From 79eb75a8dd64848f23e9efc465f06326b5d4b680 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Wed, 29 Nov 2023 14:40:21 +0900
Subject: [PATCH] [Bug #20025] Check if upper/lower before fallback to
 case-folding

---
 symbol.c                       | 4 ++--
 test/-ext-/symbol/test_type.rb | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/symbol.c b/symbol.c
index 2447b1ec10..6a0c926db8 100644
--- a/symbol.c
+++ b/symbol.c
@@ -225,10 +225,10 @@ rb_sym_constant_char_p(const char *name, long nlen, rb_encoding *enc)
     if (!MBCLEN_CHARFOUND_P(c)) return FALSE;
     len = MBCLEN_CHARFOUND_LEN(c);
     c = rb_enc_mbc_to_codepoint(name, end, enc);
+    if (rb_enc_isupper(c, enc)) return TRUE;
+    if (rb_enc_islower(c, enc)) return FALSE;
     if (ONIGENC_IS_UNICODE(enc)) {
         static int ctype_titlecase = 0;
-        if (rb_enc_isupper(c, enc)) return TRUE;
-        if (rb_enc_islower(c, enc)) return FALSE;
         if (!ctype_titlecase) {
             static const UChar cname[] = "titlecaseletter";
             static const UChar *const end = cname + sizeof(cname) - 1;
diff --git a/test/-ext-/symbol/test_type.rb b/test/-ext-/symbol/test_type.rb
index fdee692fe4..2b0fbe5b79 100644
--- a/test/-ext-/symbol/test_type.rb
+++ b/test/-ext-/symbol/test_type.rb
@@ -134,5 +134,10 @@ module Test_Symbol
         Bug::Symbol.find(cx)
       }
     end
+
+    def test_const_name_type
+      sym = "\xb5".force_encoding(Encoding::Windows_1253)
+      assert_not_operator Bug::Symbol, :const?, sym, sym.encode(Encoding::UTF_8)
+    end
   end
 end