Rollup merge of #92875 - BoxyUwU:infer_arg_opt_const_param_of, r=lcnr

Make `opt_const_param_of` work in the presence of `GenericArg::Infer`

highly recommend viewing the first and second commits on their own rather than looking at file changes :rofl:

Because we filtered args down to just const args we would ignore `GenericArg::Infer` which made us get a `arg_index` which was wrong by however many const `GenericArg::Infer` came previously

[example](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=46dba6a53aca6333028a10908ef16e0b) of the [bugs](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=a8eebced26eefa4119fc2e7ae0c76de6) fixed.

r? ```@lcnr```

1 files changed, 7 insertions, 0 deletions

diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index 1c3a01e2cfa..0bd96f8f865 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -31,6 +31,13 @@ impl GenericParamDefKind {
             GenericParamDefKind::Const { .. } => ast::ParamKindOrd::Const,
         }
     }
+
+    pub fn is_ty_or_const(&self) -> bool {
+        match self {
+            GenericParamDefKind::Lifetime => false,
+            GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => true,
+        }
+    }
 }
 
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]