convert static to instance: don't check interface inheritance for java 1.8+

check used references for java 1.8- as call sites would call abstract method of interface anyway (IDEA-187991)

java/java-impl/src/com/intellij/refactoring/convertToInstanceMethod/ConvertToInstanceMethodProcessor.java

@@ -41,7 +41,6 @@ import com.intellij.usageView.UsageInfo;
 import com.intellij.usageView.UsageViewDescriptor;
 import com.intellij.util.IncorrectOperationException;
 import com.intellij.util.VisibilityUtil;
-import java.util.HashMap;
 import com.intellij.util.containers.MultiMap;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -173,14 +172,14 @@ public class ConvertToInstanceMethodProcessor extends BaseRefactoringProcessor {
     UsageInfo[] usagesIn = refUsages.get();
     MultiMap<PsiElement, String> conflicts = new MultiMap<>();
     final Set<PsiMember> methods = Collections.singleton((PsiMember)myMethod);
-    if (!myTargetClass.isInterface()) {
-      RefactoringConflictsUtil.analyzeAccessibilityConflicts(methods, myTargetClass, conflicts, myNewVisibility);
-    }
-    else {
+    //check that method to call would be still accessible from the call places
+    RefactoringConflictsUtil.analyzeAccessibilityConflicts(methods, myTargetClass, conflicts, myNewVisibility);
+    //additionally check that body of method contains only accessible in the inheritors references
+    if (myTargetClass.isInterface() && !PsiUtil.isLanguageLevel8OrHigher(myTargetClass)) {
       for (final UsageInfo usage : usagesIn) {
         if (usage instanceof ImplementingClassUsageInfo) {
-          RefactoringConflictsUtil
-            .analyzeAccessibilityConflicts(methods, ((ImplementingClassUsageInfo)usage).getPsiClass(), conflicts, PsiModifier.PUBLIC);
+          PsiClass targetClass = ((ImplementingClassUsageInfo)usage).getPsiClass();
+          RefactoringConflictsUtil.checkUsedElements(myMethod, myMethod, methods, null, targetClass, targetClass, conflicts);
         }
       }
     }

java/java-tests/testData/refactoring/convertToInstance8Method/StaticMethodOfInterfaceWithNonAccessibleInheritor.java

@@ -0,0 +1,13 @@
+interface I {
+  static void f<caret>oo(I i) {}
+}
+
+class WithPrivateInner {
+  private class Inner implements I {}
+}
+
+class WithUsage {
+  void n(I i) {
+    I.foo(i);
+  }
+}

java/java-tests/testData/refactoring/convertToInstance8Method/StaticMethodOfInterfaceWithNonAccessibleInheritor.java.after

@@ -0,0 +1,13 @@
+interface I {
+    default void foo() {}
+}
+
+class WithPrivateInner {
+  private class Inner implements I {}
+}
+
+class WithUsage {
+  void n(I i) {
+    i.foo();
+  }
+}

java/java-tests/testSrc/com/intellij/java/refactoring/convertToInstanceMethod/ConvertToInstance8MethodTest.java

@@ -37,6 +37,10 @@ public class ConvertToInstance8MethodTest extends ConvertToInstanceMethodTest {
     doTest(-1);
   }
 
+  public void testStaticMethodOfInterfaceWithNonAccessibleInheritor() {
+    doTest(0);
+  }
+
   public void testConvertToInstanceMethodOfTheSameClassWithTypeParams() {
     try {
       doTest(-1);