Don't warn when underscore is passed to macro

Author: Jules-Bertholet

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1341,6 +1341,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 }
                 if ident.name == kw::Underscore
                     && !matches!(item.vis.kind, VisibilityKind::Inherited)
+                    && ident.span.eq_ctxt(item.vis.span)
                 {
                     self.lint_buffer.buffer_lint(
                         UNUSED_VISIBILITIES,

tests/ui/lint/unused-visibilities.fixed

@@ -9,4 +9,21 @@
  const _: () = {};
 //~^WARN visibility qualifiers have no effect on `const _` declarations
 
+macro_rules! foo {
+    () => {
+         const _: () = {};
+        //~^WARN visibility qualifiers have no effect on `const _` declarations
+    };
+}
+
+foo!();
+
+macro_rules! bar {
+    ($tt:tt) => {
+        pub const $tt: () = {};
+    };
+}
+
+bar!(_);
+
 fn main() {}

tests/ui/lint/unused-visibilities.rs

@@ -9,4 +9,21 @@ pub const _: () = {};
 pub(self) const _: () = {};
 //~^WARN visibility qualifiers have no effect on `const _` declarations
 
+macro_rules! foo {
+    () => {
+        pub const _: () = {};
+        //~^WARN visibility qualifiers have no effect on `const _` declarations
+    };
+}
+
+foo!();
+
+macro_rules! bar {
+    ($tt:tt) => {
+        pub const $tt: () = {};
+    };
+}
+
+bar!(_);
+
 fn main() {}

tests/ui/lint/unused-visibilities.stderr

@@ -16,5 +16,16 @@ warning: visibility qualifiers have no effect on `const _` declarations
 LL | pub(self) const _: () = {};
    | ^^^^^^^^^ help: remove the qualifier
 
-warning: 2 warnings emitted
+warning: visibility qualifiers have no effect on `const _` declarations
+  --> $DIR/unused-visibilities.rs:14:9
+   |
+LL |         pub const _: () = {};
+   |         ^^^ help: remove the qualifier
+...
+LL | foo!();
+   | ------ in this macro invocation
+   |
+   = note: this warning originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+warning: 3 warnings emitted