Annotated the return type of 'elvis' function with @Exact

fun <T> ELVIS(T?, T): @Exact T

compiler/testData/diagnostics/tests/resolve/specialConstructions/inferenceForElvis.kt

@@ -0,0 +1,8 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE
+// !CHECK_TYPE
+
+fun <T: Any> foo(f: (T) -> Unit): T? = null // T is used only as return type
+fun test() {
+    val x = foo { it checkType { _<String>() }} ?: "" // foo() is inferred as foo<String>, which isn't very good
+    val y: Any = foo { it checkType { _<Any>() } } ?: "" // but for now it's fixed by specifying expected type
+}

compiler/testData/diagnostics/tests/resolve/specialConstructions/inferenceForElvis.txt

@@ -0,0 +1,4 @@
+package
+
+public fun </*0*/ T : kotlin.Any> foo(/*0*/ f: (T) -> kotlin.Unit): T?
+public fun test(): kotlin.Unit