Rollup merge of #66967 - Nadrieril:remove-or-pat-hack, r=varkor

Remove hack for top-level or-patterns in match checking

Follow-up to #66612.

Or-patterns are now truly first-class in match checking. As a side-effect, redundant subpatterns are linted as such, making the `unreachable_patterns` lint a bit more general.

cc #54883

r? @varkor

2 files changed, 124 insertions, 0 deletions

diff --git a/src/test/ui/pattern/usefulness/top-level-alternation.rs b/src/test/ui/pattern/usefulness/top-level-alternation.rs
new file mode 100644
index 00000000000..4b47b978930
--- /dev/null
+++ b/src/test/ui/pattern/usefulness/top-level-alternation.rs
@@ -0,0 +1,56 @@
+#![deny(unreachable_patterns)]
+
+fn main() {
+    while let 0..=2 | 1 = 0 {} //~ ERROR unreachable pattern
+    if let 0..=2 | 1 = 0 {} //~ ERROR unreachable pattern
+
+    match 0u8 {
+        0
+            | 0 => {} //~ ERROR unreachable pattern
+        _ => {}
+    }
+    match Some(0u8) {
+        Some(0)
+            | Some(0) => {} //~ ERROR unreachable pattern
+        _ => {}
+    }
+    match (0u8, 0u8) {
+        (0, _) | (_, 0) => {}
+        (0, 0) => {} //~ ERROR unreachable pattern
+        (1, 1) => {}
+        _ => {}
+    }
+    match (0u8, 0u8) {
+        (0, 1) | (2, 3) => {}
+        (0, 3) => {}
+        (2, 1) => {}
+        _ => {}
+    }
+    match (0u8, 0u8) {
+        (_, 0) | (_, 1) => {}
+        _ => {}
+    }
+    match (0u8, 0u8) {
+        (0, _) | (1, _) => {}
+        _ => {}
+    }
+    match Some(0u8) {
+        None | Some(_) => {}
+        _ => {} //~ ERROR unreachable pattern
+    }
+    match Some(0u8) {
+        None | Some(_) => {}
+        Some(_) => {} //~ ERROR unreachable pattern
+        None => {} //~ ERROR unreachable pattern
+    }
+    match Some(0u8) {
+        Some(_) => {}
+        None => {}
+        None | Some(_) => {} //~ ERROR unreachable pattern
+    }
+    match 0u8 {
+        1 | 2 => {},
+        1..=2 => {}, //~ ERROR unreachable pattern
+        _ => {},
+    }
+}
diff --git a/src/test/ui/pattern/usefulness/top-level-alternation.stderr b/src/test/ui/pattern/usefulness/top-level-alternation.stderr
new file mode 100644
index 00000000000..7c7c4fc4eba
--- /dev/null
+++ b/src/test/ui/pattern/usefulness/top-level-alternation.stderr
@@ -0,0 +1,68 @@
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:4:23
+   |
+LL |     while let 0..=2 | 1 = 0 {}
+   |                       ^
+   |
+note: lint level defined here
+  --> $DIR/top-level-alternation.rs:1:9
+   |
+LL | #![deny(unreachable_patterns)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:5:20
+   |
+LL |     if let 0..=2 | 1 = 0 {}
+   |                    ^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:9:15
+   |
+LL |             | 0 => {}
+   |               ^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:14:15
+   |
+LL |             | Some(0) => {}
+   |               ^^^^^^^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:19:9
+   |
+LL |         (0, 0) => {}
+   |         ^^^^^^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:39:9
+   |
+LL |         _ => {}
+   |         ^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:43:9
+   |
+LL |         Some(_) => {}
+   |         ^^^^^^^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:44:9
+   |
+LL |         None => {}
+   |         ^^^^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:49:9
+   |
+LL |         None | Some(_) => {}
+   |         ^^^^^^^^^^^^^^
+
+error: unreachable pattern
+  --> $DIR/top-level-alternation.rs:53:9
+   |
+LL |         1..=2 => {},
+   |         ^^^^^
+
+error: aborting due to 10 previous errors
+