A proof-of-concept implementation of the proposed RFC #1583; provides macros for parsing generics and where clauses. Note: requires a compatible nightly compiler. For a stable alternative, see the parse-generics-shim crate.

macro, plugin, parse, generics, where


Daniel Keep

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This repository contains several pieces related to the proposed RFC #1583:

  • parse-generics-poc - a proof-of-concept implementation of the RFC.
  • parse-generics-shim - a "polyfill" shim containing an implementation of a subset of the RFC in stable macro_rules!.
  • parse-macros - a crate containing higher-level parsing macros built on top of parse-generics-shim.

A very basic example of using parse-macros in a crate, and then using that crate, is provided by the enum-as-str and enum-as-str-test crates. Further examples can be found by looking at the parse-macro crate's tests directory. Specifically:

  • - a stable implementation of the built-in Clone derivation compiler plugin.
  • - a stable implementation of the built-in PartialOrd derivation compiler plugin. I was once assured this was impossible by a member of the core team.
  • - a stable derivation macro for [serde]'s Serialize trait. Does not support attributes (e.g. custom field names).
  • - a very minimal compile-time reflection derivation macro. Progress is blocked on not being able to define generic constants/statics, not on parsing or generation complexity.


Supporting RFC #1583

The core team currently feels uneasy about accepting RFC #1583, due to its complexity and the lack of demonstrable support for being able to correctly process generics and where clauses in macros.

If you would like to see it accepted, using the parse-generics-shim crate (and supporting its use-parse-generics-poc feature) will help demonstrate the desire for these macros to be accepted into the compiler.


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