Made decreasing ranges inside character classes illegal to comply with Java/JS regex standards.

Author: lmasroca

core/src/main/kotlin/org/evomaster/core/utils/CharacterRange.kt

@@ -1,13 +1,14 @@
 package org.evomaster.core.utils
 
-class CharacterRange private constructor(val start: Char, val end: Char){
-    companion object {
-        operator fun invoke(a: Char, b: Char): CharacterRange =
-            if (a <= b) CharacterRange(a, b) else CharacterRange(b, a)
-    }
-
+class CharacterRange constructor(val start: Char, val end: Char){
     constructor(a: Int, b: Int) : this(a.toChar(), b.toChar())
 
+    init {
+        if (start > end){
+            throw IllegalArgumentException("Range out of order in character class")
+        }
+    }
+
     val size: Int
         get() = end.code - start.code + 1
     operator fun contains(char: Char): Boolean = char in start..end

core/src/test/kotlin/org/evomaster/core/parser/GeneRegexJavaVisitorTest.kt

@@ -66,13 +66,6 @@ class GeneRegexJavaVisitorTest : GeneRegexEcma262VisitorTest() {
         checkSameAsJava("[ -!]")
     }
 
-    @Test
-    fun testDecreasingRange(){
-        //checkSameAsJava("[!- ]") //not valid in Java
-        //checkSameAsJava("[9-1]") //not valid in Java
-        checkCanSample("[9-1]", listOf("1","5","9"),200)
-    }
-
     @Test
     fun testJavaHexEscape(){
         checkSameAsJava("""x{3}\x{0}\x{FFFf}\x{0FFFf}\x{01FFFf}\x{10FFFf}""")

core/src/test/kotlin/org/evomaster/core/parser/RegexHandlerTest.kt

@@ -160,12 +160,14 @@ internal class RegexHandlerTest{
         assertThrows(IllegalArgumentException::class.java) { RegexHandler.createGeneForJVM("\\x{ffffff}") }
         assertThrows(ParseCancellationException::class.java) { RegexHandler.createGeneForJVM("\\0") }
         assertThrows(ParseCancellationException::class.java) { RegexHandler.createGeneForJVM("\\09") }
+        assertThrows(IllegalArgumentException::class.java) { RegexHandler.createGeneForJVM("[9-1]") }
     }
 
     @Test
     fun testCreateGeneForEcma262InvalidRegex() {
 
         assertThrows(ParseCancellationException::class.java) { RegexHandler.createGeneForEcma262("\\xR") }
         assertThrows(ParseCancellationException::class.java) { RegexHandler.createGeneForJVM("\\ugggg") }
+        assertThrows(IllegalArgumentException::class.java) { RegexHandler.createGeneForJVM("[9-1]") }
     }
 }