ECMA-402's ToRawFixed runs on every Intl.NumberFormat format call and every
Intl.PluralRules select, and both rounding candidates do
`.div(roundingIncrement)` and `.times(roundingIncrement)` where
roundingIncrement defaults to 1. Without a fast path, div(1) performs a
10^34 BigInt scale-up, a BigInt division, and a trailing-zero strip that
undoes the scaling - pure waste that profiled at 7.3% of JS-busy self time
(the `div` frame) during a heavy release-build feed scroll, because this app
force-installs the formatjs polyfill (see src/locale/i18n.ts).
The patch returns the existing immutable instance when multiplying or
dividing by exactly 1 (mantissa 1n, exponent 0 - the normalized
representation of 1).
Verified: byte-identical output across 104,800 assertions (4 locales x 3
option sets x ~8,700 values through NumberFormat.format plus
PluralRules.select), and 2.4x faster per compact format call in Node.
Candidate for upstreaming to formatjs.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Tomek Zawadzki
94cbd85480