Explicitly depend on ena in rustc_type_ir and make the UnifyKey and UnifyValue imports non-nightly

Author: jackh726

Cargo.lock

@@ -4581,6 +4581,7 @@ version = "0.0.0"
 dependencies = [
  "bitflags",
  "derive-where",
+ "ena",
  "indexmap",
  "rustc-hash 1.1.0",
  "rustc_ast_ir",

compiler/rustc_type_ir/Cargo.toml

@@ -7,6 +7,7 @@ edition = "2024"
 # tidy-alphabetical-start
 bitflags = "2.4.1"
 derive-where = "1.2.7"
+ena = "0.14.3"
 indexmap = "2.0.0"
 rustc-hash = "1.1.0"
 rustc_ast_ir = { path = "../rustc_ast_ir", default-features = false }

compiler/rustc_type_ir/src/ty_kind.rs

@@ -2,12 +2,13 @@ use std::fmt;
 use std::ops::Deref;
 
 use derive_where::derive_where;
+// We *would* normally import these through `rustc_data_structures`, but external
+// users (i.e. rust-analyzer) may need the impls for these traits.
+use ena::unify::{NoError, UnifyKey, UnifyValue};
 use rustc_ast_ir::Mutability;
 #[cfg(feature = "nightly")]
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 #[cfg(feature = "nightly")]
-use rustc_data_structures::unify::{NoError, UnifyKey, UnifyValue};
-#[cfg(feature = "nightly")]
 use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_NoContext};
 use rustc_type_ir_macros::{Lift_Generic, TypeFoldable_Generic, TypeVisitable_Generic};
 
@@ -796,7 +797,6 @@ pub enum InferTy {
 
 /// Raw `TyVid` are used as the unification key for `sub_relations`;
 /// they carry no values.
-#[cfg(feature = "nightly")]
 impl UnifyKey for TyVid {
     type Value = ();
     #[inline]
@@ -812,7 +812,6 @@ impl UnifyKey for TyVid {
     }
 }
 
-#[cfg(feature = "nightly")]
 impl UnifyValue for IntVarValue {
     type Error = NoError;
 
@@ -832,7 +831,6 @@ impl UnifyValue for IntVarValue {
     }
 }
 
-#[cfg(feature = "nightly")]
 impl UnifyKey for IntVid {
     type Value = IntVarValue;
     #[inline] // make this function eligible for inlining - it is quite hot.
@@ -848,7 +846,6 @@ impl UnifyKey for IntVid {
     }
 }
 
-#[cfg(feature = "nightly")]
 impl UnifyValue for FloatVarValue {
     type Error = NoError;
 
@@ -866,7 +863,6 @@ impl UnifyValue for FloatVarValue {
     }
 }
 
-#[cfg(feature = "nightly")]
 impl UnifyKey for FloatVid {
     type Value = FloatVarValue;
     #[inline]