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Fix optimized ASCII case-insensitive matching #893

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Merged
natecook1000 merged 1 commit into from
Oct 8, 2026
Merged

Fix optimized ASCII case-insensitive matching #893

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2 changes: 1 addition & 1 deletion Sources/_StringProcessing/Utility/AsciiBitset.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ extension DSLTree.CustomCharacterClass {
setBit(val)
if isCaseInsensitive {
switch val {
case 64...90: setBit(val + 32)
case 65...90: setBit(val + 32)
case 97...122: setBit(val - 32)
default: break
}
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23 changes: 23 additions & 0 deletions Tests/RegexTests/MatchTests.swift
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Expand Up @@ -1458,6 +1458,29 @@ extension RegexTests {
firstMatchTest(
"(?i)[X-cD]", input: input, match: input, semanticLevel: semantics)
}

// Boundary tests for case insensitive ASCII matching.
firstMatchTest(
"(?i)[@]", input: "@", match: "@", semanticLevel: semantics)
firstMatchTest(
"(?i)[@]", input: "`", match: nil, semanticLevel: semantics)
firstMatchTest(
"(?i)[`]", input: "`", match: "`", semanticLevel: semantics)
firstMatchTest(
"(?i)[`]", input: "@", match: nil, semanticLevel: semantics)
// A range that spans the "@"/"A" boundary folds "A" but not "@".
firstMatchTest(
"(?i)[?-A]", input: "a", match: "a", semanticLevel: semantics)
firstMatchTest(
"(?i)[?-A]", input: "`", match: nil, semanticLevel: semantics)
// The letter ends of each range still fold.
for (pattern, input) in [
("(?i)[A]", "a"), ("(?i)[a]", "A"),
("(?i)[Z]", "z"), ("(?i)[z]", "Z"),
] {
firstMatchTest(
pattern, input: input, match: input, semanticLevel: semantics)
}
}
}

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