Change Signature: Fix replacement of implicit Unit return type

idea/testData/refactoring/changeSignature/ChangeReturnTypeToNonUnitAfter.kt

@@ -0,0 +1,11 @@
+open class A {
+    open fun foo(): Int {
+
+    }
+}
+
+class B : A() {
+    override fun foo(): Int {
+
+    }
+}

idea/testData/refactoring/changeSignature/ChangeReturnTypeToNonUnitBefore.kt

@@ -0,0 +1,11 @@
+open class A {
+    open fun <caret>foo() {
+
+    }
+}
+
+class B : A() {
+    override fun foo() {
+
+    }
+}