Only apply NoMangle lint to plain const items

Author: reddevilmidzy

compiler/rustc_lint/src/builtin.rs

@@ -997,18 +997,23 @@ impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
                     self.check_no_mangle_on_generic_fn(cx, attr_span, it.owner_id.def_id);
                 }
             }
-            hir::ItemKind::Const(..) => {
+            hir::ItemKind::Const(_, generics, ..) => {
                 if find_attr!(attrs, AttributeKind::NoMangle(..)) {
-                    // account for "pub const" (#45562)
-                    let start = cx
-                        .tcx
-                        .sess
-                        .source_map()
-                        .span_to_snippet(it.span)
-                        .map(|snippet| snippet.find("const").unwrap_or(0))
-                        .unwrap_or(0) as u32;
-                    // `const` is 5 chars
-                    let suggestion = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
+                    let suggestion =
+                        if generics.params.is_empty() && !generics.has_where_clause_predicates {
+                            // account for "pub const" (#45562)
+                            let start = cx
+                                .tcx
+                                .sess
+                                .source_map()
+                                .span_to_snippet(it.span)
+                                .map(|snippet| snippet.find("const").unwrap_or(0))
+                                .unwrap_or(0) as u32;
+                            // `const` is 5 chars
+                            Some(it.span.with_hi(BytePos(it.span.lo().0 + start + 5)))
+                        } else {
+                            None
+                        };
 
                     // Const items do not refer to a particular location in memory, and therefore
                     // don't have anything to attach a symbol to

compiler/rustc_lint/src/lints.rs

@@ -230,7 +230,7 @@ pub(crate) struct BuiltinNoMangleGeneric {
 #[diag(lint_builtin_const_no_mangle)]
 pub(crate) struct BuiltinConstNoMangle {
     #[suggestion(code = "pub static", applicability = "machine-applicable")]
-    pub suggestion: Span,
+    pub suggestion: Option<Span>,
 }
 
 #[derive(LintDiagnostic)]

tests/ui/lint/force-warn/no-mangle-const-suggestion-suppressed.rs

@@ -0,0 +1,21 @@
+//! Ensure the `no_mangle_const_items` lint triggers but does not offer a `pub static`
+//! suggestion for consts that have generics or a where-clause.
+//! regression test for <https://github.com/rust-lang/rust/issues/149511>
+//@ check-pass
+//@ compile-flags: --force-warn no_mangle_const_items
+
+#![feature(generic_const_items)]
+#![allow(incomplete_features)]
+trait Trait {
+    const ASSOC: u32;
+}
+
+#[unsafe(no_mangle)]
+const WHERE_BOUND: u32 = <&'static ()>::ASSOC where for<'a> &'a (): Trait;
+//~^ WARN: const items should never be `#[no_mangle]`
+
+#[unsafe(no_mangle)]
+pub const GENERIC<const N: usize>: usize = N;
+//~^ WARN: const items should never be `#[no_mangle]`
+
+fn main() {}

tests/ui/lint/force-warn/no-mangle-const-suggestion-suppressed.stderr

@@ -0,0 +1,16 @@
+warning: const items should never be `#[no_mangle]`
+  --> $DIR/no-mangle-const-suggestion-suppressed.rs:14:1
+   |
+LL | const WHERE_BOUND: u32 = <&'static ()>::ASSOC where for<'a> &'a (): Trait;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: requested on the command line with `--force-warn no-mangle-const-items`
+
+warning: const items should never be `#[no_mangle]`
+  --> $DIR/no-mangle-const-suggestion-suppressed.rs:18:1
+   |
+LL | pub const GENERIC<const N: usize>: usize = N;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: 2 warnings emitted
+