Override/Implement: Use function body template when generating functions with default body

#KT-11807 Fixed

idea/idea-core/src/org/jetbrains/kotlin/idea/core/overrideImplement/OverrideMemberChooserObject.kt

@@ -24,6 +24,8 @@ import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.idea.codeInsight.DescriptorToSourceUtilsIde
+import org.jetbrains.kotlin.idea.core.TemplateKind
+import org.jetbrains.kotlin.idea.core.getFunctionBodyTextFromTemplate
 import org.jetbrains.kotlin.idea.core.util.DescriptorMemberChooserObject
 import org.jetbrains.kotlin.idea.util.IdeDescriptorRenderers
 import org.jetbrains.kotlin.psi.*
@@ -115,7 +117,7 @@ private fun generateProperty(project: Project, descriptor: PropertyDescriptor, b
     val body = buildString {
         append("\nget()")
         append(" = ")
-        append(generateUnsupportedOrSuperCall(descriptor, bodyType))
+        append(generateUnsupportedOrSuperCall(project, descriptor, bodyType))
         if (descriptor.isVar) {
             append("\nset(value) {}")
         }
@@ -139,17 +141,26 @@ private fun generateFunction(project: Project, descriptor: FunctionDescriptor, b
     val returnsNotUnit = returnType != null && !KotlinBuiltIns.isUnit(returnType)
 
     val body = if (bodyType != OverrideMemberChooserObject.BodyType.NO_BODY) {
-        val delegation = generateUnsupportedOrSuperCall(descriptor, bodyType)
-        "{" + (if (returnsNotUnit && bodyType != OverrideMemberChooserObject.BodyType.EMPTY) "return " else "") + delegation + "}"
+        val delegation = generateUnsupportedOrSuperCall(project, descriptor, bodyType)
+        "{" + (if (returnsNotUnit && bodyType != OverrideMemberChooserObject.BodyType.EMPTY) "return " else "") + delegation + "\n}"
     }
     else ""
 
     return KtPsiFactory(project).createFunction(OVERRIDE_RENDERER.render(newDescriptor) + body)
 }
 
-fun generateUnsupportedOrSuperCall(descriptor: CallableMemberDescriptor, bodyType: OverrideMemberChooserObject.BodyType): String {
+fun generateUnsupportedOrSuperCall(
+        project: Project,
+        descriptor: CallableMemberDescriptor,
+        bodyType: OverrideMemberChooserObject.BodyType
+): String {
     if (bodyType == OverrideMemberChooserObject.BodyType.EMPTY) {
-        return "throw UnsupportedOperationException()"
+        if (descriptor !is FunctionDescriptor) return "throw UnsupportedOperationException()"
+        return getFunctionBodyTextFromTemplate(project,
+                                               TemplateKind.FUNCTION,
+                                               descriptor.name.asString(),
+                                               descriptor.returnType?.let { IdeDescriptorRenderers.SOURCE_CODE.renderType(it) } ?: "Unit",
+                                               null)
     }
     else {
         return buildString {
@@ -165,7 +176,7 @@ fun generateUnsupportedOrSuperCall(descriptor: CallableMemberDescriptor, bodyTyp
                     val renderedName = it.name.render()
                     if (it.varargElementType != null) "*$renderedName" else renderedName
                 }
-                paramTexts.joinTo(this, prefix="(", postfix=")")
+                paramTexts.joinTo(this, prefix = "(", postfix = ")")
             }
         }
     }

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

@@ -0,0 +1,65 @@
+/*
+ * 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.ide.fileTemplates.FileTemplate
+import com.intellij.ide.fileTemplates.FileTemplateManager
+import com.intellij.openapi.progress.ProcessCanceledException
+import com.intellij.openapi.project.Project
+import com.intellij.util.IncorrectOperationException
+import org.jetbrains.kotlin.name.FqName
+import java.util.*
+
+private val FUNCTION_BODY_TEMPLATE = "New Kotlin Function Body.kt"
+private val SECONDARY_CONSTRUCTOR_BODY_TEMPLATE = "New Kotlin Secondary Constructor Body.kt"
+private val ATTRIBUTE_FUNCTION_NAME = "FUNCTION_NAME"
+
+enum class TemplateKind(val templateFileName: String) {
+    FUNCTION(FUNCTION_BODY_TEMPLATE), SECONDARY_CONSTRUCTOR(SECONDARY_CONSTRUCTOR_BODY_TEMPLATE)
+}
+
+fun getFunctionBodyTextFromTemplate(
+        project: Project,
+        kind: TemplateKind,
+        name: String?,
+        returnType: String,
+        classFqName: FqName? = null
+): String {
+    val fileTemplate = FileTemplateManager.getInstance(project)!!.getCodeTemplate(kind.templateFileName)
+
+    val properties = Properties()
+    properties.setProperty(FileTemplate.ATTRIBUTE_RETURN_TYPE, returnType)
+    if (classFqName != null) {
+        properties.setProperty(FileTemplate.ATTRIBUTE_CLASS_NAME, classFqName.asString())
+        properties.setProperty(FileTemplate.ATTRIBUTE_SIMPLE_CLASS_NAME, classFqName.shortName().asString())
+    }
+    if (name != null) {
+        properties.setProperty(ATTRIBUTE_FUNCTION_NAME, name)
+    }
+
+    return try {
+        fileTemplate!!.getText(properties)
+    }
+    catch (e: ProcessCanceledException) {
+        throw e
+    }
+    catch (e: Throwable) {
+        // TODO: This is dangerous.
+        // Is there any way to avoid catching all exceptions?
+        throw IncorrectOperationException("Failed to parse file template", e)
+    }
+}