[Timur Vural (timurzvural)]

Summary

Fixes two native Go / TS7+ bugs:

Fixes #64883 — Escaped in / instanceof after class field initializers

After a class field initializer, Unicode-escaped \u{69}n / \u{69}nstanceof on the next line were parsed as the in / instanceof operators (TS1260 + parse error). Per ECMA-262, keyword terminals cannot be expressed with Unicode escapes, so these should be IdentifierNames (matching V8).

Change: Treat escaped keywords as non-operators in the binary-operator path so ASI can end the previous expression and the escaped name can start a new class member. Unescaped in after a field initializer still continues the expression (test262 fields-asi-5.js).

Fixes #64981 — new (f() as T).C() drops required parentheses on emit

new (getPlugins() as any).Linker() was emitted as new getPlugins().Linker() (i.e. (new getPlugins()).Linker()), causing a runtime TypeError.

Change: Parenthesize when the leftmost expression (stopping at calls, walking through parentheses / partially-emitted / assertion wrappers) is a CallExpression, matching classic TS6 emit: new (getPlugins().Linker)().

Test plan

• Added Go unit tests in parser_test.go, printer_test.go, and typeeraser_test.go
• CI / existing test suite

AI assistance disclosure

This change was authored with Cursor Agent (an LLM-based coding agent). A human operator directed the investigation at these specific open issues, reviewed the resulting patch, and is submitting it for review. Per CONTRIBUTING.md, AI tool use is disclosed here.

[Jake Bailey (jakebailey)]

Why are there two fixes in one PR

[Timur Vural (timurzvural)]

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[Copilot]

🟡 Changes recommended

The shared helper’s deeper traversal adds redundant parentheses to already-parenthesized arrow bodies, conflicting with existing emit baselines; it should be scoped to the new-expression check.

1 open issue

• Avoid double-wrapping parenthesized arrow function bodies · New

What changed in this PR

This PR addresses two native TypeScript compiler bugs: escaped keywords preventing automatic semicolon insertion after class fields (#64883), and missing parentheses changing the meaning of emitted new expressions (#64981).

Changes:

• Exclude Unicode-escaped keywords from binary-operator parsing.
• Detect calls within constructor expressions to preserve required parentheses.
• Add parser, printer, and type-erasure regression tests.

File	Description
tsc/​internal/​transformers/​tstransforms/​typeeraser_test.go	Tests constructor grouping after type syntax is erased.
tsc/​internal/​printer/​printer.go	Extends call detection when emitting new expressions.
tsc/​internal/​printer/​printer_test.go	Tests constructor property access rooted in a call.
tsc/​internal/​parser/​parser.go	Prevents escaped keywords from acting as binary operators.
tsc/​internal/​parser/​parser_test.go	Tests escaped class fields and unescaped in continuation.
tsc/​internal/​ast/​precedence.go	Makes leftmost-expression traversal cross parentheses.

_{Review effort: Balanced}

[Timur Vural (timurzvural)]

Closing this combined PR in favor of two focused single-issue PRs (one bug each):

• Fix escaped keyword ASI after class field initializers (#64883) #65014 — Fix escaped keyword ASI after class field initializers (Escaped in / instanceof after a class field initializer is parsed as a binary operator instead of a new member #64883) — timurzvural:fix/64883-escaped-keyword-asi
• Fix new-expression emit parentheses after type erasure (#64981) #65015 — Fix new-expression emit parentheses after type erasure (TS7+ drops required parentheses in new (f() as T).C(), emitting incorrectly as new f().C() #64981) — timurzvural:fix/64981-new-expression-parens

Please review those instead. Thanks!

[Timur Vural (timurzvural)]

Replaced by focused PRs #65014 (#64883) and #65015 (#64981).