[groovy] process $$ before $ in dollar-slashy strings (IDEA-164748)

plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/lexer/groovy.flex

@@ -610,7 +610,7 @@ mGSTRING_LITERAL = \"\"
 }
 
 <IN_DOLLAR_SLASH_REGEX> {
-  "/""$"                                  {  if (!gStringStack.isEmpty()) {
+  "/$"                                    {  if (!gStringStack.isEmpty()) {
                                                gStringStack.pop();
                                              }
                                              if (blockStack.isEmpty()){
@@ -620,15 +620,19 @@ mGSTRING_LITERAL = \"\"
                                              }
                                              return GroovyTokenTypes.mDOLLAR_SLASH_REGEX_END; }
 
+  "$$"                                    {  return GroovyTokenTypes.mDOLLAR_SLASH_REGEX_CONTENT; }
+
+  "$"                                     {
+                                             yybegin(IN_DOLLAR_SLASH_REGEX_DOLLAR);
+                                             return GroovyTokenTypes.mDOLLAR;
+                                          }
+
   {mDOLLAR_SLASH_REGEX_CONTENT}? "$"
     /[^"{"[:letter:]"_"]                  {  return GroovyTokenTypes.mDOLLAR_SLASH_REGEX_CONTENT; }
 
   "/"                                     {  return GroovyTokenTypes.mDOLLAR_SLASH_REGEX_CONTENT; }
 
   {mDOLLAR_SLASH_REGEX_CONTENT}           {  return GroovyTokenTypes.mDOLLAR_SLASH_REGEX_CONTENT; }
-
-  "$"                                     {  yybegin(IN_DOLLAR_SLASH_REGEX_DOLLAR);
-                                             return GroovyTokenTypes.mDOLLAR;}
 }
 
 <IN_DOLLAR_SLASH_REGEX_DOLLAR> {

plugins/groovy/test/org/jetbrains/plugins/groovy/lang/parser/ExpressionsParsingTest.groovy

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2016 JetBrains s.r.o.
+ * Copyright 2000-2017 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -352,6 +352,8 @@ class ExpressionsParsingTest extends GroovyParsingTestCase {
 
   void testregex$dollarSlashy9() throws Throwable { doTest() }
 
+  void testregex$dollarSlashy10() { doTest() }
+
   void testregex$dollarSlashyCode() throws Throwable { doTest() }
 
   void testregex$dollarSlashyCodeUnfinished() throws Throwable { doTest() }

plugins/groovy/testdata/parsing/groovy/expressions/regex/dollarSlashy10.test

@@ -0,0 +1,14 @@
+print($/$$/$)
+-----
+Groovy script
+  Method call
+    Reference expression
+      PsiElement(identifier)('print')
+    Arguments
+      PsiElement(()('(')
+      Literal
+        GroovyASTPsiElementImpl($/ regex literal)
+          PsiElement($/ regex begin)('$/')
+          PsiElement($/ regex content)('$$')
+          PsiElement($/ regex end)('/$')
+      PsiElement())(')')