2 files changed, 72 insertions, 0 deletions
diff --git a/build/rust/bitflags/Cargo.toml b/build/rust/bitflags/Cargo.toml
new file mode 100644
index 0000000000..7595f3b5bb
--- /dev/null
+++ b/build/rust/bitflags/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "bitflags"
+version = "1.999.999"
+edition = "2018"
+license = "MIT/Apache-2.0"
+
+[lib]
+path = "lib.rs"
+
+[dependencies.bitflags]
+version = "2"
diff --git a/build/rust/bitflags/lib.rs b/build/rust/bitflags/lib.rs
new file mode 100644
index 0000000000..3a3c67e4fd
--- /dev/null
+++ b/build/rust/bitflags/lib.rs
@@ -0,0 +1,61 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub use bitflags::bitflags as bitflags2;
+pub use bitflags::parser;
+
+// Copy of the macro from bitflags 1.3.2, with the implicit derives
+// removed, because in 2.0, they're expected to be explicitly given
+// in the macro invocation. And because bitflags 1.3.2 itself always
+// adds an impl Debug, we need to remove #[derive(Debug)] from what
+// is passed in, which is what the __impl_bitflags_remove_derive_debug
+// macro does.
+#[macro_export(local_inner_macros)]
+macro_rules! bitflags {
+    (
+        $(#[$($outer:tt)+])*
+        $vis:vis struct $BitFlags:ident: $T:ty {
+            $(
+                $(#[$inner:ident $($args:tt)*])*
+                const $Flag:ident = $value:expr;
+            )*
+        }
+
+        $($t:tt)*
+    ) => {
+        $(#[$($outer)+])*
+        #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+        $vis struct $BitFlags($T);
+
+        impl core::fmt::Debug for $BitFlags {
+            fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+                if self.is_empty() {
+                    core::write!(f, "{:#x}", Self::empty().bits())
+                } else {
+                    $crate::parser::to_writer(self, f)
+                }
+            }
+        }
+
+        bitflags2! {
+            impl $BitFlags: $T {
+                $(
+                    $(#[$inner $($args)*])*
+                    const $Flag = $value;
+                )*
+            }
+        }
+
+        bitflags! {
+            $($t)*
+        }
+    };
+    () => {};
+}