Rollup merge of #111649 - Nilstrieb:derive-const-param-ty, r=BoxyUwU

Add derive for `core::marker::ConstParamTy`

This makes it easier to implement it for a type, just like `Copy`.

`@BoxyUwU` half asked me to add it

2 files changed, 24 insertions, 0 deletions

diff --git a/compiler/rustc_builtin_macros/src/deriving/bounds.rs b/compiler/rustc_builtin_macros/src/deriving/bounds.rs
index 0481a118906..2c8e6f99c67 100644
--- a/compiler/rustc_builtin_macros/src/deriving/bounds.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/bounds.rs
@@ -27,3 +27,26 @@ pub fn expand_deriving_copy(
 
     trait_def.expand(cx, mitem, item, push);
 }
+
+pub fn expand_deriving_const_param_ty(
+    cx: &mut ExtCtxt<'_>,
+    span: Span,
+    mitem: &MetaItem,
+    item: &Annotatable,
+    push: &mut dyn FnMut(Annotatable),
+    is_const: bool,
+) {
+    let trait_def = TraitDef {
+        span,
+        path: path_std!(marker::ConstParamTy),
+        skip_path_as_bound: false,
+        needs_copy_as_bound_if_packed: false,
+        additional_bounds: Vec::new(),
+        supports_unions: false,
+        methods: Vec::new(),
+        associated_types: Vec::new(),
+        is_const,
+    };
+
+    trait_def.expand(cx, mitem, item, push);
+}
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index 4e5edb4d6b1..ebf1448f55c 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -115,6 +115,7 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
     register_derive! {
         Clone: clone::expand_deriving_clone,
         Copy: bounds::expand_deriving_copy,
+        ConstParamTy: bounds::expand_deriving_const_param_ty,
         Debug: debug::expand_deriving_debug,
         Default: default::expand_deriving_default,
         Eq: eq::expand_deriving_eq,