Allow parsing foreign impl blocks #102376
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| Some changes occurred in src/tools/rustfmt cc @rust-lang/rustfmt |
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Allow `impl` blocks in foreign modules for more ergonomic use in macros. `impl` blocks still have no meaning in foreign modules and will cause an error if still present during lowering. Also adds explicit tests for the previous similar foreign module macro extensions to ensure that neither this nor those are accepted or crash the compiler when *not* fed to a macro.
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| I'm not sure they'll accept this, given that #78849 was rejected. Maybe one could generally make parsing weaker for attr proc macros: #78849 (comment) Edit: obviously good C++ compatibility is more important than postfix macros, but the general argument of not adding even more exceptions to the tokens, and this seems to be a big exception, still exists. |
| I’m thinking that this probably wants an compiler team MCP with all the votes and such before this can land. |
| ☔ The latest upstream changes (presumably #102461) made this pull request unmergeable. Please resolve the merge conflicts. |
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Allow parsing foreign
implblocks for use by proc macros.This allows more ergonomic description of methods and associated functions both when describing rust types to be exported and when importing class-like objects from other languages.
My primary motivation for this change is clean support for C++ static methods - this could be done with alternate syntax (e.g. explicit attributes to associate these functions with classes), but this seems much cleaner and potentially useful for interfacing with other languages beyond C++.
The Rust language itself remains unmodified - foreign
implblocks which make it past the macro expansion stage will not compile, and additional tests have been added to ensure this remains the case.#75857 is prior art on this kind of change, but is substantially less involved.
cc @dtolnay