dtolnay/cxx

Raw identifiers in methods in extern "C++" block leads to wrong C++ code generation

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#1324 opened on Mar 11, 2024

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help wanted

Description

For example

pub fn highlight(r#type: i32);

leads to

void ffi$cxxbridge1$highlight(::std::int32_t r#type) noexcept { ... }

I wish it could be unraw-ed if being a valid C++ identifier. Currently workaround with type_.

Contributor guide

Tech stack
rustcpp
Domain
developer experience
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic Rust syntaxUnderstanding of raw identifiersFamiliarity with C++ identifier rules
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75
Research direction
Investigate how the code generator handles raw identifiers (r#) in the `extern "C++"` block. Look at the code generation logic, likely in `src/gen.rs` or similar files, that transforms Rust function parameters into C++ function signatures. The fix requires checking if the identifier after `r#` is a valid C++ identifier (does not clash with C++ keywords) and stripping the `r#` prefix in that case. Refer to the issue description for the failing example and expected behavior.