[turbofan] Fix typing rule for CheckBounds.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index ca5f7b47b4d32865cff77cac6c9db6cb84c15454..c44d191652e076639122dfe80b0551dc01e86c6f 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -1810,6 +1810,9 @@ Type* Typer::Visitor::TypeStringIndexOf(Node* node) {
 Type* Typer::Visitor::TypeCheckBounds(Node* node) {
   Type* index = Operand(node, 0);
   Type* length = Operand(node, 1);
+  if (index->Maybe(Type::MinusZero())) {
+    index = Type::Union(index, typer_->cache_.kSingletonZero, zone());
+  }
   index = Type::Intersect(index, Type::Integral32(), zone());
   if (!index->IsInhabited() || !length->IsInhabited()) return Type::None();
   double min = std::max(index->Min(), 0.0);