refactor(parser): simplify ModifierFlags

[overlookmotel]

The types for modifiers were confusing. We had ModifierFlags type defined with bitflags! macro, and ModifierKind enum which represents the different possible flags.

The two types weren't statically related, and consuming code needed to manually relate the two e.g. pairing usage of ModifierFlags::DECLARE with ModifierKind::Declare. This is unnecessarily complicated, and error-prone.

This PR turns ModifierFlags into a wrapper around a u16 and adds methods to construct, query, and set bits in the set by passing a ModifierKind or a set of ModifierKinds. Consuming code now only has one type to deal with which is the single source of truth about what modifiers are available - ModifierKind.

Code is more verbose in some places, but personally I think this more explicit style is clearer. ModifierFlags::new is a const function, so even sizeable calls e.g. ModifierFlags::new([ModifierKind::Public, ModifierKind::Private, ModifierKind::Protected]) is boiled down to a static u16 at compile time. It compiles down to the same as the bitflags! version.

This change also enables #20742, which improves the storage of Modifiers.

[overlookmotel]

• perf(parser): defer calculation of Modifier spans #20823 : 2 dependent PRs (#20824 , #20826 )
• perf(parser): remove branch from parse_modifiers #20821
• perf(parser): reduce Kind to ModifierKind conversions in eat_modifiers_before_declaration #20820
• refactor(parser): shorten code handling illegal modifiers #20781
• perf(parser): fast path for no syntax errors when checking modifiers #20748
• perf(parser): remove a lookahead from eat_modifiers_before_declaration #20755
• refactor(parser): nest modifiers types in modules #20754
• refactor(parser): re-order modifiers code #20753
• perf(parser): store Modifiers on stack #20742
• perf(parser): add Modifiers::get method #20741
• refactor(parser): rename ModifierKinds::empty to none #20740
• refactor(parser): rename ModifierFlags to ModifierKinds #20739
• refactor(parser): simplify ModifierFlags #20738 👈 (View in Graphite)
• refactor(parser): import from std at top level #20737
• refactor(parser): remove Modifier::is_static() #20736
• refactor(parser): remove dead code from modifier parsing #20735
• main

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[codspeed-hq]

Merging this PR will not alter performance

✅ 48 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing om/03-23-refactor_parser_simplify_modifierflags_ (5aee74c) with main (caf8231)²}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (5aee74c) during the generation of this report, so caf8231 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Copilot]

Pull request overview

Refactors the parser’s modifier tracking to make ModifierKind the single source of truth by replacing the bitflags!-based ModifierFlags with a compact u16 bitfield wrapper and ModifierKind-centric constructors/query APIs, simplifying call sites and reducing the chance of mismatched flag/kind pairs.

Changes:

• Replaced bitflags! ModifierFlags with a u16-backed ModifierFlags wrapper plus new/all_except/contains/with/without APIs.
• Updated parser call sites to construct/check allowed modifiers via ModifierKind arrays instead of |, !, and from(...) conversions.
• Adjusted diagnostics helper text generation and accessor-specific “allowed modifiers” computation to use the new APIs.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
crates/oxc_parser/src/modifiers.rs	Introduces new ModifierFlags bitfield wrapper and updates modifier parsing/verification to use ModifierKind-based operations.
crates/oxc_parser/src/diagnostics.rs	Updates allowed-modifier help text logic and accessor modifier diagnostics to use count()/without().
crates/oxc_parser/src/ts/types.rs	Updates verify_modifiers call sites to use ModifierFlags::new / all_except.
crates/oxc_parser/src/ts/statement.rs	Updates verify_modifiers call sites to use ModifierKind-based flag construction.
crates/oxc_parser/src/js/statement.rs	Updates TS enum const-modifier construction to use ModifierFlags::new([Const]).
crates/oxc_parser/src/js/object.rs	Imports ModifierKind and updates async modifier verification to ModifierFlags::new([Async]).
crates/oxc_parser/src/js/module.rs	Updates abstract modifier construction for export default class handling.
crates/oxc_parser/src/js/function.rs	Updates constructor/function allowed-modifier sets to ModifierFlags::new([...]).
crates/oxc_parser/src/js/class.rs	Updates multiple modifier allow/deny sets to new/all_except and refactors one diagnostic helper to a const ALLOWED.

[graphite-app]

Merge activity

• Mar 26, 1:07 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Mar 26, 1:12 PM UTC: Merged by the Graphite merge queue.