Use delay_span_bug instead of panic in layout_scalar_valid_range

83054 introduced validation of scalar range attributes, but panicking
code that uses the attribute remained reachable. Use `delay_span_bug`
instead to avoid the ICE.

compiler/rustc_middle/src/ty/context.rs

@@ -1091,13 +1091,16 @@ impl<'tcx> TyCtxt<'tcx> {
                 None => return Bound::Unbounded,
             };
             debug!("layout_scalar_valid_range: attr={:?}", attr);
-            for meta in attr.meta_item_list().expect("rustc_layout_scalar_valid_range takes args") {
-                match meta.literal().expect("attribute takes lit").kind {
-                    ast::LitKind::Int(a, _) => return Bound::Included(a),
-                    _ => span_bug!(attr.span, "rustc_layout_scalar_valid_range expects int arg"),
-                }
+            if let Some(
+                &[ast::NestedMetaItem::Literal(ast::Lit { kind: ast::LitKind::Int(a, _), .. })],
+            ) = attr.meta_item_list().as_deref()
+            {
+                Bound::Included(a)
+            } else {
+                self.sess
+                    .delay_span_bug(attr.span, "invalid rustc_layout_scalar_valid_range attribute");
+                Bound::Unbounded
             }
-            span_bug!(attr.span, "no arguments to `rustc_layout_scalar_valid_range` attribute");
         };
         (
             get(sym::rustc_layout_scalar_valid_range_start),

src/test/ui/invalid/invalid_rustc_layout_scalar_valid_range.rs

@@ -15,6 +15,13 @@ enum E {
     Y = 14,
 }
 
+#[rustc_layout_scalar_valid_range_start(rustc_layout_scalar_valid_range_start)] //~ ERROR
+struct NonZero<T>(T);
+
+fn not_field() -> impl Send {
+    NonZero(false)
+}
+
 fn main() {
     let _ = A(0);
     let _ = B(0);

src/test/ui/invalid/invalid_rustc_layout_scalar_valid_range.stderr

@@ -27,5 +27,11 @@ LL | |     Y = 14,
 LL | | }
    | |_- not a struct
 
-error: aborting due to 4 previous errors
+error: expected exactly one integer literal argument
+  --> $DIR/invalid_rustc_layout_scalar_valid_range.rs:18:1
+   |
+LL | #[rustc_layout_scalar_valid_range_start(rustc_layout_scalar_valid_range_start)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors