overload resolution: compare functional interfaces for specific if they are not assignable (IDEA-140987)

java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java

@@ -1360,17 +1360,16 @@ public class InferenceSession {
     for (int i = 0; i < paramsLength; i++) {
       PsiType sType = getParameterType(parameters1, i, PsiSubstitutor.EMPTY, false);
       PsiType tType = session.substituteWithInferenceVariables(getParameterType(parameters2, i, PsiSubstitutor.EMPTY, varargs));
-      if (session.isProperType(sType) && session.isProperType(tType)) {
-        if (!TypeConversionUtil.isAssignable(tType, sType)) {
-          return false;
-        }
-        continue;
-      }
       if (LambdaUtil.isFunctionalType(sType) && LambdaUtil.isFunctionalType(tType) && !relates(sType, tType)) {
         if (!isFunctionalTypeMoreSpecific(sType, tType, session, args[i])) {
           return false;
         }
       } else {
+        if (session.isProperType(tType)) {
+          if (!TypeConversionUtil.isAssignable(tType, sType)) {
+            return false;
+          }
+        }
         session.addConstraint(new StrictSubtypingConstraint(tType, sType));
       }
     }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/overloadResolution/ProperUnrelatedFunctionalInterfacesTypesComparison.java

@@ -0,0 +1,24 @@
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+class Test {
+  private static  <T> T withProject(final Function<ProjectEnvironment, T> calculation) {
+    System.out.println(calculation);
+    return null;
+  }
+
+  private static <T> T <warning descr="Private method 'withProject(java.util.function.Consumer<ProjectEnvironment>)' is never used">withProject</warning>(final Consumer<ProjectEnvironment> calculation){
+    System.out.println(calculation);
+    return null;
+  }
+
+  public static String foo() {
+    return withProject(ProjectEnvironment::getProject);
+  }
+}
+
+class ProjectEnvironment {
+  String getProject() {
+    return null;
+  }
+}

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

@@ -122,6 +122,10 @@ public class OverloadResolutionTest extends LightDaemonAnalyzerTestCase {
     doTest();
   }
 
+  public void testProperUnrelatedFunctionalInterfacesTypesComparison() throws Exception {
+    doTest();
+  }
+
   private void doTest() {
     doTest(true);
   }