Auto merge of #131226 - nnethercote:rustc_infer-cleanups, r=lcnr

`rustc_infer` cleanups

Various small improvements I found while reading over this code.

r? `@lcnr`

compiler/rustc_errors/src/lib.rs

@@ -925,18 +925,6 @@ impl<'a> DiagCtxtHandle<'a> {
         self.inner.borrow_mut().emit_stashed_diagnostics()
     }
 
-    /// This excludes lint errors, and delayed bugs.
-    #[inline]
-    pub fn err_count_excluding_lint_errs(&self) -> usize {
-        let inner = self.inner.borrow();
-        inner.err_guars.len()
-            + inner
-                .stashed_diagnostics
-                .values()
-                .filter(|(diag, guar)| guar.is_some() && diag.is_lint.is_none())
-                .count()
-    }
-
     /// This excludes delayed bugs.
     #[inline]
     pub fn err_count(&self) -> usize {

compiler/rustc_infer/src/infer/at.rs

@@ -82,7 +82,6 @@ impl<'tcx> InferCtxt<'tcx> {
             reported_trait_errors: self.reported_trait_errors.clone(),
             reported_signature_mismatch: self.reported_signature_mismatch.clone(),
             tainted_by_errors: self.tainted_by_errors.clone(),
-            err_count_on_creation: self.err_count_on_creation,
             universe: self.universe.clone(),
             intercrate,
             next_trait_solver: self.next_trait_solver,
@@ -382,21 +381,7 @@ impl<'tcx> ToTrace<'tcx> for ty::GenericArg<'tcx> {
                 (GenericArgKind::Const(a), GenericArgKind::Const(b)) => {
                     ValuePairs::Terms(ExpectedFound::new(true, a.into(), b.into()))
                 }
-
-                (
-                    GenericArgKind::Lifetime(_),
-                    GenericArgKind::Type(_) | GenericArgKind::Const(_),
-                )
-                | (
-                    GenericArgKind::Type(_),
-                    GenericArgKind::Lifetime(_) | GenericArgKind::Const(_),
-                )
-                | (
-                    GenericArgKind::Const(_),
-                    GenericArgKind::Lifetime(_) | GenericArgKind::Type(_),
-                ) => {
-                    bug!("relating different kinds: {a:?} {b:?}")
-                }
+                _ => bug!("relating different kinds: {a:?} {b:?}"),
             },
         }
     }

compiler/rustc_infer/src/infer/mod.rs

@@ -14,7 +14,8 @@ use region_constraints::{
     GenericKind, RegionConstraintCollector, RegionConstraintStorage, VarInfos, VerifyBound,
 };
 pub use relate::StructurallyRelateAliases;
-pub use relate::combine::{CombineFields, PredicateEmittingRelation};
+use relate::combine::CombineFields;
+pub use relate::combine::PredicateEmittingRelation;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_data_structures::sync::Lrc;
@@ -50,23 +51,22 @@ use snapshot::undo_log::InferCtxtUndoLogs;
 use tracing::{debug, instrument};
 use type_variable::TypeVariableOrigin;
 
-use crate::infer::relate::RelateResult;
 use crate::traits::{self, ObligationCause, ObligationInspector, PredicateObligation, TraitEngine};
 
 pub mod at;
 pub mod canonical;
 mod context;
-pub mod free_regions;
+mod free_regions;
 mod freshen;
 mod lexical_region_resolve;
-pub mod opaque_types;
+mod opaque_types;
 pub mod outlives;
 mod projection;
 pub mod region_constraints;
 pub mod relate;
 pub mod resolve;
 pub(crate) mod snapshot;
-pub mod type_variable;
+mod type_variable;
 
 #[must_use]
 #[derive(Debug)]
@@ -76,8 +76,7 @@ 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<T> = Result<T, FixupError>; // "fixup result"
+pub(crate) 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>>,
@@ -202,7 +201,7 @@ impl<'tcx> InferCtxtInner<'tcx> {
     }
 
     #[inline]
-    pub fn opaque_types(&mut self) -> opaque_types::OpaqueTypeTable<'_, 'tcx> {
+    fn opaque_types(&mut self) -> opaque_types::OpaqueTypeTable<'_, 'tcx> {
         self.opaque_type_storage.with_log(&mut self.undo_log)
     }
 
@@ -280,27 +279,14 @@ pub struct InferCtxt<'tcx> {
     pub reported_signature_mismatch: RefCell<FxHashSet<(Span, Option<Span>)>>,
 
     /// When an error occurs, we want to avoid reporting "derived"
-    /// errors that are due to this original failure. Normally, we
-    /// handle this with the `err_count_on_creation` count, which
-    /// basically just tracks how many errors were reported when we
-    /// started type-checking a fn and checks to see if any new errors
-    /// have been reported since then. Not great, but it works.
-    ///
-    /// However, when errors originated in other passes -- notably
-    /// resolve -- this heuristic breaks down. Therefore, we have this
-    /// auxiliary flag that one can set whenever one creates a
-    /// type-error that is due to an error in a prior pass.
+    /// errors that are due to this original failure. We have this
+    /// flag that one can set whenever one creates a type-error that
+    /// is due to an error in a prior pass.
     ///
     /// Don't read this flag directly, call `is_tainted_by_errors()`
     /// and `set_tainted_by_errors()`.
     tainted_by_errors: Cell<Option<ErrorGuaranteed>>,
 
-    /// Track how many errors were reported when this infcx is created.
-    /// If the number of errors increases, that's also a sign (like
-    /// `tainted_by_errors`) to avoid reporting certain kinds of errors.
-    // FIXME(matthewjasper) Merge into `tainted_by_errors`
-    err_count_on_creation: usize,
-
     /// What is the innermost universe we have created? Starts out as
     /// `UniverseIndex::root()` but grows from there as we enter
     /// universal quantifiers.
@@ -509,46 +495,41 @@ pub enum NllRegionVariableOrigin {
     },
 }
 
-// FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`.
 #[derive(Copy, Clone, Debug)]
-pub enum FixupError {
-    UnresolvedIntTy(IntVid),
-    UnresolvedFloatTy(FloatVid),
-    UnresolvedTy(TyVid),
-    UnresolvedConst(ConstVid),
-    UnresolvedEffect(EffectVid),
-}
-
-/// See the `region_obligations` field for more information.
-#[derive(Clone, Debug)]
-pub struct RegionObligation<'tcx> {
-    pub sub_region: ty::Region<'tcx>,
-    pub sup_type: Ty<'tcx>,
-    pub origin: SubregionOrigin<'tcx>,
+pub struct FixupError {
+    unresolved: TyOrConstInferVar,
 }
 
 impl fmt::Display for FixupError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        use self::FixupError::*;
+        use TyOrConstInferVar::*;
 
-        match *self {
-            UnresolvedIntTy(_) => write!(
+        match self.unresolved {
+            TyInt(_) => write!(
                 f,
                 "cannot determine the type of this integer; \
                  add a suffix to specify the type explicitly"
             ),
-            UnresolvedFloatTy(_) => write!(
+            TyFloat(_) => write!(
                 f,
                 "cannot determine the type of this number; \
                  add a suffix to specify the type explicitly"
             ),
-            UnresolvedTy(_) => write!(f, "unconstrained type"),
-            UnresolvedConst(_) => write!(f, "unconstrained const value"),
-            UnresolvedEffect(_) => write!(f, "unconstrained effect value"),
+            Ty(_) => write!(f, "unconstrained type"),
+            Const(_) => write!(f, "unconstrained const value"),
+            Effect(_) => write!(f, "unconstrained effect value"),
         }
     }
 }
 
+/// See the `region_obligations` field for more information.
+#[derive(Clone, Debug)]
+pub struct RegionObligation<'tcx> {
+    pub sub_region: ty::Region<'tcx>,
+    pub sup_type: Ty<'tcx>,
+    pub origin: SubregionOrigin<'tcx>,
+}
+
 /// Used to configure inference contexts before their creation.
 pub struct InferCtxtBuilder<'tcx> {
     tcx: TyCtxt<'tcx>,
@@ -588,14 +569,6 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
         self
     }
 
-    pub fn with_defining_opaque_types(
-        mut self,
-        defining_opaque_types: &'tcx ty::List<LocalDefId>,
-    ) -> Self {
-        self.defining_opaque_types = defining_opaque_types;
-        self
-    }
-
     pub fn with_next_trait_solver(mut self, next_trait_solver: bool) -> Self {
         self.next_trait_solver = next_trait_solver;
         self
@@ -624,14 +597,15 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
     /// the bound values in `C` to their instantiated values in `V`
     /// (in other words, `S(C) = V`).
     pub fn build_with_canonical<T>(
-        self,
+        mut self,
         span: Span,
         canonical: &Canonical<'tcx, T>,
     ) -> (InferCtxt<'tcx>, T, CanonicalVarValues<'tcx>)
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
-        let infcx = self.with_defining_opaque_types(canonical.defining_opaque_types).build();
+        self.defining_opaque_types = canonical.defining_opaque_types;
+        let infcx = self.build();
         let (value, args) = infcx.instantiate_canonical(span, canonical);
         (infcx, value, args)
     }
@@ -657,7 +631,6 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
             reported_trait_errors: Default::default(),
             reported_signature_mismatch: Default::default(),
             tainted_by_errors: Cell::new(None),
-            err_count_on_creation: tcx.dcx().err_count_excluding_lint_errs(),
             universe: Cell::new(ty::UniverseIndex::ROOT),
             intercrate,
             next_trait_solver,
@@ -919,28 +892,16 @@ impl<'tcx> InferCtxt<'tcx> {
         ty::Const::new_var(self.tcx, vid)
     }
 
-    pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid {
-        self.inner
-            .borrow_mut()
-            .const_unification_table()
-            .new_key(ConstVariableValue::Unknown { origin, universe: self.universe() })
-            .vid
-    }
-
-    fn next_int_var_id(&self) -> IntVid {
-        self.inner.borrow_mut().int_unification_table().new_key(ty::IntVarValue::Unknown)
-    }
-
     pub fn next_int_var(&self) -> Ty<'tcx> {
-        Ty::new_int_var(self.tcx, self.next_int_var_id())
-    }
-
-    fn next_float_var_id(&self) -> FloatVid {
-        self.inner.borrow_mut().float_unification_table().new_key(ty::FloatVarValue::Unknown)
+        let next_int_var_id =
+            self.inner.borrow_mut().int_unification_table().new_key(ty::IntVarValue::Unknown);
+        Ty::new_int_var(self.tcx, next_int_var_id)
     }
 
     pub fn next_float_var(&self) -> Ty<'tcx> {
-        Ty::new_float_var(self.tcx, self.next_float_var_id())
+        let next_float_var_id =
+            self.inner.borrow_mut().float_unification_table().new_key(ty::FloatVarValue::Unknown);
+        Ty::new_float_var(self.tcx, next_float_var_id)
     }
 
     /// Creates a fresh region variable with the next available index.
@@ -1353,7 +1314,7 @@ impl<'tcx> InferCtxt<'tcx> {
     }
 
     /// See the [`region_constraints::RegionConstraintCollector::verify_generic_bound`] method.
-    pub fn verify_generic_bound(
+    pub(crate) fn verify_generic_bound(
         &self,
         origin: SubregionOrigin<'tcx>,
         kind: GenericKind<'tcx>,

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

@@ -13,16 +13,15 @@ use rustc_middle::ty::{
 use rustc_span::Span;
 use tracing::{debug, instrument};
 
+use super::DefineOpaqueTypes;
 use crate::errors::OpaqueHiddenTypeDiag;
 use crate::infer::{InferCtxt, InferOk};
 use crate::traits::{self, Obligation};
 
 mod table;
 
-pub type OpaqueTypeMap<'tcx> = FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueTypeDecl<'tcx>>;
-pub use table::{OpaqueTypeStorage, OpaqueTypeTable};
-
-use super::DefineOpaqueTypes;
+pub(crate) type OpaqueTypeMap<'tcx> = FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueTypeDecl<'tcx>>;
+pub(crate) use table::{OpaqueTypeStorage, OpaqueTypeTable};
 
 /// Information about the opaque types whose values we
 /// are inferring in this function (these are the `impl Trait` that
@@ -377,9 +376,9 @@ impl<'tcx> InferCtxt<'tcx> {
 ///
 /// We ignore any type parameters because impl trait values are assumed to
 /// capture all the in-scope type parameters.
-pub struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP: FnMut(ty::Region<'tcx>)> {
-    pub tcx: TyCtxt<'tcx>,
-    pub op: OP,
+struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP: FnMut(ty::Region<'tcx>)> {
+    tcx: TyCtxt<'tcx>,
+    op: OP,
 }
 
 impl<'tcx, OP> TypeVisitor<TyCtxt<'tcx>> for ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
@@ -455,20 +454,6 @@ where
     }
 }
 
-pub enum UseKind {
-    DefiningUse,
-    OpaqueUse,
-}
-
-impl UseKind {
-    pub fn is_defining(self) -> bool {
-        match self {
-            UseKind::DefiningUse => true,
-            UseKind::OpaqueUse => false,
-        }
-    }
-}
-
 impl<'tcx> InferCtxt<'tcx> {
     #[instrument(skip(self), level = "debug")]
     fn register_hidden_type(

compiler/rustc_infer/src/infer/opaque_types/table.rs

@@ -7,7 +7,7 @@ use super::{OpaqueTypeDecl, OpaqueTypeMap};
 use crate::infer::snapshot::undo_log::{InferCtxtUndoLogs, UndoLog};
 
 #[derive(Default, Debug, Clone)]
-pub struct OpaqueTypeStorage<'tcx> {
+pub(crate) struct OpaqueTypeStorage<'tcx> {
     /// Opaque types found in explicit return types and their
     /// associated fresh inference variable. Writeback resolves these
     /// variables to get the concrete type, which can be used to
@@ -46,7 +46,7 @@ impl<'tcx> Drop for OpaqueTypeStorage<'tcx> {
     }
 }
 
-pub struct OpaqueTypeTable<'a, 'tcx> {
+pub(crate) struct OpaqueTypeTable<'a, 'tcx> {
     storage: &'a mut OpaqueTypeStorage<'tcx>,
 
     undo_log: &'a mut InferCtxtUndoLogs<'tcx>,

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

@@ -14,7 +14,7 @@ pub mod env;
 pub mod for_liveness;
 pub mod obligations;
 pub mod test_type_match;
-pub mod verify;
+pub(crate) mod verify;
 
 #[instrument(level = "debug", skip(param_env), ret)]
 pub fn explicit_outlives_bounds<'tcx>(