1 files changed, 20 insertions, 1 deletions

diff --git a/crates/hir_ty/src/diagnostics/pattern/usefulness.rs b/crates/hir_ty/src/diagnostics/pattern/usefulness.rs
index 4b55aee97..2df87ccea 100644
--- a/crates/hir_ty/src/diagnostics/pattern/usefulness.rs
+++ b/crates/hir_ty/src/diagnostics/pattern/usefulness.rs
@@ -3,7 +3,11 @@
 
 use std::{cell::RefCell, iter::FromIterator, ops::Index, sync::Arc};
 
-use hir_def::{ModuleId, body::Body, expr::{ExprId, Pat, PatId}};
+use hir_def::{
+    body::Body,
+    expr::{ExprId, Pat, PatId},
+    HasModule, ModuleId,
+};
 use la_arena::Arena;
 use once_cell::unsync::OnceCell;
 use rustc_hash::FxHashMap;
@@ -36,6 +40,21 @@ impl<'a> MatchCheckCtx<'a> {
         false
     }
 
+    /// Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`.
+    pub(super) fn is_foreign_non_exhaustive_enum(&self, enum_id: hir_def::EnumId) -> bool {
+        let has_non_exhaustive_attr =
+            self.db.attrs(enum_id.into()).by_key("non_exhaustive").exists();
+        let is_local =
+            hir_def::AdtId::from(enum_id).module(self.db.upcast()).krate() == self.module.krate();
+        has_non_exhaustive_attr && !is_local
+    }
+
+    // Rust feature described as "Allows exhaustive pattern matching on types that contain uninhabited types."
+    pub(super) fn feature_exhaustive_patterns(&self) -> bool {
+        // TODO
+        false
+    }
+
     pub(super) fn alloc_pat(&self, pat: Pat, ty: &Ty) -> PatId {
         self.pattern_arena.borrow_mut().alloc(pat, ty)
     }