Auto merge of #122392 - BoxyUwU:misc_cleanup, r=lcnr

misc cleanups from debugging something

rename `instantiate_canonical_with_fresh_inference_vars` to `instantiate_canonical`  the substs for the canonical are not solely infer vars as that would be wildly wrong and it is rather confusing to see this method called and think that the entire canonicalization setup is completely broken when it is not :thumbsup:

also update region debug printing to be more like the custom impls for Ty/Const, right now regions in debug output are horribly verbose and make it incredibly hard to read but with this atleast boundvars and placeholders when debugging the new solver do not take up excessive amounts of space.

r? `@lcnr`

8 files changed, 37 insertions, 24 deletions

diff --git a/compiler/rustc_borrowck/src/type_check/canonical.rs b/compiler/rustc_borrowck/src/type_check/canonical.rs
index e5ebf97cfc4..a673c4c2aca 100644
--- a/compiler/rustc_borrowck/src/type_check/canonical.rs
+++ b/compiler/rustc_borrowck/src/type_check/canonical.rs
@@ -61,7 +61,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         Ok(output)
     }
 
-    pub(super) fn instantiate_canonical_with_fresh_inference_vars<T>(
+    pub(super) fn instantiate_canonical<T>(
         &mut self,
         span: Span,
         canonical: &Canonical<'tcx, T>,
@@ -69,8 +69,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
-        let (instantiated, _) =
-            self.infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
+        let (instantiated, _) = self.infcx.instantiate_canonical(span, canonical);
         instantiated
     }
 
diff --git a/compiler/rustc_borrowck/src/type_check/input_output.rs b/compiler/rustc_borrowck/src/type_check/input_output.rs
index 8af78b08f69..575aab47ac7 100644
--- a/compiler/rustc_borrowck/src/type_check/input_output.rs
+++ b/compiler/rustc_borrowck/src/type_check/input_output.rs
@@ -39,8 +39,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         // (e.g., the `_` in the code above) with fresh variables.
         // Then replace the bound items in the fn sig with fresh variables,
         // so that they represent the view from "inside" the closure.
-        let user_provided_sig = self
-            .instantiate_canonical_with_fresh_inference_vars(body.span, &user_provided_poly_sig);
+        let user_provided_sig = self.instantiate_canonical(body.span, &user_provided_poly_sig);
         let mut user_provided_sig = self.infcx.instantiate_binder_with_fresh_vars(
             body.span,
             BoundRegionConversionTime::FnCall,
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 412d50f493e..acda2a7524c 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -1109,7 +1109,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         let tcx = self.tcx();
         for user_annotation in self.user_type_annotations {
             let CanonicalUserTypeAnnotation { span, ref user_ty, inferred_ty } = *user_annotation;
-            let annotation = self.instantiate_canonical_with_fresh_inference_vars(span, user_ty);
+            let annotation = self.instantiate_canonical(span, user_ty);
             if let ty::UserType::TypeOf(def, args) = annotation
                 && let DefKind::InlineConst = tcx.def_kind(def)
             {
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 193ea040899..eada5a0bc30 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -386,10 +386,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 let infcx = &self.infcx;
                 let (ParamEnvAnd { param_env: _, value: self_ty }, canonical_inference_vars) =
-                    infcx.instantiate_canonical_with_fresh_inference_vars(
-                        span,
-                        &param_env_and_self_ty,
-                    );
+                    infcx.instantiate_canonical(span, &param_env_and_self_ty);
                 debug!(
                     "probe_op: Mode::Path, param_env_and_self_ty={:?} self_ty={:?}",
                     param_env_and_self_ty, self_ty
@@ -661,13 +658,13 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 // of the iterations in the autoderef loop, so there is no problem with it
                 // being discoverable in another one of these iterations.
                 //
-                // Using `instantiate_canonical_with_fresh_inference_vars` on our
+                // Using `instantiate_canonical` on our
                 // `Canonical<QueryResponse<Ty<'tcx>>>` and then *throwing away* the
                 // `CanonicalVarValues` will exactly give us such a generalization - it
                 // will still match the original object type, but it won't pollute our
                 // type variables in any form, so just do that!
                 let (QueryResponse { value: generalized_self_ty, .. }, _ignored_var_values) =
-                    self.fcx.instantiate_canonical_with_fresh_inference_vars(self.span, self_ty);
+                    self.fcx.instantiate_canonical(self.span, self_ty);
 
                 self.assemble_inherent_candidates_from_object(generalized_self_ty);
                 self.assemble_inherent_impl_candidates_for_type(p.def_id());
diff --git a/compiler/rustc_infer/src/infer/canonical/mod.rs b/compiler/rustc_infer/src/infer/canonical/mod.rs
index 1d203a29b14..bcc476393ea 100644
--- a/compiler/rustc_infer/src/infer/canonical/mod.rs
+++ b/compiler/rustc_infer/src/infer/canonical/mod.rs
@@ -38,8 +38,8 @@ mod instantiate;
 pub mod query_response;
 
 impl<'tcx> InferCtxt<'tcx> {
-    /// Creates an instantiation S for the canonical value with fresh
-    /// inference variables and applies it to the canonical value.
+    /// Creates an instantiation S for the canonical value with fresh inference
+    /// variables and placeholders then applies it to the canonical value.
     /// Returns both the instantiated result *and* the instantiation S.
     ///
     /// This can be invoked as part of constructing an
@@ -50,7 +50,7 @@ impl<'tcx> InferCtxt<'tcx> {
     /// At the end of processing, the instantiation S (once
     /// canonicalized) then represents the values that you computed
     /// for each of the canonical inputs to your query.
-    pub fn instantiate_canonical_with_fresh_inference_vars<T>(
+    pub fn instantiate_canonical<T>(
         &self,
         span: Span,
         canonical: &Canonical<'tcx, T>,
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 44e14387c5c..a3ff655b609 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -678,7 +678,7 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
         let infcx = self.build();
-        let (value, args) = infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
+        let (value, args) = infcx.instantiate_canonical(span, canonical);
         (infcx, value, args)
     }
 
diff --git a/compiler/rustc_middle/src/ty/region.rs b/compiler/rustc_middle/src/ty/region.rs
index 7abc3cd2838..d21f0e6385c 100644
--- a/compiler/rustc_middle/src/ty/region.rs
+++ b/compiler/rustc_middle/src/ty/region.rs
@@ -336,7 +336,9 @@ pub struct EarlyParamRegion {
 
 impl std::fmt::Debug for EarlyParamRegion {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{:?}, {}, {}", self.def_id, self.index, self.name)
+        // 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)
     }
 }
 
@@ -381,13 +383,25 @@ pub enum BoundRegionKind {
     BrEnv,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, PartialOrd, Ord)]
 #[derive(HashStable)]
 pub struct BoundRegion {
     pub var: BoundVar,
     pub kind: BoundRegionKind,
 }
 
+impl core::fmt::Debug for BoundRegion {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self.kind {
+            BoundRegionKind::BrAnon => write!(f, "{:?}", self.var),
+            BoundRegionKind::BrEnv => write!(f, "{:?}.Env", self.var),
+            BoundRegionKind::BrNamed(def, symbol) => {
+                write!(f, "{:?}.Named({:?}, {:?})", self.var, def, symbol)
+            }
+        }
+    }
+}
+
 impl BoundRegionKind {
     pub fn is_named(&self) -> bool {
         match *self {
diff --git a/compiler/rustc_type_ir/src/region_kind.rs b/compiler/rustc_type_ir/src/region_kind.rs
index cf13f066cbf..2e8481df56d 100644
--- a/compiler/rustc_type_ir/src/region_kind.rs
+++ b/compiler/rustc_type_ir/src/region_kind.rs
@@ -223,23 +223,27 @@ impl<I: Interner> DebugWithInfcx<I> for RegionKind<I> {
         f: &mut core::fmt::Formatter<'_>,
     ) -> core::fmt::Result {
         match this.data {
-            ReEarlyParam(data) => write!(f, "ReEarlyParam({data:?})"),
+            ReEarlyParam(data) => write!(f, "{data:?}"),
 
             ReBound(binder_id, bound_region) => {
-                write!(f, "ReBound({binder_id:?}, {bound_region:?})")
+                write!(f, "'")?;
+                crate::debug_bound_var(f, *binder_id, bound_region)
             }
 
             ReLateParam(fr) => write!(f, "{fr:?}"),
 
-            ReStatic => f.write_str("ReStatic"),
+            ReStatic => f.write_str("'static"),
 
             ReVar(vid) => write!(f, "{:?}", &this.wrap(vid)),
 
-            RePlaceholder(placeholder) => write!(f, "RePlaceholder({placeholder:?})"),
+            RePlaceholder(placeholder) => write!(f, "{placeholder:?}"),
 
-            ReErased => f.write_str("ReErased"),
+            // Use `'{erased}` as the output instead of `'erased` so that its more obviously distinct from
+            // a `ReEarlyParam` named `'erased`. Technically that would print as `'erased/#IDX` so this is
+            // not strictly necessary but *shrug*
+            ReErased => f.write_str("'{erased}"),
 
-            ReError(_) => f.write_str("ReError"),
+            ReError(_) => f.write_str("'{region error}"),
         }
     }
 }