Remove DefId from EarlyParamRegion (type system)

Author: BoxyUwU

compiler/rustc_hir_analysis/src/check/check.rs

@@ -538,11 +538,9 @@ fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDe
                 // the cases that were stabilized with the `impl_trait_projection`
                 // feature -- see <https://github.com/rust-lang/rust/pull/115659>.
                 if let DefKind::LifetimeParam = tcx.def_kind(def_id)
-                    && let ty::ReEarlyParam(ty::EarlyParamRegion { def_id, .. })
-                    | ty::ReLateParam(ty::LateParamRegion {
-                        bound_region: ty::BoundRegionKind::BrNamed(def_id, _),
-                        ..
-                    }) = *tcx.map_opaque_lifetime_to_parent_lifetime(def_id.expect_local())
+                    && let Some(def_id) = tcx
+                        .map_opaque_lifetime_to_parent_lifetime(def_id.expect_local())
+                        .opt_param_def_id(tcx, tcx.parent(opaque_def_id.to_def_id()))
                 {
                     shadowed_captures.insert(def_id);
                 }
@@ -585,12 +583,9 @@ fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDe
                     // Check if the lifetime param was captured but isn't named in the precise captures list.
                     if variances[param.index as usize] == ty::Invariant {
                         if let DefKind::OpaqueTy = tcx.def_kind(tcx.parent(param.def_id))
-                            && let ty::ReEarlyParam(ty::EarlyParamRegion { def_id, .. })
-                            | ty::ReLateParam(ty::LateParamRegion {
-                                bound_region: ty::BoundRegionKind::BrNamed(def_id, _),
-                                ..
-                            }) = *tcx
+                            && let Some(def_id) = tcx
                                 .map_opaque_lifetime_to_parent_lifetime(param.def_id.expect_local())
+                                .opt_param_def_id(tcx, tcx.parent(opaque_def_id.to_def_id()))
                         {
                             tcx.dcx().emit_err(errors::LifetimeNotCaptured {
                                 opaque_span,

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -876,7 +876,8 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
             ty::ReLateParam(_) => {}
             // Remap early-bound regions as long as they don't come from the `impl` itself,
             // in which case we don't really need to renumber them.
-            ty::ReEarlyParam(ebr) if self.tcx.parent(ebr.def_id) != self.impl_def_id => {}
+            ty::ReEarlyParam(ebr)
+                if ebr.index >= self.tcx.generics_of(self.impl_def_id).count() as u32 => {}
             _ => return Ok(region),
         }
 
@@ -889,12 +890,8 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
                 );
             }
         } else {
-            let guar = match region.kind() {
-                ty::ReEarlyParam(ty::EarlyParamRegion { def_id, .. })
-                | ty::ReLateParam(ty::LateParamRegion {
-                    bound_region: ty::BoundRegionKind::BrNamed(def_id, _),
-                    ..
-                }) => {
+            let guar = match region.opt_param_def_id(self.tcx, self.tcx.parent(self.def_id)) {
+                Some(def_id) => {
                     let return_span = if let ty::Alias(ty::Opaque, opaque_ty) = self.ty.kind() {
                         self.tcx.def_span(opaque_ty.def_id)
                     } else {
@@ -914,7 +911,7 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
                         .with_note(format!("hidden type inferred to be `{}`", self.ty))
                         .emit()
                 }
-                _ => {
+                None => {
                     // This code path is not reached in any tests, but may be
                     // reachable. If this is triggered, it should be converted
                     // to `delayed_bug` and the triggering case turned into a

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -2101,16 +2101,14 @@ fn lint_redundant_lifetimes<'tcx>(
         }
 
         for &victim in &lifetimes[(idx + 1)..] {
-            // We should only have late-bound lifetimes of the `BrNamed` variety,
-            // since we get these signatures straight from `hir_lowering`. And any
-            // other regions (ReError/ReStatic/etc.) shouldn't matter, since we
+            // All region parameters should have a `DefId` available as:
+            // - Late-bound parameters should be of the`BrNamed` variety,
+            // since we get these signatures straight from `hir_lowering`.
+            // - Early-bound parameters unconditionally have a `DefId` available.
+            //
+            // Any other regions (ReError/ReStatic/etc.) shouldn't matter, since we
             // can't really suggest to remove them.
-            let (ty::ReEarlyParam(ty::EarlyParamRegion { def_id, .. })
-            | ty::ReLateParam(ty::LateParamRegion {
-                bound_region: ty::BoundRegionKind::BrNamed(def_id, _),
-                ..
-            })) = victim.kind()
-            else {
+            let Some(def_id) = victim.opt_param_def_id(tcx, owner_id.to_def_id()) else {
                 continue;
             };
 

compiler/rustc_middle/src/ty/region.rs

@@ -320,6 +320,21 @@ impl<'tcx> Region<'tcx> {
             _ => bug!("expected region {:?} to be of kind ReVar", self),
         }
     }
+
+    /// Given some item `binding_item`, check if this region is a generic parameter introduced by it
+    /// or one of the parent generics. Returns the `DefId` of the parameter definition if so.
+    pub fn opt_param_def_id(self, tcx: TyCtxt<'tcx>, binding_item: DefId) -> Option<DefId> {
+        match self.kind() {
+            ty::ReEarlyParam(ebr) => {
+                Some(tcx.generics_of(binding_item).region_param(ebr, tcx).def_id)
+            }
+            ty::ReLateParam(ty::LateParamRegion {
+                bound_region: ty::BoundRegionKind::BrNamed(def_id, _),
+                ..
+            }) => Some(def_id),
+            _ => None,
+        }
+    }
 }
 
 impl<'tcx> Deref for Region<'tcx> {
@@ -334,16 +349,13 @@ impl<'tcx> Deref for Region<'tcx> {
 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub struct EarlyParamRegion {
-    pub def_id: DefId,
     pub index: u32,
     pub name: Symbol,
 }
 
 impl std::fmt::Debug for EarlyParamRegion {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        // FIXME(BoxyUwU): self.def_id goes first because of `erased-regions-in-hidden-ty.rs` being impossible to write
-        // error annotations for otherwise. :). Ideally this would be `self.name, self.index, self.def_id`.
-        write!(f, "{:?}_{}/#{}", self.def_id, self.name, self.index)
+        write!(f, "{}/#{}", self.name, self.index)
     }
 }