From 683fbc7652376924565b50d232a8931210d4800c Mon Sep 17 00:00:00 2001
From: Geod24 <pro.mathias.lang@gmail.com>
Date: Tue, 28 Feb 2023 11:33:57 +0100
Subject: [PATCH] Change how preview=in is detected

This is a minor internal change, but will allow us to deprecate in ref at the parser level.
---
 std/format/internal/write.d | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/std/format/internal/write.d b/std/format/internal/write.d
index 3a6842b3cd6..7f127c09847 100644
--- a/std/format/internal/write.d
+++ b/std/format/internal/write.d
@@ -1829,7 +1829,8 @@ enum HasToStringResult
     customPutWriterFormatSpec,
 }
 
-private enum hasPreviewIn = !is(typeof(mixin(q{(in ref int a) => a})));
+private alias DScannerBug895 = int[256];
+private immutable bool hasPreviewIn = ((in DScannerBug895 a) { return __traits(isRef, a); })(DScannerBug895.init);
 
 template hasToString(T, Char)
 {