RegExp: options can be member of branch (IDEA-190180)

RegExpSupport/src/org/intellij/lang/regexp/RegExpElementTypes.java

@@ -45,7 +45,7 @@ public interface RegExpElementTypes {
     IElementType NUMBER = new RegExpElementType("NUMBER");
 
     TokenSet ATOMS = TokenSet.create(CLOSURE, BOUNDARY, SIMPLE_CLASS, CLASS, CHAR, GROUP, PROPERTY, BACKREF, NAMED_GROUP_REF,
-                                     PY_COND_REF, NAMED_CHARACTER);
+                                     PY_COND_REF, NAMED_CHARACTER, SET_OPTIONS);
 
     TokenSet CLASS_ELEMENTS = TokenSet.create(CHAR, CHAR_RANGE, SIMPLE_CLASS, CLASS, INTERSECTION, PROPERTY);
 }

RegExpSupport/test/org/intellij/lang/regexp/inspection/SingleCharAlternationInspectionTest.java

@@ -32,6 +32,10 @@ public class SingleCharAlternationInspectionTest extends RegExpInspectionTestCas
     highlightTest("a|b|cc|d");
   }
 
+  public void testNoWarnNoException() {
+    highlightTest("(?i)x|y");
+  }
+
   public void testQuickfix() {
     quickfixTest("<warning descr=\"Single character alternation in RegExp\">x|y|z</warning>", "[xyz]", "Replace with '[xyz]'");
   }