From fc7c77754ea38a8fd8ffdb60628b4d03583f5112 Mon Sep 17 00:00:00 2001
From: Bas Leijdekkers <bas.leijdekkers@jetbrains.com>
Date: Thu, 26 Mar 2026 17:16:48 +0100
Subject: [PATCH] IDEA-386847 [java]: add default modifier when making
 interface method non-static

GitOrigin-RevId: fde665d19cdb6fef9cf81e81c93ac8ddcf05789f
---
 .../codeInsight/daemon/impl/quickfix/ModifierFix.java     | 8 ++++++++
 .../modifier/beforeMakeInterfaceMethodNonStatic.java      | 8 ++++++++
 .../modifier8/afterMakeInterfaceMethodNonStatic.java      | 8 ++++++++
 .../modifier8/beforeMakeInterfaceMethodNonStatic.java     | 8 ++++++++
 4 files changed, 32 insertions(+)
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier/beforeMakeInterfaceMethodNonStatic.java
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier8/afterMakeInterfaceMethodNonStatic.java
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier8/beforeMakeInterfaceMethodNonStatic.java

diff --git a/java/java-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ModifierFix.java b/java/java-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ModifierFix.java
index d99d9b0a9327..49a8898b48e5 100644
--- a/java/java-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ModifierFix.java
+++ b/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);
   }
 
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier/beforeMakeInterfaceMethodNonStatic.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier/beforeMakeInterfaceMethodNonStatic.java
new file mode 100644
index 000000000000..a65e229ccbb1
--- /dev/null
+++ b/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
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier8/afterMakeInterfaceMethodNonStatic.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier8/afterMakeInterfaceMethodNonStatic.java
new file mode 100644
index 000000000000..2c0a9f9d7253
--- /dev/null
+++ b/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
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier8/beforeMakeInterfaceMethodNonStatic.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/modifier8/beforeMakeInterfaceMethodNonStatic.java
new file mode 100644
index 000000000000..f86efa53a532
--- /dev/null
+++ b/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
+  }
+}
\ No newline at end of file