Fix #190 for submodules

src/missed_spans.rs

@@ -44,7 +44,7 @@ impl<'a> FmtVisitor<'a> {
 
         if start == end {
             // Do nothing if this is the beginning of the file.
-            if start == BytePos(0) {
+            if start == self.codemap.lookup_char_pos(start).file.start_pos {
                 return;
             }
             process_last_snippet(self, "", "");

tests/source/mod-2.rs

@@ -1,3 +1,4 @@
 // Some nested mods
 
 mod nestedmod;
+mod no_new_line_beginning;

tests/source/no_new_line_beginning.rs

@@ -0,0 +1,2 @@
+fn main() {
+}

tests/target/mod-2.rs

@@ -1,3 +1,4 @@
 // Some nested mods
 
 mod nestedmod;
+mod no_new_line_beginning;