dtolnay/cxx

Implement glob import semantics for builtin type names

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#682 opened on Jan 16, 2021

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 (6 comments) (0 reactions) (0 assignees)Rust (253 forks)batch import
help wanted

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Description

Currently we disallow any user-defined type name that collides with one of the builtin type names.

error[cxxbridge]: reserved name
  ┌─ src/main.rs:3:12
  │
3 │     struct UniquePtr { broken: bool }
  │            ^^^^^^^^^ reserved name

error[cxxbridge]: reserved name
  ┌─ src/main.rs:5:12
  │
5 │     struct c_char { broken: bool }
  │            ^^^^^^ reserved name

However, this is bad because it makes it a breaking change for us to add new builtin bindings, such as #681. If the user already had their own type with the same name as the new binding, that code needs to continue to work.

We need to implement basically the same semantics that Rust has for prelude types and glob imports — a user-defined type replaces any builtin binding of the same name.

Contributor guide

Research direction
Study Rust's prelude and glob import semantics for name resolution. Then modify the cxx parser to allow user defined types to shadow builtin types, similar to how Rust's glob imports override prelude types.
Tech stack
rust
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Rust
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65