IDEA-386847 [java]: add default modifier when making interface method non-static

GitOrigin-RevId: fde665d19cdb6fef9cf81e81c93ac8ddcf05789f

java/java-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ModifierFix.java

@@ -238,6 +238,14 @@ public class ModifierFix extends PsiBasedModCommandAction<PsiModifierListOwner>
         removeFinalModifierFromMethods(aClass);
       }
     }
+    else {
+      if (owner instanceof PsiMethod method && PsiModifier.STATIC.equals(myModifier)) {
+        PsiClass containingClass = method.getContainingClass();
+        if (containingClass != null && containingClass.isInterface()) {
+          modifierList.setModifierProperty(PsiModifier.DEFAULT, true);
+        }
+      }
+    }
     changeModifierList(modifierList);
   }
 

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier/beforeMakeInterfaceMethodNonStatic.java

@@ -0,0 +1,8 @@
+// "Make 'y())' not static" "false"
+abstract interface Interface {
+  int f();
+
+  static void y() {
+    <caret>f(); // <- Error
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier8/afterMakeInterfaceMethodNonStatic.java

@@ -0,0 +1,8 @@
+// "Make 'y()' not static" "true"
+abstract interface Interface {
+  int f();
+
+  default void y() {
+    f(); // <- Error
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier8/beforeMakeInterfaceMethodNonStatic.java

@@ -0,0 +1,8 @@
+// "Make 'y()' not static" "true"
+abstract interface Interface {
+  int f();
+
+  static void y() {
+    <caret>f(); // <- Error
+  }
+}