2 files changed, 39 insertions, 17 deletions
diff --git a/compiler/rustc_pattern_analysis/src/errors.rs b/compiler/rustc_pattern_analysis/src/errors.rs
index 1f7852e5190..e60930d6cd2 100644
--- a/compiler/rustc_pattern_analysis/src/errors.rs
+++ b/compiler/rustc_pattern_analysis/src/errors.rs
@@ -1,4 +1,4 @@
-use rustc_errors::{Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic};
+use rustc_errors::{Diag, EmissionGuarantee, Subdiagnostic};
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
 use rustc_span::Span;
@@ -55,11 +55,7 @@ pub struct Overlap {
 }
 
 impl Subdiagnostic for Overlap {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         let Overlap { span, range } = self;
 
         // FIXME(mejrs) unfortunately `#[derive(LintDiagnostic)]`
@@ -103,11 +99,7 @@ pub struct GappedRange {
 }
 
 impl Subdiagnostic for GappedRange {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         let GappedRange { span, gap, first_range } = self;
 
         // FIXME(mejrs) unfortunately `#[derive(LintDiagnostic)]`
diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index 31c4ee0fa0b..7c12f69f14c 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -1,5 +1,6 @@
 use std::fmt;
 use std::iter::once;
+use std::ops::ControlFlow;
 
 use rustc_abi::{FIRST_VARIANT, FieldIdx, Integer, VariantIdx};
 use rustc_arena::DroplessArena;
@@ -11,7 +12,8 @@ use rustc_middle::mir::{self, Const};
 use rustc_middle::thir::{self, Pat, PatKind, PatRange, PatRangeBoundary};
 use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::ty::{
-    self, FieldDef, OpaqueTypeKey, ScalarInt, Ty, TyCtxt, TypeVisitableExt, VariantDef,
+    self, FieldDef, OpaqueTypeKey, ScalarInt, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt, TypeVisitor, VariantDef,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
@@ -135,11 +137,22 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// Returns the hidden type corresponding to this key if the body under analysis is allowed to
     /// know it.
     fn reveal_opaque_key(&self, key: OpaqueTypeKey<'tcx>) -> Option<Ty<'tcx>> {
-        self.typeck_results
-            .concrete_opaque_types
-            .get(&key.def_id)
-            .map(|x| ty::EarlyBinder::bind(x.ty).instantiate(self.tcx, key.args))
+        if let Some(hidden_ty) = self.typeck_results.concrete_opaque_types.get(&key.def_id) {
+            let ty = ty::EarlyBinder::bind(hidden_ty.ty).instantiate(self.tcx, key.args);
+            if ty.visit_with(&mut RecursiveOpaque { def_id: key.def_id.into() }).is_continue() {
+                Some(ty)
+            } else {
+                // HACK: We skip revealing opaque types which recursively expand
+                // to themselves. This is because we may infer hidden types like
+                // `Opaque<T> = Opaque<Opaque<T>>` or `Opaque<T> = Opaque<(T,)>`
+                // in hir typeck.
+                None
+            }
+        } else {
+            None
+        }
     }
+
     // This can take a non-revealed `Ty` because it reveals opaques itself.
     pub fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
         !ty.inhabited_predicate(self.tcx).apply_revealing_opaque(
@@ -460,7 +473,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
             PatKind::AscribeUserType { subpattern, .. }
             | PatKind::ExpandedConstant { subpattern, .. } => return self.lower_pat(subpattern),
             PatKind::Binding { subpattern: Some(subpat), .. } => return self.lower_pat(subpat),
-            PatKind::Binding { subpattern: None, .. } | PatKind::Wild => {
+            PatKind::Missing | PatKind::Binding { subpattern: None, .. } | PatKind::Wild => {
                 ctor = Wildcard;
                 fields = vec![];
                 arity = 0;
@@ -1105,3 +1118,20 @@ pub fn analyze_match<'p, 'tcx>(
 
     Ok(report)
 }
+
+struct RecursiveOpaque {
+    def_id: DefId,
+}
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for RecursiveOpaque {
+    type Result = ControlFlow<()>;
+
+    fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
+        if let ty::Alias(ty::Opaque, alias_ty) = t.kind() {
+            if alias_ty.def_id == self.def_id {
+                return ControlFlow::Break(());
+            }
+        }
+
+        if t.has_opaque_types() { t.super_visit_with(self) } else { ControlFlow::Continue(()) }
+    }
+}