Auto merge of rust-lang#16698 - regexident:param-derives, r=Veykril

Derive `PartialEq`, `Eq` & `Hash` for `hir::Param`

Since `hir::SelfParam`, as well as all members of `hir::Param` already implement `PartialEq`, `Eq` & `Hash` it seems reasonable to also make `hir::Param` implement those.

(the change is motivated by an outside use of the `ra_ap_hir` crate that would benefit from being able to collect params in a `HashSet`)

Author: bors

crates/hir/src/lib.rs

@@ -2088,7 +2088,7 @@ impl From<hir_ty::Mutability> for Access {
     }
 }
 
-#[derive(Clone, Debug)]
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub struct Param {
     func: Function,
     /// The index in parameter list, including self parameter.