Point at variant on pattern field count mismatch

src/librustc_typeck/check/pat.rs

@@ -675,21 +675,39 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self.tcx.check_stability(variant.fields[i].did, Some(pat.hir_id), subpat.span);
             }
         } else {
-            let subpats_ending = if subpats.len() == 1 { "" } else { "s" };
-            let fields_ending = if variant.fields.len() == 1 { "" } else { "s" };
-            struct_span_err!(tcx.sess, pat.span, E0023,
-                             "this pattern has {} field{}, but the corresponding {} has {} field{}",
-                             subpats.len(), subpats_ending, res.descr(),
-                             variant.fields.len(),  fields_ending)
-                .span_label(pat.span, format!("expected {} field{}, found {}",
-                                              variant.fields.len(), fields_ending, subpats.len()))
-                .emit();
+            // Pattern has wrong number of fields.
+            self.e0023(pat.span, res, &subpats, &variant.fields);
             on_error();
             return tcx.types.err;
         }
         pat_ty
     }
 
+    fn e0023(&self, pat_span: Span, res: Res, subpats: &'tcx [P<Pat>], fields: &[ty::FieldDef]) {
+        let subpats_ending = if subpats.len() == 1 { "" } else { "s" };
+        let fields_ending = if fields.len() == 1 { "" } else { "s" };
+        let res_span = self.tcx.def_span(res.def_id());
+        struct_span_err!(
+            self.tcx.sess,
+            pat_span,
+            E0023,
+            "this pattern has {} field{}, but the corresponding {} has {} field{}",
+            subpats.len(),
+            subpats_ending,
+            res.descr(),
+            fields.len(),
+            fields_ending,
+        )
+            .span_label(pat_span, format!(
+                "expected {} field{}, found {}",
+                fields.len(),
+                fields_ending,
+                subpats.len(),
+            ))
+            .span_label(res_span, format!("{} defined here", res.descr()))
+            .emit();
+    }
+
     fn check_pat_tuple(
         &self,
         span: Span,

src/test/ui/error-codes/E0023.stderr

@@ -1,18 +1,27 @@
 error[E0023]: this pattern has 1 field, but the corresponding tuple variant has 2 fields
   --> $DIR/E0023.rs:10:9
    |
+LL |     Apple(String, String),
+   |     --------------------- tuple variant defined here
+...
 LL |         Fruit::Apple(a) => {},
    |         ^^^^^^^^^^^^^^^ expected 2 fields, found 1
 
 error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
   --> $DIR/E0023.rs:11:9
    |
+LL |     Apple(String, String),
+   |     --------------------- tuple variant defined here
+...
 LL |         Fruit::Apple(a, b, c) => {},
    |         ^^^^^^^^^^^^^^^^^^^^^ expected 2 fields, found 3
 
 error[E0023]: this pattern has 2 fields, but the corresponding tuple variant has 1 field
   --> $DIR/E0023.rs:12:9
    |
+LL |     Pear(u32),
+   |     --------- tuple variant defined here
+...
 LL |         Fruit::Pear(1, 2) => {},
    |         ^^^^^^^^^^^^^^^^^ expected 1 field, found 2
 

src/test/ui/match/match-pattern-field-mismatch.stderr

@@ -1,6 +1,9 @@
 error[E0023]: this pattern has 2 fields, but the corresponding tuple variant has 3 fields
   --> $DIR/match-pattern-field-mismatch.rs:10:11
    |
+LL |         Rgb(usize, usize, usize),
+   |         ------------------------ tuple variant defined here
+...
 LL |           Color::Rgb(_, _) => { }
    |           ^^^^^^^^^^^^^^^^ expected 3 fields, found 2
 

src/test/ui/pattern/pat-tuple-overfield.stderr

@@ -19,12 +19,18 @@ LL |         (1, 2, .., 3, 4) => {}
 error[E0023]: this pattern has 4 fields, but the corresponding tuple struct has 3 fields
   --> $DIR/pat-tuple-overfield.rs:10:9
    |
+LL | struct S(u8, u8, u8);
+   | --------------------- tuple struct defined here
+...
 LL |         S(1, 2, 3, 4) => {}
    |         ^^^^^^^^^^^^^ expected 3 fields, found 4
 
 error[E0023]: this pattern has 4 fields, but the corresponding tuple struct has 3 fields
   --> $DIR/pat-tuple-overfield.rs:12:9
    |
+LL | struct S(u8, u8, u8);
+   | --------------------- tuple struct defined here
+...
 LL |         S(1, 2, .., 3, 4) => {}
    |         ^^^^^^^^^^^^^^^^^ expected 3 fields, found 4
 

src/test/ui/pattern/pattern-error-continue.stderr

@@ -15,6 +15,9 @@ LL |         A::D(_) => (),
 error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
   --> $DIR/pattern-error-continue.rs:17:9
    |
+LL |     B(isize, isize),
+   |     --------------- tuple variant defined here
+...
 LL |         A::B(_, _, _) => (),
    |         ^^^^^^^^^^^^^ expected 2 fields, found 3