Delete groupTransform from AST.

Sources/_MatchingEngine/Regex/AST/AST.swift

@@ -65,10 +65,6 @@ extension AST {
     case absentFunction(AbsentFunction)
 
     case empty(Empty)
-
-    // FIXME: Move off the regex literal AST
-    case groupTransform(
-      Group, transform: CaptureTransform)
   }
 }
 
@@ -91,9 +87,6 @@ extension AST.Node {
     case let .customCharacterClass(v):  return v
     case let .empty(v):                 return v
     case let .absentFunction(v):        return v
-
-    case let .groupTransform(g, _):
-      return g // FIXME: get this out of here
     }
   }
 
@@ -121,8 +114,7 @@ extension AST.Node {
   /// Whether this node has nested somewhere inside it a capture
   public var hasCapture: Bool {
     switch self {
-    case .group(let g) where g.kind.value.isCapturing,
-         .groupTransform(let g, _) where g.kind.value.isCapturing:
+    case .group(let g) where g.kind.value.isCapturing:
       return true
     default:
       break
@@ -139,7 +131,7 @@ extension AST.Node {
     case .group, .conditional, .customCharacterClass, .absentFunction:
       return true
     case .alternation, .concatenation, .quantification, .quote, .trivia,
-        .empty, .groupTransform:
+        .empty:
       return false
     }
   }

Sources/_MatchingEngine/Regex/AST/Atom.swift

@@ -697,7 +697,7 @@ extension AST.Node {
     case .alternation, .concatenation, .group,
         .conditional, .quantification, .quote,
         .trivia, .customCharacterClass, .empty,
-        .groupTransform, .absentFunction:
+        .absentFunction:
       return nil
     }
   }

Sources/_MatchingEngine/Regex/Parse/CaptureStructure.swift

@@ -176,12 +176,6 @@ extension AST.Node {
     case let .group(g):
       return constructor.grouping(g.child, as: g.kind.value)
 
-    case .groupTransform(let g, let transform):
-      return constructor.grouping(
-        g.child,
-        as: g.kind.value,
-        withTransform: transform)
-
     case .conditional(let c):
       return constructor.condition(
         c.condition.kind,

Sources/_MatchingEngine/Regex/Printing/PrintAsCanonical.swift

@@ -104,9 +104,6 @@ extension PrettyPrinter {
 
     case .empty:
       output("")
-
-    case .groupTransform:
-      output("/* TODO: get groupTransform out of AST */")
     }
   }
 

Sources/_StringProcessing/RegexDSL/ASTConversion.swift

@@ -131,11 +131,6 @@ extension AST.Node {
       case .empty(_):
         return .empty
 
-      case let .groupTransform(v, transform):
-        let child = v.child.dslTreeNode
-        return .groupTransform(
-          v.kind.value, child, transform)
-
       case let .absentFunction(a):
         // TODO: What should this map to?
         return .absentFunction(a)