Address PR comments

Author: Jacob Hearst

Sources/_StringProcessing/ByteCodeGen.swift

@@ -109,6 +109,7 @@ fileprivate extension Compiler.ByteCodeGen {
   }
 
   mutating func emitQuotedLiteral(_ s: String) {
+    assert(!reverse)
     guard options.semanticLevel == .graphemeCluster else {
       for char in s {
         for scalar in char.unicodeScalars {
@@ -137,6 +138,7 @@ fileprivate extension Compiler.ByteCodeGen {
   }
 
   mutating func emitReverseQuotedLiteral(_ s: String) {
+    assert(reverse)
     guard options.semanticLevel == .graphemeCluster else {
       for char in s {
         for scalar in char.unicodeScalars.reversed() {
@@ -408,13 +410,14 @@ fileprivate extension Compiler.ByteCodeGen {
     _ kind: (forwards: Bool, positive: Bool),
     _ child: DSLTree.Node
   ) throws {
+    let previousReverse = reverse
     reverse = !kind.forwards
     if kind.positive {
       try emitPositiveLookaround(child)
     } else {
       try emitNegativeLookaround(child)
     }
-    reverse = false
+    reverse = previousReverse
   }
 
   mutating func emitAtomicNoncapturingGroup(
@@ -1116,9 +1119,9 @@ fileprivate extension Compiler.ByteCodeGen {
     if let asciiBitset = ccc.asAsciiBitset(options),
         optimizationsEnabled {
       if options.semanticLevel == .unicodeScalar {
-        builder.buildScalarMatchAsciiBitset(asciiBitset)
+        builder.buildScalarMatchAsciiBitset(asciiBitset, reverse: reverse)
       } else {
-        builder.buildMatchAsciiBitset(asciiBitset)
+        builder.buildMatchAsciiBitset(asciiBitset, reverse: reverse)
       }
       return
     }

Sources/_StringProcessing/Engine/MEBuilder.swift

@@ -194,17 +194,21 @@ extension MEProgram.Builder {
   }
 
   mutating func buildMatchAsciiBitset(
-    _ b: DSLTree.CustomCharacterClass.AsciiBitset
+    _ b: DSLTree.CustomCharacterClass.AsciiBitset,
+    reverse: Bool
   ) {
+    let opcode = reverse ? Instruction.OpCode.reverseMatchBitset : .matchBitset
     instructions.append(.init(
-      .matchBitset, .init(bitset: makeAsciiBitset(b), isScalar: false)))
+      opcode, .init(bitset: makeAsciiBitset(b), isScalar: false)))
   }
 
   mutating func buildScalarMatchAsciiBitset(
-    _ b: DSLTree.CustomCharacterClass.AsciiBitset
+    _ b: DSLTree.CustomCharacterClass.AsciiBitset,
+    reverse: Bool
   ) {
+    let opcode = reverse ? Instruction.OpCode.reverseMatchBitset : .matchBitset
     instructions.append(.init(
-      .matchBitset, .init(bitset: makeAsciiBitset(b), isScalar: true)))
+      opcode, .init(bitset: makeAsciiBitset(b), isScalar: true)))
   }
 
   mutating func buildMatchBuiltin(model: _CharacterClassModel, reverse: Bool) {

Sources/_StringProcessing/Engine/MEBuiltins.swift

@@ -163,7 +163,10 @@ extension String {
   /// - Returns: The character at `pos`, bounded by `end`, if it exists, along
   ///   with the upper bound of that character. The upper bound is always
   ///   scalar-aligned.
-  func characterAndEnd(at pos: String.Index, limitedBy end: String.Index) -> (Character, String.Index)? {
+  func characterAndEnd(
+    at pos: String.Index,
+    limitedBy end: String.Index
+  ) -> (Character, characterEnd: String.Index)? {
     // FIXME: Sink into the stdlib to avoid multiple boundary calculations
     guard pos < end else { return nil }
     let next = index(after: pos)
@@ -204,7 +207,10 @@ extension String {
   /// - Returns: The character at `pos`, bounded by `start`, if it exists, along
   ///   with the lower bound of that character. The lower bound is always
   ///   scalar-aligned.
-  func characterAndStart(at pos: String.Index, limitedBy start: String.Index) -> (Character, String.Index)? {
+  func characterAndStart(
+    at pos: String.Index,
+    limitedBy start: String.Index
+  ) -> (Character, characterStart: String.Index)? {
     // FIXME: Sink into the stdlib to avoid multiple boundary calculations
     guard pos > start else { return nil }
     let previous = index(before: pos)

Tests/RegexTests/MatchTests.swift

@@ -1587,9 +1587,8 @@ extension RegexTests {
       #"(*positive_lookbehind:USD)\d+"#,
       input: "Price: USD100", match: "100")
 
-    // TODO: Why is a match not found when unoptimized?
     firstMatchTest(
-      #"\d{3}(?<=USD\d{3})"#, input: "Price: USD100", match: "100", validateOptimizations: false)
+      #"\d{3}(?<=USD\d{3})"#, input: "Price: USD100", match: "100")
 
     firstMatchTest(
       #"(?<!USD)\d+"#, input: "Price: JYP100", match: "100")
@@ -1602,33 +1601,34 @@ extension RegexTests {
     firstMatchTest(
       #"\d{3}(?<!USD\d{3})"#, input: "Price: JYP100", match: "100")
 
-    firstMatchTest(#"(?<=abc)def"#, input: "abcdefg", match: "def", validateOptimizations: false)
-    firstMatchTests(
-      #"(?<=az|b|c)def"#,
-      ("azdefg", "def"),
-      ("bdefg", "def"),
-      ("cdefg", "def"),
-      ("123defg", nil),
-      validateOptimizations: false
-    )
-
-    // FIXME: quickMatch and thoroughMatch have different results
-    firstMatchTest(
-      #"(?<=\d{1,3}-.{1,3}-\d{1,3})suffix"#,
-      input: "123-_+/-789suffix",
-      match: "suffix",
-      validateOptimizations: false
-    )
-
-    firstMatchTests(
-      #"(?<=^\d{1,3})abc"#,
-      ("123abc", "abc"),
-      ("12abc", "abc"),
-      ("1abc", "abc"),
-      ("1234abc", nil), // FIXME: Shouldn't match but does because `^` assertions are broken
-      ("z123abc", nil), // FIXME: Same as above
-      validateOptimizations: false
-    )
+    firstMatchTest(#"(?<=abc)def"#, input: "abcdefg", match: "def")
+   firstMatchTests(
+     #"(?<=az|b|c)def"#,
+     ("azdefg", "def"),
+     ("bdefg", "def"),
+     ("cdefg", "def"),
+     ("123defg", nil),
+     validateOptimizations: false
+   )
+
+   firstMatchTest(#"abcd(?<=bc(?=d).)"#, input: "abcdefg", match: "abcd")
+
+// FIXME: quickMatch and thoroughMatch have different results
+//    firstMatchTest(
+//      #"(?<=\d{1,3}-.{1,3}-\d{1,3})suffix"#,
+//      input: "123-_+/-789suffix",
+//      match: "suffix",
+//      validateOptimizations: false
+//    )
+
+   firstMatchTests(
+     #"(?<=^\d{1,3})abc"#,
+     ("123abc", "abc"),
+     ("12abc", "abc"),
+     ("1abc", "abc"),
+     ("1234abc", nil), // FIXME: Shouldn't match but does because `^` assertions are broken
+     ("z123abc", nil) // FIXME: Same as above
+   )
   }
 
   func testMatchAnchors() throws {