Add matching support for \p{Lc} and \p{L&}

.gitignore

@@ -1,5 +1,8 @@
 .DS_Store
 
+# The current toolchain is dumping files in the package root, rude
+*.emit-module.*
+
 # Xcode
 #
 # gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore

Sources/_RegexParser/Regex/Parse/CharacterPropertyClassification.swift

@@ -32,8 +32,8 @@ extension Source {
   static private func classifyGeneralCategory(
     _ str: String
   ) -> Unicode.ExtendedGeneralCategory? {
-    // This uses the aliases defined in
-    // https://www.unicode.org/Public/UCD/latest/ucd/PropertyValueAliases.txt.
+    // This uses the aliases defined in https://www.unicode.org/Public/UCD/latest/ucd/PropertyValueAliases.txt.
+    // Additionally, uses the `L& = Lc` alias defined by PCRE.
     withNormalizedForms(str) { str in
       switch str {
       case "c", "other":                   return .other
@@ -43,7 +43,7 @@ extension Source {
       case "co", "privateuse":             return .privateUse
       case "cs", "surrogate":              return .surrogate
       case "l", "letter":                  return .letter
-      case "lc", "casedletter":            return .casedLetter
+      case "lc", "l&", "casedletter":      return .casedLetter
       case "ll", "lowercaseletter":        return .lowercaseLetter
       case "lm", "modifierletter":         return .modifierLetter
       case "lo", "otherletter":            return .otherLetter

Sources/_StringProcessing/ConsumerInterface.swift

@@ -691,8 +691,9 @@ extension Unicode.ExtendedGeneralCategory {
       ])
 
     case .casedLetter:
-      throw Unsupported(
-        "TODO: cased letter? not the property?")
+      return consumeScalarGCs([
+        .uppercaseLetter, .lowercaseLetter, .titlecaseLetter
+      ])
 
     case .control:
       return consumeScalarGC(.control)

Tests/RegexTests/MatchTests.swift

@@ -693,6 +693,14 @@ extension RegexTests {
     firstMatchTest(#"\p{gc=L}"#, input: "123abcXYZ", match: "a")
     firstMatchTest(#"\p{Lu}"#, input: "123abcXYZ", match: "X")
 
+    // U+0374 GREEK NUMERAL SIGN (Lm)
+    // U+00AA FEMININE ORDINAL INDICATOR (Lo)
+    firstMatchTest(#"\p{L}"#, input: "\u{0374}\u{00AA}123abcXYZ", match: "\u{0374}")
+    firstMatchTest(#"\p{Lc}"#, input: "\u{0374}\u{00AA}123abcXYZ", match: "a")
+    firstMatchTest(#"\p{Lc}"#, input: "\u{0374}\u{00AA}123XYZ", match: "X")
+    firstMatchTest(#"\p{L&}"#, input: "\u{0374}\u{00AA}123abcXYZ", match: "a")
+    firstMatchTest(#"\p{L&}"#, input: "\u{0374}\u{00AA}123XYZ", match: "X")
+
     firstMatchTest(
       #"\P{Cc}"#, input: "\n\n\nXYZ", match: "X")
     firstMatchTest(

Tests/RegexTests/ParseTests.swift

@@ -1156,6 +1156,9 @@ extension RegexTests {
       #"\p{C}+"#,
       oneOrMore(of: prop(.generalCategory(.other))))
 
+    // L& defined by PCRE.
+    parseTest(#"\p{L&}"#, prop(.generalCategory(.casedLetter)))
+
     // UAX44-LM3 means all of the below are equivalent.
     let lowercaseLetter = prop(.generalCategory(.lowercaseLetter))
     parseTest(#"\p{ll}"#, lowercaseLetter)