Make min_exhaustive_patterns match exhaustive_patterns better

compiler/rustc_mir_build/src/build/matches/simplify.rs

@@ -271,7 +271,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             PatKind::Variant { adt_def, args, variant_index, ref subpatterns } => {
                 let irrefutable = adt_def.variants().iter_enumerated().all(|(i, v)| {
                     i == variant_index || {
-                        self.tcx.features().exhaustive_patterns
+                        (self.tcx.features().exhaustive_patterns
+                            || self.tcx.features().min_exhaustive_patterns)
                             && !v
                                 .inhabited_predicate(self.tcx, adt_def)
                                 .instantiate(self.tcx, args)

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

@@ -665,7 +665,8 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
 
         // Emit an extra note if the first uncovered witness would be uninhabited
         // if we disregard visibility.
-        let witness_1_is_privately_uninhabited = if self.tcx.features().exhaustive_patterns
+        let witness_1_is_privately_uninhabited = if (self.tcx.features().exhaustive_patterns
+            || self.tcx.features().min_exhaustive_patterns)
             && let Some(witness_1) = witnesses.get(0)
             && let ty::Adt(adt, args) = witness_1.ty().kind()
             && adt.is_enum()

tests/ui/closures/2229_closure_analysis/run_pass/multivariant.min_exhaustive_patterns.stderr

@@ -0,0 +1,11 @@
+warning: the feature `min_exhaustive_patterns` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/multivariant.rs:7:46
+   |
+LL | #![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+   |                                              ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #119612 <https://github.com/rust-lang/rust/issues/119612> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+

tests/ui/closures/2229_closure_analysis/run_pass/multivariant.rs

@@ -1,8 +1,11 @@
 // Test precise capture of a multi-variant enum (when remaining variants are
 // visibly uninhabited).
+// revisions: min_exhaustive_patterns exhaustive_patterns
 // edition:2021
 // run-pass
-#![feature(exhaustive_patterns)]
+#![cfg_attr(exhaustive_patterns, feature(exhaustive_patterns))]
+#![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+//[min_exhaustive_patterns]~^ WARN the feature `min_exhaustive_patterns` is incomplete
 #![feature(never_type)]
 
 pub fn main() {

tests/ui/pattern/usefulness/always-inhabited-union-ref.stderr → tests/ui/pattern/usefulness/always-inhabited-union-ref.exhaustive_patterns.stderr

@@ -1,5 +1,5 @@
 error[E0004]: non-exhaustive patterns: type `&!` is non-empty
-  --> $DIR/always-inhabited-union-ref.rs:23:11
+  --> $DIR/always-inhabited-union-ref.rs:26:11
    |
 LL |     match uninhab_ref() {
    |           ^^^^^^^^^^^^^
@@ -14,13 +14,13 @@ LL +     }
    |
 
 error[E0004]: non-exhaustive patterns: type `Foo` is non-empty
-  --> $DIR/always-inhabited-union-ref.rs:27:11
+  --> $DIR/always-inhabited-union-ref.rs:30:11
    |
 LL |     match uninhab_union() {
    |           ^^^^^^^^^^^^^^^
    |
 note: `Foo` defined here
-  --> $DIR/always-inhabited-union-ref.rs:10:11
+  --> $DIR/always-inhabited-union-ref.rs:13:11
    |
 LL | pub union Foo {
    |           ^^^

tests/ui/pattern/usefulness/always-inhabited-union-ref.min_exhaustive_patterns.stderr

@@ -0,0 +1,46 @@
+warning: the feature `min_exhaustive_patterns` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/always-inhabited-union-ref.rs:7:46
+   |
+LL | #![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+   |                                              ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #119612 <https://github.com/rust-lang/rust/issues/119612> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0004]: non-exhaustive patterns: type `&!` is non-empty
+  --> $DIR/always-inhabited-union-ref.rs:26:11
+   |
+LL |     match uninhab_ref() {
+   |           ^^^^^^^^^^^^^
+   |
+   = note: the matched value is of type `&!`
+   = note: references are always considered inhabited
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
+   |
+LL ~     match uninhab_ref() {
+LL +         _ => todo!(),
+LL +     }
+   |
+
+error[E0004]: non-exhaustive patterns: type `Foo` is non-empty
+  --> $DIR/always-inhabited-union-ref.rs:30:11
+   |
+LL |     match uninhab_union() {
+   |           ^^^^^^^^^^^^^^^
+   |
+note: `Foo` defined here
+  --> $DIR/always-inhabited-union-ref.rs:13:11
+   |
+LL | pub union Foo {
+   |           ^^^
+   = note: the matched value is of type `Foo`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
+   |
+LL ~     match uninhab_union() {
+LL +         _ => todo!(),
+LL +     }
+   |
+
+error: aborting due to 2 previous errors; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0004`.

tests/ui/pattern/usefulness/always-inhabited-union-ref.rs

@@ -1,9 +1,12 @@
+// revisions: min_exhaustive_patterns exhaustive_patterns
+
 // The precise semantics of inhabitedness with respect to unions and references is currently
 // undecided. This test file currently checks a conservative choice.
 
-#![feature(exhaustive_patterns)]
+#![cfg_attr(exhaustive_patterns, feature(exhaustive_patterns))]
+#![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+//[min_exhaustive_patterns]~^ WARN the feature `min_exhaustive_patterns` is incomplete
 #![feature(never_type)]
-
 #![allow(dead_code)]
 #![allow(unreachable_code)]
 

tests/ui/pattern/usefulness/match-privately-empty.stderr → tests/ui/pattern/usefulness/match-privately-empty.exhaustive_patterns.stderr

@@ -1,5 +1,5 @@
 error[E0004]: non-exhaustive patterns: `Some(Private { misc: true, .. })` not covered
-  --> $DIR/match-privately-empty.rs:13:11
+  --> $DIR/match-privately-empty.rs:16:11
    |
 LL |     match private::DATA {
    |           ^^^^^^^^^^^^^ pattern `Some(Private { misc: true, .. })` not covered
@@ -12,7 +12,7 @@ note: `Option<Private>` defined here
    = note: the matched value is of type `Option<Private>`
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
-LL ~         }) => {},
+LL ~         Some(private::Private { misc: false, .. }) => {},
 LL +         Some(Private { misc: true, .. }) => todo!()
    |
 

tests/ui/pattern/usefulness/match-privately-empty.min_exhaustive_patterns.stderr

@@ -0,0 +1,30 @@
+warning: the feature `min_exhaustive_patterns` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/match-privately-empty.rs:3:46
+   |
+LL | #![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+   |                                              ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #119612 <https://github.com/rust-lang/rust/issues/119612> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0004]: non-exhaustive patterns: `Some(Private { misc: true, .. })` not covered
+  --> $DIR/match-privately-empty.rs:16:11
+   |
+LL |     match private::DATA {
+   |           ^^^^^^^^^^^^^ pattern `Some(Private { misc: true, .. })` not covered
+   |
+note: `Option<Private>` defined here
+  --> $SRC_DIR/core/src/option.rs:LL:COL
+  ::: $SRC_DIR/core/src/option.rs:LL:COL
+   |
+   = note: not covered
+   = note: the matched value is of type `Option<Private>`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
+   |
+LL ~         Some(private::Private { misc: false, .. }) => {},
+LL +         Some(Private { misc: true, .. }) => todo!()
+   |
+
+error: aborting due to 1 previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0004`.

tests/ui/pattern/usefulness/match-privately-empty.rs

@@ -1,5 +1,8 @@
+// revisions: min_exhaustive_patterns exhaustive_patterns
+#![cfg_attr(exhaustive_patterns, feature(exhaustive_patterns))]
+#![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+//[min_exhaustive_patterns]~^ WARN the feature `min_exhaustive_patterns` is incomplete
 #![feature(never_type)]
-#![feature(exhaustive_patterns)]
 
 mod private {
     pub struct Private {
@@ -11,11 +14,8 @@ mod private {
 
 fn main() {
     match private::DATA {
-    //~^ ERROR non-exhaustive patterns: `Some(Private { misc: true, .. })` not covered
+        //~^ ERROR non-exhaustive patterns: `Some(Private { misc: true, .. })` not covered
         None => {}
-        Some(private::Private {
-            misc: false,
-            ..
-        }) => {}
+        Some(private::Private { misc: false, .. }) => {}
     }
 }

tests/ui/pattern/usefulness/slice_of_empty.stderr → tests/ui/pattern/usefulness/slice_of_empty.exhaustive_patterns.stderr

@@ -1,5 +1,5 @@
 error[E0004]: non-exhaustive patterns: `&[]` not covered
-  --> $DIR/slice_of_empty.rs:18:11
+  --> $DIR/slice_of_empty.rs:22:11
    |
 LL |     match nevers {
    |           ^^^^^^ pattern `&[]` not covered

tests/ui/pattern/usefulness/slice_of_empty.min_exhaustive_patterns.stderr

@@ -0,0 +1,38 @@
+warning: the feature `min_exhaustive_patterns` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/slice_of_empty.rs:3:46
+   |
+LL | #![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+   |                                              ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #119612 <https://github.com/rust-lang/rust/issues/119612> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0004]: non-exhaustive patterns: `&[_, ..]` not covered
+  --> $DIR/slice_of_empty.rs:11:11
+   |
+LL |     match nevers {
+   |           ^^^^^^ pattern `&[_, ..]` not covered
+   |
+   = note: the matched value is of type `&[!]`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
+   |
+LL ~         &[] => (),
+LL ~         &[_, ..] => todo!(),
+   |
+
+error[E0004]: non-exhaustive patterns: `&[]` and `&[_, _, ..]` not covered
+  --> $DIR/slice_of_empty.rs:22:11
+   |
+LL |     match nevers {
+   |           ^^^^^^ patterns `&[]` and `&[_, _, ..]` not covered
+   |
+   = note: the matched value is of type `&[!]`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
+   |
+LL ~         &[_] => (),
+LL ~         &[] | &[_, _, ..] => todo!(),
+   |
+
+error: aborting due to 2 previous errors; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0004`.

tests/ui/pattern/usefulness/slice_of_empty.rs

@@ -1,11 +1,15 @@
+// revisions: min_exhaustive_patterns exhaustive_patterns
+#![cfg_attr(exhaustive_patterns, feature(exhaustive_patterns))]
+#![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+//[min_exhaustive_patterns]~^ WARN the feature `min_exhaustive_patterns` is incomplete
 #![feature(never_type)]
-#![feature(exhaustive_patterns)]
 #![deny(unreachable_patterns)]
 
 fn main() {}
 
 fn foo(nevers: &[!]) {
     match nevers {
+        //[min_exhaustive_patterns]~^ ERROR non-exhaustive patterns: `&[_, ..]` not covered
         &[] => (),
     };
 
@@ -16,7 +20,8 @@ fn foo(nevers: &[!]) {
     };
 
     match nevers {
-        //~^ ERROR non-exhaustive patterns: `&[]` not covered
+        //[exhaustive_patterns]~^ ERROR non-exhaustive patterns: `&[]` not covered
+        //[min_exhaustive_patterns]~^^ ERROR non-exhaustive patterns: `&[]` and `&[_, _, ..]` not covered
         &[_] => (),
     };
 }

tests/ui/rfcs/rfc-0000-never_patterns/typeck.rs

@@ -2,7 +2,7 @@
 //[pass] check-pass
 //[fail] check-fail
 #![feature(never_patterns)]
-#![feature(exhaustive_patterns)]
+#![feature(min_exhaustive_patterns)]
 #![allow(incomplete_features)]
 
 #[derive(Copy, Clone)]
@@ -107,7 +107,7 @@ fn never_pattern_typeck_pass(void: Void) {
     }
     match (&[] as &[Void]) {
         [] => {}
-        [!],
+        [!, ..],
     }
     // Accept on a composite empty type.
     match None::<&(u32, Void)> {

tests/ui/rfcs/rfc-0000-never_patterns/unreachable.rs

@@ -2,7 +2,7 @@
 //[normal] check-pass
 #![feature(never_patterns)]
 #![allow(incomplete_features)]
-#![cfg_attr(exh_pats, feature(exhaustive_patterns))]
+#![cfg_attr(exh_pats, feature(min_exhaustive_patterns))]
 #![allow(dead_code, unreachable_code)]
 #![deny(unreachable_patterns)]
 

tests/ui/uninhabited/uninhabited-irrefutable.stderr → tests/ui/uninhabited/uninhabited-irrefutable.exhaustive_patterns.stderr

@@ -1,13 +1,13 @@
 error[E0005]: refutable pattern in local binding
-  --> $DIR/uninhabited-irrefutable.rs:29:9
+  --> $DIR/uninhabited-irrefutable.rs:32:9
    |
 LL |     let Foo::D(_y, _z) = x;
    |         ^^^^^^^^^^^^^^ pattern `Foo::A(_)` not covered
    |
    = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
 note: `Foo` defined here
-  --> $DIR/uninhabited-irrefutable.rs:18:6
+  --> $DIR/uninhabited-irrefutable.rs:21:6
    |
 LL | enum Foo {
    |      ^^^

tests/ui/uninhabited/uninhabited-irrefutable.min_exhaustive_patterns.stderr

@@ -0,0 +1,26 @@
+error[E0005]: refutable pattern in local binding
+  --> $DIR/uninhabited-irrefutable.rs:32:9
+   |
+LL |     let Foo::D(_y, _z) = x;
+   |         ^^^^^^^^^^^^^^ pattern `Foo::A(_)` not covered
+   |
+   = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
+   = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
+note: `Foo` defined here
+  --> $DIR/uninhabited-irrefutable.rs:21:6
+   |
+LL | enum Foo {
+   |      ^^^
+LL |
+LL |     A(foo::SecretlyEmpty),
+   |     - not covered
+   = note: pattern `Foo::A(_)` is currently uninhabited, but this variant contains private fields which may become inhabited in the future
+   = note: the matched value is of type `Foo`
+help: you might want to use `let else` to handle the variant that isn't matched
+   |
+LL |     let Foo::D(_y, _z) = x else { todo!() };
+   |                            ++++++++++++++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0005`.

tests/ui/uninhabited/uninhabited-irrefutable.rs

@@ -1,5 +1,8 @@
+// revisions: min_exhaustive_patterns exhaustive_patterns
+#![cfg_attr(exhaustive_patterns, feature(exhaustive_patterns))]
+#![cfg_attr(min_exhaustive_patterns, feature(min_exhaustive_patterns))]
+#![cfg_attr(min_exhaustive_patterns, allow(incomplete_features))]
 #![feature(never_type)]
-#![feature(exhaustive_patterns)]
 
 mod foo {
     pub struct SecretlyEmpty {