Fix Repeat off-by-one error

Adjust the upper bound of the Range down when
forming the quantification, as it expects an
inclusive upper bound.

Author: hamishknight

Sources/_StringProcessing/Regex/DSLTree.swift

@@ -856,22 +856,35 @@ extension DSLTree.Node {
     assert(range.lowerBound >= 0, "Cannot specify a negative lower bound")
     assert(!range.isEmpty, "Cannot specify an empty range")
 
-    let kind: DSLTree.QuantificationKind = behavior.map { .explicit($0.dslTreeKind) } ?? .default
-    
-    switch (range.lowerBound, range.upperBound) {
-    case (0, Int.max): // 0...
-      return .quantification(.zeroOrMore, kind, node)
-    case (1, Int.max): // 1...
-      return .quantification(.oneOrMore, kind, node)
-    case _ where range.count == 1: // ..<1 or ...0 or any range with count == 1
+    let kind: DSLTree.QuantificationKind = behavior
+      .map { .explicit($0.dslTreeKind) } ?? .default
+
+    // The upper bound needs adjusting down as
+    // `.quantification` expects a closed range.
+    let lower = range.lowerBound
+    let upperInclusive = range.upperBound - 1
+
+    // Unbounded cases
+    if range.upperBound == Int.max {
+      switch lower {
+      case 0: // 0...
+        return .quantification(.zeroOrMore, kind, node)
+      case 1: // 1...
+        return .quantification(.oneOrMore, kind, node)
+      default: // n...
+        return .quantification(.nOrMore(lower), kind, node)
+      }
+    }
+    if range.count == 1 {
+      // ..<1 or ...0 or any range with count == 1
       // Note: `behavior` is ignored in this case
-      return .quantification(.exactly(range.lowerBound), .default, node)
-    case (0, _): // 0..<n or 0...n or ..<n or ...n
-      return .quantification(.upToN(range.upperBound), kind, node)
-    case (_, Int.max): // n...
-      return .quantification(.nOrMore(range.lowerBound), kind, node)
-    default: // any other range
-      return .quantification(.range(range.lowerBound, range.upperBound), kind, node)
+      return .quantification(.exactly(lower), .default, node)
+    }
+    switch lower {
+    case 0: // 0..<n or 0...n or ..<n or ...n
+      return .quantification(.upToN(upperInclusive), kind, node)
+    default:
+      return .quantification(.range(lower, upperInclusive), kind, node)
     }
   }
 }

Tests/RegexBuilderTests/RegexDSLTests.swift

@@ -450,9 +450,13 @@ class RegexDSLTests: XCTestCase {
 
     try _testDSLCaptures(
       ("aaabbbcccdddeeefff", "aaabbbcccdddeeefff"),
+      ("aaabbbcccccdddeeefff", "aaabbbcccccdddeeefff"),
+      ("aaabbbcccddddeeefff", "aaabbbcccddddeeefff"),
+      ("aaabbbccccccdddeeefff", nil),
       ("aaaabbbcccdddeeefff", nil),
       ("aaacccdddeeefff", nil),
       ("aaabbbcccccccdddeeefff", nil),
+      ("aaabbbcccdddddeeefff", nil),
       ("aaabbbcccddddddeeefff", nil),
       ("aaabbbcccdddefff", nil),
       ("aaabbbcccdddeee", "aaabbbcccdddeee"),
@@ -465,7 +469,102 @@ class RegexDSLTests: XCTestCase {
       Repeat(2...) { "e" }
       Repeat(0...) { "f" }
     }
-    
+
+    try _testDSLCaptures(
+      ("", nil),
+      ("a", nil),
+      ("aa", "aa"),
+      ("aaa", "aaa"),
+      matchType: Substring.self, ==)
+    {
+      Repeat(2...) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", ""),
+      ("a", "a"),
+      ("aa", "aa"),
+      ("aaa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(...2) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", ""),
+      ("a", "a"),
+      ("aa", nil),
+      ("aaa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(..<2) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", ""),
+      ("a", nil),
+      ("aa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(...0) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", ""),
+      ("a", nil),
+      ("aa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(0 ... 0) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", ""),
+      ("a", "a"),
+      ("aa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(0 ... 1) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", nil),
+      ("a", "a"),
+      ("aa", "aa"),
+      ("aaa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(1 ... 2) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", ""),
+      ("a", nil),
+      ("aa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(0 ..< 1) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", ""),
+      ("a", "a"),
+      ("aa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(0 ..< 2) { "a" }
+    }
+
+    try _testDSLCaptures(
+      ("", nil),
+      ("a", "a"),
+      ("aa", "aa"),
+      ("aaa", nil),
+      matchType: Substring.self, ==)
+    {
+      Repeat(1 ..< 3) { "a" }
+    }
+
     let octoDecimalRegex: Regex<(Substring, Int?)> = Regex {
       let charClass = CharacterClass(.digit, "a"..."h")//.ignoringCase()
       Capture {