"if-then to safe access" inspection: support call expression -> let

#KT-7675 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/branchedTransformations/IfThenToSafeAccessInspection.kt

@@ -19,13 +19,16 @@ package org.jetbrains.kotlin.idea.inspections.branchedTransformations
 import com.intellij.codeInspection.ProblemHighlightType
 import com.intellij.openapi.editor.Editor
 import com.intellij.openapi.project.Project
+import com.intellij.psi.PsiDocumentManager
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.idea.core.replaced
 import org.jetbrains.kotlin.idea.inspections.AbstractApplicabilityBasedInspection
 import org.jetbrains.kotlin.idea.intentions.branchedTransformations.*
+import org.jetbrains.kotlin.idea.refactoring.rename.KotlinVariableInplaceRenameHandler
 import org.jetbrains.kotlin.idea.util.application.runWriteAction
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
+import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.resolve.bindingContextUtil.isUsedAsExpression
 import org.jetbrains.kotlin.resolve.calls.callUtil.getType
 
@@ -73,8 +76,9 @@ class IfThenToSafeAccessInspection : AbstractApplicabilityBasedInspection<KtIfEx
             KtPsiUtil.deparenthesize(newExpr)
         }
 
-        if (editor != null) {
-            (resultExpr as? KtSafeQualifiedExpression)?.inlineReceiverIfApplicableWithPrompt(editor)
+        if (editor != null && resultExpr is KtSafeQualifiedExpression) {
+            resultExpr.inlineReceiverIfApplicableWithPrompt(editor)
+            resultExpr.renameLetParameter(editor)
         }
     }
 
@@ -83,6 +87,22 @@ class IfThenToSafeAccessInspection : AbstractApplicabilityBasedInspection<KtIfEx
         negatedClause == null && baseClause.isUsedAsExpression(context) -> false
         negatedClause != null && !negatedClause.isNullExpression() -> false
         else -> baseClause.evaluatesTo(receiverExpression) || baseClause.hasFirstReceiverOf(receiverExpression) ||
-                receiverExpression is KtThisExpression && getImplicitReceiver()?.let { it.type == receiverExpression.getType(context) } == true
+                receiverExpression is KtThisExpression && getImplicitReceiver()?.let { it.type == receiverExpression.getType(context) } == true ||
+                replaceableCallExpression()
+    }
+
+    private fun IfThenToSelectData.replaceableCallExpression(): Boolean {
+        val callExpression = baseClause as? KtCallExpression ?: return false
+        val arguments = callExpression.valueArguments.map { it.getArgumentExpression() }
+        return arguments.any { it?.evaluatesTo(receiverExpression) == true } && arguments.all { it is KtNameReferenceExpression }
+    }
+
+    private fun KtSafeQualifiedExpression.renameLetParameter(editor: Editor) {
+        val callExpression = selectorExpression as? KtCallExpression ?: return
+        if (callExpression.calleeExpression?.text != "let") return
+        val parameter = callExpression.lambdaArguments.singleOrNull()?.getLambdaExpression()?.valueParameters?.singleOrNull() ?: return
+        PsiDocumentManager.getInstance(project).doPostponedOperationsAndUnblockDocument(editor.document)
+        editor.caretModel.moveToOffset(parameter.startOffset)
+        KotlinVariableInplaceRenameHandler().doRename(parameter, editor, null)
     }
 }

idea/src/org/jetbrains/kotlin/idea/intentions/branchedTransformations/IfThenUtils.kt

@@ -25,6 +25,7 @@ import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.caches.resolve.findModuleDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.getResolutionFacade
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToCall
+import org.jetbrains.kotlin.idea.core.KotlinNameSuggester
 import org.jetbrains.kotlin.idea.core.replaced
 import org.jetbrains.kotlin.idea.intentions.getLeftMostReceiverExpression
 import org.jetbrains.kotlin.idea.intentions.replaceFirstReceiver
@@ -33,7 +34,10 @@ import org.jetbrains.kotlin.idea.refactoring.introduce.introduceVariable.KotlinI
 import org.jetbrains.kotlin.idea.refactoring.isMultiLine
 import org.jetbrains.kotlin.idea.references.mainReference
 import org.jetbrains.kotlin.idea.resolve.frontendService
+import org.jetbrains.kotlin.idea.util.getResolutionScope
+import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.DescriptorUtils
@@ -43,6 +47,7 @@ import org.jetbrains.kotlin.resolve.calls.resolvedCallUtil.getImplicitReceiverVa
 import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowValue
 import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowValueFactory
 import org.jetbrains.kotlin.resolve.scopes.receivers.ImplicitReceiver
+import org.jetbrains.kotlin.resolve.scopes.utils.findVariable
 import org.jetbrains.kotlin.types.TypeUtils
 import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
 import org.jetbrains.kotlin.utils.addToStdlib.constant
@@ -211,10 +216,12 @@ data class IfThenToSelectData(
                         hasImplicitReceiver() -> factory.createExpressionByPattern("$0?.$1", newReceiver!!, baseClause).insertSafeCalls(
                             factory
                         )
+                        baseClause is KtCallExpression -> replacedBaseClause(baseClause, newReceiver!!, factory)
                         else -> error("Illegal state")
                     }
                 }
                 hasImplicitReceiver() -> factory.createExpressionByPattern("this?.$0", baseClause).insertSafeCalls(factory)
+                baseClause is KtCallExpression -> replacedBaseClause(baseClause, receiverExpression, factory)
                 else -> baseClause.insertSafeCalls(factory)
             }
         }
@@ -223,6 +230,32 @@ data class IfThenToSelectData(
     internal fun getImplicitReceiver(): ImplicitReceiver? = baseClause.getResolvedCall(context)?.getImplicitReceiverValue()
 
     internal fun hasImplicitReceiver(): Boolean = getImplicitReceiver() != null
+
+    private fun replacedBaseClause(baseClause: KtCallExpression, receiver: KtExpression, factory: KtPsiFactory): KtExpression {
+        val needExplicitParameter = baseClause.valueArguments.any { it.getArgumentExpression()?.text == "it" }
+        val parameterName = if (needExplicitParameter) {
+            val scope = baseClause.getResolutionScope()
+            KotlinNameSuggester.suggestNameByName("it") { scope.findVariable(Name.identifier(it), NoLookupLocation.FROM_IDE) == null }
+        } else {
+            "it"
+        }
+        return factory.buildExpression {
+            appendExpression(receiver)
+            appendFixedText("?.let {")
+            if (needExplicitParameter) appendFixedText(" $parameterName ->")
+            appendExpression(baseClause.calleeExpression)
+            appendFixedText("(")
+            baseClause.valueArguments.forEachIndexed { index, arg ->
+                if (index != 0) appendFixedText(", ")
+                val argExpression = arg.getArgumentExpression()
+                if (argExpression?.evaluatesTo(receiverExpression) == true)
+                    appendFixedText(parameterName)
+                else
+                    appendExpression(argExpression)
+            }
+            appendFixedText(") }")
+        }
+    }
 }
 
 internal fun KtIfExpression.buildSelectTransformationData(): IfThenToSelectData? {