Merging upstream version 1.66.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

7 files changed, 132 insertions, 98 deletions

diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index d059877f8..c7a7c3e3f 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -48,6 +48,8 @@ impl<'tcx> Cx<'tcx> {
             _ => None,
         };
 
+        trace!(?expr.ty);
+
         // Now apply adjustments, if any.
         for adjustment in self.typeck_results.expr_adjustments(hir_expr) {
             trace!(?expr, ?adjustment);
@@ -56,6 +58,8 @@ impl<'tcx> Cx<'tcx> {
                 self.apply_adjustment(hir_expr, expr, adjustment, adjustment_span.unwrap_or(span));
         }
 
+        trace!(?expr.ty, "after adjustments");
+
         // Next, wrap this up in the expr's scope.
         expr = Expr {
             temp_lifetime,
@@ -155,6 +159,7 @@ impl<'tcx> Cx<'tcx> {
             Adjust::Borrow(AutoBorrow::RawPtr(mutability)) => {
                 ExprKind::AddressOf { mutability, arg: self.thir.exprs.push(expr) }
             }
+            Adjust::DynStar => ExprKind::Cast { source: self.thir.exprs.push(expr) },
         };
 
         Expr { temp_lifetime, ty: adjustment.target, span, kind }
@@ -994,7 +999,7 @@ impl<'tcx> Cx<'tcx> {
             .temporary_scope(self.region_scope_tree, closure_expr.hir_id.local_id);
         let var_ty = place.base_ty;
 
-        // The result of capture analysis in `rustc_typeck/check/upvar.rs`represents a captured path
+        // The result of capture analysis in `rustc_hir_analysis/check/upvar.rs`represents a captured path
         // as it's seen for use within the closure and not at the time of closure creation.
         //
         // That is we see expect to see it start from a captured upvar and not something that is local
diff --git a/compiler/rustc_mir_build/src/thir/cx/mod.rs b/compiler/rustc_mir_build/src/thir/cx/mod.rs
index 3ef1b263f..1d95d6b53 100644
--- a/compiler/rustc_mir_build/src/thir/cx/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/mod.rs
@@ -15,7 +15,7 @@ use rustc_hir::HirId;
 use rustc_hir::Node;
 use rustc_middle::middle::region;
 use rustc_middle::thir::*;
-use rustc_middle::ty::{self, RvalueScopes, Subst, TyCtxt};
+use rustc_middle::ty::{self, RvalueScopes, TyCtxt};
 use rustc_span::Span;
 
 pub(crate) fn thir_body<'tcx>(
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index d45b88690..858129c74 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -7,7 +7,7 @@ use super::{PatCtxt, PatternError};
 use rustc_arena::TypedArena;
 use rustc_ast::Mutability;
 use rustc_errors::{
-    error_code, pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder,
+    error_code, pluralize, struct_span_err, Applicability, DelayDm, Diagnostic, DiagnosticBuilder,
     ErrorGuaranteed, MultiSpan,
 };
 use rustc_hir as hir;
@@ -347,27 +347,35 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
             let span_end = affix.last().unwrap().unwrap().0;
             let span = span_start.to(span_end);
             let cnt = affix.len();
-            cx.tcx.struct_span_lint_hir(IRREFUTABLE_LET_PATTERNS, top, span, |lint| {
-                let s = pluralize!(cnt);
-                let mut diag = lint.build(&format!("{kind} irrefutable pattern{s} in let chain"));
-                diag.note(&format!(
-                    "{these} pattern{s} will always match",
-                    these = pluralize!("this", cnt),
-                ));
-                diag.help(&format!(
-                    "consider moving {} {suggestion}",
-                    if cnt > 1 { "them" } else { "it" }
-                ));
-                diag.emit()
-            });
+            let s = pluralize!(cnt);
+            cx.tcx.struct_span_lint_hir(
+                IRREFUTABLE_LET_PATTERNS,
+                top,
+                span,
+                format!("{kind} irrefutable pattern{s} in let chain"),
+                |lint| {
+                    lint.note(format!(
+                        "{these} pattern{s} will always match",
+                        these = pluralize!("this", cnt),
+                    ))
+                    .help(format!(
+                        "consider moving {} {suggestion}",
+                        if cnt > 1 { "them" } else { "it" }
+                    ))
+                },
+            );
         };
         if let Some(until) = chain_refutabilities.iter().position(|r| !matches!(*r, Some((_, false)))) && until > 0 {
             // The chain has a non-zero prefix of irrefutable `let` statements.
 
             // Check if the let source is while, for there is no alternative place to put a prefix,
             // and we shouldn't lint.
+            // For let guards inside a match, prefixes might use bindings of the match pattern,
+            // so can't always be moved out.
+            // FIXME: Add checking whether the bindings are actually used in the prefix,
+            // and lint if they are not.
             let let_source = let_source_parent(self.tcx, top, None);
-            if !matches!(let_source, LetSource::WhileLet) {
+            if !matches!(let_source, LetSource::WhileLet | LetSource::IfLetGuard) {
                 // Emit the lint
                 let prefix = &chain_refutabilities[..until];
                 lint_affix(prefix, "leading", "outside of the construct");
@@ -487,7 +495,7 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
                     ],
                     Applicability::HasPlaceholders,
                 );
-                if !bindings.is_empty() && cx.tcx.sess.is_nightly_build() {
+                if !bindings.is_empty() {
                     err.span_suggestion_verbose(
                         semi_span.shrink_to_lo(),
                         &format!(
@@ -561,26 +569,28 @@ fn check_for_bindings_named_same_as_variants(
                 BINDINGS_WITH_VARIANT_NAME,
                 p.hir_id,
                 p.span,
+                DelayDm(|| format!(
+                    "pattern binding `{}` is named the same as one \
+                        of the variants of the type `{}`",
+                    ident, cx.tcx.def_path_str(edef.did())
+                )),
                 |lint| {
                     let ty_path = cx.tcx.def_path_str(edef.did());
-                    let mut err = lint.build(&format!(
-                        "pattern binding `{}` is named the same as one \
-                         of the variants of the type `{}`",
-                        ident, ty_path
-                    ));
-                    err.code(error_code!(E0170));
+                    lint.code(error_code!(E0170));
+
                     // If this is an irrefutable pattern, and there's > 1 variant,
                     // then we can't actually match on this. Applying the below
                     // suggestion would produce code that breaks on `check_irrefutable`.
                     if rf == Refutable || variant_count == 1 {
-                        err.span_suggestion(
+                        lint.span_suggestion(
                             p.span,
                             "to match on the variant, qualify the path",
                             format!("{}::{}", ty_path, ident),
                             Applicability::MachineApplicable,
                         );
                     }
-                    err.emit();
+
+                    lint
                 },
             )
         }
@@ -598,14 +608,13 @@ fn pat_is_catchall(pat: &DeconstructedPat<'_, '_>) -> bool {
 }
 
 fn unreachable_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, catchall: Option<Span>) {
-    tcx.struct_span_lint_hir(UNREACHABLE_PATTERNS, id, span, |lint| {
-        let mut err = lint.build("unreachable pattern");
+    tcx.struct_span_lint_hir(UNREACHABLE_PATTERNS, id, span, "unreachable pattern", |lint| {
         if let Some(catchall) = catchall {
             // We had a catchall pattern, hint at that.
-            err.span_label(span, "unreachable pattern");
-            err.span_label(catchall, "matches any value");
+            lint.span_label(span, "unreachable pattern");
+            lint.span_label(catchall, "matches any value");
         }
-        err.emit();
+        lint
     });
 }
 
@@ -621,6 +630,11 @@ fn irrefutable_let_patterns(
     count: usize,
     span: Span,
 ) {
+    let span = match source {
+        LetSource::LetElse(span) => span,
+        _ => span,
+    };
+
     macro_rules! emit_diag {
         (
             $lint:expr,
@@ -630,18 +644,23 @@ fn irrefutable_let_patterns(
         ) => {{
             let s = pluralize!(count);
             let these = pluralize!("this", count);
-            let mut diag = $lint.build(&format!("irrefutable {} pattern{s}", $source_name));
-            diag.note(&format!("{these} pattern{s} will always match, so the {}", $note_sufix));
-            diag.help(concat!("consider ", $help_sufix));
-            diag.emit()
+            tcx.struct_span_lint_hir(
+                IRREFUTABLE_LET_PATTERNS,
+                id,
+                span,
+                format!("irrefutable {} pattern{s}", $source_name),
+                |lint| {
+                    lint.note(&format!(
+                        "{these} pattern{s} will always match, so the {}",
+                        $note_sufix
+                    ))
+                    .help(concat!("consider ", $help_sufix))
+                },
+            )
         }};
     }
 
-    let span = match source {
-        LetSource::LetElse(span) => span,
-        _ => span,
-    };
-    tcx.struct_span_lint_hir(IRREFUTABLE_LET_PATTERNS, id, span, |lint| match source {
+    match source {
         LetSource::GenericLet => {
             emit_diag!(lint, "`let`", "`let` is useless", "removing `let`");
         }
@@ -677,7 +696,7 @@ fn irrefutable_let_patterns(
                 "instead using a `loop { ... }` with a `let` inside it"
             );
         }
-    });
+    };
 }
 
 fn is_let_irrefutable<'p, 'tcx>(
@@ -985,8 +1004,8 @@ fn maybe_point_at_variant<'a, 'p: 'a, 'tcx: 'a>(
 }
 
 /// Check if a by-value binding is by-value. That is, check if the binding's type is not `Copy`.
-fn is_binding_by_move(cx: &MatchVisitor<'_, '_, '_>, hir_id: HirId, span: Span) -> bool {
-    !cx.typeck_results.node_type(hir_id).is_copy_modulo_regions(cx.tcx.at(span), cx.param_env)
+fn is_binding_by_move(cx: &MatchVisitor<'_, '_, '_>, hir_id: HirId) -> bool {
+    !cx.typeck_results.node_type(hir_id).is_copy_modulo_regions(cx.tcx, cx.param_env)
 }
 
 /// Check that there are no borrow or move conflicts in `binding @ subpat` patterns.
@@ -1012,7 +1031,7 @@ fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_, '_>, pat: &Pa
 
     // Get the binding move, extract the mutability if by-ref.
     let mut_outer = match typeck_results.extract_binding_mode(sess, pat.hir_id, pat.span) {
-        Some(ty::BindByValue(_)) if is_binding_by_move(cx, pat.hir_id, pat.span) => {
+        Some(ty::BindByValue(_)) if is_binding_by_move(cx, pat.hir_id) => {
             // We have `x @ pat` where `x` is by-move. Reject all borrows in `pat`.
             let mut conflicts_ref = Vec::new();
             sub.each_binding(|_, hir_id, span, _| {
@@ -1051,7 +1070,7 @@ fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_, '_>, pat: &Pa
                 (Mutability::Mut, Mutability::Mut) => conflicts_mut_mut.push((span, name)), // 2x `ref mut`.
                 _ => conflicts_mut_ref.push((span, name)), // `ref` + `ref mut` in either direction.
             },
-            Some(ty::BindByValue(_)) if is_binding_by_move(cx, hir_id, span) => {
+            Some(ty::BindByValue(_)) if is_binding_by_move(cx, hir_id) => {
                 conflicts_move.push((span, name)) // `ref mut?` + by-move conflict.
             }
             Some(ty::BindByValue(_)) | None => {} // `ref mut?` + by-copy is fine.
@@ -1136,10 +1155,14 @@ fn let_source_parent(tcx: TyCtxt<'_>, parent: HirId, pat_id: Option<HirId>) -> L
 
     let parent_parent = hir.get_parent_node(parent);
     let parent_parent_node = hir.get(parent_parent);
-    if let hir::Node::Stmt(hir::Stmt { kind: hir::StmtKind::Local(_), span, .. }) =
-        parent_parent_node
-    {
-        return LetSource::LetElse(*span);
+    match parent_parent_node {
+        hir::Node::Stmt(hir::Stmt { kind: hir::StmtKind::Local(_), span, .. }) => {
+            return LetSource::LetElse(*span);
+        }
+        hir::Node::Arm(hir::Arm { guard: Some(hir::Guard::If(_)), .. }) => {
+            return LetSource::IfLetGuard;
+        }
+        _ => {}
     }
 
     let parent_parent_parent = hir.get_parent_node(parent_parent);
diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
index b58685e89..ad12e0116 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
@@ -1,3 +1,4 @@
+use rustc_errors::DelayDm;
 use rustc_hir as hir;
 use rustc_index::vec::Idx;
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
@@ -27,14 +28,13 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         span: Span,
         mir_structural_match_violation: bool,
     ) -> Box<Pat<'tcx>> {
-        self.tcx.infer_ctxt().enter(|infcx| {
-            let mut convert = ConstToPat::new(self, id, span, infcx);
-            convert.to_pat(cv, mir_structural_match_violation)
-        })
+        let infcx = self.tcx.infer_ctxt().build();
+        let mut convert = ConstToPat::new(self, id, span, infcx);
+        convert.to_pat(cv, mir_structural_match_violation)
     }
 }
 
-struct ConstToPat<'a, 'tcx> {
+struct ConstToPat<'tcx> {
     id: hir::HirId,
     span: Span,
     param_env: ty::ParamEnv<'tcx>,
@@ -54,7 +54,7 @@ struct ConstToPat<'a, 'tcx> {
     behind_reference: Cell<bool>,
 
     // inference context used for checking `T: Structural` bounds.
-    infcx: InferCtxt<'a, 'tcx>,
+    infcx: InferCtxt<'tcx>,
 
     include_lint_checks: bool,
 
@@ -70,21 +70,19 @@ mod fallback_to_const_ref {
     /// hoops to get a reference to the value.
     pub(super) struct FallbackToConstRef(());
 
-    pub(super) fn fallback_to_const_ref<'a, 'tcx>(
-        c2p: &super::ConstToPat<'a, 'tcx>,
-    ) -> FallbackToConstRef {
+    pub(super) fn fallback_to_const_ref<'tcx>(c2p: &super::ConstToPat<'tcx>) -> FallbackToConstRef {
         assert!(c2p.behind_reference.get());
         FallbackToConstRef(())
     }
 }
 use fallback_to_const_ref::{fallback_to_const_ref, FallbackToConstRef};
 
-impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
+impl<'tcx> ConstToPat<'tcx> {
     fn new(
         pat_ctxt: &PatCtxt<'_, 'tcx>,
         id: hir::HirId,
         span: Span,
-        infcx: InferCtxt<'a, 'tcx>,
+        infcx: InferCtxt<'tcx>,
     ) -> Self {
         trace!(?pat_ctxt.typeck_results.hir_owner);
         ConstToPat {
@@ -205,9 +203,8 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                         lint::builtin::INDIRECT_STRUCTURAL_MATCH,
                         self.id,
                         self.span,
-                        |lint| {
-                            lint.build(&msg).emit();
-                        },
+                        msg,
+                        |lint| lint,
                     );
                 } else {
                     debug!(
@@ -286,9 +283,8 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                         lint::builtin::ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
                         id,
                         span,
-                        |lint| {
-                            lint.build("floating-point types cannot be used in patterns").emit();
-                        },
+                        "floating-point types cannot be used in patterns",
+                        |lint| lint,
                     );
                 }
                 PatKind::Constant { value: cv }
@@ -340,15 +336,15 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                         lint::builtin::INDIRECT_STRUCTURAL_MATCH,
                         id,
                         span,
-                        |lint| {
-                            let msg = format!(
+                        DelayDm(|| {
+                            format!(
                                 "to use a constant of type `{}` in a pattern, \
                                  `{}` must be annotated with `#[derive(PartialEq, Eq)]`",
                                 cv.ty(),
                                 cv.ty(),
-                            );
-                            lint.build(&msg).emit();
-                        },
+                            )
+                        }),
+                        |lint| lint,
                     );
                 }
                 // Since we are behind a reference, we can just bubble the error up so we get a
@@ -488,7 +484,8 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                                 lint::builtin::INDIRECT_STRUCTURAL_MATCH,
                                 self.id,
                                 self.span,
-                                |lint| {lint.build(&msg).emit();},
+                                msg,
+                                |lint| lint,
                             );
                         }
                         PatKind::Constant { value: cv }
@@ -509,7 +506,7 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                 // convert the dereferenced constant to a pattern that is the sub-pattern of the
                 // deref pattern.
                 _ => {
-                    if !pointee_ty.is_sized(tcx.at(span), param_env) {
+                    if !pointee_ty.is_sized(tcx, param_env) {
                         // `tcx.deref_mir_constant()` below will ICE with an unsized type
                         // (except slices, which are handled in a separate arm above).
                         let msg = format!("cannot use unsized non-slice type `{}` in constant patterns", pointee_ty);
@@ -537,7 +534,7 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
             ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::FnDef(..) => {
                 PatKind::Constant { value: cv }
             }
-            ty::RawPtr(pointee) if pointee.ty.is_sized(tcx.at(span), param_env) => {
+            ty::RawPtr(pointee) if pointee.ty.is_sized(tcx, param_env) => {
                 PatKind::Constant { value: cv }
             }
             // FIXME: these can have very surprising behaviour where optimization levels or other
@@ -556,9 +553,8 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                         lint::builtin::POINTER_STRUCTURAL_MATCH,
                         id,
                         span,
-                        |lint| {
-                            lint.build(msg).emit();
-                        },
+                        msg,
+                        |lint| lint,
                     );
                 }
                 PatKind::Constant { value: cv }
@@ -594,9 +590,8 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                 lint::builtin::NONTRIVIAL_STRUCTURAL_MATCH,
                 id,
                 span,
-                |lint| {
-                    lint.build(&msg).emit();
-                },
+                msg,
+                |lint| lint,
             );
         }
 
diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
index 5105f059f..595abc8f6 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
@@ -299,10 +299,10 @@ impl IntRange {
                 lint::builtin::OVERLAPPING_RANGE_ENDPOINTS,
                 hir_id,
                 pcx.span,
+                "multiple patterns overlap on their endpoints",
                 |lint| {
-                    let mut err = lint.build("multiple patterns overlap on their endpoints");
                     for (int_range, span) in overlaps {
-                        err.span_label(
+                        lint.span_label(
                             span,
                             &format!(
                                 "this range overlaps on `{}`...",
@@ -310,9 +310,9 @@ impl IntRange {
                             ),
                         );
                     }
-                    err.span_label(pcx.span, "... with this range");
-                    err.note("you likely meant to write mutually exclusive ranges");
-                    err.emit();
+                    lint.span_label(pcx.span, "... with this range");
+                    lint.note("you likely meant to write mutually exclusive ranges");
+                    lint
                 },
             );
         }
@@ -988,10 +988,12 @@ impl<'tcx> SplitWildcard<'tcx> {
                     .filter(|(_, v)| {
                         // If `exhaustive_patterns` is enabled, we exclude variants known to be
                         // uninhabited.
-                        let is_uninhabited = is_exhaustive_pat_feature
-                            && v.uninhabited_from(cx.tcx, substs, def.adt_kind(), cx.param_env)
-                                .contains(cx.tcx, cx.module);
-                        !is_uninhabited
+                        !is_exhaustive_pat_feature
+                            || v.inhabited_predicate(cx.tcx, *def).subst(cx.tcx, substs).apply(
+                                cx.tcx,
+                                cx.param_env,
+                                cx.module,
+                            )
                     })
                     .map(|(idx, _)| Variant(idx))
                     .collect();
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index 0edf6a983..2526522a2 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -86,7 +86,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         // ```
         //
         // the type assigned to `Some(n)` in `unadjusted_pat` would be `Option<i32>` (this is
-        // determined in rustc_typeck::check::match). The adjustments would be
+        // determined in rustc_hir_analysis::check::match). The adjustments would be
         //
         // `vec![&&Option<i32>, &Option<i32>]`.
         //
@@ -200,6 +200,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         }
     }
 
+    #[instrument(skip(self), level = "debug")]
     fn lower_pattern_unadjusted(&mut self, pat: &'tcx hir::Pat<'tcx>) -> Box<Pat<'tcx>> {
         let mut ty = self.typeck_results.node_type(pat.hir_id);
         let mut span = pat.span;
@@ -432,7 +433,8 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                 | DefKind::AssocTy,
                 _,
             )
-            | Res::SelfTy { .. }
+            | Res::SelfTyParam { .. }
+            | Res::SelfTyAlias { .. }
             | Res::SelfCtor(..) => PatKind::Leaf { subpatterns },
             _ => {
                 let pattern_error = match res {
@@ -684,7 +686,7 @@ macro_rules! ClonePatternFoldableImpls {
 }
 
 ClonePatternFoldableImpls! { <'tcx>
-    Span, Field, Mutability, Symbol, LocalVarId, usize, ty::Const<'tcx>,
+    Span, Field, Mutability, Symbol, LocalVarId, usize,
     Region<'tcx>, Ty<'tcx>, BindingMode, AdtDef<'tcx>,
     SubstsRef<'tcx>, &'tcx GenericArg<'tcx>, UserType<'tcx>,
     UserTypeProjection, CanonicalUserTypeAnnotation<'tcx>
diff --git a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
index 115d34ff8..8dc9976ea 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
@@ -746,7 +746,7 @@ impl<'p, 'tcx> Witness<'p, 'tcx> {
 /// Report that a match of a `non_exhaustive` enum marked with `non_exhaustive_omitted_patterns`
 /// is not exhaustive enough.
 ///
-/// NB: The partner lint for structs lives in `compiler/rustc_typeck/src/check/pat.rs`.
+/// NB: The partner lint for structs lives in `compiler/rustc_hir_analysis/src/check/pat.rs`.
 fn lint_non_exhaustive_omitted_patterns<'p, 'tcx>(
     cx: &MatchCheckCtxt<'p, 'tcx>,
     scrut_ty: Ty<'tcx>,
@@ -754,9 +754,8 @@ fn lint_non_exhaustive_omitted_patterns<'p, 'tcx>(
     hir_id: HirId,
     witnesses: Vec<DeconstructedPat<'p, 'tcx>>,
 ) {
-    cx.tcx.struct_span_lint_hir(NON_EXHAUSTIVE_OMITTED_PATTERNS, hir_id, sp, |build| {
+    cx.tcx.struct_span_lint_hir(NON_EXHAUSTIVE_OMITTED_PATTERNS, hir_id, sp, "some variants are not matched explicitly", |lint| {
         let joined_patterns = joined_uncovered_patterns(cx, &witnesses);
-        let mut lint = build.build("some variants are not matched explicitly");
         lint.span_label(sp, pattern_not_covered_label(&witnesses, &joined_patterns));
         lint.help(
             "ensure that all variants are matched explicitly by adding the suggested match arms",
@@ -765,7 +764,7 @@ fn lint_non_exhaustive_omitted_patterns<'p, 'tcx>(
             "the matched value is of type `{}` and the `non_exhaustive_omitted_patterns` attribute was found",
             scrut_ty,
         ));
-        lint.emit();
+        lint
     });
 }
 
@@ -842,7 +841,15 @@ fn is_useful<'p, 'tcx>(
             }
         }
     } else {
-        let ty = v.head().ty();
+        let mut ty = v.head().ty();
+
+        // Opaque types can't get destructured/split, but the patterns can
+        // actually hint at hidden types, so we use the patterns' types instead.
+        if let ty::Opaque(..) = ty.kind() {
+            if let Some(row) = rows.first() {
+                ty = row.head().ty();
+            }
+        }
         let is_non_exhaustive = cx.is_foreign_non_exhaustive_enum(ty);
         debug!("v.head: {:?}, v.span: {:?}", v.head(), v.head().span());
         let pcx = &PatCtxt { cx, ty, span: v.head().span(), is_top_level, is_non_exhaustive };
@@ -878,7 +885,7 @@ fn is_useful<'p, 'tcx>(
             // that has the potential to trigger the `non_exhaustive_omitted_patterns` lint.
             // To understand the workings checkout `Constructor::split` and `SplitWildcard::new/into_ctors`
             if is_non_exhaustive_and_wild
-                // We check that the match has a wildcard pattern and that that wildcard is useful,
+                // We check that the match has a wildcard pattern and that wildcard is useful,
                 // meaning there are variants that are covered by the wildcard. Without the check
                 // for `witness_preference` the lint would trigger on `if let NonExhaustiveEnum::A = foo {}`
                 && usefulness.is_useful() && matches!(witness_preference, RealArm)