[compiler] Fix typing of NumberToString operator.

GeorgNeis · Commit Bot · commit 8bfbe25a7cbe · 2018-01-23T13:23:00.000Z
It must be monotone. R=bmeurer@chromium.org Bug: v8:7354 Change-Id: I08dcd3333518029eef08c074c2b91b5c20ad699e Reviewed-on: https://chromium-review.googlesource.com/880982 Reviewed-by: Benedikt Meurer <bmeurer@chromium.org> Commit-Queue: Georg Neis <neis@chromium.org> Cr-Commit-Position: refs/heads/master@{#50801}
diff --git a/src/compiler/operation-typer.cc b/src/compiler/operation-typer.cc
@@ -507,7 +507,7 @@ Type* OperationTyper::NumberToInt32(Type* type) {
 
 Type* OperationTyper::NumberToString(Type* type) {
   DCHECK(type->Is(Type::Number()));
-
+  if (type->IsNone()) return type;
   if (type->Is(Type::NaN())) return singleton_NaN_string_;
   if (type->Is(cache_.kZeroOrMinusZero)) return singleton_zero_string_;
   return Type::SeqString();
