moved renamed docs formatted auxiliary | issue-16822.rs

Author: Kivooeo

tests/ui/auxiliary/issue-16822.rs renamed to tests/ui/cross-crate/auxiliary/cross-crate-refcell-match.rs

@@ -0,0 +1,39 @@
+//! Regression test for https://github.com/rust-lang/rust/issues/16822
+//
+//! ICE when using RefCell::borrow_mut()
+//! inside match statement with cross-crate generics.
+//!
+//! The bug occurred when:
+//! - A library defines a generic struct with RefCell<T> and uses borrow_mut() in match
+//! - Main crate implements the library trait for its own type
+//! - Cross-crate generic constraint causes type inference issues
+//!
+//! The problematic match statement is in the auxiliary file, this file triggers it.
+//! Original error: assertion failed in ty.rs:2481 during type inference.
+
+//@ run-pass
+//@ aux-build:cross-crate-refcell-match.rs
+
+extern crate cross_crate_refcell_match as lib;
+
+use std::cell::RefCell;
+
+struct App {
+    i: isize,
+}
+
+impl lib::Update for App {
+    fn update(&mut self) {
+        self.i += 1;
+    }
+}
+
+fn main() {
+    let app = App { i: 5 };
+    let window = lib::Window {
+        data: RefCell::new(app),
+    };
+    // This specific pattern (RefCell::borrow_mut in match with cross-crate generics)
+    // caused the ICE in the original issue
+    window.update(1);
+}