Useless call on collection: propose 'Replace with toList()' instead of 'Remove useless call' if receiver is array type

#KT-38961 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/collections/UselessCallOnCollectionInspection.kt

@@ -7,7 +7,9 @@ package org.jetbrains.kotlin.idea.inspections.collections
 
 import com.intellij.codeInspection.ProblemHighlightType
 import com.intellij.openapi.util.TextRange
+import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.idea.KotlinBundle
+import org.jetbrains.kotlin.idea.quickfix.ReplaceSelectorOfQualifiedExpressionFix
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtQualifiedExpression
 import org.jetbrains.kotlin.psi.psiUtil.endOffset
@@ -15,6 +17,8 @@ import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 import org.jetbrains.kotlin.resolve.calls.callUtil.getType
+import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
+import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeUtils
 import org.jetbrains.kotlin.types.isFlexible
 import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
@@ -68,6 +72,11 @@ class UselessCallOnCollectionInspection : AbstractUselessCallInspection() {
             )
             holder.registerProblem(descriptor)
         } else {
+            val fix = if (resolvedCall.resultingDescriptor.returnType.isList() && !receiverType.isList()) {
+                ReplaceSelectorOfQualifiedExpressionFix("toList()")
+            } else {
+                RemoveUselessCallFix()
+            }
             val descriptor = holder.manager.createProblemDescriptor(
                 expression,
                 TextRange(
@@ -77,9 +86,11 @@ class UselessCallOnCollectionInspection : AbstractUselessCallInspection() {
                 KotlinBundle.message("useless.call.on.collection.type"),
                 ProblemHighlightType.LIKE_UNUSED_SYMBOL,
                 isOnTheFly,
-                RemoveUselessCallFix()
+                fix
             )
             holder.registerProblem(descriptor)
         }
     }
+
+    private fun KotlinType?.isList() = this?.constructor?.declarationDescriptor?.fqNameSafe == KotlinBuiltIns.FQ_NAMES.list
 }

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

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.idea.quickfix
+
+import com.intellij.codeInspection.LocalQuickFix
+import com.intellij.codeInspection.ProblemDescriptor
+import com.intellij.openapi.project.Project
+import org.jetbrains.kotlin.idea.KotlinBundle
+import org.jetbrains.kotlin.psi.KtPsiFactory
+import org.jetbrains.kotlin.psi.KtQualifiedExpression
+import org.jetbrains.kotlin.psi.createExpressionByPattern
+
+class ReplaceSelectorOfQualifiedExpressionFix(private val newSelector: String) : LocalQuickFix {
+    override fun getName() = KotlinBundle.message("replace.with.0", newSelector)
+
+    override fun getFamilyName() = name
+
+    override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
+        (descriptor.psiElement as? KtQualifiedExpression)?.let {
+            it.replace(KtPsiFactory(it).createExpressionByPattern("$0.$newSelector", it.receiverExpression))
+        }
+    }
+}

idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterIsExactInstanceOnArray.kt

@@ -0,0 +1,3 @@
+// WITH_RUNTIME
+
+val x: List<String> = arrayOf("1").<caret>filterIsInstance<String>()

idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterIsExactInstanceOnArray.kt.after

@@ -0,0 +1,3 @@
+// WITH_RUNTIME
+
+val x: List<String> = arrayOf("1").toList()

idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnArray.kt

@@ -0,0 +1,3 @@
+// WITH_RUNTIME
+
+val x: List<String> = arrayOf("1").<caret>filterNotNull()

idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnArray.kt.after

@@ -0,0 +1,3 @@
+// WITH_RUNTIME
+
+val x: List<String> = arrayOf("1").toList()

idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnIterable.kt

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun test(iterable: Iterable<Int>): List<Int> {
+    return iterable.<caret>filterNotNull()
+}

idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnIterable.kt.after

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun test(iterable: Iterable<Int>): List<Int> {
+    return iterable.toList()
+}

idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnSet.kt

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun test(): List<Int> {
+    return setOf(1).<caret>filterNotNull()
+}

idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnSet.kt.after

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun test(): List<Int> {
+    return setOf(1).toList()
+}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -1935,6 +1935,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
                 runTest("idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterIsExactInstanceFake.kt");
             }
 
+            @TestMetadata("FilterIsExactInstanceOnArray.kt")
+            public void testFilterIsExactInstanceOnArray() throws Exception {
+                runTest("idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterIsExactInstanceOnArray.kt");
+            }
+
             @TestMetadata("FilterIsForFlexible.kt")
             public void testFilterIsForFlexible() throws Exception {
                 runTest("idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterIsForFlexible.kt");
@@ -1960,6 +1965,21 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
                 runTest("idea/testData/inspectionsLocal/collections/uselessCallOnCollection/filterNotNullFake.kt");
             }
 
+            @TestMetadata("FilterNotNullOnArray.kt")
+            public void testFilterNotNullOnArray() throws Exception {
+                runTest("idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnArray.kt");
+            }
+
+            @TestMetadata("FilterNotNullOnIterable.kt")
+            public void testFilterNotNullOnIterable() throws Exception {
+                runTest("idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnIterable.kt");
+            }
+
+            @TestMetadata("FilterNotNullOnSet.kt")
+            public void testFilterNotNullOnSet() throws Exception {
+                runTest("idea/testData/inspectionsLocal/collections/uselessCallOnCollection/FilterNotNullOnSet.kt");
+            }
+
             @TestMetadata("MapIndexedNotNullTo.kt")
             public void testMapIndexedNotNullTo() throws Exception {
                 runTest("idea/testData/inspectionsLocal/collections/uselessCallOnCollection/MapIndexedNotNullTo.kt");