Change how preview=in is detected

Geod24 · Geod24 · commit 683fbc765237 · 2023-02-28T12:25:52.000+01:00
This is a minor internal change, but will allow us to deprecate in ref at the parser level.
diff --git 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)
 {

Original file line number	Diff line number	Diff line change
`@@ -1829,7 +1829,8 @@ enum HasToStringResult`
`1829`	`1829`	`customPutWriterFormatSpec,`
`1830`	`1830`	`}`
`1831`	`1831`
`1832`		`-private enum hasPreviewIn = !is(typeof(mixin(q{(in ref int a) => a})));`
	`1832`	`+private alias DScannerBug895 = int[256];`
	`1833`	`+private immutable bool hasPreviewIn = ((in DScannerBug895 a) { return __traits(isRef, a); })(DScannerBug895.init);`
`1833`	`1834`
`1834`	`1835`	`template hasToString(T, Char)`
`1835`	`1836`	`{`