gccrs: Fix rust breakage with nr2

Nr2 did not emit the correct error message for break identifier "rust".

gcc/rust/ChangeLog:

	* resolve/rust-late-name-resolver-2.0.cc (Late::visit): Add "rust"
	identifier detection akin to nr1.
	(funny_ice_finalizer): Copy ICE finalizer from nr1.
	* resolve/rust-late-name-resolver-2.0.h: Add funny_error member
	context state.
	* Make-lang.in: Add new translation unit for new ice finalizer.
	* resolve/rust-ast-resolve-expr.cc: Move ice
	finalizer to it's own file.
	* resolve/rust-ice-finalizer.cc: New file.
	* resolve/rust-ice-finalizer.h: New file.

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: Remove break-rust3.rs from exclude list.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/gcc/rust/resolve/rust-ice-finalizer.h b/gcc/rust/resolve/rust-ice-finalizer.h
new file mode 100644
index 0000000..85ab88f
--- /dev/null
+++ b/gcc/rust/resolve/rust-ice-finalizer.h
@@ -0,0 +1,65 @@
+// Copyright (C) 2020-2024 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_ICE_FINALIZER_H
+#define RUST_ICE_FINALIZER_H
+
+#include "rust-linemap.h"
+#include "diagnostic.h"
+
+namespace Rust {
+namespace Resolver {
+
+/* The "break rust" Easter egg.
+
+   Backstory: once upon a time, there used to be a bug in rustc: it would ICE
+   during typechecking on a 'break' with an expression outside of a loop.  The
+   issue has been reported [0] and fixed [1], but in recognition of this, as a
+   special Easter egg, "break rust" was made to intentionally cause an ICE.
+
+   [0]: https://github.com/rust-lang/rust/issues/43162
+   [1]: https://github.com/rust-lang/rust/pull/43745
+
+   This was made in a way that does not break valid programs: namely, it only
+   happens when the 'break' is outside of a loop (so invalid anyway).
+
+   GCC Rust supports this essential feature as well, but in a slightly
+   different way.  Instead of delaying the error until type checking, we emit
+   it here in the resolution phase.  We, too, only do this to programs that
+   are already invalid: we only emit our funny ICE if the name "rust" (which
+   must be immediately inside a break-with-a-value expression) fails to
+   resolve.  Note that "break (rust)" does not trigger our ICE, only using
+   "break rust" directly does, and only if there's no "rust" in scope.  We do
+   this in the same way regardless of whether the "break" is outside of a loop
+   or inside one.
+
+   As a GNU extension, we also support "break gcc", much to the same effect,
+   subject to the same rules.  */
+
+/* The finalizer for our funny ICE.  This prints a custom message instead of
+   the default bug reporting instructions, as there is no bug to report.  */
+
+void ATTRIBUTE_NORETURN
+funny_ice_text_finalizer (diagnostic_text_output_format &text_output,
+			  const diagnostic_info *diagnostic,
+			  diagnostic_t diag_kind);
+
+} // namespace Resolver
+} // namespace Rust
+
+#endif /* ! RUST_ICE_FINALIZER_H */