windows-clang type value collisions

[Kenny Kerr (kennykerr)]

Fixes #4941.

C permits a type and an object-like macro to share the same spelling. windows-clang previously selected the type and discarded the constant because planning and emission treated every projected name as globally unique. Preserve both output categories while continuing to reject duplicate values and incompatible translation-unit dependency graphs explicitly.

Add focused test_clang and test_rdl fixtures for supported type/value and type/function names. Full SDK regeneration surfaces the canonical HTTP_VERSION case as both a struct and an ANSI string constant, and tool-package projects both declarations into the same Rust module for windows and windows-sys.

This PR is intentionally scoped to object-like macro constants. GUID, property-key, and coclass facts also emit values but currently participate in type-root planning and have separate exclusion and UM/KM ownership behavior. A follow-up will separate those facts throughout planning and apply metadata exclusions consistently; full generation shows that work will remove redundant UM-owned GUIDs from the additive WDK RDL while leaving the merged WinMD unchanged.

Validation:

• cargo test -p windows-clang -p test_clang -p test_rdl
• cargo clippy -p windows-clang --all-targets
• cargo check -p windows --features http
• cargo check -p windows-sys --features http
• cargo run -p tool-roundtrip --quiet
• cargo run -p tool-package --quiet
• cargo run -p tool-features --quiet
• Two complete tool-win32 runs produced identical output in 470.66s and 455.12s.

[Copilot]

🟡 Changes recommended

Root planning can still discard constants during type exclusions and function collisions.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

This PR preserves colliding C type/value names through RDL and Rust projection.

Changes:

• Separates type and value output-name tracking.
• Adds collision fixtures and dependency-planning tests.
• Regenerates HTTP bindings with both HTTP_VERSION declarations.

File summaries

File	Description
metadata/win32/http.rdl	Adds the HTTP_VERSION constant.
docs/crates/windows-clang.md	Documents collision handling.
crates/tests/libs/rdl/input/type_value_name_collision.rdl	Tests type/constant collisions.
crates/tests/libs/rdl/input/type_function_name_collision.rdl	Tests type/function collisions.
crates/tests/libs/clang/input/type_value_name_collision.h	Adds the Clang fixture input.
crates/tests/libs/clang/expected/type_value_name_collision.rdl	Defines expected extraction output.
crates/libs/windows/src/Windows/Win32/http/mod.rs	Projects the Windows HTTP constant.
crates/libs/sys/src/Windows/Win32/http/mod.rs	Projects the windows-sys HTTP constant.
crates/libs/clang/tests/checkpoint3.rs	Updates dependency-collision expectations.
crates/libs/clang/src/lib.rs	Separates output namespaces and revises planning.

Review details

• Files reviewed: 10/11 changed files
• Comments generated: 1
• Review effort level: Balanced

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[Copilot]

🔵 Needs a closer look

Planning still rejects collisions between real types and value-emitting GUID, property-key, or class facts.

Review details

Suppressed comments (1)

Previously missed (1) — in code that hasn't changed since the last review.

crates/libs/clang/src/lib.rs:520

• The category split happens only after planning. plan() still puts FactData::Guid, PropertyKey, and Class in Roots.types, so a real type with the same projected name reaches choose_type_root_cached as an incompatible pair and fails with ambiguous type root before this classification runs. For example, valid C containing struct Shared { ... }; DEFINE_GUID(Shared, ...) should produce a struct and GUID constant. Please separate these value-emitting facts during planning as well, while continuing to reject collisions with other values, and cover this case with a fixture.

• Files reviewed: 10/11 changed files
• Comments generated: 0 new
• Review effort level: Balanced

[Copilot]

🟡 Changes recommended

The new value-fact path ignores constant exclusions and can re-emit values already present in referenced metadata.

Get a fresh assessment by requesting another Copilot review.

Review details

• Files reviewed: 12/13 changed files
• Comments generated: 1
• Review effort level: Balanced