fix(ts/fast-strip): reject unsafe assertion erasure in binary expressions#11828
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Pull request overview
Adds safety checks to swc_ts_fast_strip to avoid producing incorrect JavaScript when stripping TypeScript-only operators (as / satisfies) inside binary-expression chains where erasure would change parse grouping.
Changes:
- Track the current binary-expression “path” during AST visitation and reject unsafe
as/satisfieserasure when it would change binary grouping. - Add new non-error fixtures covering “safe” precedence/associativity scenarios for assertion erasure.
- Add new error fixtures asserting diagnostics for known-unsafe precedence/associativity cases.
Reviewed changes
Copilot reviewed 12 out of 12 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| crates/swc_ts_fast_strip/src/lib.rs | Adds binary-path tracking and grouping-safety detection; emits diagnostics for unsafe as/satisfies stripping. |
| crates/swc_ts_fast_strip/tests/fixture/type-assertions/precedence-non-errors.ts | New fixture enumerating “safe to erase” cases across operators and precedence tiers. |
| crates/swc_ts_fast_strip/tests/fixture/type-assertions/precedence-non-errors.js | Expected StripOnly output for the new “safe cases” fixture. |
| crates/swc_ts_fast_strip/tests/fixture/type-assertions/precedence-non-errors.transform.js | Expected Transform-mode output for the new “safe cases” fixture. |
| crates/swc_ts_fast_strip/tests/errors/assertion-precedence-as.ts | New StripOnly error fixture for unsafe precedence change with as. |
| crates/swc_ts_fast_strip/tests/errors/assertion-precedence-as.swc-stderr | Expected diagnostic output for the unsafe precedence as case. |
| crates/swc_ts_fast_strip/tests/errors/assertion-precedence-satisfies.ts | New StripOnly error fixture for unsafe precedence change with satisfies. |
| crates/swc_ts_fast_strip/tests/errors/assertion-precedence-satisfies.swc-stderr | Expected diagnostic output for the unsafe precedence satisfies case. |
| crates/swc_ts_fast_strip/tests/errors/assertion-associativity-as.ts | New StripOnly error fixture for unsafe associativity change with as and **. |
| crates/swc_ts_fast_strip/tests/errors/assertion-associativity-as.swc-stderr | Expected diagnostic output for the unsafe associativity as case. |
| crates/swc_ts_fast_strip/tests/errors/assertion-associativity-satisfies.ts | New StripOnly error fixture for unsafe associativity change with satisfies and **. |
| crates/swc_ts_fast_strip/tests/errors/assertion-associativity-satisfies.swc-stderr | Expected diagnostic output for the unsafe associativity satisfies case. |
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