Some trivia fixes

Sources/_RegexParser/Regex/AST/CustomCharClass.swift

@@ -51,11 +51,16 @@ extension AST {
       public var lhs: Atom
       public var dashLoc: SourceLocation
       public var rhs: Atom
+      public var trivia: [AST.Trivia]
 
-      public init(_ lhs: Atom, _ dashLoc: SourceLocation, _ rhs: Atom) {
+      public init(
+        _ lhs: Atom, _ dashLoc: SourceLocation, _ rhs: Atom,
+        trivia: [AST.Trivia]
+      ) {
         self.lhs = lhs
         self.dashLoc = dashLoc
         self.rhs = rhs
+        self.trivia = trivia
       }
     }
     public enum SetOp: String, Hashable {
@@ -95,6 +100,11 @@ extension CustomCC.Member {
     return false
   }
 
+  public var asTrivia: AST.Trivia? {
+    guard case .trivia(let t) = self else { return nil }
+    return t
+  }
+
   public var isSemantic: Bool {
     !isTrivia
   }

Sources/_RegexParser/Regex/Parse/LexicalAnalysis.swift

@@ -149,6 +149,14 @@ extension Source {
     return result
   }
 
+  /// Perform a lookahead using a temporary source. Within the body of the
+  /// lookahead, any modifications to the source will not be reflected outside
+  /// the body.
+  func lookahead<T>(_ body: (inout Source) throws -> T) rethrows -> T {
+    var src = self
+    return try body(&src)
+  }
+
   /// Attempt to eat the given character, returning its source location if
   /// successful, `nil` otherwise.
   mutating func tryEatWithLoc(_ c: Character) -> SourceLocation? {
@@ -413,9 +421,7 @@ extension Source {
   ) throws -> (Located<Quant.Amount>, Located<Quant.Kind>, [AST.Trivia])? {
     var trivia: [AST.Trivia] = []
 
-    if let t = try lexNonSemanticWhitespace(context: context) {
-      trivia.append(t)
-    }
+    if let t = lexNonSemanticWhitespace(context: context) { trivia.append(t) }
 
     let amt: Located<Quant.Amount>? = try recordLoc { src in
       if src.tryEat("*") { return .zeroOrMore }
@@ -424,7 +430,7 @@ extension Source {
 
       return try src.tryEating { src in
         guard src.tryEat("{"),
-              let range = try src.lexRange(context: context),
+              let range = try src.lexRange(context: context, trivia: &trivia),
               src.tryEat("}")
         else { return nil }
         return range.value
@@ -433,9 +439,7 @@ extension Source {
     guard let amt = amt else { return nil }
 
     // PCRE allows non-semantic whitespace here in extended syntax mode.
-    if let t = try lexNonSemanticWhitespace(context: context) {
-      trivia.append(t)
-    }
+    if let t = lexNonSemanticWhitespace(context: context) { trivia.append(t) }
 
     let kind: Located<Quant.Kind> = recordLoc { src in
       if src.tryEat("?") { return .reluctant  }
@@ -452,11 +456,17 @@ extension Source {
   ///                  | ExpRange
   ///     ExpRange    -> '..<' <Int> | '...' <Int>
   ///                  | <Int> '..<' <Int> | <Int> '...' <Int>?
-  mutating func lexRange(context: ParsingContext) throws -> Located<Quant.Amount>? {
+  mutating func lexRange(
+    context: ParsingContext, trivia: inout [AST.Trivia]
+  ) throws -> Located<Quant.Amount>? {
     try recordLoc { src in
       try src.tryEating { src in
+        if let t = src.lexWhitespace() { trivia.append(t) }
+
         let lowerOpt = try src.lexNumber()
 
+        if let t = src.lexWhitespace() { trivia.append(t) }
+
         // ',' or '...' or '..<' or nothing
         // TODO: We ought to try and consume whitespace here and emit a
         // diagnostic for the user warning them that it would cause the range to
@@ -476,11 +486,15 @@ extension Source {
           closedRange = nil
         }
 
+        if let t = src.lexWhitespace() { trivia.append(t) }
+
         let upperOpt = try src.lexNumber()?.map { upper in
           // If we have an open range, the upper bound should be adjusted down.
           closedRange == true ? upper : upper - 1
         }
 
+        if let t = src.lexWhitespace() { trivia.append(t) }
+
         switch (lowerOpt, closedRange, upperOpt) {
         case let (l?, nil, nil):
           return .exactly(l)
@@ -625,11 +639,11 @@ extension Source {
   ///
   mutating func lexComment(context: ParsingContext) throws -> AST.Trivia? {
     let trivia: Located<String>? = try recordLoc { src in
-      if src.tryEat(sequence: "(?#") {
-        return try src.expectQuoted(endingWith: ")").value
+      if !context.isInCustomCharacterClass && src.tryEat(sequence: "(?#") {
+        return try src.lexUntil(eating: ")").value
       }
       if context.experimentalComments, src.tryEat(sequence: "/*") {
-        return try src.expectQuoted(endingWith: "*/").value
+        return try src.lexUntil(eating: "*/").value
       }
       if context.endOfLineComments, src.tryEat("#") {
         // Try eat until we either exhaust the input, or hit a newline. Note
@@ -667,7 +681,7 @@ extension Source {
   /// Does nothing unless `SyntaxOptions.nonSemanticWhitespace` is set
   mutating func lexNonSemanticWhitespace(
     context: ParsingContext
-  ) throws -> AST.Trivia? {
+  ) -> AST.Trivia? {
     guard context.ignoreWhitespace else { return nil }
 
     // FIXME: PCRE only treats space and tab characters as whitespace when
@@ -699,7 +713,7 @@ extension Source {
     if let comment = try lexComment(context: context) {
       return comment
     }
-    if let whitespace = try lexNonSemanticWhitespace(context: context) {
+    if let whitespace = lexNonSemanticWhitespace(context: context) {
       return whitespace
     }
     return nil
@@ -1178,8 +1192,7 @@ extension Source {
     }
   }
 
-  mutating func lexCustomCCStart(
-  ) throws -> Located<CustomCC.Start>? {
+  mutating func lexCustomCCStart() -> Located<CustomCC.Start>? {
     recordLoc { src in
       // Make sure we don't have a POSIX character property. This may require
       // walking to its ending to make sure we have a closing ':]', as otherwise
@@ -1240,8 +1253,9 @@ extension Source {
 
   private func canLexPOSIXCharacterProperty() -> Bool {
     do {
-      var src = self
-      return try src.lexPOSIXCharacterProperty() != nil
+      return try lookahead { src in
+        try src.lexPOSIXCharacterProperty() != nil
+      }
     } catch {
       // We want to tend on the side of lexing a POSIX character property, so
       // even if it is invalid in some way (e.g invalid property names), still
@@ -1394,10 +1408,11 @@ extension Source {
 
   /// Checks whether a numbered reference can be lexed.
   private func canLexNumberedReference() -> Bool {
-    var src = self
-    _ = src.tryEat(anyOf: "+", "-")
-    guard let next = src.peek() else { return false }
-    return RadixKind.decimal.characterFilter(next)
+    lookahead { src in
+      _ = src.tryEat(anyOf: "+", "-")
+      guard let next = src.peek() else { return false }
+      return RadixKind.decimal.characterFilter(next)
+    }
   }
 
   /// Eat a named reference up to a given closing delimiter.
@@ -1587,53 +1602,55 @@ extension Source {
 
   /// Whether we can lex a group-like reference after the specifier '(?'.
   private func canLexGroupLikeReference() -> Bool {
-    var src = self
-    if src.tryEat("P") {
-      return src.tryEat(anyOf: "=", ">") != nil
-    }
-    if src.tryEat(anyOf: "&", "R") != nil {
-      return true
+    lookahead { src in
+      if src.tryEat("P") {
+        return src.tryEat(anyOf: "=", ">") != nil
+      }
+      if src.tryEat(anyOf: "&", "R") != nil {
+        return true
+      }
+      return src.canLexNumberedReference()
     }
-    return src.canLexNumberedReference()
   }
 
   private func canLexMatchingOptionsAsAtom(context: ParsingContext) -> Bool {
-    var src = self
-
-    // See if we can lex a matching option sequence that terminates in ')'. Such
-    // a sequence is an atom. If an error is thrown, there are invalid elements
-    // of the matching option sequence. In such a case, we can lex as a group
-    // and diagnose the invalid group kind.
-    guard (try? src.lexMatchingOptionSequence(context: context)) != nil else {
-      return false
+    lookahead { src in
+      // See if we can lex a matching option sequence that terminates in ')'.
+      // Such a sequence is an atom. If an error is thrown, there are invalid
+      // elements of the matching option sequence. In such a case, we can lex as
+      // a group and diagnose the invalid group kind.
+      guard (try? src.lexMatchingOptionSequence(context: context)) != nil else {
+        return false
+      }
+      return src.tryEat(")")
     }
-    return src.tryEat(")")
   }
 
   /// Whether a group specifier should be lexed as an atom instead of a group.
   private func shouldLexGroupLikeAtom(context: ParsingContext) -> Bool {
-    var src = self
-    guard src.tryEat("(") else { return false }
+    lookahead { src in
+      guard src.tryEat("(") else { return false }
 
-    if src.tryEat("?") {
-      // The start of a reference '(?P=', '(?R', ...
-      if src.canLexGroupLikeReference() { return true }
+      if src.tryEat("?") {
+        // The start of a reference '(?P=', '(?R', ...
+        if src.canLexGroupLikeReference() { return true }
 
-      // The start of a PCRE callout.
-      if src.tryEat("C") { return true }
+        // The start of a PCRE callout.
+        if src.tryEat("C") { return true }
 
-      // The start of an Oniguruma 'of-contents' callout.
-      if src.tryEat("{") { return true }
+        // The start of an Oniguruma 'of-contents' callout.
+        if src.tryEat("{") { return true }
 
-      // A matching option atom (?x), (?i), ...
-      if src.canLexMatchingOptionsAsAtom(context: context) { return true }
+        // A matching option atom (?x), (?i), ...
+        if src.canLexMatchingOptionsAsAtom(context: context) { return true }
+
+        return false
+      }
+      // The start of a backreference directive or Oniguruma named callout.
+      if src.tryEat("*") { return true }
 
       return false
     }
-    // The start of a backreference directive or Oniguruma named callout.
-    if src.tryEat("*") { return true }
-
-    return false
   }
 
   /// Consume an escaped atom, starting from after the backslash
@@ -2022,20 +2039,11 @@ extension Source {
     return AST.Atom(kind.value, kind.location)
   }
 
-  /// Try to lex the end of a range in a custom character class, which consists
-  /// of a '-' character followed by an atom.
-  mutating func lexCustomCharClassRangeEnd(
-    context: ParsingContext
-  ) throws -> (dashLoc: SourceLocation, AST.Atom)? {
-    // Make sure we don't have a binary operator e.g '--', and the '-' is not
-    // ending the custom character class (in which case it is literal).
-    guard peekCCBinOp() == nil, !starts(with: "-]"),
-          let dash = tryEatWithLoc("-"),
-          let end = try lexAtom(context: context)
-    else {
-      return nil
-    }
-    return (dash, end)
+  /// Try to lex the range operator '-' for a custom character class.
+  mutating func lexCustomCharacterClassRangeOperator() -> SourceLocation? {
+    // Eat a '-', making sure we don't have a binary op such as '--'.
+    guard peekCCBinOp() == nil else { return nil }
+    return tryEatWithLoc("-")
   }
 
   /// Try to consume a newline sequence matching option kind.