KT-47939 basic fun interface constructor reference box test

compiler/testData/codegen/box/callableReference/funInterfaceConstructor/funInterfaceConstructor.kt

@@ -0,0 +1,13 @@
+// !LANGUAGE: +AllowKotlinFunInterfaceConstructorReference
+// IGNORE_BACKEND: JVM, JS
+//  ^ feature supported in IR-based backends only
+
+fun interface KSupplier<T> {
+    fun get(): T
+}
+
+val ks: (() -> String) -> KSupplier<String> =
+    ::KSupplier
+
+fun box(): String =
+    ks { "OK" }.get()