Support smart casts for functions of local variable delegates

compiler/testData/diagnostics/tests/delegatedProperty/localWithSmartCast.kt

@@ -0,0 +1,15 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+interface A {
+    operator fun getValue(x: Any?, y: Any?): Any?
+}
+
+interface B : A {
+    override fun getValue(x: Any?, y: Any?): Int
+}
+
+fun test(a: A) {
+    if (a is B) {
+        val x: Int by <!DEBUG_INFO_SMARTCAST!>a<!>
+    }
+}