suggest adding a #[macro_export] to a private macro

Author: TaKO8Ki

compiler/rustc_resolve/src/imports.rs

@@ -12,7 +12,7 @@ use rustc_ast::NodeId;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::intern::Interned;
 use rustc_errors::{pluralize, struct_span_err, Applicability, MultiSpan};
-use rustc_hir::def::{self, PartialRes};
+use rustc_hir::def::{self, DefKind, PartialRes};
 use rustc_middle::metadata::ModChild;
 use rustc_middle::span_bug;
 use rustc_middle::ty;
@@ -922,11 +922,35 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                         .note(&format!("consider declaring type or module `{}` with `pub`", ident))
                         .emit();
                 } else {
-                    let note_msg =
-                        format!("consider marking `{}` as `pub` in the imported module", ident);
-                    struct_span_err!(self.r.session, import.span, E0364, "{}", error_msg)
-                        .span_note(import.span, &note_msg)
-                        .emit();
+                    let mut err =
+                        struct_span_err!(self.r.session, import.span, E0364, "{error_msg}");
+                    match binding.kind {
+                        NameBindingKind::Res(Res::Def(DefKind::Macro(_), _def_id), _)
+                            // exclude decl_macro
+                            if !self.r.session.features_untracked().decl_macro
+                                || !self
+                                    .r
+                                    .session
+                                    .source_map()
+                                    .span_to_snippet(binding.span)
+                                    .map(|snippet| snippet.starts_with("macro "))
+                                    .unwrap_or(true) =>
+                        {
+                            err.span_help(
+                                binding.span,
+                                "consider adding a `#[macro_export]` to the macro in the imported module",
+                            );
+                        }
+                        _ => {
+                            err.span_note(
+                                import.span,
+                                &format!(
+                                    "consider marking `{ident}` as `pub` in the imported module"
+                                ),
+                            );
+                        }
+                    }
+                    err.emit();
                 }
             }
         }

src/test/ui/privacy/macro-private-reexport.rs

@@ -0,0 +1,11 @@
+// edition:2018
+
+mod foo {
+    macro_rules! bar {
+        () => {};
+    }
+
+    pub use bar as _; //~ ERROR `bar` is only public within the crate, and cannot be re-exported outside
+}
+
+fn main() {}

src/test/ui/privacy/macro-private-reexport.stderr

@@ -0,0 +1,17 @@
+error[E0364]: `bar` is only public within the crate, and cannot be re-exported outside
+  --> $DIR/macro-private-reexport.rs:8:13
+   |
+LL |     pub use bar as _;
+   |             ^^^^^^^^
+   |
+help: consider adding a `#[macro_export]` to the macro in the imported module
+  --> $DIR/macro-private-reexport.rs:4:5
+   |
+LL | /     macro_rules! bar {
+LL | |         () => {};
+LL | |     }
+   | |_____^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0364`.

src/test/ui/rust-2018/uniform-paths/macro-rules.stderr

@@ -4,11 +4,11 @@ error[E0364]: `legacy_macro` is only public within the crate, and cannot be re-e
 LL |     pub use legacy_macro as _;
    |             ^^^^^^^^^^^^^^^^^
    |
-note: consider marking `legacy_macro` as `pub` in the imported module
-  --> $DIR/macro-rules.rs:11:13
+help: consider adding a `#[macro_export]` to the macro in the imported module
+  --> $DIR/macro-rules.rs:7:5
    |
-LL |     pub use legacy_macro as _;
-   |             ^^^^^^^^^^^^^^^^^
+LL |     macro_rules! legacy_macro { () => () }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0659]: `legacy_macro` is ambiguous
   --> $DIR/macro-rules.rs:31:13