new inference: reject varargs as method reference target

(cherry picked from commit 77017d7790b78c5bb20c591e2588c1eccd0f96d7)

java/java-psi-api/src/com/intellij/psi/util/TypeConversionUtil.java

@@ -706,7 +706,7 @@ public class TypeConversionUtil {
         final PsiType lType = ((PsiMethodReferenceType)left).getExpression().getFunctionalInterfaceType();
         return Comparing.equal(rType, lType);
       }
-      return methodReferenceExpression.isAcceptable(left);
+      return !(left instanceof PsiArrayType) && methodReferenceExpression.isAcceptable(left);
     }
     if (right instanceof PsiLambdaExpressionType) {
       final PsiLambdaExpression rLambdaExpression = ((PsiLambdaExpressionType)right).getExpression();

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newMethodRef/AmbiguityVarargs.java

@@ -0,0 +1,20 @@
+class Test {
+
+  interface IntMapper {
+    int map();
+  }
+
+  interface LongMapper {
+    long map();
+  }
+
+  void m(IntMapper im1, IntMapper... im) { }
+  void m(LongMapper... lm) { }
+  
+  {
+      m<error descr="Ambiguous method call: both 'Test.m(IntMapper, IntMapper...)' and 'Test.m(LongMapper...)' match">(this ::ii)</error>;
+  }
+
+  int ii() {return 0;}
+
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/NewMethodRefHighlightingTest.java

@@ -189,6 +189,10 @@ public class NewMethodRefHighlightingTest extends LightDaemonAnalyzerTestCase {
     doTest();
   }
 
+  public void testAmbiguityVarargs() throws Exception {
+    doTest();
+  }
+
   private void doTest() {
     doTest(false);
   }