add test for incremental ICE: slice-pattern-const.rs #83085

Fixes #83085

tests/incremental/slice-pattern-const-ice-83085.rs

@@ -0,0 +1,39 @@
+//@ compile-flags: -Zincremental-verify-ich=yes
+// issue: rust-lang/rust#83085 incremental ICE: forcing query with already existing `DepNode`
+// this used to fail to build straight away without needing any kind of
+// stage1/2 builds but tidy demands it
+//@ revisions:rpass1 rpass2
+
+fn main() {
+    const BOO: &[u8; 0] = &[];
+    match &[] {
+        BOO => (),
+        b"" => (),
+        _ => (),
+    }
+}
+
+#[derive(PartialEq, Eq)]
+struct Id<'a> {
+    ns: &'a str,
+}
+fn visit_struct() {
+    let id = Id { ns: "random1" };
+    const FLAG: Id<'static> = Id {
+        ns: "needs_to_be_the_same",
+    };
+    match id {
+        FLAG => {}
+        _ => {}
+    }
+}
+fn visit_struct2() {
+    let id = Id { ns: "random2" };
+    const FLAG: Id<'static> = Id {
+        ns: "needs_to_be_the_same",
+    };
+    match id {
+        FLAG => {}
+        _ => {}
+    }
+}