[turbofan] First step towards sanitizing for-in and making it optimizable.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index dafd3c95a128f317d0033d1d0b6aeb2e0441f0a2..782c8e3352a2c09b43936b573d6826656b70ad07 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -1602,6 +1602,30 @@ Bounds Typer::Visitor::TypeJSCallRuntime(Node* node) {
 }
 
 
+Bounds Typer::Visitor::TypeJSForInNext(Node* node) {
+  return Bounds(Type::None(zone()),
+                Type::Union(Type::Name(), Type::Undefined(), zone()));
+}
+
+
+Bounds Typer::Visitor::TypeJSForInPrepare(Node* node) {
+  // TODO(bmeurer): Return a tuple type here.
+  return Bounds::Unbounded(zone());
+}
+
+
+Bounds Typer::Visitor::TypeJSForInDone(Node* node) {
+  return Bounds(Type::None(zone()), Type::Boolean(zone()));
+}
+
+
+Bounds Typer::Visitor::TypeJSForInStep(Node* node) {
+  STATIC_ASSERT(Map::EnumLengthBits::kMax <= FixedArray::kMaxLength);
+  return Bounds(Type::None(zone()),
+                Type::Range(1, FixedArray::kMaxLength + 1, zone()));
+}
+
+
 Bounds Typer::Visitor::TypeJSStackCheck(Node* node) {
   return Bounds::Unbounded(zone());
 }