Change Signature: Warn about safe call receiver being transformed to value argument

#KT-8744 Fixed

idea/src/org/jetbrains/kotlin/idea/refactoring/changeSignature/KotlinChangeSignatureUsageProcessor.kt

@@ -584,6 +584,7 @@ class KotlinChangeSignatureUsageProcessor : ChangeSignatureUsageProcessor {
         if (function is KtCallableDeclaration && newReceiverInfo != originalReceiverInfo) {
             findReceiverIntroducingConflicts(result, function, newReceiverInfo)
             findInternalExplicitReceiverConflicts(refUsages.get(), result, originalReceiverInfo)
+            findReceiverToParameterInSafeCallsConflicts(refUsages.get(), result, info)
             findThisLabelConflicts(refUsages, result, info, function)
         }
 
@@ -674,6 +675,28 @@ class KotlinChangeSignatureUsageProcessor : ChangeSignatureUsageProcessor {
         }
     }
 
+    private fun findReceiverToParameterInSafeCallsConflicts(
+            usages: Array<UsageInfo>,
+            result: MultiMap<PsiElement, String>,
+            changeInfo: KotlinChangeInfo
+    ) {
+        val originalReceiverInfo = changeInfo.methodDescriptor.receiver
+        if (originalReceiverInfo == null || originalReceiverInfo !in changeInfo.getNonReceiverParameters()) return
+
+        for (usageInfo in usages) {
+            if (!(usageInfo is KotlinFunctionCallUsage || usageInfo is KotlinPropertyCallUsage)) continue
+
+            val callElement = usageInfo.element as? KtElement ?: continue
+            val qualifiedExpression = callElement.getQualifiedExpressionForSelector()
+            if (qualifiedExpression is KtSafeQualifiedExpression) {
+                result.putValue(
+                        callElement,
+                        "Receiver can't be safely transformed to value argument: ${CommonRefactoringUtil.htmlEmphasize(qualifiedExpression.text)}"
+                )
+            }
+        }
+    }
+
     private fun findReceiverIntroducingConflicts(
             result: MultiMap<PsiElement, String>,
             callable: PsiElement,

idea/testData/refactoring/changeSignature/ReceiverInSafeCallBefore.kt

@@ -0,0 +1,5 @@
+interface A {
+    val parent: A?
+}
+
+fun A.<caret>ext(): Int = 1 + (parent?.ext() ?: 0)

idea/testData/refactoring/changeSignature/ReceiverInSafeCallMessages.txt

@@ -0,0 +1 @@
+Receiver can't be safely transformed to value argument: parent?.ext()

idea/tests/org/jetbrains/kotlin/idea/refactoring/changeSignature/KotlinChangeSignatureTest.kt

@@ -949,4 +949,6 @@ class KotlinChangeSignatureTest : KotlinCodeInsightTestCase() {
         receiverParameterInfo = null
         newParameters[0].name = "a"
     }
+
+    fun testReceiverInSafeCall() = doTestConflict { receiverParameterInfo = null }
 }