[Experiment] Rewrite exhaustiveness in one pass

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

@@ -279,8 +279,10 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
         } else {
             // Check the pattern for some things unrelated to exhaustiveness.
             let refutable = if cx.refutable { Refutable } else { Irrefutable };
-            pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat));
-            pat.walk_always(|pat| check_for_bindings_named_same_as_variants(self, pat, refutable));
+            pat.walk_always(|pat| {
+                check_borrow_conflicts_in_at_patterns(self, pat);
+                check_for_bindings_named_same_as_variants(self, pat, refutable);
+            });
             Ok(cx.pattern_arena.alloc(DeconstructedPat::from_pat(cx, pat)))
         }
     }

tests/ui/or-patterns/exhaustiveness-pass.rs

@@ -35,6 +35,17 @@ fn main() {
         ((0, 0) | (1, 0),) => {}
         _ => {}
     }
+    match ((0, 0),) {
+        // Note how the second one would be redundant without the guard.
+        ((x, y) | (y, x),) if x == 0 => {}
+        _ => {}
+    }
+    match 0 {
+        // We don't warn the second one as redundant in general because of cases like the one above.
+        // We could technically do it if there are no bindings.
+        0 | 0 if 0 == 0 => {}
+        _ => {}
+    }
 
     // This one caused ICE https://github.com/rust-lang/rust/issues/117378
     match (0u8, 0) {

tests/ui/or-patterns/exhaustiveness-unreachable-pattern.rs

@@ -1,6 +1,7 @@
 #![deny(unreachable_patterns)]
 
 // We wrap patterns in a tuple because top-level or-patterns were special-cased.
+#[rustfmt::skip]
 fn main() {
     match (0u8,) {
         (1 | 2,) => {}
@@ -73,6 +74,11 @@ fn main() {
             | 0] => {} //~ ERROR unreachable
         _ => {}
     }
+    match (true, 0) {
+        (true, 0 | 0) => {} //~ ERROR unreachable
+        (_, 0 | 0) => {} //~ ERROR unreachable
+        _ => {}
+    }
     match &[][..] {
         [0] => {}
         [0, _] => {}
@@ -149,4 +155,8 @@ fn main() {
             | true, //~ ERROR unreachable
             false | true) => {}
     }
+    match (true, true) {
+        (x, y)
+            | (y, x) => {} //~ ERROR unreachable
+    }
 }

tests/ui/or-patterns/exhaustiveness-unreachable-pattern.stderr

@@ -1,5 +1,5 @@
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:7:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:8:9
    |
 LL |         (1,) => {}
    |         ^^^^
@@ -11,128 +11,140 @@ LL | #![deny(unreachable_patterns)]
    |         ^^^^^^^^^^^^^^^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:12:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:13:9
    |
 LL |         (2,) => {}
    |         ^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:18:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:19:9
    |
 LL |         (1 | 2,) => {}
    |         ^^^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:23:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:24:9
    |
 LL |         (1, 3) => {}
    |         ^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:24:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:25:9
    |
 LL |         (1, 4) => {}
    |         ^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:25:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:26:9
    |
 LL |         (2, 4) => {}
    |         ^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:26:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:27:9
    |
 LL |         (2 | 1, 4) => {}
    |         ^^^^^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:28:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:29:9
    |
 LL |         (1, 4 | 5) => {}
    |         ^^^^^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:36:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:37:9
    |
 LL |         (Some(1),) => {}
    |         ^^^^^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:37:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:38:9
    |
 LL |         (None,) => {}
    |         ^^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:42:9
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:43:9
    |
 LL |         ((1..=4,),) => {}
    |         ^^^^^^^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:47:14
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:48:14
    |
 LL |         (1 | 1,) => {}
    |              ^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:51:19
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:52:19
    |
 LL |         (0 | 1) | 1 => {}
    |                   ^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:57:14
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:58:14
    |
 LL |         0 | (0 | 0) => {}
    |              ^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:57:18
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:58:18
    |
 LL |         0 | (0 | 0) => {}
    |                  ^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:65:13
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:66:13
    |
 LL | /             Some(
 LL | |                 0 | 0) => {}
    | |______________________^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:71:15
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:72:15
    |
 LL |             | 0
    |               ^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:73:15
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:74:15
    |
 LL |             | 0] => {}
    |               ^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:81:10
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:78:20
+   |
+LL |         (true, 0 | 0) => {}
+   |                    ^
+
+error: unreachable pattern
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:79:17
+   |
+LL |         (_, 0 | 0) => {}
+   |                 ^
+
+error: unreachable pattern
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:87:10
    |
 LL |         [1
    |          ^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:93:10
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:99:10
    |
 LL |         [true
    |          ^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:100:36
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:106:36
    |
 LL |         (true | false, None | Some(true
    |                                    ^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:105:14
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:111:14
    |
 LL |             (true
    |              ^^^^
@@ -143,28 +155,34 @@ LL |         (true | false, None | Some(t_or_f!())) => {}
    = note: this error originates in the macro `t_or_f` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:116:14
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:122:14
    |
 LL |         Some(0
    |              ^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:135:19
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:141:19
    |
 LL |                 | false) => {}
    |                   ^^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:143:15
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:149:15
    |
 LL |             | true) => {}
    |               ^^^^
 
 error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:149:15
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:155:15
    |
 LL |             | true,
    |               ^^^^
 
-error: aborting due to 26 previous errors
+error: unreachable pattern
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:160:15
+   |
+LL |             | (y, x) => {}
+   |               ^^^^^^
+
+error: aborting due to 29 previous errors
 

tests/ui/pattern/usefulness/integer-ranges/pointer-sized-int.allow.stderr

@@ -1,5 +1,5 @@
 error[E0004]: non-exhaustive patterns: type `usize` is non-empty
-  --> $DIR/pointer-sized-int.rs:54:11
+  --> $DIR/pointer-sized-int.rs:59:11
    |
 LL |     match 7usize {}
    |           ^^^^^^