[WIP] NumberToString operator in TF.

src/compiler/operation-typer.cc

Index: src/compiler/operation-typer.cc
diff --git a/src/compiler/operation-typer.cc b/src/compiler/operation-typer.cc
index f3ef778dc020d40213b1f5b2bb984031421816e5..564b3981020d72787fcf98d818b150cdd428bc7c 100644
--- a/src/compiler/operation-typer.cc
+++ b/src/compiler/operation-typer.cc
@@ -17,7 +17,7 @@ namespace internal {
 namespace compiler {
 
 OperationTyper::OperationTyper(Isolate* isolate, Zone* zone)
-    : zone_(zone), cache_(TypeCache::Get()) {
+    : isolate_(isolate), zone_(zone), cache_(TypeCache::Get()) {
   Factory* factory = isolate->factory();
   infinity_ = Type::Constant(factory->infinity_value(), zone);
   minus_infinity_ = Type::Constant(factory->minus_infinity_value(), zone);
@@ -484,6 +484,25 @@ Type* OperationTyper::NumberToUint32(Type* type) {
   return Type::Unsigned32();
 }
 
+Type* OperationTyper::NumberToString(Type* lhs, Type* rhs) {
+  DCHECK(lhs->Is(Type::Number()));
+  DCHECK(rhs->Is(Type::Unsigned30()));
+  if (!lhs->IsInhabited()) return Type::None();
+  if (lhs->Is(Type::NaN())) {
+    return Type::Constant(factory()->nan_string(), zone());
+  }
+  if (lhs->Is(cache_.kZeroish)) {
+    return Type::Constant(factory()->zero_string(), zone());
+  }
+  if (lhs->Is(infinity_)) {
+    return Type::Constant(factory()->infinity_string(), zone());
+  }
+  if (lhs->Is(minus_infinity_)) {
+    return Type::Constant(factory()->minus_infinity_string(), zone());
+  }
+  return Type::String();
+}
+
 Type* OperationTyper::NumberSilenceNaN(Type* type) {
   DCHECK(type->Is(Type::Number()));
   // TODO(jarin): This is a terrible hack; we definitely need a dedicated type
@@ -963,6 +982,8 @@ Type* OperationTyper::TypeTypeGuard(const Operator* sigma_op, Type* input) {
   return Type::Intersect(input, TypeGuardTypeOf(sigma_op), zone());
 }
 
+Factory* OperationTyper::factory() const { return isolate()->factory(); }
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8