Auto merge of #117139 - compiler-errors:vid-lifetimes, r=BoxyUwU

Get rid of `'tcx` lifetime on `ConstVid`, `EffectVid`

These are simply newtyped numbers, so don't really have a reason (per se) to have a lifetime -- `TyVid` and `RegionVid` do not, for example.

The only consequence of this is that we need to use a new key type for `UnifyKey` that mentions `'tcx`. This is already done for `RegionVid`, with `RegionVidKey<'tcx>`, but this `UnifyKey` trait implementation may have been the original reason to give `ConstVid` a lifetime. See the changes to `compiler/rustc_middle/src/infer/unify_key.rs` specifically.

I consider the code cleaner this way, though -- we removed quite a few unnecessary `'tcx` in the process. This also makes it easier to uplift these two ids to `rustc_type_ir`, which I plan on doing in a follow-up PR.

r? `@BoxyUwU`

compiler/rustc_infer/src/infer/canonical/mod.rs

@@ -152,7 +152,7 @@ impl<'tcx> InferCtxt<'tcx> {
                 )
                 .into(),
             CanonicalVarKind::Effect => {
-                let vid = self.inner.borrow_mut().effect_unification_table().new_key(None);
+                let vid = self.inner.borrow_mut().effect_unification_table().new_key(None).vid;
                 ty::Const::new_infer(self.tcx, ty::InferConst::EffectVar(vid), self.tcx.types.bool)
                     .into()
             }

compiler/rustc_infer/src/infer/combine.rs

@@ -320,7 +320,7 @@ impl<'tcx> InferCtxt<'tcx> {
     #[instrument(level = "debug", skip(self))]
     fn unify_const_variable(
         &self,
-        target_vid: ty::ConstVid<'tcx>,
+        target_vid: ty::ConstVid,
         ct: ty::Const<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
     ) -> RelateResult<'tcx, ty::Const<'tcx>> {
@@ -381,7 +381,7 @@ impl<'tcx> InferCtxt<'tcx> {
     fn unify_effect_variable(
         &self,
         vid_is_expected: bool,
-        vid: ty::EffectVid<'tcx>,
+        vid: ty::EffectVid,
         val: EffectVarValue<'tcx>,
     ) -> RelateResult<'tcx, ty::Const<'tcx>> {
         self.inner

compiler/rustc_infer/src/infer/freshen.rs

@@ -42,7 +42,7 @@ pub struct TypeFreshener<'a, 'tcx> {
     ty_freshen_count: u32,
     const_freshen_count: u32,
     ty_freshen_map: FxHashMap<ty::InferTy, Ty<'tcx>>,
-    const_freshen_map: FxHashMap<ty::InferConst<'tcx>, ty::Const<'tcx>>,
+    const_freshen_map: FxHashMap<ty::InferConst, ty::Const<'tcx>>,
 }
 
 impl<'a, 'tcx> TypeFreshener<'a, 'tcx> {
@@ -79,12 +79,12 @@ impl<'a, 'tcx> TypeFreshener<'a, 'tcx> {
     fn freshen_const<F>(
         &mut self,
         opt_ct: Option<ty::Const<'tcx>>,
-        key: ty::InferConst<'tcx>,
+        key: ty::InferConst,
         freshener: F,
         ty: Ty<'tcx>,
     ) -> ty::Const<'tcx>
     where
-        F: FnOnce(u32) -> ty::InferConst<'tcx>,
+        F: FnOnce(u32) -> ty::InferConst,
     {
         if let Some(ct) = opt_ct {
             return ct.fold_with(self);

compiler/rustc_infer/src/infer/fudge.rs

@@ -1,3 +1,4 @@
+use rustc_middle::infer::unify_key::ConstVidKey;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::{self, ConstVid, FloatVid, IntVid, RegionVid, Ty, TyCtxt, TyVid};
 
@@ -23,14 +24,14 @@ where
 }
 
 fn const_vars_since_snapshot<'tcx>(
-    table: &mut UnificationTable<'_, 'tcx, ConstVid<'tcx>>,
+    table: &mut UnificationTable<'_, 'tcx, ConstVidKey<'tcx>>,
     snapshot_var_len: usize,
-) -> (Range<ConstVid<'tcx>>, Vec<ConstVariableOrigin>) {
+) -> (Range<ConstVid>, Vec<ConstVariableOrigin>) {
     let range = vars_since_snapshot(table, snapshot_var_len);
     (
-        range.start..range.end,
-        (range.start.index..range.end.index)
-            .map(|index| table.probe_value(ConstVid::from_index(index)).origin)
+        range.start.vid..range.end.vid,
+        (range.start.index()..range.end.index())
+            .map(|index| table.probe_value(ConstVid::from_u32(index)).origin)
             .collect(),
     )
 }
@@ -172,7 +173,7 @@ pub struct InferenceFudger<'a, 'tcx> {
     int_vars: Range<IntVid>,
     float_vars: Range<FloatVid>,
     region_vars: (Range<RegionVid>, Vec<RegionVariableOrigin>),
-    const_vars: (Range<ConstVid<'tcx>>, Vec<ConstVariableOrigin>),
+    const_vars: (Range<ConstVid>, Vec<ConstVariableOrigin>),
 }
 
 impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for InferenceFudger<'a, 'tcx> {
@@ -235,7 +236,7 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for InferenceFudger<'a, 'tcx> {
             if self.const_vars.0.contains(&vid) {
                 // This variable was created during the fudging.
                 // Recreate it with a fresh variable here.
-                let idx = (vid.index - self.const_vars.0.start.index) as usize;
+                let idx = (vid.index() - self.const_vars.0.start.index()) as usize;
                 let origin = self.const_vars.1[idx];
                 self.infcx.next_const_var(ct.ty(), origin)
             } else {

compiler/rustc_infer/src/infer/generalize.rs

@@ -17,7 +17,7 @@ pub(super) fn generalize<'tcx, D: GeneralizerDelegate<'tcx>, T: Into<Term<'tcx>>
     infcx: &InferCtxt<'tcx>,
     delegate: &mut D,
     term: T,
-    for_vid: impl Into<ty::TermVid<'tcx>>,
+    for_vid: impl Into<ty::TermVid>,
     ambient_variance: ty::Variance,
 ) -> RelateResult<'tcx, Generalization<T>> {
     let (for_universe, root_vid) = match for_vid.into() {
@@ -27,7 +27,7 @@ pub(super) fn generalize<'tcx, D: GeneralizerDelegate<'tcx>, T: Into<Term<'tcx>>
         ),
         ty::TermVid::Const(ct_vid) => (
             infcx.probe_const_var(ct_vid).unwrap_err(),
-            ty::TermVid::Const(infcx.inner.borrow_mut().const_unification_table().find(ct_vid)),
+            ty::TermVid::Const(infcx.inner.borrow_mut().const_unification_table().find(ct_vid).vid),
         ),
     };
 
@@ -127,7 +127,7 @@ struct Generalizer<'me, 'tcx, D> {
     /// The vid of the type variable that is in the process of being
     /// instantiated. If we find this within the value we are folding,
     /// that means we would have created a cyclic value.
-    root_vid: ty::TermVid<'tcx>,
+    root_vid: ty::TermVid,
 
     /// The universe of the type variable that is in the process of being
     /// instantiated. If we find anything that this universe cannot name,
@@ -376,7 +376,7 @@ where
                 // `vid` are related and we'd be inferring an infinitely
                 // deep const.
                 if ty::TermVid::Const(
-                    self.infcx.inner.borrow_mut().const_unification_table().find(vid),
+                    self.infcx.inner.borrow_mut().const_unification_table().find(vid).vid,
                 ) == self.root_vid
                 {
                     return Err(self.cyclic_term_error());
@@ -394,10 +394,14 @@ where
                         if self.for_universe.can_name(universe) {
                             Ok(c)
                         } else {
-                            let new_var_id = variable_table.new_key(ConstVarValue {
-                                origin: var_value.origin,
-                                val: ConstVariableValue::Unknown { universe: self.for_universe },
-                            });
+                            let new_var_id = variable_table
+                                .new_key(ConstVarValue {
+                                    origin: var_value.origin,
+                                    val: ConstVariableValue::Unknown {
+                                        universe: self.for_universe,
+                                    },
+                                })
+                                .vid;
                             Ok(ty::Const::new_var(self.tcx(), new_var_id, c.ty()))
                         }
                     }

compiler/rustc_infer/src/infer/mod.rs

@@ -6,7 +6,9 @@ pub use self::RegionVariableOrigin::*;
 pub use self::SubregionOrigin::*;
 pub use self::ValuePairs::*;
 pub use combine::ObligationEmittingRelation;
+use rustc_data_structures::captures::Captures;
 use rustc_data_structures::undo_log::UndoLogs;
+use rustc_middle::infer::unify_key::{ConstVidKey, EffectVidKey};
 
 use self::opaque_types::OpaqueTypeStorage;
 pub(crate) use self::undo_log::{InferCtxtUndoLogs, Snapshot, UndoLog};
@@ -40,7 +42,6 @@ use rustc_span::{Span, DUMMY_SP};
 
 use std::cell::{Cell, RefCell};
 use std::fmt;
-use std::marker::PhantomData;
 
 use self::combine::CombineFields;
 use self::error_reporting::TypeErrCtxt;
@@ -85,7 +86,7 @@ pub struct InferOk<'tcx, T> {
 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
 
 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
-pub type FixupResult<'tcx, T> = Result<T, FixupError<'tcx>>; // "fixup result"
+pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
 
 pub(crate) type UnificationTable<'a, 'tcx, T> = ut::UnificationTable<
     ut::InPlace<T, &'a mut ut::UnificationStorage<T>, &'a mut InferCtxtUndoLogs<'tcx>>,
@@ -108,7 +109,7 @@ pub struct InferCtxtInner<'tcx> {
     type_variable_storage: type_variable::TypeVariableStorage<'tcx>,
 
     /// Map from const parameter variable to the kind of const it represents.
-    const_unification_storage: ut::UnificationTableStorage<ty::ConstVid<'tcx>>,
+    const_unification_storage: ut::UnificationTableStorage<ConstVidKey<'tcx>>,
 
     /// Map from integral variable to the kind of integer it represents.
     int_unification_storage: ut::UnificationTableStorage<ty::IntVid>,
@@ -117,7 +118,7 @@ pub struct InferCtxtInner<'tcx> {
     float_unification_storage: ut::UnificationTableStorage<ty::FloatVid>,
 
     /// Map from effect variable to the effect param it represents.
-    effect_unification_storage: ut::UnificationTableStorage<ty::EffectVid<'tcx>>,
+    effect_unification_storage: ut::UnificationTableStorage<EffectVidKey<'tcx>>,
 
     /// Tracks the set of region variables and the constraints between them.
     ///
@@ -224,11 +225,11 @@ impl<'tcx> InferCtxtInner<'tcx> {
     }
 
     #[inline]
-    fn const_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ty::ConstVid<'tcx>> {
+    fn const_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ConstVidKey<'tcx>> {
         self.const_unification_storage.with_log(&mut self.undo_log)
     }
 
-    fn effect_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ty::EffectVid<'tcx>> {
+    fn effect_unification_table(&mut self) -> UnificationTable<'_, 'tcx, EffectVidKey<'tcx>> {
         self.effect_unification_storage.with_log(&mut self.undo_log)
     }
 
@@ -359,7 +360,7 @@ impl<'tcx> ty::InferCtxtLike for InferCtxt<'tcx> {
         }
     }
 
-    fn universe_of_ct(&self, ct: ty::InferConst<'tcx>) -> Option<ty::UniverseIndex> {
+    fn universe_of_ct(&self, ct: ty::InferConst) -> Option<ty::UniverseIndex> {
         use ty::InferConst::*;
         match ct {
             // Same issue as with `universe_of_ty`
@@ -548,11 +549,11 @@ pub enum NllRegionVariableOrigin {
 
 // FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`.
 #[derive(Copy, Clone, Debug)]
-pub enum FixupError<'tcx> {
+pub enum FixupError {
     UnresolvedIntTy(IntVid),
     UnresolvedFloatTy(FloatVid),
     UnresolvedTy(TyVid),
-    UnresolvedConst(ConstVid<'tcx>),
+    UnresolvedConst(ConstVid),
 }
 
 /// See the `region_obligations` field for more information.
@@ -563,7 +564,7 @@ pub struct RegionObligation<'tcx> {
     pub origin: SubregionOrigin<'tcx>,
 }
 
-impl<'tcx> fmt::Display for FixupError<'tcx> {
+impl fmt::Display for FixupError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use self::FixupError::*;
 
@@ -794,7 +795,7 @@ impl<'tcx> InferCtxt<'tcx> {
         let mut table = inner.effect_unification_table();
 
         (0..table.len())
-            .map(|i| ty::EffectVid { index: i as u32, phantom: PhantomData })
+            .map(|i| ty::EffectVid::from_usize(i))
             .filter(|&vid| table.probe_value(vid).is_none())
             .map(|v| {
                 ty::Const::new_infer(self.tcx, ty::InferConst::EffectVar(v), self.tcx.types.bool)
@@ -1072,15 +1073,20 @@ impl<'tcx> InferCtxt<'tcx> {
             .inner
             .borrow_mut()
             .const_unification_table()
-            .new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe } });
+            .new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe } })
+            .vid;
         ty::Const::new_var(self.tcx, vid, ty)
     }
 
-    pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid<'tcx> {
-        self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
-            origin,
-            val: ConstVariableValue::Unknown { universe: self.universe() },
-        })
+    pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid {
+        self.inner
+            .borrow_mut()
+            .const_unification_table()
+            .new_key(ConstVarValue {
+                origin,
+                val: ConstVariableValue::Unknown { universe: self.universe() },
+            })
+            .vid
     }
 
     fn next_int_var_id(&self) -> IntVid {
@@ -1194,11 +1200,15 @@ impl<'tcx> InferCtxt<'tcx> {
                     ),
                     span,
                 };
-                let const_var_id =
-                    self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
+                let const_var_id = self
+                    .inner
+                    .borrow_mut()
+                    .const_unification_table()
+                    .new_key(ConstVarValue {
                         origin,
                         val: ConstVariableValue::Unknown { universe: self.universe() },
-                    });
+                    })
+                    .vid;
                 ty::Const::new_var(
                     self.tcx,
                     const_var_id,
@@ -1213,7 +1223,7 @@ impl<'tcx> InferCtxt<'tcx> {
     }
 
     pub fn var_for_effect(&self, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
-        let effect_vid = self.inner.borrow_mut().effect_unification_table().new_key(None);
+        let effect_vid = self.inner.borrow_mut().effect_unification_table().new_key(None).vid;
         let ty = self
             .tcx
             .type_of(param.def_id)
@@ -1333,12 +1343,12 @@ impl<'tcx> InferCtxt<'tcx> {
         self.inner.borrow_mut().type_variables().root_var(var)
     }
 
-    pub fn root_const_var(&self, var: ty::ConstVid<'tcx>) -> ty::ConstVid<'tcx> {
-        self.inner.borrow_mut().const_unification_table().find(var)
+    pub fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid {
+        self.inner.borrow_mut().const_unification_table().find(var).vid
     }
 
-    pub fn root_effect_var(&self, var: ty::EffectVid<'tcx>) -> ty::EffectVid<'tcx> {
-        self.inner.borrow_mut().effect_unification_table().find(var)
+    pub fn root_effect_var(&self, var: ty::EffectVid) -> ty::EffectVid {
+        self.inner.borrow_mut().effect_unification_table().find(var).vid
     }
 
     /// Resolves an int var to a rigid int type, if it was constrained to one,
@@ -1402,17 +1412,14 @@ impl<'tcx> InferCtxt<'tcx> {
         value.visit_with(&mut resolve::UnresolvedTypeOrConstFinder::new(self)).break_value()
     }
 
-    pub fn probe_const_var(
-        &self,
-        vid: ty::ConstVid<'tcx>,
-    ) -> Result<ty::Const<'tcx>, ty::UniverseIndex> {
+    pub fn probe_const_var(&self, vid: ty::ConstVid) -> Result<ty::Const<'tcx>, ty::UniverseIndex> {
         match self.inner.borrow_mut().const_unification_table().probe_value(vid).val {
             ConstVariableValue::Known { value } => Ok(value),
             ConstVariableValue::Unknown { universe } => Err(universe),
         }
     }
 
-    pub fn probe_effect_var(&self, vid: EffectVid<'tcx>) -> Option<EffectVarValue<'tcx>> {
+    pub fn probe_effect_var(&self, vid: EffectVid) -> Option<EffectVarValue<'tcx>> {
         self.inner.borrow_mut().effect_unification_table().probe_value(vid)
     }
 
@@ -1423,7 +1430,7 @@ impl<'tcx> InferCtxt<'tcx> {
     ///
     /// This method is idempotent, but it not typically not invoked
     /// except during the writeback phase.
-    pub fn fully_resolve<T: TypeFoldable<TyCtxt<'tcx>>>(&self, value: T) -> FixupResult<'tcx, T> {
+    pub fn fully_resolve<T: TypeFoldable<TyCtxt<'tcx>>>(&self, value: T) -> FixupResult<T> {
         match resolve::fully_resolve(self, value) {
             Ok(value) => {
                 if value.has_non_region_infer() {
@@ -1647,11 +1654,11 @@ impl<'tcx> InferCtxt<'tcx> {
     #[inline]
     pub fn is_ty_infer_var_definitely_unchanged<'a>(
         &'a self,
-    ) -> (impl Fn(TyOrConstInferVar<'tcx>) -> bool + 'a) {
+    ) -> (impl Fn(TyOrConstInferVar) -> bool + Captures<'tcx> + 'a) {
         // This hoists the borrow/release out of the loop body.
         let inner = self.inner.try_borrow();
 
-        return move |infer_var: TyOrConstInferVar<'tcx>| match (infer_var, &inner) {
+        return move |infer_var: TyOrConstInferVar| match (infer_var, &inner) {
             (TyOrConstInferVar::Ty(ty_var), Ok(inner)) => {
                 use self::type_variable::TypeVariableValue;
 
@@ -1674,7 +1681,7 @@ impl<'tcx> InferCtxt<'tcx> {
     /// inference variables), and it handles both `Ty` and `ty::Const` without
     /// having to resort to storing full `GenericArg`s in `stalled_on`.
     #[inline(always)]
-    pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar<'tcx>) -> bool {
+    pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar) -> bool {
         match infer_var {
             TyOrConstInferVar::Ty(v) => {
                 use self::type_variable::TypeVariableValue;
@@ -1781,7 +1788,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 /// Helper for [InferCtxt::ty_or_const_infer_var_changed] (see comment on that), currently
 /// used only for `traits::fulfill`'s list of `stalled_on` inference variables.
 #[derive(Copy, Clone, Debug)]
-pub enum TyOrConstInferVar<'tcx> {
+pub enum TyOrConstInferVar {
     /// Equivalent to `ty::Infer(ty::TyVar(_))`.
     Ty(TyVid),
     /// Equivalent to `ty::Infer(ty::IntVar(_))`.
@@ -1790,12 +1797,12 @@ pub enum TyOrConstInferVar<'tcx> {
     TyFloat(FloatVid),
 
     /// Equivalent to `ty::ConstKind::Infer(ty::InferConst::Var(_))`.
-    Const(ConstVid<'tcx>),
+    Const(ConstVid),
     /// Equivalent to `ty::ConstKind::Infer(ty::InferConst::EffectVar(_))`.
-    Effect(EffectVid<'tcx>),
+    Effect(EffectVid),
 }
 
-impl<'tcx> TyOrConstInferVar<'tcx> {
+impl<'tcx> TyOrConstInferVar {
     /// Tries to extract an inference variable from a type or a constant, returns `None`
     /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and
     /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).