[stdlib] Fix backwards count of Indic graphemes #41389
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milseman
approved these changes
Feb 16, 2022
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When determining the grapheme boundaries of Indic sequences while walking backwards, there were some cases that were incorrectly being labeled as an Indic sequences.
For example, राज् is composed of:
[.linkingConsonant, .spacingMark, .linkingConsonant, .virama]The rule defined by the CLDR here: https://github.com/unicode-org/cldr/tree/main/common/properties/segments
9.3) LinkingConsonant ExtCccZwj* Virama ExtCccZwj* × LinkingConsonantwas being incorrectly applied to the last two scalars when walking backwards, and as a result, the whole string was being counted as a singular grapheme instead of 2 (
\u{930}\u{93e}and\u{91c}\u{94d})We have to at least be in an Indic sequence already when we see
(.linkingConsonant, .virama)while walking backwards to be able to resolve any sort of state.Resolves: rdar://88893489 & rdar://88866287