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Fix forward progress detection for lookaround groups #866

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Fix forward progress detection for lookaround groups #866

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2 changes: 2 additions & 0 deletions Sources/_StringProcessing/ByteCodeGen+DSLList.swift
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Expand Up @@ -369,6 +369,8 @@ fileprivate extension Compiler.ByteCodeGen {
case .nonCapturingGroup(let kind):
switch kind.ast {
case .lookahead, .negativeLookahead, .lookbehind, .negativeLookbehind:
list.skipNode(&position)
position += 1
return false
default:
return _guaranteesForwardProgressImpl(list, position: &position)
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1 change: 1 addition & 0 deletions Tests/RegexTests/CompileTests.swift
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Expand Up @@ -531,6 +531,7 @@ extension RegexTests {
expectProgram(for: #"(?:\w|(?i))+"#, contains: [.moveCurrentPosition, .condBranchSamePosition])
expectProgram(for: #"(?:A*(?:b|c*))*"#, contains: [.moveCurrentPosition, .condBranchSamePosition])
expectProgram(for: #"(?:[^/]*(?:/|$))*"#, contains: [.moveCurrentPosition, .condBranchSamePosition])
expectProgram(for: #"(?:(?!a)\d*)*"#, contains: [.moveCurrentPosition, .condBranchSamePosition])

// Bounded quantification, don't emit position checking
expectProgram(for: #"(?:(?=a)){1,4}"#, doesNotContain: [.moveCurrentPosition, .condBranchSamePosition])
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1 change: 1 addition & 0 deletions Tests/RegexTests/MatchTests.swift
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Expand Up @@ -2856,6 +2856,7 @@ extension RegexTests {

expectCompletion(regex: #"(?:A*(?:b|c*))*"#, in: "ABC")
expectCompletion(regex: #"^(?:(?:[^/]*(?:/|$))*)(?:[^/]*)$"#, in: "Sources/main.swift")
expectCompletion(regex: #"(?:(?!a)\d*)*"#, in: "A")
}

func testQuantifyOptimization() throws {
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