Introduce single-project extensions with static types for Kotlin target

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/KotlinGradlePluginIT.kt

@@ -891,4 +891,34 @@ class KotlinGradleIT : BaseGradleIT() {
             assertNotContains(MULTIPLE_KOTLIN_PLUGINS_SPECIFIC_PROJECTS_WARNING)
         }
     }
+
+    @Test
+    fun testNewModelInOldJvmPlugin() = with(Project("new-model-in-old-plugin", GradleVersionRequired.AtLeast("4.10.2"))) {
+        setupWorkingDir()
+        gradleBuildScript().modify(::transformBuildScriptWithPluginsDsl)
+
+        build("publish", "check", "runBenchmark") {
+            assertSuccessful()
+            assertTasksExecuted(":compileKotlin", ":compileTestKotlin", ":compileBenchmarkKotlin", ":test", ":runBenchmark")
+
+            // Find the benchmark output:
+            assertContains("f ran at the speed of light")
+
+            val moduleDir = "build/repo/com/example/new-model/1.0/"
+
+            val publishedJar = fileInWorkingDir(moduleDir + "new-model-1.0.jar")
+            ZipFile(publishedJar).use { zip ->
+                val entries = zip.entries().asSequence().map { it.name }
+                assertTrue { "com/example/A.class" in entries }
+            }
+
+            val publishedPom = fileInWorkingDir(moduleDir + "new-model-1.0.pom")
+            val kotlinVersion = defaultBuildOptions().kotlinVersion
+            val pomText = publishedPom.readText().replace(Regex("\\s+"), "")
+            assertTrue { "kotlin-gradle-plugin-api</artifactId><version>$kotlinVersion</version><scope>compile</scope>" in pomText }
+            assertTrue { "kotlin-stdlib-jdk8</artifactId><version>$kotlinVersion</version><scope>runtime</scope>" in pomText }
+
+            assertFileExists(moduleDir + "new-model-1.0-sources.jar")
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-model-in-old-plugin/build.gradle.kts

@@ -0,0 +1,60 @@
+plugins {
+    kotlin("jvm").version("<pluginMarkerVersion>")
+    `maven-publish`
+}
+
+group = "com.example"
+version = "1.0"
+
+repositories {
+    mavenLocal()
+    jcenter()
+}
+
+kotlin.target.compilations {
+    all {
+        kotlinOptions {
+            allWarningsAsErrors = true
+            jvmTarget = "1.8"
+        }
+    }
+
+    val main by getting {
+        defaultSourceSet.dependencies {
+            api(kotlin("gradle-plugin-api"))
+            implementation(kotlin("stdlib-jdk8"))
+        }
+    }
+
+    val test by getting {
+        defaultSourceSet.dependencies {
+            implementation(kotlin("test-junit"))
+        }
+    }
+
+    val benchmark by creating {
+        defaultSourceSet.dependencies {
+            implementation(main.compileDependencyFiles + main.output.allOutputs)
+            runtimeOnly(main.runtimeDependencyFiles)
+
+            implementation(kotlin("reflect"))
+        }
+    }
+}
+
+val runBenchmark by tasks.registering(JavaExec::class) {
+    classpath = kotlin.target.compilations["benchmark"].run { runtimeDependencyFiles + output.allOutputs }
+    main = "com.example.ABenchmarkKt"
+}
+
+publishing {
+    publications {
+        create("default", MavenPublication::class) {
+            from(kotlin.target.components.single())
+            artifact(tasks.getByName("kotlinSourcesJar"))
+        }
+    }
+    repositories {
+        maven("${buildDir}/repo")
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-model-in-old-plugin/settings.gradle.kts

@@ -0,0 +1,8 @@
+pluginManagement {
+    repositories {
+        mavenLocal()
+        gradlePluginPortal()
+    }
+}
+
+rootProject.name = "new-model"

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-model-in-old-plugin/src/benchmark/kotlin/ABenchmark.kt

@@ -0,0 +1,8 @@
+package com.example
+
+fun main() {
+    val a = A()
+    val f = a::f
+    f()
+    println("${a::f.name} ran at the speed of light")
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-model-in-old-plugin/src/main/kotlin/A.kt

@@ -0,0 +1,5 @@
+package com.example
+
+class A {
+    fun f(): String = "hello".also(::println)
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-model-in-old-plugin/src/test/kotlin/ATest.kt

@@ -0,0 +1,11 @@
+package com.example
+
+import kotlin.test.*
+
+class ATest {
+    @Test
+    fun testF() {
+        val f = A().f()
+        assertEquals("hello", f)
+    }
+}