new inference: method refs: accept qualifier substitutor when nothing more could be inferred

java/java-psi-impl/src/com/intellij/psi/impl/source/tree/java/PsiMethodReferenceExpressionImpl.java

@@ -499,6 +499,7 @@ public class PsiMethodReferenceExpressionImpl extends PsiReferenceExpressionBase
                         final PsiClass pClass = pResult.getElement();
                         final PsiSubstitutor receiverSubstitutor = pClass != null ? TypeConversionUtil.getClassSubstitutor(containingClass, pClass, pResult.getSubstitutor()) : null;
                         if (receiverSubstitutor != null) {
+                          if (!method.hasTypeParameters() && signature.getParameterTypes().length == 1) return receiverSubstitutor;
                           psiSubstitutor = receiverSubstitutor;
                         }
                       }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/methodRef/ReturnTypeSpecific.java

@@ -29,7 +29,7 @@ class MyTest {
     }
 
     public static void main(String[] args) {
-        foo<error descr="Ambiguous method call: both 'MyTest.foo(I1)' and 'MyTest.foo(I2)' match">(Foo::m)</error>;
+        foo<error descr="Ambiguous method call: both 'MyTest.foo(I2)' and 'MyTest.foo(I3)' match">(Foo::m)</error>;
     }
 }
 

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

@@ -0,0 +1,15 @@
+class Test {
+
+  static class Foo<X> {
+    X m() { return null;}
+  }
+
+  interface I {
+    Foo<Object> _i(Foo<String> fs);
+  }
+
+  static void foo(I i) { }
+  {
+    foo(<error descr="Bad return type in method reference: cannot convert java.lang.String to Test.Foo<java.lang.Object>">Foo::m</error>);
+  }
+}

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

@@ -173,6 +173,10 @@ public class NewMethodRefHighlightingTest extends LightDaemonAnalyzerTestCase {
     doTest();
   }
 
+  public void testReturnTypeCheckForRawReceiver() throws Exception {
+    doTest();
+  }
+
   private void doTest() {
     doTest(false);
   }