Introduce "Remove fun modifier" quick fix for FUN_INTERFACE_WRONG_COUNT_OF_ABSTRACT_MEMBERS error

#KT-37539 Fixed

idea/src/org/jetbrains/kotlin/idea/quickfix/QuickFixRegistrar.kt

@@ -642,5 +642,7 @@ class QuickFixRegistrar : QuickFixContributor {
         MUST_BE_INITIALIZED.registerFactory(ChangeVariableMutabilityFix.MUST_BE_INITIALIZED_FACTORY)
 
         TOO_MANY_ARGUMENTS.registerFactory(RemoveArgumentFix)
+
+        FUN_INTERFACE_WRONG_COUNT_OF_ABSTRACT_MEMBERS.registerFactory(RemoveModifierFix.createRemoveFunFromInterfaceFactory())
     }
 }

idea/src/org/jetbrains/kotlin/idea/quickfix/RemoveModifierFix.kt

@@ -120,5 +120,18 @@ class RemoveModifierFix(
                 }
             }
         }
+
+        fun createRemoveFunFromInterfaceFactory(): KotlinSingleIntentionActionFactory {
+            return object : KotlinSingleIntentionActionFactory() {
+                override fun createAction(diagnostic: Diagnostic): RemoveModifierFix? {
+                    val keyword = diagnostic.psiElement
+                    val modifierList = keyword.parent as? KtDeclarationModifierList ?: return null
+                    val funInterface = (modifierList.parent as? KtClass)?.takeIf {
+                        it.isInterface() && it.hasModifier(KtTokens.FUN_KEYWORD)
+                    } ?: return null
+                    return RemoveModifierFix(funInterface, KtTokens.FUN_KEYWORD, isRedundant = false)
+                }
+            }
+        }
     }
 }

idea/testData/quickfix/redundantFun/simple.kt

@@ -0,0 +1,2 @@
+// "Remove 'fun' modifier" "true"
+<caret>fun interface WrongFunFace

idea/testData/quickfix/redundantFun/simple.kt.after

@@ -0,0 +1,2 @@
+// "Remove 'fun' modifier" "true"
+interface WrongFunFace

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixMultiFileTestGenerated.java

@@ -3619,6 +3619,19 @@ public class QuickFixMultiFileTestGenerated extends AbstractQuickFixMultiFileTes
         }
     }
 
+    @TestMetadata("idea/testData/quickfix/redundantFun")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class RedundantFun extends AbstractQuickFixMultiFileTest {
+        private void runTest(String testDataFilePath) throws Exception {
+            KotlinTestUtils.runTest(this::doTestWithExtraFile, this, testDataFilePath);
+        }
+
+        public void testAllFilesPresentInRedundantFun() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("idea/testData/quickfix/redundantFun"), Pattern.compile("^(\\w+)\\.((before\\.Main\\.\\w+)|(test))$"), null, true);
+        }
+    }
+
     @TestMetadata("idea/testData/quickfix/redundantIf")
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -10199,6 +10199,24 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
         }
     }
 
+    @TestMetadata("idea/testData/quickfix/redundantFun")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class RedundantFun extends AbstractQuickFixTest {
+        private void runTest(String testDataFilePath) throws Exception {
+            KotlinTestUtils.runTest(this::doTest, this, testDataFilePath);
+        }
+
+        public void testAllFilesPresentInRedundantFun() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("idea/testData/quickfix/redundantFun"), Pattern.compile("^([\\w\\-_]+)\\.kt$"), null, true);
+        }
+
+        @TestMetadata("simple.kt")
+        public void testSimple() throws Exception {
+            runTest("idea/testData/quickfix/redundantFun/simple.kt");
+        }
+    }
+
     @TestMetadata("idea/testData/quickfix/redundantIf")
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)