Regression test for incremental treatment of rustc_scalar_valid_range_{start,end}.

Author: pnkfelix

src/test/incremental/issue-59524-layout-scalar-valid-range-is-not-unused.rs

@@ -0,0 +1,19 @@
+// We should not see the unused_attributes lint fire for
+// rustc_layout_scalar_valid_range_start, but with this bug we are
+// seeing it fire (on subsequent runs) if incremental compilation is
+// enabled.
+
+// revisions: rpass1 rpass2
+// compile-pass
+
+#![feature(rustc_attrs)]
+#![deny(unused_attributes)]
+
+#[rustc_layout_scalar_valid_range_start(10)]
+#[rustc_layout_scalar_valid_range_end(30)]
+struct RestrictedRange(u32);
+const OKAY_RANGE: RestrictedRange = unsafe { RestrictedRange(20) };
+
+fn main() {
+    OKAY_RANGE.0;
+}