Rename: Warn about function name conflicts

#KT-13239 Fixed

ChangeLog.md

@@ -263,6 +263,7 @@ Using 'this' as function argument in constructor of non-final class
 - [`KT-13277`](https://youtrack.jetbrains.com/issue/KT-13277) Change Signature: Fix usage processing to prevent interfering with Python support plugin
 - [`KT-13254`](https://youtrack.jetbrains.com/issue/KT-13254) Rename: Conflict detection for type parameters
 - [`KT-13282`](https://youtrack.jetbrains.com/issue/KT-13282), [`KT-13283`](https://youtrack.jetbrains.com/issue/KT-13283) Rename: Fix name quoting for automatic renamers
+- [`KT-13239`](https://youtrack.jetbrains.com/issue/KT-13239) Rename: Warn about function name conflicts
 
 ##### New features
 

idea/src/org/jetbrains/kotlin/idea/refactoring/rename/RenameKotlinFunctionProcessor.kt

@@ -80,7 +80,11 @@ class RenameKotlinFunctionProcessor : RenameKotlinPsiProcessor() {
             allRenames: Map<out PsiElement, String>,
             result: MutableList<UsageInfo>
     ) {
+        if (newName == null) return
+        val declaration = element.unwrapped as? KtNamedFunction ?: return
+        val descriptor = declaration.resolveToDescriptor()
         checkConflictsAndReplaceUsageInfos(element, allRenames, result)
+        checkRedeclarations(descriptor, newName, result)
     }
 
     override fun substituteElementToRename(element: PsiElement?, editor: Editor?): PsiElement?  {

idea/src/org/jetbrains/kotlin/idea/refactoring/rename/renameConflictUtils.kt

@@ -52,6 +52,7 @@ import org.jetbrains.kotlin.resolve.descriptorUtil.getImportableDescriptor
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
 import org.jetbrains.kotlin.resolve.scopes.LexicalScope
+import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.resolve.scopes.getDescriptorsFiltered
 import org.jetbrains.kotlin.resolve.scopes.utils.findClassifier
 import org.jetbrains.kotlin.resolve.scopes.utils.getImplicitReceiversHierarchy
@@ -81,6 +82,16 @@ internal fun checkRedeclarations(
         newName: String,
         result: MutableList<UsageInfo>
 ) {
+    fun MemberScope.findSiblingByName(): DeclarationDescriptor? {
+        val descriptorKindFilter = when (descriptor) {
+            is ClassDescriptor -> DescriptorKindFilter.CLASSIFIERS
+            is PropertyDescriptor -> DescriptorKindFilter.VARIABLES
+            is FunctionDescriptor -> DescriptorKindFilter.FUNCTIONS
+            else -> return null
+        }
+        return getDescriptorsFiltered(descriptorKindFilter) { it.asString() == newName }.firstOrNull { it != descriptor }
+    }
+
     fun getSiblingWithNewName(): DeclarationDescriptor? {
         val containingDescriptor = descriptor.containingDeclaration
 
@@ -104,17 +115,23 @@ internal fun checkRedeclarations(
             return context[BindingContext.VARIABLE, dummyVar]?.type?.constructor?.declarationDescriptor
         }
 
-        val containingScope = when (containingDescriptor) {
-            is ClassDescriptor -> containingDescriptor.unsubstitutedMemberScope
-            is PackageFragmentDescriptor -> containingDescriptor.getMemberScope()
-            else -> return null
+        return when (containingDescriptor) {
+            is ClassDescriptor -> containingDescriptor.unsubstitutedMemberScope.findSiblingByName()
+            is PackageFragmentDescriptor -> containingDescriptor.getMemberScope().findSiblingByName()
+            else -> {
+                val block = (descriptor as? DeclarationDescriptorWithSource)?.source?.getPsi()?.parent as? KtBlockExpression
+                            ?: return null
+                (block.statements.firstOrNull {
+                    if (it.name != newName) return@firstOrNull false
+                    when (descriptor) {
+                        is ClassDescriptor -> it is KtClassOrObject
+                        is PropertyDescriptor -> it is KtProperty
+                        is FunctionDescriptor -> it is KtNamedFunction
+                        else -> false
+                    }
+                } as? KtDeclaration)?.resolveToDescriptor()
+            }
         }
-        val descriptorKindFilter = when (descriptor) {
-            is ClassDescriptor -> DescriptorKindFilter.CLASSIFIERS
-            is PropertyDescriptor -> DescriptorKindFilter.VARIABLES
-            else -> return null
-        }
-        return containingScope.getDescriptorsFiltered(descriptorKindFilter) { it.asString() == newName }.firstOrNull()
     }
 
     val candidateDescriptor = getSiblingWithNewName() ?: return

idea/testData/refactoring/rename/memberFunctionRedeclaration/before/test/test.kt

@@ -0,0 +1,11 @@
+package test
+
+class A {
+    fun /*rename*/namedFunA() {}
+    fun namedFunB() {}
+
+    fun useNames() {
+        namedFunA()
+        namedFunB()
+    }
+}

idea/testData/refactoring/rename/memberFunctionRedeclaration/memberFunctionRedeclaration.test

@@ -0,0 +1,7 @@
+{
+  "type": "MARKED_ELEMENT",
+  "mainFile": "test/test.kt",
+  "newName": "namedFunB",
+  "withRuntime": "true",
+  "hint": "Function 'namedFunB' is already declared in class 'A'"
+}

idea/testData/refactoring/rename/topLevelFunctionRedeclaration/before/test/test.kt

@@ -0,0 +1,9 @@
+package test
+
+fun /*rename*/namedFunA() {}
+fun namedFunB() {}
+
+fun useNames() {
+    namedFunA()
+    namedFunB()
+}

idea/testData/refactoring/rename/topLevelFunctionRedeclaration/topLevelFunctionRedeclaration.test

@@ -0,0 +1,7 @@
+{
+  "type": "MARKED_ELEMENT",
+  "mainFile": "test/test.kt",
+  "newName": "namedFunB",
+  "withRuntime": "true",
+  "hint": "Function 'namedFunB' is already declared in package 'test'"
+}

idea/tests/org/jetbrains/kotlin/idea/refactoring/rename/RenameTestGenerated.java

@@ -185,6 +185,12 @@ public class RenameTestGenerated extends AbstractRenameTest {
         doTest(fileName);
     }
 
+    @TestMetadata("memberFunctionRedeclaration/memberFunctionRedeclaration.test")
+    public void testMemberFunctionRedeclaration_MemberFunctionRedeclaration() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/rename/memberFunctionRedeclaration/memberFunctionRedeclaration.test");
+        doTest(fileName);
+    }
+
     @TestMetadata("memberPropertyRedeclaration/memberPropertyRedeclaration.test")
     public void testMemberPropertyRedeclaration_MemberPropertyRedeclaration() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/rename/memberPropertyRedeclaration/memberPropertyRedeclaration.test");
@@ -1007,6 +1013,12 @@ public class RenameTestGenerated extends AbstractRenameTest {
         doTest(fileName);
     }
 
+    @TestMetadata("topLevelFunctionRedeclaration/topLevelFunctionRedeclaration.test")
+    public void testTopLevelFunctionRedeclaration_TopLevelFunctionRedeclaration() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/rename/topLevelFunctionRedeclaration/topLevelFunctionRedeclaration.test");
+        doTest(fileName);
+    }
+
     @TestMetadata("topLevelPropertyRedeclaration/topLevelPropertyRedeclaration.test")
     public void testTopLevelPropertyRedeclaration_TopLevelPropertyRedeclaration() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/rename/topLevelPropertyRedeclaration/topLevelPropertyRedeclaration.test");