From e7f3412fc0ec598daf0042e80dc3b4c8dc45f34e Mon Sep 17 00:00:00 2001
From: Alejandro Alonso <alejandro_alonso@apple.com>
Date: Mon, 18 Jul 2022 12:32:51 -0700
Subject: [PATCH] Print Lookahead and NegativeLookahead

---
 .../_StringProcessing/PrintAsPattern.swift    | 10 +++++++
 Tests/RegexTests/RenderDSLTests.swift         | 26 +++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/Sources/_StringProcessing/PrintAsPattern.swift b/Sources/_StringProcessing/PrintAsPattern.swift
index 80f2e7697..54ce66d0d 100644
--- a/Sources/_StringProcessing/PrintAsPattern.swift
+++ b/Sources/_StringProcessing/PrintAsPattern.swift
@@ -119,6 +119,16 @@ extension PrettyPrinter {
           printer.printAsPattern(convertedFromAST: child)
         }
         
+      case .lookahead:
+        printBlock("Lookahead") { printer in
+          printer.printAsPattern(convertedFromAST: child)
+        }
+        
+      case .negativeLookahead:
+        printBlock("NegativeLookahead") { printer in
+          printer.printAsPattern(convertedFromAST: child)
+        }
+        
       default:
         printAsPattern(convertedFromAST: child)
       }
diff --git a/Tests/RegexTests/RenderDSLTests.swift b/Tests/RegexTests/RenderDSLTests.swift
index 3b0a8d5b3..52906d1ad 100644
--- a/Tests/RegexTests/RenderDSLTests.swift
+++ b/Tests/RegexTests/RenderDSLTests.swift
@@ -98,6 +98,32 @@ extension RenderDSLTests {
         /$/
       }
       """#)
+    
+    try testConversion(#"foo(?=bar)"#, #"""
+      Regex {
+        "foo"
+        Lookahead {
+          "bar"
+        }
+      }
+      """#)
+    
+    try testConversion(#"abc(?=def(?!ghi)|xyz)"#, #"""
+      Regex {
+        "abc"
+        Lookahead {
+          ChoiceOf {
+            Regex {
+              "def"
+              NegativeLookahead {
+                "ghi"
+              }
+            }
+            "xyz"
+          }
+        }
+      }
+      """#)
   }
 
   func testOptions() throws {