Mark only unreachable parts of element if it has reachable parts

like for 'return todo()' mark only 'return'

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInUnaryExpr.kt

@@ -0,0 +1,15 @@
+fun testPrefix() {
+    fun Any.not() {}
+    <!UNREACHABLE_CODE!>!<!>todo()
+}
+
+fun testPostfixWithCall(n: Nothing) {
+    fun Nothing.inc(): Nothing = this
+    n<!UNREACHABLE_CODE!>++<!>
+}
+
+fun testPostfixSpecial() {
+    todo()<!UNNECESSARY_NOT_NULL_ASSERTION, UNREACHABLE_CODE!>!!<!>
+}
+
+fun todo() = throw Exception()