assertion for only collection nll region variable information for debug in non-canonicalization contexts

compiler/rustc_infer/src/infer/at.rs

@@ -30,6 +30,8 @@ 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
@@ -82,6 +84,7 @@ 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

@@ -561,6 +561,8 @@ 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::NEEDS_INFER |
             TypeFlags::HAS_FREE_REGIONS | // `HAS_RE_PLACEHOLDER` implies `HAS_FREE_REGIONS`

compiler/rustc_infer/src/infer/mod.rs

@@ -39,6 +39,7 @@ 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;
@@ -342,6 +343,11 @@ 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.
@@ -633,6 +639,7 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
             skip_leak_check: Cell::new(false),
             universe: Cell::new(ty::UniverseIndex::ROOT),
             intercrate,
+            inside_canonicalization_ctxt: Cell::new(false),
         }
     }
 }
@@ -1728,6 +1735,31 @@ 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> {