Auto merge of #88710 - Mark-Simulacrum:tyvid-idx, r=jackh726

Use index newtyping for TyVid

This is useful for using TyVid in types like VecGraph, and just otherwise seems like a small win.

compiler/rustc_infer/src/infer/fudge.rs

@@ -187,7 +187,7 @@ fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
                 if self.type_vars.0.contains(&vid) {
                     // This variable was created during the fudging.
                     // Recreate it with a fresh variable here.
-                    let idx = (vid.index - self.type_vars.0.start.index) as usize;
+                    let idx = (vid.as_usize() - self.type_vars.0.start.as_usize()) as usize;
                     let origin = self.type_vars.1[idx];
                     self.infcx.next_ty_var(origin)
                 } else {

compiler/rustc_infer/src/infer/type_variable.rs

@@ -196,7 +196,7 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
     /// Note that this function does not return care whether
     /// `vid` has been unified with something else or not.
     pub fn var_diverges(&self, vid: ty::TyVid) -> Diverging {
-        self.storage.values.get(vid.index as usize).diverging
+        self.storage.values.get(vid.index()).diverging
     }
 
     /// Returns the origin that was given when `vid` was created.
@@ -204,7 +204,7 @@ pub fn var_diverges(&self, vid: ty::TyVid) -> Diverging {
     /// Note that this function does not return care whether
     /// `vid` has been unified with something else or not.
     pub fn var_origin(&self, vid: ty::TyVid) -> &TypeVariableOrigin {
-        &self.storage.values.get(vid.index as usize).origin
+        &self.storage.values.get(vid.as_usize()).origin
     }
 
     /// Records that `a == b`, depending on `dir`.
@@ -269,7 +269,7 @@ pub fn new_var(
         assert_eq!(eq_key.vid, sub_key);
 
         let index = self.values().push(TypeVariableData { origin, diverging });
-        assert_eq!(eq_key.vid.index, index as u32);
+        assert_eq!(eq_key.vid.as_u32(), index as u32);
 
         debug!(
             "new_var(index={:?}, universe={:?}, diverging={:?}, origin={:?}",
@@ -357,11 +357,11 @@ pub fn vars_since_snapshot(
         &mut self,
         value_count: usize,
     ) -> (Range<TyVid>, Vec<TypeVariableOrigin>) {
-        let range = TyVid { index: value_count as u32 }..TyVid { index: self.num_vars() as u32 };
+        let range = TyVid::from_usize(value_count)..TyVid::from_usize(self.num_vars());
         (
             range.start..range.end,
-            (range.start.index..range.end.index)
-                .map(|index| self.storage.values.get(index as usize).origin)
+            (range.start.as_usize()..range.end.as_usize())
+                .map(|index| self.storage.values.get(index).origin)
                 .collect(),
         )
     }
@@ -371,7 +371,7 @@ pub fn vars_since_snapshot(
     pub fn unsolved_variables(&mut self) -> Vec<ty::TyVid> {
         (0..self.storage.values.len())
             .filter_map(|i| {
-                let vid = ty::TyVid { index: i as u32 };
+                let vid = ty::TyVid::from_usize(i);
                 match self.probe(vid) {
                     TypeVariableValue::Unknown { .. } => Some(vid),
                     TypeVariableValue::Known { .. } => None,
@@ -424,10 +424,10 @@ impl<'tcx> ut::UnifyKey for TyVidEqKey<'tcx> {
     type Value = TypeVariableValue<'tcx>;
     #[inline(always)]
     fn index(&self) -> u32 {
-        self.vid.index
+        self.vid.as_u32()
     }
     fn from_index(i: u32) -> Self {
-        TyVidEqKey::from(ty::TyVid { index: i })
+        TyVidEqKey::from(ty::TyVid::from_u32(i))
     }
     fn tag() -> &'static str {
         "TyVidEqKey"

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1244,7 +1244,7 @@ fn report_closure_arg_mismatch(
             let sig = if let ty::Tuple(inputs) = inputs.kind() {
                 tcx.mk_fn_sig(
                     inputs.iter().map(|k| k.expect_ty()),
-                    tcx.mk_ty_infer(ty::TyVar(ty::TyVid { index: 0 })),
+                    tcx.mk_ty_infer(ty::TyVar(ty::TyVid::from_u32(0))),
                     false,
                     hir::Unsafety::Normal,
                     abi::Abi::Rust,
@@ -1252,7 +1252,7 @@ fn report_closure_arg_mismatch(
             } else {
                 tcx.mk_fn_sig(
                     std::iter::once(inputs),
-                    tcx.mk_ty_infer(ty::TyVar(ty::TyVid { index: 0 })),
+                    tcx.mk_ty_infer(ty::TyVar(ty::TyVid::from_u32(0))),
                     false,
                     hir::Unsafety::Normal,
                     abi::Abi::Rust,

compiler/rustc_type_ir/src/lib.rs

@@ -363,10 +363,11 @@ pub enum IntVarValue {
 #[derive(Clone, Copy, PartialEq, Eq)]
 pub struct FloatVarValue(pub FloatTy);
 
-/// A **ty**pe **v**ariable **ID**.
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Encodable, Decodable)]
-pub struct TyVid {
-    pub index: u32,
+rustc_index::newtype_index! {
+    /// A **ty**pe **v**ariable **ID**.
+    pub struct TyVid {
+        DEBUG_FORMAT = "_#{}t"
+    }
 }
 
 /// An **int**egral (`u32`, `i32`, `usize`, etc.) type **v**ariable **ID**.
@@ -422,10 +423,10 @@ pub enum InferTy {
 impl UnifyKey for TyVid {
     type Value = ();
     fn index(&self) -> u32 {
-        self.index
+        self.as_u32()
     }
     fn from_index(i: u32) -> TyVid {
-        TyVid { index: i }
+        TyVid::from_u32(i)
     }
     fn tag() -> &'static str {
         "TyVid"
@@ -558,7 +559,7 @@ impl<CTX> HashStable<CTX> for InferTy {
     fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
         use InferTy::*;
         match self {
-            TyVar(v) => v.index.hash_stable(ctx, hasher),
+            TyVar(v) => v.as_u32().hash_stable(ctx, hasher),
             IntVar(v) => v.index.hash_stable(ctx, hasher),
             FloatVar(v) => v.index.hash_stable(ctx, hasher),
             FreshTy(v) | FreshIntTy(v) | FreshFloatTy(v) => v.hash_stable(ctx, hasher),
@@ -587,12 +588,6 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     }
 }
 
-impl fmt::Debug for TyVid {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "_#{}t", self.index)
-    }
-}
-
 impl fmt::Debug for IntVid {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "_#{}i", self.index)

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -742,7 +742,7 @@ fn report_function<T: std::fmt::Display>(
                                 let projection_ty = pred.skip_binder().projection_ty;
 
                                 let substs_with_infer_self = tcx.mk_substs(
-                                    iter::once(tcx.mk_ty_var(ty::TyVid { index: 0 }).into())
+                                    iter::once(tcx.mk_ty_var(ty::TyVid::from_u32(0)).into())
                                         .chain(projection_ty.substs.iter().skip(1)),
                                 );