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-rw-r--r--crates/ra_hir_ty/src/_match.rs29
1 files changed, 23 insertions, 6 deletions
diff --git a/crates/ra_hir_ty/src/_match.rs b/crates/ra_hir_ty/src/_match.rs
index 779e78574..149f65042 100644
--- a/crates/ra_hir_ty/src/_match.rs
+++ b/crates/ra_hir_ty/src/_match.rs
@@ -573,14 +573,20 @@ pub(crate) fn is_useful(
573 matrix: &Matrix, 573 matrix: &Matrix,
574 v: &PatStack, 574 v: &PatStack,
575) -> MatchCheckResult<Usefulness> { 575) -> MatchCheckResult<Usefulness> {
576 // Handle the special case of enums with no variants. In that case, no match 576 // Handle two special cases:
577 // arm is useful. 577 // - enum with no variants
578 if let Ty::Apply(ApplicationTy { ctor: TypeCtor::Adt(AdtId::EnumId(enum_id)), .. }) = 578 // - `!` type
579 cx.infer[cx.match_expr].strip_references() 579 // In those cases, no match arm is useful.
580 { 580 match cx.infer[cx.match_expr].strip_references() {
581 if cx.db.enum_data(*enum_id).variants.is_empty() { 581 Ty::Apply(ApplicationTy { ctor: TypeCtor::Adt(AdtId::EnumId(enum_id)), .. }) => {
582 if cx.db.enum_data(*enum_id).variants.is_empty() {
583 return Ok(Usefulness::NotUseful);
584 }
585 }
586 Ty::Apply(ApplicationTy { ctor: TypeCtor::Never, .. }) => {
582 return Ok(Usefulness::NotUseful); 587 return Ok(Usefulness::NotUseful);
583 } 588 }
589 _ => (),
584 } 590 }
585 591
586 if v.is_empty() { 592 if v.is_empty() {
@@ -1918,6 +1924,17 @@ mod tests {
1918 } 1924 }
1919 1925
1920 #[test] 1926 #[test]
1927 fn type_never() {
1928 let content = r"
1929 fn test_fn(never: !) {
1930 match never {}
1931 }
1932 ";
1933
1934 check_no_diagnostic(content);
1935 }
1936
1937 #[test]
1921 fn enum_never_ref() { 1938 fn enum_never_ref() {
1922 let content = r" 1939 let content = r"
1923 enum Never {} 1940 enum Never {}