[groovy] allow new line before elvis operand (IDEA-195296)

plugins/groovy/groovy-psi/gen/org/jetbrains/plugins/groovy/lang/parser/GroovyGeneratedParser.java

@@ -7291,11 +7291,22 @@ public class GroovyGeneratedParser implements PsiParser, LightPsiParser {
     return r;
   }
 
-  // '?:' mb_nl
+  // mb_nl ('?:' mb_nl)
   private static boolean elvis_expression_0(PsiBuilder b, int l) {
     if (!recursion_guard_(b, l, "elvis_expression_0")) return false;
     boolean r;
     Marker m = enter_section_(b);
+    r = mb_nl(b, l + 1);
+    r = r && elvis_expression_0_1(b, l + 1);
+    exit_section_(b, m, null, r);
+    return r;
+  }
+
+  // '?:' mb_nl
+  private static boolean elvis_expression_0_1(PsiBuilder b, int l) {
+    if (!recursion_guard_(b, l, "elvis_expression_0_1")) return false;
+    boolean r;
+    Marker m = enter_section_(b);
     r = consumeTokenSmart(b, T_ELVIS);
     r = r && mb_nl(b, l + 1);
     exit_section_(b, m, null, r);

plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/parser/groovy.bnf

@@ -1076,7 +1076,7 @@ private conditionals ::= ternary_expression | elvis_expression
 ternary_expression ::= expression (ternary_tail_pin | ternary_tail)
 private ternary_tail_pin ::= '?' mb_nl !'[' expression mb_nl ':' mb_nl conditionals { pin = 3 consumeTokenMethod = 'consumeTokenFast' }
 private ternary_tail ::= '?' mb_nl expression mb_nl ':' mb_nl conditionals { pin = 5 consumeTokenMethod = 'consumeTokenFast' }
-elvis_expression ::= expression '?:' mb_nl expression
+elvis_expression ::= expression mb_nl ('?:' mb_nl) expression
 {
   rightAssociative = true
 }

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

@@ -81,6 +81,8 @@ class ExpressionsParsingTest extends GroovyParsingTestCase {
 
   void testconditional$elvis2() throws Throwable { doTest() }
 
+  void testconditional$elvisNlBeforeOperator() { doTest() }
+
   void testconditional$ternaryQuestionOnly() { doTest() }
 
   void testconditional$ternaryWithoutElse() { doTest() }

plugins/groovy/testdata/parsing/groovy/expressions/conditional/elvisNlBeforeOperator.test

@@ -0,0 +1,12 @@
+a
+?: b
+-----
+Groovy script
+  Elvis expression
+    Reference expression
+      PsiElement(identifier)('a')
+    PsiElement(new line)('\n')
+    PsiElement(?:)('?:')
+    PsiWhiteSpace(' ')
+    Reference expression
+      PsiElement(identifier)('b')