Rollup merge of #109838 - clubby789:non-exhaustive-span, r=Nilstrieb

Fix `non_exhaustive_omitted_patterns` lint span

Fixes #109837

`DUMMY_SP` was being passed as the span in many cases where we have a span available to use. This meant that the location of the violating pattern wasn't shown, or the list of un-covered variants

r? `@Nilstrieb`

Author: compiler-errors

compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs

@@ -1154,8 +1154,9 @@ impl<'p, 'tcx> Fields<'p, 'tcx> {
     fn wildcards_from_tys(
         cx: &MatchCheckCtxt<'p, 'tcx>,
         tys: impl IntoIterator<Item = Ty<'tcx>>,
+        span: Span,
     ) -> Self {
-        Fields::from_iter(cx, tys.into_iter().map(DeconstructedPat::wildcard))
+        Fields::from_iter(cx, tys.into_iter().map(|ty| DeconstructedPat::wildcard(ty, span)))
     }
 
     // In the cases of either a `#[non_exhaustive]` field list or a non-public field, we hide
@@ -1191,26 +1192,26 @@ impl<'p, 'tcx> Fields<'p, 'tcx> {
     pub(super) fn wildcards(pcx: &PatCtxt<'_, 'p, 'tcx>, constructor: &Constructor<'tcx>) -> Self {
         let ret = match constructor {
             Single | Variant(_) => match pcx.ty.kind() {
-                ty::Tuple(fs) => Fields::wildcards_from_tys(pcx.cx, fs.iter()),
-                ty::Ref(_, rty, _) => Fields::wildcards_from_tys(pcx.cx, once(*rty)),
+                ty::Tuple(fs) => Fields::wildcards_from_tys(pcx.cx, fs.iter(), pcx.span),
+                ty::Ref(_, rty, _) => Fields::wildcards_from_tys(pcx.cx, once(*rty), pcx.span),
                 ty::Adt(adt, substs) => {
                     if adt.is_box() {
                         // The only legal patterns of type `Box` (outside `std`) are `_` and box
                         // patterns. If we're here we can assume this is a box pattern.
-                        Fields::wildcards_from_tys(pcx.cx, once(substs.type_at(0)))
+                        Fields::wildcards_from_tys(pcx.cx, once(substs.type_at(0)), pcx.span)
                     } else {
                         let variant = &adt.variant(constructor.variant_index_for_adt(*adt));
                         let tys = Fields::list_variant_nonhidden_fields(pcx.cx, pcx.ty, variant)
                             .map(|(_, ty)| ty);
-                        Fields::wildcards_from_tys(pcx.cx, tys)
+                        Fields::wildcards_from_tys(pcx.cx, tys, pcx.span)
                     }
                 }
                 _ => bug!("Unexpected type for `Single` constructor: {:?}", pcx),
             },
             Slice(slice) => match *pcx.ty.kind() {
                 ty::Slice(ty) | ty::Array(ty, _) => {
                     let arity = slice.arity();
-                    Fields::wildcards_from_tys(pcx.cx, (0..arity).map(|_| ty))
+                    Fields::wildcards_from_tys(pcx.cx, (0..arity).map(|_| ty), pcx.span)
                 }
                 _ => bug!("bad slice pattern {:?} {:?}", constructor, pcx),
             },
@@ -1251,8 +1252,8 @@ pub(crate) struct DeconstructedPat<'p, 'tcx> {
 }
 
 impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
-    pub(super) fn wildcard(ty: Ty<'tcx>) -> Self {
-        Self::new(Wildcard, Fields::empty(), ty, DUMMY_SP)
+    pub(super) fn wildcard(ty: Ty<'tcx>, span: Span) -> Self {
+        Self::new(Wildcard, Fields::empty(), ty, span)
     }
 
     pub(super) fn new(
@@ -1269,7 +1270,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
     /// `Some(_)`.
     pub(super) fn wild_from_ctor(pcx: &PatCtxt<'_, 'p, 'tcx>, ctor: Constructor<'tcx>) -> Self {
         let fields = Fields::wildcards(pcx, &ctor);
-        DeconstructedPat::new(ctor, fields, pcx.ty, DUMMY_SP)
+        DeconstructedPat::new(ctor, fields, pcx.ty, pcx.span)
     }
 
     /// Clone this value. This method emphasizes that cloning loses reachability information and
@@ -1298,7 +1299,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                     ty::Tuple(fs) => {
                         ctor = Single;
                         let mut wilds: SmallVec<[_; 2]> =
-                            fs.iter().map(DeconstructedPat::wildcard).collect();
+                            fs.iter().map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
                         for pat in subpatterns {
                             wilds[pat.field.index()] = mkpat(&pat.pattern);
                         }
@@ -1317,11 +1318,11 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                         // normally or through box-patterns. We'll have to figure out a proper
                         // solution when we introduce generalized deref patterns. Also need to
                         // prevent mixing of those two options.
-                        let pat = subpatterns.into_iter().find(|pat| pat.field.index() == 0);
-                        let pat = if let Some(pat) = pat {
+                        let pattern = subpatterns.into_iter().find(|pat| pat.field.index() == 0);
+                        let pat = if let Some(pat) = pattern {
                             mkpat(&pat.pattern)
                         } else {
-                            DeconstructedPat::wildcard(substs.type_at(0))
+                            DeconstructedPat::wildcard(substs.type_at(0), pat.span)
                         };
                         ctor = Single;
                         fields = Fields::singleton(cx, pat);
@@ -1343,7 +1344,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                                 ty
                             });
                         let mut wilds: SmallVec<[_; 2]> =
-                            tys.map(DeconstructedPat::wildcard).collect();
+                            tys.map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
                         for pat in subpatterns {
                             if let Some(i) = field_id_to_id[pat.field.index()] {
                                 wilds[i] = mkpat(&pat.pattern);
@@ -1566,8 +1567,10 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                         };
                         let prefix = &self.fields.fields[..prefix];
                         let suffix = &self.fields.fields[self_slice.arity() - suffix..];
-                        let wildcard: &_ =
-                            pcx.cx.pattern_arena.alloc(DeconstructedPat::wildcard(inner_ty));
+                        let wildcard: &_ = pcx
+                            .cx
+                            .pattern_arena
+                            .alloc(DeconstructedPat::wildcard(inner_ty, pcx.span));
                         let extra_wildcards = other_slice.arity() - self_slice.arity();
                         let extra_wildcards = (0..extra_wildcards).map(|_| wildcard);
                         prefix.iter().chain(extra_wildcards).chain(suffix).collect()

compiler/rustc_mir_build/src/thir/pattern/usefulness.rs

@@ -604,7 +604,7 @@ impl<'p, 'tcx> Usefulness<'p, 'tcx> {
                     let new_patterns = if pcx.is_non_exhaustive {
                         // Here we don't want the user to try to list all variants, we want them to add
                         // a wildcard, so we only suggest that.
-                        vec![DeconstructedPat::wildcard(pcx.ty)]
+                        vec![DeconstructedPat::wildcard(pcx.ty, pcx.span)]
                     } else {
                         let mut split_wildcard = SplitWildcard::new(pcx);
                         split_wildcard.split(pcx, matrix.heads().map(DeconstructedPat::ctor));
@@ -631,7 +631,7 @@ impl<'p, 'tcx> Usefulness<'p, 'tcx> {
                             .collect();
 
                         if hide_variant_show_wild {
-                            new.push(DeconstructedPat::wildcard(pcx.ty));
+                            new.push(DeconstructedPat::wildcard(pcx.ty, pcx.span));
                         }
 
                         new
@@ -734,7 +734,7 @@ impl<'p, 'tcx> Witness<'p, 'tcx> {
             let arity = ctor.arity(pcx);
             let pats = self.0.drain((len - arity)..).rev();
             let fields = Fields::from_iter(pcx.cx, pats);
-            DeconstructedPat::new(ctor.clone(), fields, pcx.ty, DUMMY_SP)
+            DeconstructedPat::new(ctor.clone(), fields, pcx.ty, pcx.span)
         };
 
         self.0.push(pat);
@@ -977,7 +977,7 @@ pub(crate) fn compute_match_usefulness<'p, 'tcx>(
         })
         .collect();
 
-    let wild_pattern = cx.pattern_arena.alloc(DeconstructedPat::wildcard(scrut_ty));
+    let wild_pattern = cx.pattern_arena.alloc(DeconstructedPat::wildcard(scrut_ty, DUMMY_SP));
     let v = PatStack::from_pattern(wild_pattern);
     let usefulness = is_useful(cx, &matrix, &v, FakeExtraWildcard, scrut_hir_id, false, true);
     let non_exhaustiveness_witnesses = match usefulness {

tests/ui/rfc-2008-non-exhaustive/omitted-patterns.rs

@@ -194,6 +194,14 @@ fn main() {
     let local_refutable @ NonExhaustiveEnum::Unit = NonExhaustiveEnum::Unit;
     //~^ refutable pattern in local binding
 
+    // Check that matching on a reference results in a correctly spanned diagnostic
+    #[deny(non_exhaustive_omitted_patterns)]
+    match &non_enum {
+        NonExhaustiveEnum::Unit => {}
+        NonExhaustiveEnum::Tuple(_) => {}
+        _ => {}
+    }
+    //~^^ some variants are not matched explicitly
 }
 
 #[deny(non_exhaustive_omitted_patterns)]

tests/ui/rfc-2008-non-exhaustive/omitted-patterns.stderr

@@ -198,6 +198,20 @@ help: you might want to use `let else` to handle the variant that isn't matched
 LL |     let local_refutable @ NonExhaustiveEnum::Unit = NonExhaustiveEnum::Unit else { todo!() };
    |                                                                             ++++++++++++++++
 
-error: aborting due to 9 previous errors; 6 warnings emitted
+error: some variants are not matched explicitly
+  --> $DIR/omitted-patterns.rs:202:9
+   |
+LL |         _ => {}
+   |         ^ pattern `NonExhaustiveEnum::Struct { .. }` not covered
+   |
+   = help: ensure that all variants are matched explicitly by adding the suggested match arms
+   = note: the matched value is of type `NonExhaustiveEnum` and the `non_exhaustive_omitted_patterns` attribute was found
+note: the lint level is defined here
+  --> $DIR/omitted-patterns.rs:198:12
+   |
+LL |     #[deny(non_exhaustive_omitted_patterns)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 10 previous errors; 6 warnings emitted
 
 For more information about this error, try `rustc --explain E0005`.