b41b5f6caa303862715e7de68caefd0ca4c..35c21f70e80bcbc8f6a73c2c125405a92d8aa8f5 100644
--- a/frog/leg/ssa/builder.dart
+++ b/frog/leg/ssa/builder.dart
@@ -547,19 +547,17 @@ class SsaBuilder implements Visitor {
       if (link.head is !SendSet) {
         // A super initializer or constructor redirection.
         Send call = link.head;
-        if (Initializers.isSuperConstructorCall(call)) {
-          assert(nextConstructor === null);
-          nextConstructor = elements[call];
-          // Visit arguments and map the corresponding parameter value to
-          // the resulting HInstruction value.
-          forEachArgument(call, nextConstructor, (parameter, node) {
-            visit(node);
-            HInstruction value = pop();
-            localsHandler.updateLocal(parameter, value);
-          });
-        } else {
-          compiler.unimplemented('SsaBuilder.buildFactory redirect');
-        }
+        assert(Initializers.isSuperConstructorCall(call) ||
+               Initializers.isConstructorRedirect(call));
+        assert(nextConstructor === null);
+        nextConstructor = elements[call];
+        // Visit arguments and map the corresponding parameter value to
+        // the resulting HInstruction value.
+        forEachArgument(call, nextConstructor, (parameter, node) {
+          visit(node);
+          HInstruction value = pop();
+          localsHandler.updateLocal(parameter, value);
+        });
       } else {
         // A field initializer.
         SendSet init = link.head;