Add bitclear analyzer to suggest &^= A instead of &= ^A

[jakebailey]

Go has a bit clear operator, &^= A. We've used this nearly everywhere in place of &= ^A, but some stragglers remained.

Add an analyzer that finds these cases, then allows for easy --fix.

[Copilot]

Pull request overview

Adds a custom Go lint analyzer to standardize bit-clearing patterns by suggesting &^= (bit clear) in place of &= ^, and updates remaining occurrences in the compiler code to use the idiomatic operator.

Changes:

• Replace several x &= ^y usages across internal/ with x &^= y.
• Add a new _tools/customlint analyzer (bitclear) that reports &= ^ patterns and provides an autofix.
• Add golden test coverage for the new analyzer diagnostics.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/transformers/tstransforms/runtimesyntax.go	Convert modifier mask clearing to &^=.
internal/transformers/jsxtransforms/jsx.go	Use &^= when clearing synthesized node flags.
internal/printer/printer.go	Use &^= to clear multi-line/indent formatting flags.
internal/parser/parser.go	Use &^= to clear parser context flags.
internal/checker/nodebuilderimpl.go	Use &^= to clear nodebuilder context flags.
internal/checker/jsx.go	Use &^= to clear enum flag from symbol flags.
internal/checker/checker.go	Use &^= for JSX factory symbol flag adjustments.
internal/binder/binder.go	Use &^= for clearing various node flags.
internal/ast/subtreefacts.go	Use &^= for subtree facts bit clearing.
_tools/customlint/plugin.go	Register the new bitclear analyzer in the plugin.
_tools/customlint/bitclear.go	New analyzer to detect &= ^ and provide --fix edits.
_tools/customlint/testdata/bitclear/bitclear.go	New test inputs for the analyzer.
_tools/customlint/testdata/bitclear/bitclear.go.golden	Golden output validating reported diagnostics/ranges/messages.

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