Rename: Add name suggestions to Rename dialog

#KT-6372 Fixed
(cherry picked from commit 84ca283)

ChangeLog.md

@@ -218,6 +218,7 @@
 #### Refactorings
 
 ###### New features
+- [`KT-6372`](https://youtrack.jetbrains.com/issue/KT-6372) Add name suggestions to Rename dialog
 - [`KT-7851`](https://youtrack.jetbrains.com/issue/KT-7851) Respect naming conventions in automatic variable rename
 - [`KT-8044`](https://youtrack.jetbrains.com/issue/KT-8044), [`KT-9432`](https://youtrack.jetbrains.com/issue/KT-9432) Support @JvmName annotation in rename refactoring
 - [`KT-8512`](https://youtrack.jetbrains.com/issue/KT-8512) Support "Rename tests" options in Rename dialog

idea/idea-core/src/org/jetbrains/kotlin/idea/core/KotlinNameSuggestionProvider.kt

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2010-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.idea.core
+
+import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiVariable
+import com.intellij.psi.codeStyle.JavaCodeStyleManager
+import com.intellij.psi.codeStyle.SuggestedNameInfo
+import com.intellij.psi.statistics.JavaStatisticsManager
+import com.intellij.refactoring.rename.NameSuggestionProvider
+import org.jetbrains.kotlin.asJava.toLightElements
+import org.jetbrains.kotlin.descriptors.CallableDescriptor
+import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptor
+import org.jetbrains.kotlin.psi.KtCallableDeclaration
+import org.jetbrains.kotlin.psi.KtParameter
+import org.jetbrains.kotlin.psi.KtProperty
+import org.jetbrains.kotlin.utils.SmartList
+import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstanceOrNull
+
+class KotlinNameSuggestionProvider : NameSuggestionProvider {
+    override fun getSuggestedNames(element: PsiElement, nameSuggestionContext: PsiElement?, result: MutableSet<String>): SuggestedNameInfo? {
+        if (element is KtCallableDeclaration) {
+            val context = nameSuggestionContext ?: element.parent
+            val target = if (element is KtProperty || element is KtParameter) {
+                NewDeclarationNameValidator.Target.VARIABLES
+            }
+            else {
+                NewDeclarationNameValidator.Target.FUNCTIONS_AND_CLASSES
+            }
+            val validator = NewDeclarationNameValidator(context, element, target, listOf(element))
+            val names = SmartList<String>().apply {
+                val name = element.name
+                if (!name.isNullOrBlank()) {
+                    this += KotlinNameSuggester.getCamelNames(name!!, validator, name.first().isLowerCase())
+                }
+
+                val type = (element.resolveToDescriptor() as CallableDescriptor).returnType
+                if (type != null) {
+                    this += KotlinNameSuggester.suggestNamesByType(type, validator)
+                }
+            }
+            result += names
+
+            return object : SuggestedNameInfo(names.toTypedArray()) {
+                override fun nameChosen(name: String?) {
+                    val psiVariable = element.toLightElements().firstIsInstanceOrNull<PsiVariable>() ?: return
+                    JavaStatisticsManager.incVariableNameUseCount(
+                            name,
+                            JavaCodeStyleManager.getInstance(element.project).getVariableKind(psiVariable),
+                            psiVariable.name,
+                            psiVariable.type
+                    )
+                }
+            }
+        }
+
+        return null
+    }
+}

idea/src/META-INF/plugin.xml

@@ -682,6 +682,8 @@
 
     <createFromTemplateHandler implementation="org.jetbrains.kotlin.idea.actions.KotlinCreateFromTemplateHandler"/>
 
+    <nameSuggestionProvider implementation="org.jetbrains.kotlin.idea.core.KotlinNameSuggestionProvider"/>
+
     <intentionAction>
       <className>org.jetbrains.kotlin.idea.intentions.IfNullToElvisIntention</className>
       <category>Kotlin</category>