feat: wdk_build::DerivesMap for derives collection of bindgen output

[leon-xd]

This PR introduces wdk_build::DerivesMap, a struct to collect the info of all #[derive()] attributes for each type emitted by bindgen. See #654 for the related PR.

Purpose

These changes are a pre-requisite to solve the current issues with generating bindings for mutually exclusive WDK headers (tracked by #514 , #515 , and #516 ). The solution requires types and constants for subsystems to be generated in independent bindgen runs, and will be published in a follow-up PR. In order to prevent duplicate type generation, bindgen invocation for subsystem types will utilize a blocklist_file for every file traversed in the initial base types run.

bindgen by default assumes very minimal derives when encountering a blocklisted type, so this implementation on its own would leave most subsystem types with a sparse set of automatic derives. This is a regression that is unacceptable. In order to prevent this while still keeping our mutual exclusive headers solution, we need to gather the derive information for all of the generated base types, and pass it off to subsystem bindgen type generators via the callback blocklisted_type_implements_trait.

This PR introduces the mechanism to be able to parse a bindgen generated file using syn and extract the derive information for each individual type. In practice, the future bindings generation pipeline will generate the types for the base layer of the WDK, parse it via DerivesMap::from_file, and then insert the created DerivesMap into each subsystem type bindgen via BaseDerivesCallback.

Changes

• Cargo.toml
  • Bump bindgen from 0.71.0 to 0.72.1
  • Add bitflags = "2.6.0" workspace dependency
• crates/wdk-build/Cargo.toml
  • Add bitflags dependency
  • Add syn dependency with the parsing feature enabled
• crates/wdk-build/src/lib.rs
  • Declare new pub mod derives (gated with #[doc(hidden)] since the module is intended for internal wdk-sys build-script use, not public API)
• crates/wdk-build/src/bindgen.rs
  • Pin size_t_is_usize(true) on wdk_default. size_t/ssize_t are pointer-width on every supported Windows driver target (x64, ARM64, x86), matching Rust's usize/isize. This is the invariant that derives.rs relies on when seeding stdint integer types into its derive map.
• crates/wdk-build/src/derives.rs
  • DerivesError: typed error enum for derive-map construction failures.
  • DerivesSet: a bitflags! set over the five derive traits bindgen tracks (Copy, Clone, Debug, Default, PartialEq).
  • DerivesSource: enum distinguishing whether a type's derives are immediately known (from a #[derive()] attribute or from a base type) or come from an aliased type.
  • BaseDerivesCallback: a bindgen::callbacks::ParseCallbacks implementation that answers blocklisted_type_implements_trait from a populated DerivesMap. Plugs into bindgen's chain so types blocklisted in one bindings module can still be referenced from another. Used in follow up PR.
  • DerivesMap: a map from type name to DerivesSet. Builds incrementally from Rust source files via syn, and resolves alias chains.
  • syn helpers:
    • idents_and_derives_for_items: walk a slice of Items, collect (name, DerivesSource) pairs.
    • idents_and_derives_for_mod: recurse into a mod and forward to idents_and_derives_for_items.
    • ident_and_derives_for_use: resolve a use a::b as Foo; re-export to (Foo, DerivesSource::Alias(...)).
    • derives_for_type: given a Type, classify into a DerivesSource (named alias, function pointer, primitive, etc.).
    • derives_from_attrs: extract the derive-trait names from a #[derive(...)] attribute list.
  • Small helpers: inner_is_bare_fn, path_is_option, path_is_core_ffi_type
  • Tests: unit-test coverage for parsing, alias resolution (including cycle detection and stable iteration order), classification of #[derive(...)] attributes, and stdint seeding.

Validation

Tested this with the full implementation of the mutually exclusive header resolution and ensured that all outputted bindings had full #[derive] parity against bindings generated from microsoft/main.

[Copilot]

Pull request overview

Adds an internal wdk_build::derives module that can parse bindgen-generated Rust (types.rs-style) and reconstruct which auto-derives apply to each emitted type, enabling future multi-pass bindgen runs (e.g., mutually exclusive headers) to preserve derive parity via blocklisted_type_implements_trait.

Changes:

• Introduces crates/wdk-build/src/derives.rs with DerivesMap, alias resolution, and a ParseCallbacks implementation (BaseDerivesCallback).
• Updates the default bindgen builder configuration to force size_t/ssize_t to map to usize/isize.
• Bumps workspace bindgen and adds workspace bitflags, plus syn parsing support in wdk-build.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Cargo.toml	Bumps bindgen and adds workspace bitflags dependency.
Cargo.lock	Lockfile updates for new/updated dependencies.
crates/wdk-build/Cargo.toml	Adds bitflags and syn(parsing) dependencies for derive parsing.
crates/wdk-build/src/lib.rs	Exposes internal derives module (doc-hidden).
crates/wdk-build/src/bindgen.rs	Sets size_t_is_usize(true) to match Windows driver targets and derive-map assumptions.
crates/wdk-build/src/derives.rs	New derive parsing + alias-resolution logic + unit tests.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.57602% with 30 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.69%. Comparing base (5748ea2) to head (ff10314).

Files with missing lines	Patch %	Lines
crates/wdk-build/src/derives.rs	93.57%	15 Missing and 15 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #652      +/-   ##
==========================================
+ Coverage   78.44%   79.69%   +1.24%     
==========================================
  Files          25       26       +1     
  Lines        5201     5668     +467     
  Branches     5201     5668     +467     
==========================================
+ Hits         4080     4517     +437     
- Misses       1001     1016      +15     
- Partials      120      135      +15     

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

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[gurry]

@leon-xd can parsing base types have any measurable impact on build time?

[wmmc88]

@leon-xd can parsing base types have any measurable impact on build time?

@gurry in the pr description of Leon's other pr which uses this new feature, he says:

I also timed the build process with this change to ensure there was not a significant build time regression. As it stands I am currently able to build wdk_sys with all_features in ~45 seconds, compared to microsoft/main's 60 seconds. I would not trust this number as the build script is subject to change with future revisions for this PR.

So while technically its not attributable to only this change, as a whole the change reduces build time. I think a theory was that bindgen's parsing of header seems to scale non-linearly