Migrate the transform-pipeline `Visit` implementors to `VisitJs` (#24499): `oxc_transformer` (3), `oxc_minifier` (4), `oxc_react_compiler` (1), plus the parser regex example and the coverage driver. Part of #24317; linter half in #24530. Behavior is unchanged.
Together with #24530: `oxlint` −129.4 KiB (−0.94%) stripped, `oxc_transform` napi −16.2 KiB (−0.46%).
## Why each visitor can switch
A visitor is safe on `VisitJs` when its hooks cannot observe anything inside the pruned type grammar — either the hooked node kinds are value-space-only, or the AST it walks cannot contain type nodes at that pipeline stage.
| Visitor | File | Why equivalent |
|---|---|---|
| `PrivateInExpressionDetector` | `crates/oxc_transformer/src/decorator/legacy/mod.rs` | Hooks `visit_private_in_expression` (+`visit_decorators`); `#x in y` is runtime-only and cannot occur in type grammar, even inside decorator expressions carrying casts. |
| `BindingMover` | `crates/oxc_transformer/src/es2017/async_to_generator.rs` | Its formal-parameter overrides visit only pattern + initializer (`BindingPattern` carries no type field — annotations are sibling fields it never touches); runs in the exit phase after TS strip. |
| `UsedInJSXBindingsCollector` | `crates/oxc_transformer/src/jsx/refresh.rs` | Runs on un-stripped TSX, but its hooks (JSX-shaped calls, `visit_jsx_opening_element`, declarations/imports) cannot fire inside type grammar; its hand-written `visit_ts_type_annotation` skip-stub is deleted — `VisitJs` prunes that natively. |
| `Finder` | `crates/oxc_react_compiler/src/react_compiler/entrypoint/program.rs` | Matches functions by `scope_id`; real JS function scopes never live in pure type grammar, and `VisitJs` still walks the places one could hide (enum initializers, namespace bodies, cast inner expressions). |
| `KeepVar` | `crates/oxc_minifier/src/keep_var.rs` | Hooks `visit_statement`/`visit_variable_declaration`; statements and `var` declarations don't exist in type space, and namespace/enum bodies (which can contain them) are still walked by `VisitJs`. |
| `DirectEvalFlagCheck` | `crates/oxc_minifier/src/peephole/mod.rs` | Debug-only; hooks `visit_call_expression` only — call expressions cannot occur in valid type grammar. |
| `LiveDirectEvalCollector` | `crates/oxc_minifier/src/peephole/mod.rs` | Same single call-expression hook; type-space-immune regardless of input. |
| `TestVisitor` | `crates/oxc_minifier/tests/ecmascript/prop_name.rs` | Test helper parsing `SourceType::default()` (plain JS); single non-recursing `visit_object_expression` hook. |
| `RegularExpressionVisitor` | `crates/oxc_parser/examples/regular_expression.rs` | Finds `RegExpLiteral` / `new RegExp(...)`; neither node kind can occur in type grammar. |
| `CheckASTNodes` | `tasks/coverage/src/driver.rs` | Its only active override is `visit_reg_exp_literal` (regex print idempotency); `RegExpLiteral` cannot occur in type space. (The commented-out `visit_span` full-AST check would need `Visit` if ever revived.) |
Left on `Visit`: the minifier's incremental-scoping bookkeeping (`DropDiff`, `OverPruneCheck`, `LiveRefCollector`) — dropping `let x: Foo = …` must unmark the type-space `Foo` reference, which the `peephole::remove_unused_declaration` tests verify (they fail under `VisitJs`; confirmed and reverted during this work). `ChildScopeCollector` also stays: TS type nodes (mapped/conditional/function types) carry real `scope_id`s it must collect.
---
🤖 This PR was written with the assistance of Claude Code (Claude Fable 5).
## Summary
Introduces `oxc_diagnostics::Diagnostics` — a `Vec<OxcDiagnostic>` newtype that knows the difference between errors and warnings — and makes it the standard diagnostics return value across oxc.
- **New type**: `Diagnostics` with `has_errors()`, `has_warnings()`, `errors()`, `warnings()`, plus `Vec`-like ergonomics (Deref, `IntoIterator`, `Extend`, `From`/`Into<Vec>`) so most call sites are unchanged.
- **Return types**: `ParserReturn`, `SemanticBuilderReturn`, `IsolatedDeclarationsReturn`, the React Compiler `TransformResult`/`LintResult`, and `TransformerReturn` now expose `diagnostics: Diagnostics` instead of `errors: Vec<OxcDiagnostic>` (the React Compiler's separate `errors`/`warnings` are merged into one severity-tagged list).
- **Behaviour**: a React Compiler **error** now stops the transform (no output), while **warnings** flow through and the transform continues. `compile()` aborts codegen only when `diagnostics.has_errors()` — warnings alone no longer abort (previously any diagnostic did).
## Breaking change
Consumers reading `*.errors` on these return values must read `*.diagnostics`. React Compiler consumers that read `.errors`/`.warnings` separately should use `diagnostics.has_errors()` / `diagnostics.errors()` / `diagnostics.warnings()`.
Parser/semantic/isolated-declarations fatality is otherwise unchanged. Builds on the React Compiler transform feature (#23201).
🤖 Generated with [Claude Code](https://claude.com/claude-code)
This PR contains the following updates:
| Package | Update | Change |
|---|---|---|
| [rust](https://redirect.github.com/rust-lang/rust) | minor | `1.94.1` → `1.95.0` |
---
### Release Notes
<details>
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### [`v1.95.0`](https://redirect.github.com/rust-lang/rust/compare/1.94.1...1.95.0)
[Compare Source](https://redirect.github.com/rust-lang/rust/compare/1.94.1...1.95.0)
</details>
---
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Replace `#[allow]` with `#[expect]` through the whole codebase.
This also surfaced many places where the `#[allow]` attributes were outdated/pointless and could be removed entirely.
Only places `#[allow]` remains are:
1. In generated code and macros, where lint errors may or may not be triggered depending on the generated code.
2. A few places where clippy malfunctions. These use e.g. `#[allow(unused, clippy::allow_attributes)]`.
This PR makes 2 changes to improve the existing API that are not very useful.
- Remove `(Literal)Parser` and `FlagsParser` and their ASTs
- Add `with_flags(flags_text)` helper to `ParserOptions`
Here are the details.
> Remove `(Literal)Parser` and `FlagsParser` and their ASTs
Previously, the `oxc_regular_expression` crate exposed 3 parsers.
- `(Literal)Parser`: assumes `/pattern/flags` format
- `PatternParser`: assumes `pattern` part only
- `FlagsParser`: assumes `flags` part only
However, it turns out that in actual usecases, only the `PatternParser` is actually sufficient, as the pattern and flags are validated and sliced in advance on the `oxc_parser` side.
The current usecase for `(Literal)Parser` is mostly for internal testing.
There were also some misuses of `(Literal)Parser` that restore `format!("/{pattern}/{flags}")` back and use `(Literal)Parser`.
Therefore, only `PatternParser` is now published, and unnecessary ASTs have been removed.
(This also obsoletes #5592 .)
> Added `with_flags(flags_text)` helper to `ParserOptions`
Strictly speaking, there was a subtle difference between the "flag" strings that users were aware of and the "mode" recognised by the parser.
Therefore, it was a common mistake to forget to enable `unicode_mode` when using the `v` flag.
With this helper, crate users no longer need to distinguish between flags and modes.
Boshen