Rollup merge of rust-lang#87027 - petrochenkov:builderhelp, r=oli-obk

expand: Support helper attributes for built-in derive macros

This is needed for rust-lang#86735 (derive macro `Default` should have a helper attribute `default`).

With this PR we can specify helper attributes for built-in derives using syntax `#[rustc_builtin_macro(MacroName, attributes(attr1, attr2, ...))]` which mirrors equivalent syntax for proc macros `#[proc_macro_derive(MacroName, attributes(attr1, attr2, ...))]`.
Otherwise expansion infra was already ready for this.
The attribute parsing code is shared between proc macro derives and built-in macros (`fn parse_macro_name_and_helper_attrs`).

Author: GuillaumeGomez

core/src/macros/mod.rs

@@ -1,6 +1,7 @@
 #[doc = include_str!("panic.md")]
 #[macro_export]
-#[rustc_builtin_macro = "core_panic"]
+#[cfg_attr(bootstrap, rustc_builtin_macro = "core_panic")]
+#[cfg_attr(not(bootstrap), rustc_builtin_macro(core_panic))]
 #[allow_internal_unstable(edition_panic)]
 #[stable(feature = "core", since = "1.6.0")]
 #[rustc_diagnostic_item = "core_panic_macro"]

std/src/macros.rs

@@ -6,7 +6,8 @@
 
 #[doc = include_str!("../../core/src/macros/panic.md")]
 #[macro_export]
-#[rustc_builtin_macro = "std_panic"]
+#[cfg_attr(bootstrap, rustc_builtin_macro = "std_panic")]
+#[cfg_attr(not(bootstrap), rustc_builtin_macro(std_panic))]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow_internal_unstable(edition_panic)]
 #[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_macro")]