macroexpand: stop pre-running the hygiene pass #49793
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This prepares us to delete the separate hygiene pass, and make it part of lowering resolve-scopes. This affects a few macros which expect to run macroexpand then mangle the result more, and the result of those macros is not already wrapped in `esc()`. The damage seems relatively minor however, and generally a good improvement.
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Setting `legacyscope=false` is intended to make it much easier to debug and test macro expansion, since it no longer runs a buggy symbol mangling pass automatically. Adding the mutating version (`macroexpand!`) is mainly a handy way to opt in to the new legacyscope=true, without needing to spell that out. More background: the macroexpand.scm pass design is buggy, so we'd like to stop using in the future. Currently changing the default causes visible breakage to a lot of buggy packages tests, so for now just provide the option to skip the legacy scope resolution. This is a continuation of #49793 and a prerequisite for eventually replacing the flisp code with JuliaLowering (once we can deprecate this parameter). Implement in-place macro expansion with `macroexpand!` (no corresponding `@macroexpand!`) that avoids copying AST nodes when the original expression is no longer needed anyways. But more importantly, add a `legacyscope::Bool` keyword argument to the functions that allows opting out of the legacy scope mangling. Changes: - Consolidate `jl_macroexpand` C functions with added parameters for `recursive`, `inplace`, and the (legacy) `expand_scope` control. - Add `macroexpand!` Julia function with `legacyscope=false` default. - Update `macroexpand` to have `legacyscope` (default `true`) for backward compatibility, until v2 or earlier. Added to backporting so that new code can start to be written with `legacyscope=false`. Not entirely a new feature, since this is just adding the ability to disable an old (long deprecated) feature. 🤖 Generated with Claude
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This prepares us to delete the separate hygiene pass, and make it part of lowering resolve-scopes. This affects a few macros which expect to run macroexpand then mangle the result more, and the result of those macros is not already wrapped in
esc(). The damage seems relatively minor however, and generally a good improvement.