fix overflow due to multiline error span

Author: oli-obk

src/libsyntax/errors/emitter.rs

@@ -518,7 +518,7 @@ impl EmitterWriter {
                 };
                 let lo = self.cm.lookup_char_pos(sp.lo);
                 let hi = self.cm.lookup_char_pos(sp.hi);
-                let elide_sp = (lo.line - hi.line) > MAX_SP_LINES;
+                let elide_sp = (hi.line - lo.line) > MAX_SP_LINES;
 
                 let line_num = line.line_index + 1;
                 if !(lo.line <= line_num && hi.line >= line_num) {