[Marve10s]

Summary:

TypeScript Codegen rejects positive fractional enum values but accepts negative ones. For example, enum Message { ZERO = 0, VALUE = -1.5 } passes parsing on 0.88.0 and main. Its generated C++ declaration omits the fractional initializer while the bridging code still compares and returns -1.5.

The existing integer check only examines NumericLiteral nodes. Babel represents a negative numeric initializer as a UnaryExpression, which bypasses that check. Inspect its numeric argument before applying the same integer validation.

This brings negative fractions into line with positive fractions and the Flow parser. Integer-only enums are an existing restriction established in #44326; negative integer support from #47452 is preserved.

Before: parsing the spec succeeds and emits enum class NativeFractionMessage { ZERO = 0, VALUE };.

After: parsing throws the existing UnsupportedEnumDeclarationParserError.

Changelog:

[GENERAL] [FIXED] - Reject negative fractional enum initializers in TypeScript Codegen, matching the existing integer-only enum restriction.

Test Plan:

./node_modules/.bin/jest --runInBand --watchman=false --verbose=false packages/react-native-codegen/src/parsers

All 1,974 parser tests and 188 snapshots pass across 13 suites. The four new regressions fail against the original implementation because it does not throw. They cover a fractional first member, a later member, scientific notation, and parentheses. Existing negative integer cases continue to pass.

./node_modules/.bin/eslint --max-warnings 0 packages/react-native-codegen/src/parsers/typescript/modules/index.js packages/react-native-codegen/src/parsers/typescript/modules/__tests__/typescript-module-parser-e2e-test.js
./node_modules/.bin/prettier --check packages/react-native-codegen/src/parsers/typescript/modules/index.js packages/react-native-codegen/src/parsers/typescript/modules/__tests__/typescript-module-parser-e2e-test.js
npx --yes --package=flow-bin@0.337.0 flow focus-check --max-workers 2 packages/react-native-codegen/src/parsers/typescript/modules/index.js packages/react-native-codegen/src/parsers/typescript/modules/__tests__/typescript-module-parser-e2e-test.js

ESLint, formatting, and focused Flow checking pass. node scripts/build.js from packages/react-native-codegen also passes. A probe of the rebuilt package rejects positive and negative fractions while accepting ordinary, negative, hexadecimal, and scientific-notation integers.

Native builds and full-repository checks were not run; the defect and regressions reproduce entirely within the parser.