Added support for -- subtraction opetor.

javascript/extractor/src/com/semmle/js/ast/regexp/CharacterClassSubtraction.java

@@ -0,0 +1,22 @@
+package com.semmle.js.ast.regexp;
+
+import com.semmle.js.ast.SourceLocation;
+import java.util.List;
+
+public class CharacterClassSubtraction extends RegExpTerm {
+    private final List<RegExpTerm> subtraction;
+
+    public CharacterClassSubtraction(SourceLocation loc, List<RegExpTerm> subtraction) {
+        super(loc, "CharacterClassSubtraction");
+        this.subtraction = subtraction;
+    }
+
+    @Override
+    public void accept(Visitor v) {
+        v.visit(this);
+    }
+
+    public List<RegExpTerm> getSubtraction() {
+        return subtraction;
+    }
+}

javascript/extractor/src/com/semmle/js/ast/regexp/Visitor.java

@@ -65,4 +65,6 @@ public interface Visitor {
   public void visit(CharacterClassQuotedString nd);
 
   public void visit(CharacterClassIntersection nd);
+
+  public void visit(CharacterClassSubtraction nd);
 }

javascript/extractor/src/com/semmle/js/extractor/RegExpExtractor.java

@@ -12,6 +12,7 @@
 import com.semmle.js.ast.regexp.CharacterClassEscape;
 import com.semmle.js.ast.regexp.CharacterClassQuotedString;
 import com.semmle.js.ast.regexp.CharacterClassRange;
+import com.semmle.js.ast.regexp.CharacterClassSubtraction;
 import com.semmle.js.ast.regexp.Constant;
 import com.semmle.js.ast.regexp.ControlEscape;
 import com.semmle.js.ast.regexp.ControlLetter;
@@ -96,6 +97,7 @@ public RegExpExtractor(TrapWriter trapwriter, LocationManager locationManager) {
     termkinds.put("UnicodePropertyEscape", 27);
     termkinds.put("CharacterClassQuotedString", 28);
     termkinds.put("CharacterClassIntersection", 29);
+    termkinds.put("CharacterClassSubtraction", 30);
   }
 
   private static final String[] errmsgs =
@@ -362,6 +364,14 @@ public void visit(CharacterClassIntersection nd) {
       for (RegExpTerm element : nd.getIntersections())
         visit(element, lbl, i++);
     }
+
+    @Override
+    public void visit(CharacterClassSubtraction nd) {
+      Label lbl = extractTerm(nd, parent, idx);
+      int i = 0;
+      for (RegExpTerm element : nd.getSubtraction())
+        visit(element, lbl, i++);
+    }
   }
 
   public void extract(String src, SourceMap sourceMap, Node parent, boolean isSpeculativeParsing, String flags) {

javascript/extractor/src/com/semmle/js/parser/RegExpParser.java

@@ -8,6 +8,7 @@
 import com.semmle.js.ast.regexp.CharacterClassEscape;
 import com.semmle.js.ast.regexp.CharacterClassQuotedString;
 import com.semmle.js.ast.regexp.CharacterClassRange;
+import com.semmle.js.ast.regexp.CharacterClassSubtraction;
 import com.semmle.js.ast.regexp.Constant;
 import com.semmle.js.ast.regexp.ControlEscape;
 import com.semmle.js.ast.regexp.ControlLetter;
@@ -566,6 +567,7 @@ private RegExpTerm parseCharacterClass() {
   private enum CharacterClassType {
     STANDARD,
     INTERSECTION,
+    SUBTRACTION,
   }
 
   // ECMA 2024 `v` flag allows nested character classes.
@@ -588,6 +590,10 @@ else if (lookahead("&&")) {
         this.match("&&");
         classType = CharacterClassType.INTERSECTION;
       }
+      else if (lookahead("--")) {
+        this.match("--");
+        classType = CharacterClassType.SUBTRACTION;
+      }
       else {
         elements.add(this.parseCharacterClassElement());
       }
@@ -597,6 +603,8 @@ else if (lookahead("&&")) {
     switch (classType) {
       case INTERSECTION:
         return this.finishTerm(new CharacterClass(loc, Collections.singletonList(new CharacterClassIntersection(loc, elements)), inverted));
+      case SUBTRACTION:
+        return this.finishTerm(new CharacterClass(loc, Collections.singletonList(new CharacterClassSubtraction(loc, elements)), inverted));
       case STANDARD:
       default:
         return this.finishTerm(new CharacterClass(loc, elements, inverted));
@@ -614,7 +622,7 @@ private RegExpTerm parseCharacterClassElement() {
           return atom;
       }
     }
-    if (!this.lookahead("-]") && this.match("-") && !(atom instanceof CharacterClassEscape))
+    if (!this.lookahead("-]") && !this.lookahead("--") && this.match("-") && !(atom instanceof CharacterClassEscape))
       return this.finishTerm(new CharacterClassRange(loc, atom, this.parseCharacterClassAtom()));
     return atom;
   }