Fix _str.bytes to trivial version.

src/rt/rust_builtin.cpp

@@ -219,6 +219,32 @@ str_buf(rust_task *task, rust_str *s)
     return (char const *)&s->data[0];
 }
 
+extern "C" CDECL rust_vec*
+str_vec(rust_task *task, rust_str *s)
+{
+    // FIXME: this should just upref s and return it, but we
+    // accidentally made too much of the language and runtime know
+    // and care about the difference between str and vec (trailing null);
+    // eliminate these differences and then rewrite this back to just
+    // the following:
+    //
+    // if (s->ref_count != CONST_REFCOUNT)
+    //    s->ref();
+    // return s;
+
+    rust_str *v =
+        vec_alloc_with_data(task,
+                            s->fill - 1,
+                            s->fill - 1,
+                            1,
+                            (s->fill - 1) ? (void*)s->data : NULL);
+    if (!v) {
+        task->fail(2);
+        return NULL;
+    }
+    return v;
+}
+
 extern "C" CDECL size_t
 str_byte_len(rust_task *task, rust_str *s)
 {