Auto merge of #133274 - ehuss:macro_rules-edition-from-pm, r=<try>

Use edition of `macro_rules` when compiling the macro

This changes the edition assigned to a macro_rules macro when it is compiled to use the edition of where the macro came from instead of the local crate's edition.

This fixes a problem when a macro_rules macro is created by a proc-macro. Previously that macro would be tagged with the local edition, which would cause problems with using the correct edition behavior inside the macro. For example, the check for unsafe attributes would cause errors in 2024 when using proc-macros from older editions.

This is partially related to #132906. Unfortunately this is only a half fix for that issue. It fixes the error that happens in 2024, but does not fix the lint firing in 2021. I'm still trying to think of some way to fix that, but I'm running low on ideas.

compiler/rustc_resolve/src/def_collector.rs

@@ -191,7 +191,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
             ItemKind::Const(..) => DefKind::Const,
             ItemKind::Fn(..) | ItemKind::Delegation(..) => DefKind::Fn,
             ItemKind::MacroDef(def) => {
-                let edition = self.resolver.tcx.sess.edition();
+                let edition = i.span.edition();
                 let macro_data =
                     self.resolver.compile_macro(def, i.ident, &i.attrs, i.span, i.id, edition);
                 let macro_kind = macro_data.ext.macro_kind();

tests/ui/proc-macro/auxiliary/macro_rules_edition_pm.rs

@@ -0,0 +1,42 @@
+//@ force-host
+//@ no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn make_edition_macro(_input: TokenStream) -> TokenStream {
+    "macro_rules! edition {
+        ($_:expr) => {
+            2024
+        };
+        (const {}) => {
+            2021
+        };
+    }
+    "
+    .parse()
+    .unwrap()
+}
+
+#[proc_macro]
+pub fn make_nested_edition_macro(_input: TokenStream) -> TokenStream {
+    "macro_rules! make_inner {
+        () => {
+            macro_rules! edition_inner {
+                ($_:expr) => {
+                    2024
+                };
+                (const {}) => {
+                    2021
+                };
+            }
+        };
+    }
+    "
+    .parse()
+    .unwrap()
+}

tests/ui/proc-macro/macro_rules_edition_from_pm.rs

@@ -0,0 +1,27 @@
+// Tests how edition hygiene works for macro_rules macros generated from a
+// proc-macro.
+// See https://github.com/rust-lang/rust/issues/132906
+
+//@ aux-crate: macro_rules_edition_pm=macro_rules_edition_pm.rs
+//@ revisions: edition2021 edition2024
+//@[edition2021] edition:2021
+//@[edition2024] edition:2024
+//@[edition2024] compile-flags: -Zunstable-options
+//@ check-pass
+
+// This checks how the expr fragment specifier works.
+macro_rules_edition_pm::make_edition_macro!{}
+
+const _: () = {
+    assert!(edition!(const {}) == 2021);
+};
+
+// This checks how the expr fragment specifier from a nested macro.
+macro_rules_edition_pm::make_nested_edition_macro!{}
+make_inner!{}
+
+const _: () = {
+    assert!(edition_inner!(const {}) == 2021);
+};
+
+fn main() {}

tests/ui/rust-2024/unsafe-attributes/auxiliary/unsafe-attributes-pm.rs

@@ -0,0 +1,22 @@
+//@ force-host
+//@ no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn missing_unsafe(_input: TokenStream) -> TokenStream {
+    "#[no_mangle] pub fn abc() {}".parse().unwrap()
+}
+
+#[proc_macro]
+pub fn macro_rules_missing_unsafe(_input: TokenStream) -> TokenStream {
+    "macro_rules! make_fn {
+        () => { #[no_mangle] pub fn foo() { } };
+    }"
+    .parse()
+    .unwrap()
+}

tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-from-pm.rs

@@ -0,0 +1,17 @@
+// Test for unsafe attributes generated by a proc-macro.
+// See https://github.com/rust-lang/rust/issues/132906
+
+//@ revisions: edition2021 edition2024
+//@ check-pass
+//@[edition2021] edition:2021
+//@[edition2024] edition:2024
+//@[edition2024] compile-flags: -Zunstable-options
+//@ aux-crate: unsafe_attributes_pm=unsafe-attributes-pm.rs
+
+unsafe_attributes_pm::missing_unsafe!();
+
+unsafe_attributes_pm::macro_rules_missing_unsafe!();
+
+make_fn!();
+
+fn main() {}