Avoid follow-up errors on erroneous patterns

Author: oli-obk

compiler/rustc_hir_typeck/src/pat.rs

@@ -1223,12 +1223,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Type-check the tuple struct pattern against the expected type.
         let diag = self.demand_eqtype_pat_diag(pat.span, expected, pat_ty, pat_info.top_info);
-        let had_err = if let Some(err) = diag {
-            err.emit();
-            true
-        } else {
-            false
-        };
+        let had_err = diag.map(|diag| diag.emit());
 
         // Type-check subpatterns.
         if subpats.len() == variant.fields.len()
@@ -1249,6 +1244,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     None,
                 );
             }
+            if let Some(e) = had_err {
+                on_error(e);
+                return Ty::new_error(tcx, e);
+            }
         } else {
             let e = self.emit_err_pat_wrong_number_of_fields(
                 pat.span,
@@ -1257,7 +1256,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 subpats,
                 &variant.fields.raw,
                 expected,
-                had_err,
+                had_err.is_some(),
             );
             on_error(e);
             return Ty::new_error(tcx, e);

tests/ui/issues/issue-7092.rs

@@ -9,7 +9,6 @@ fn foo(x: Whatever) {
 //~| expected enum `Whatever`
 //~| found enum `Option<_>`
             field.access(),
-            //~^ ERROR: type annotations needed
     }
 }
 

tests/ui/issues/issue-7092.stderr

@@ -9,13 +9,6 @@ LL |         Some(field) =>
    = note: expected enum `Whatever`
               found enum `Option<_>`
 
-error[E0282]: type annotations needed
-  --> $DIR/issue-7092.rs:11:19
-   |
-LL |             field.access(),
-   |                   ^^^^^^ cannot infer type
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0282, E0308.
-For more information about an error, try `rustc --explain E0282`.
+For more information about this error, try `rustc --explain E0308`.