remove inside_canonicalization_ctxt flag

we never reach the code checking for this flag while the
flag is enabled, so it does not change the behavior
of the code.

compiler/rustc_borrowck/src/lib.rs

@@ -498,11 +498,11 @@ impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
         let next_region = self.infcx.next_region_var(origin);
         let vid = next_region.as_var();
 
-        if cfg!(debug_assertions) && !self.inside_canonicalization_ctxt() {
+        if cfg!(debug_assertions) {
             debug!("inserting vid {:?} with origin {:?} into var_to_origin", vid, origin);
             let ctxt = get_ctxt_fn();
             let mut var_to_origin = self.reg_var_to_origin.borrow_mut();
-            var_to_origin.insert(vid, ctxt);
+            assert_eq!(var_to_origin.insert(vid, ctxt), None);
         }
 
         next_region
@@ -520,11 +520,11 @@ impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
         let next_region = self.infcx.next_nll_region_var(origin);
         let vid = next_region.as_var();
 
-        if cfg!(debug_assertions) && !self.inside_canonicalization_ctxt() {
+        if cfg!(debug_assertions) {
             debug!("inserting vid {:?} with origin {:?} into var_to_origin", vid, origin);
             let ctxt = get_ctxt_fn();
             let mut var_to_origin = self.reg_var_to_origin.borrow_mut();
-            var_to_origin.insert(vid, ctxt);
+            assert_eq!(var_to_origin.insert(vid, ctxt), None);
         }
 
         next_region

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -131,9 +131,13 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
             ty::BoundRegionKind::BrEnv => BoundRegionInfo::Name(sym::env),
         };
 
-        if cfg!(debug_assertions) && !self.type_checker.infcx.inside_canonicalization_ctxt() {
+        if cfg!(debug_assertions) {
             let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
-            var_to_origin.insert(reg.as_var(), RegionCtxt::Placeholder(reg_info));
+            let new = RegionCtxt::Placeholder(reg_info);
+            let prev = var_to_origin.insert(reg.as_var(), new);
+            if let Some(prev) = prev {
+                assert_eq!(new, prev);
+            }
         }
 
         reg
@@ -146,9 +150,10 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
             universe,
         );
 
-        if cfg!(debug_assertions) && !self.type_checker.infcx.inside_canonicalization_ctxt() {
+        if cfg!(debug_assertions) {
             let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
-            var_to_origin.insert(reg.as_var(), RegionCtxt::Existential(None));
+            let prev = var_to_origin.insert(reg.as_var(), RegionCtxt::Existential(None));
+            assert_eq!(prev, None);
         }
 
         reg

compiler/rustc_infer/src/infer/at.rs

@@ -30,8 +30,6 @@ use super::*;
 use rustc_middle::ty::relate::{Relate, TypeRelation};
 use rustc_middle::ty::{Const, ImplSubject};
 
-use std::cell::Cell;
-
 /// Whether we should define opaque types or just treat them opaquely.
 ///
 /// Currently only used to prevent predicate matching from matching anything
@@ -84,7 +82,6 @@ impl<'tcx> InferCtxt<'tcx> {
             in_snapshot: self.in_snapshot.clone(),
             universe: self.universe.clone(),
             intercrate: self.intercrate,
-            inside_canonicalization_ctxt: Cell::new(self.inside_canonicalization_ctxt()),
         }
     }
 }

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

@@ -561,8 +561,6 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
     where
         V: TypeFoldable<TyCtxt<'tcx>>,
     {
-        let _inside_canonical_ctxt_guard = infcx.set_canonicalization_ctxt();
-
         let needs_canonical_flags = if canonicalize_region_mode.any() {
             TypeFlags::HAS_INFER |
             TypeFlags::HAS_FREE_REGIONS | // `HAS_RE_PLACEHOLDER` implies `HAS_FREE_REGIONS`

compiler/rustc_infer/src/infer/mod.rs

@@ -39,7 +39,6 @@ use rustc_span::Span;
 
 use std::cell::{Cell, RefCell};
 use std::fmt;
-use std::ops::Drop;
 
 use self::combine::CombineFields;
 use self::error_reporting::TypeErrCtxt;
@@ -342,11 +341,6 @@ pub struct InferCtxt<'tcx> {
     /// there is no type that the user could *actually name* that
     /// would satisfy it. This avoids crippling inference, basically.
     pub intercrate: bool,
-
-    /// Flag that is set when we enter canonicalization. Used for debugging to ensure
-    /// that we only collect region information for `BorrowckInferCtxt::reg_var_to_origin`
-    /// inside non-canonicalization contexts.
-    inside_canonicalization_ctxt: Cell<bool>,
 }
 
 /// See the `error_reporting` module for more details.
@@ -638,7 +632,6 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
             skip_leak_check: Cell::new(false),
             universe: Cell::new(ty::UniverseIndex::ROOT),
             intercrate,
-            inside_canonicalization_ctxt: Cell::new(false),
         }
     }
 }
@@ -1636,31 +1629,6 @@ impl<'tcx> InferCtxt<'tcx> {
             }
         }
     }
-
-    pub fn inside_canonicalization_ctxt(&self) -> bool {
-        self.inside_canonicalization_ctxt.get()
-    }
-
-    pub fn set_canonicalization_ctxt(&self) -> CanonicalizationCtxtGuard<'_, 'tcx> {
-        let prev_ctxt = self.inside_canonicalization_ctxt();
-        self.inside_canonicalization_ctxt.set(true);
-        CanonicalizationCtxtGuard { prev_ctxt, infcx: self }
-    }
-
-    fn set_canonicalization_ctxt_to(&self, ctxt: bool) {
-        self.inside_canonicalization_ctxt.set(ctxt);
-    }
-}
-
-pub struct CanonicalizationCtxtGuard<'cx, 'tcx> {
-    prev_ctxt: bool,
-    infcx: &'cx InferCtxt<'tcx>,
-}
-
-impl<'cx, 'tcx> Drop for CanonicalizationCtxtGuard<'cx, 'tcx> {
-    fn drop(&mut self) {
-        self.infcx.set_canonicalization_ctxt_to(self.prev_ctxt)
-    }
 }
 
 impl<'tcx> TypeErrCtxt<'_, 'tcx> {