add regression test

tests/ui/pattern/issue-110508.rs

@@ -0,0 +1,38 @@
+// run-pass
+
+#[derive(PartialEq, Eq)]
+pub enum Foo {
+    FooA(()),
+    FooB(Vec<()>),
+}
+
+impl Foo {
+    const A1: Foo = Foo::FooA(());
+    const A2: Foo = Self::FooA(());
+    const A3: Self = Foo::FooA(());
+    const A4: Self = Self::FooA(());
+}
+
+fn main() {
+    let foo = Foo::FooA(());
+
+    match foo {
+        Foo::A1 => {},
+        _ => {},
+    }
+
+    match foo {
+        Foo::A2 => {},
+        _ => {},
+    }
+
+    match foo {
+        Foo::A3 => {},
+        _ => {},
+    }
+
+    match foo {
+        Foo::A4 => {},
+        _ => {},
+    }
+}