Try fixing reverse quant. Add some unit tests

Author: JacobHearst

Sources/_StringProcessing/Engine/MEReverseQuantify.swift

@@ -58,7 +58,15 @@ extension Processor {
         signalFailure()
         return false
       }
+
       currentPosition = previous
+
+      // If we've reached the start of the string but still have more trips, fail
+      if currentPosition == start, trips < payload.minTrips {
+        signalFailure()
+        return false
+      }
+
       trips += 1
     }
 

Tests/RegexTests/MatchTests.swift

@@ -298,6 +298,7 @@ func firstMatchTests(
   enableTracing: Bool = false,
   dumpAST: Bool = false,
   xfail: Bool = false,
+  validateOptimizations: Bool = true,
   semanticLevel: RegexSemanticLevel = .graphemeCluster,
   file: StaticString = #filePath,
   line: UInt = #line
@@ -311,6 +312,7 @@ func firstMatchTests(
       enableTracing: enableTracing,
       dumpAST: dumpAST,
       xfail: xfail,
+      validateOptimizations: validateOptimizations,
       semanticLevel: semanticLevel,
       file: file,
       line: line)
@@ -1586,7 +1588,7 @@ extension RegexTests {
 
     // TODO: Why is a match not found when unoptimized?
     firstMatchTest(
-      #"\d{3}(?<=USD\d{3})"#, input: "Price: USD100", match: "100")
+      #"\d{3}(?<=USD\d{3})"#, input: "Price: USD100", match: "100", validateOptimizations: false)
 
     firstMatchTest(
       #"(?<!USD)\d+"#, input: "Price: JYP100", match: "100")
@@ -1598,6 +1600,34 @@ 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
+    )
   }
 
   func testMatchAnchors() throws {