String#toLowerCase fails to lower final sigma after a space or non-cased character #3063

Bug description

String#toLowerCase() lowers Greek Σ (U+03A3) at the end of a word to medial σ (U+03C3) instead of final ς (U+03C2) whenever a non-cased, non-case-ignorable character (such as a space or digit) appears earlier in the string within the lookbehind window.

Single-word "ΟΔΟΣ".toLowerCase() returns "οδος" as expected, but "Η ΟΔΟΣ".toLowerCase() returns "η οδοσ" instead of "η οδος", and "1 AΣ".toLowerCase() returns "1 aσ" instead of "1 aς". In JavaScript, Σ is lowered to ς whenever it is immediately preceded by a cased character (ignoring case-ignorable characters) and not followed by one.

In isFinalSigma, the backward loop sets found = true when it matches a preceding cased character, but is missing a break;, so it continues scanning backwards and returns false upon hitting an earlier space or other non-cased character.

Steps to reproduce

assert("ΟΔΟΣ".toLowerCase() == "οδος");     // passes
assert("Η ΟΔΟΣ".toLowerCase() == "η οδος"); // fails: returns "η οδοσ"
assert("1 AΣ".toLowerCase() == "1 aς");     // fails: returns "1 aσ"

Credit: https://ucsbplse.github.io/

AssemblyScript version

v0.28.20

Playground

https://www.assemblyscript.org/editor.html#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

Click Run: t1 (single word) prints true, but t2 and t3 (a space before the word) print false.