From 9e8cbe813fc4b290196d292686fd43eeef0923ef Mon Sep 17 00:00:00 2001
From: N5N3 <2642243996@qq.com>
Date: Mon, 18 Dec 2023 21:12:45 +0800
Subject: [PATCH] inference: fix `istuple` check in `apply_type_tfunc`

---
 base/compiler/tfuncs.jl    | 2 +-
 test/compiler/inference.jl | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/base/compiler/tfuncs.jl b/base/compiler/tfuncs.jl
index bb8712458e0be..a5790c052e24b 100644
--- a/base/compiler/tfuncs.jl
+++ b/base/compiler/tfuncs.jl
@@ -1743,7 +1743,7 @@ const _tvarnames = Symbol[:_A, :_B, :_C, :_D, :_E, :_F, :_G, :_H, :_I, :_J, :_K,
         end
         return allconst ? Const(ty) : Type{ty}
     end
-    istuple = isa(headtype, Type) && (headtype == Tuple)
+    istuple = headtype === Tuple
     if !istuple && !isa(headtype, UnionAll) && !isvarargtype(headtype)
         return Union{}
     end
diff --git a/test/compiler/inference.jl b/test/compiler/inference.jl
index c71fd3ca9b265..5e302f1743008 100644
--- a/test/compiler/inference.jl
+++ b/test/compiler/inference.jl
@@ -5609,3 +5609,8 @@ let x = 1, _Any = Any
     foo27031() = bar27031((x, 1.0), Val{_Any})
     @test foo27031() == "OK"
 end
+
+# Issue #51927
+let 𝕃 = Core.Compiler.fallback_lattice
+    @test apply_type_tfunc(𝕃, Const(Tuple{Vararg{Any,N}} where N), Int) == Type{NTuple{_A, Any}} where _A
+end