syntax: add test for intersection pattern parser recovery

1 files changed, 40 insertions, 0 deletions

diff --git a/src/test/ui/parser/intersection-patterns.rs b/src/test/ui/parser/intersection-patterns.rs
new file mode 100644
index 00000000000..1dda21519e3
--- /dev/null
+++ b/src/test/ui/parser/intersection-patterns.rs
@@ -0,0 +1,40 @@
+// This tests the parser recovery in `recover_intersection_pat`
+// and serves as a regression test for the diagnostics issue #65400.
+//
+// The general idea is that for `$pat_lhs @ $pat_rhs` where
+// `$pat_lhs` is not generated by `ref? mut? $ident` we want
+// to suggest either switching the order or note that intersection
+// patterns are not allowed.
+
+fn main() {
+    let s: Option<u8> = None;
+
+    match s {
+        Some(x) @ y => {}
+        //~^ ERROR pattern on wrong side of `@`
+        //~| pattern on the left, should be to the right
+        //~| binding on the right, should be to the left
+        //~| HELP switch the order
+        //~| SUGGESTION y@Some(x)
+        _ => {}
+    }
+
+    match s {
+        Some(x) @ Some(y) => {}
+        //~^ ERROR left-hand side of `@` must be a binding pattern
+        //~| interpreted as a pattern, not a binding
+        //~| also a pattern
+        //~| NOTE bindings are `x`, `mut x`, `ref x`, and `ref mut x`
+        _ => {}
+    }
+
+    match 2 {
+        1 ..= 5 @ e => {}
+        //~^ ERROR pattern on wrong side of `@`
+        //~| pattern on the left, should be to the right
+        //~| binding on the right, should be to the left
+        //~| HELP switch the order
+        //~| SUGGESTION e@1 ..=5
+        _ => {}
+    }
+}