rust-lang / rust-lang/rustc_public

Request: expose stable hash value for DefId

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#102 0 comments 1 reaction 0 assignees View on GitHub

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Dominant language
Rust
Stars
125
Forks
19
PR merge metrics
No merged PRs in 30d

Description

TyCtxt::def_path_hash provides stable hash value for DefId.

A stable hash is important for cross-platform or cache-sensitive code.

To keep API simple, instead of returning DefPathHash, the hash value can just be two u64s.


Updated: it seems DefPathHash is also platform-dependent due to SVH. (Context)
In this case, there is no such stable DefId hash across platforms.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with TyCtxt::def_path_hash and DefPathHash, the two APIs linked in the issue, then verify the updated claim that DefPathHash is platform-dependent. Done means establishing whether a cross-platform stable DefId hash is possible and, if so, defining the public API; the issue supplies no file or test path.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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