perf(oxc_ast): optimize ast layout

[IWANABETHATGUY]

1. as perf(ast): reduce AST memory usage #5601 (comment) suggested, this time only box FunctionBody.directives.
2. Also change ast_tools to support auto generated Box<Vec<T>>

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[codspeed-hq]

CodSpeed Performance Report

Merging #5658 will not alter performance

_{Comparing perf/optimize-ast-layout2 (da01b26) with main (20a7861)}

Summary

✅ 29 untouched benchmarks

[Boshen]

Box<Vec<_>> feels weird, let me think about this.

[IWANABETHATGUY]

Box<Vec<_>> feels weird, let me think about this.

#5601 (comment))

[overlookmotel]

A ThinVec type would be preferable for this use case (oxc-project/backlog#113). But who knows when we'll get around to implementing that?

In the meantime, I think Box<Vec<T>> is the best solution we have available.

Personally I think we should consider re-opening this and likely merging it. At the very least, the changes to ast_tools and the Traverse codegen are worthwhile. @Boshen?

[Boshen]

A ThinVec type would be preferable for this use case (oxc-project/backlog#113). But who knows when we'll get around to implementing that?

In the meantime, I think Box<Vec<T>> is the best solution we have available.

Personally I think we should consider re-opening this and likely merging it. At the very least, the changes to ast_tools and the Traverse codegen are worthwhile. @Boshen?

<Box<Vec_>> looks too strange, and there is no observable performance impact to get this merged.

[overlookmotel]

@IWANABETHATGUY I'm sorry I "led you up the garden path" with my comment #5601 (comment). It seems Boshen and I disagree on this one. It's unfortunate we didn't realize that before you started on PRs. Sorry.

[IWANABETHATGUY]

@IWANABETHATGUY I'm sorry I "led you up the garden path" with my comment #5601 (comment). It seems Boshen and I disagree on this one. It's unfortunate we didn't realize that before you started on PRs. Sorry.

that's fine