refactor(ast_codegen): simplify derive_get_span generator

[overlookmotel]

Simplify derive_get_span generator that was introduced in #4735. No change to functionality, just aiming for greater readability.

In particular:

• Move defining idents/tokens which are specific to GetSpan / GetSpanMut into those specific generators, rather than branching on MUT later on.
• Remove const MUT param.
• Remove the confusing pairs of closures and functions both called derive_enum / derive_struct.
• Inline function which generates the impls - prioritizing readability over DRY code.

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[overlookmotel]

• refactor(ast_codegen): simplify derive_get_span generator #4757 👈
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging #4757 will not alter performance

_{Comparing 08-08-refactor_ast_codegen_simplify_derive_get_span_generator (790c551) with main (2f6c3b9)}

Summary

✅ 29 untouched benchmarks

[overlookmotel]

What do you think @rzvxa? Personally I find this style less convoluted and a lot easier to understand.

NB: Rather than looking at the diff, I'd suggest comparing before and after.

[rzvxa]

What do you think @rzvxa? Personally I find this style less convoluted and a lot easier to understand.

TBH, I don't have a strong preference here. I'll merge it in if you like it more this way.

[graphite-app]

Merge activity

• Aug 8, 6:46 AM EDT: The merge label 'merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Aug 8, 6:46 AM EDT: rzvxa added this pull request to the Graphite merge queue.
• Aug 8, 6:50 AM EDT: rzvxa merged this pull request with the Graphite merge queue.