[RFC PATCH 4/6] rust: subprojects: add bitfield-struct

[Paolo Bonzini <pbonzini@redhat.com>]

The bitfield-struct is much smaller than "bilge" and supports "const"
expressions better.  The main disadvantage is that it does not let you
annotate enums as bitfields and does not integrate with arbitrary-int,
thus requiring manual size annotations for anything that is not a bool,
iNN or uNN.

Lack of support for arbitrary-int is a very minor change; enums are a
bit more annoying because they require manual implementation of two
functions from_bits() and into_bits(); however, that is already handled
by QEMU's bits! and #[derive(qemu_api_macros::TryInto)] utilities.
Together, these basically make the manual work go away.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/meson.build                              |  3 ++
 subprojects/.gitignore                        |  1 +
 subprojects/bitfield-struct-0.9-rs.wrap       |  7 ++++
 .../bitfield-struct-0.9-rs/meson.build        | 36 +++++++++++++++++++
 4 files changed, 47 insertions(+)
 create mode 100644 subprojects/bitfield-struct-0.9-rs.wrap
 create mode 100644 subprojects/packagefiles/bitfield-struct-0.9-rs/meson.build

diff --git a/rust/meson.build b/rust/meson.build
index f370b0ec939..58f14a70d6d 100644
--- a/rust/meson.build
+++ b/rust/meson.build
@@ -1,3 +1,6 @@
+subproject('bitfield-struct-0.9-rs', required: true)
+bitfield_struct_dep = dependency('bitfield-struct-0.9-rs')
+
 subdir('qemu-api-macros')
 subdir('bits')
 subdir('qemu-api')
diff --git a/subprojects/.gitignore b/subprojects/.gitignore
index d12d34618cc..180c3134864 100644
--- a/subprojects/.gitignore
+++ b/subprojects/.gitignore
@@ -9,6 +9,7 @@
 /arbitrary-int-1.2.7
 /bilge-0.2.0
 /bilge-impl-0.2.0
+/bitfield-struct-0.9.5
 /either-1.12.0
 /itertools-0.11.0
 /libc-0.2.162
diff --git a/subprojects/bitfield-struct-0.9-rs.wrap b/subprojects/bitfield-struct-0.9-rs.wrap
new file mode 100644
index 00000000000..dfdbbc853af
--- /dev/null
+++ b/subprojects/bitfield-struct-0.9-rs.wrap
@@ -0,0 +1,7 @@
+[wrap-file]
+directory = bitfield-struct-0.9.5
+source_url = https://crates.io/api/v1/crates/bitfield-struct/0.9.5/download
+source_filename = bitfield-struct-0.9.5.tar.gz
+source_hash = b2869c63ccf4f8bf0d485070b880e60e097fb7aeea80ee82a0a94a957e372a0b
+#method = cargo
+patch_directory = bitfield-struct-0.9-rs
diff --git a/subprojects/packagefiles/bitfield-struct-0.9-rs/meson.build b/subprojects/packagefiles/bitfield-struct-0.9-rs/meson.build
new file mode 100644
index 00000000000..e8badb7da18
--- /dev/null
+++ b/subprojects/packagefiles/bitfield-struct-0.9-rs/meson.build
@@ -0,0 +1,36 @@
+project('bitfield-struct-0.9-rs', 'rust',
+  meson_version: '>=1.5.0',
+  version: '0.9.5',
+  license: 'MIT',
+  default_options: [])
+
+subproject('quote-1-rs', required: true)
+subproject('syn-2-rs', required: true)
+subproject('proc-macro2-1-rs', required: true)
+
+quote_dep = dependency('quote-1-rs', native: true)
+syn_dep = dependency('syn-2-rs', native: true)
+proc_macro2_dep = dependency('proc-macro2-1-rs', native: true)
+
+rust = import('rust')
+
+_bitfield_struct_rs = rust.proc_macro(
+  'bitfield_struct',
+  files('src/lib.rs'),
+  override_options: ['rust_std=2021', 'build.rust_std=2021'],
+  rust_args: [
+    '--cap-lints', 'allow',
+    '--cfg', 'use_fallback',
+  ],
+  dependencies: [
+    quote_dep,
+    syn_dep,
+    proc_macro2_dep,
+  ],
+)
+
+bitfield_struct_dep = declare_dependency(
+  link_with: _bitfield_struct_rs,
+)
+
+meson.override_dependency('bitfield-struct-0.9-rs', bitfield_struct_dep)
-- 
2.49.0