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/crashes/109812.rs

@@ -0,0 +1,25 @@
+//! This test used to ICE: rust-lang/rust#125914
+//! Instead of actually analyzing the erroneous patterns,
+//! we instead stop after typeck where errors are already
+//! reported.
+//!
+enum AstKind<'ast> {
+    //~^ ERROR: `'ast` is never used
+    ExprInt,
+}
+
+enum Foo {
+    Bar(isize),
+    Baz,
+}
+
+enum Other {
+    Other1(Foo),
+    Other2(AstKind), //~ ERROR: missing lifetime specifier
+}
+
+fn main() {
+    match Other::Other1(Foo::Baz) {
+        ::Other::Other2(::Foo::Bar(..)) => {}
+    }
+}

tests/crashes/125914.rs

@@ -0,0 +1,25 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/missing_lifetime.rs:18:12
+   |
+LL |     Other2(AstKind),
+   |            ^^^^^^^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ enum Other<'a> {
+LL |     Other1(Foo),
+LL ~     Other2(AstKind<'a>),
+   |
+
+error[E0392]: lifetime parameter `'ast` is never used
+  --> $DIR/missing_lifetime.rs:6:14
+   |
+LL | enum AstKind<'ast> {
+   |              ^^^^ unused lifetime parameter
+   |
+   = help: consider removing `'ast`, referring to it in a field, or using a marker such as `PhantomData`
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0106, E0392.
+For more information about an error, try `rustc --explain E0106`.

tests/ui/pattern/missing_lifetime.rs

@@ -0,0 +1,30 @@
+//! This test used to ICE: rust-lang/rust#109812
+//! Instead of actually analyzing the erroneous patterns,
+//! we instead stop after typeck where errors are already
+//! reported.
+
+#![warn(rust_2021_incompatible_closure_captures)]
+
+enum Either {
+    One(X),
+    Two(X),
+}
+
+struct X(Y);
+
+struct Y;
+
+fn consume_fnmut(_: impl FnMut()) {}
+
+fn move_into_fnmut() {
+    let x = X(Y);
+
+    consume_fnmut(|| {
+        let Either::Two(ref mut _t) = x;
+        //~^ ERROR: mismatched types
+
+        let X(mut _t) = x;
+    });
+}
+
+fn main() {}

tests/ui/pattern/missing_lifetime.stderr

@@ -0,0 +1,11 @@
+error[E0308]: mismatched types
+  --> $DIR/type_mismatch.rs:23:13
+   |
+LL |         let Either::Two(ref mut _t) = x;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^   - this expression has type `X`
+   |             |
+   |             expected `X`, found `Either`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.