Mark only unreachable parts of element if it has reachable parts

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

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

@@ -0,0 +1,24 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun unreachable0() {
+    return
+    <!UNREACHABLE_CODE!>return todo()<!>
+}
+
+fun unreachable2() {
+    return
+    <!UNREACHABLE_CODE!>val a = todo()<!>
+}
+
+fun unreachable3() {
+    return
+    <!UNREACHABLE_CODE!>bar(todo())<!>
+}
+
+fun unreachable4(array: Array<Any>) {
+    return
+    <!UNREACHABLE_CODE!>array[todo()]<!>
+}
+
+fun bar(a: Any) {}
+fun todo() = throw Exception()