Fix index bug in write_snippet_inner

src/missed_spans.rs

@@ -173,7 +173,7 @@ impl<'a> FmtVisitor<'a> {
                         if !subslice
                                .split('\n')
                                .map(|s| s.trim_left())
-                               .any(|s| s.len() > 2 && &s[0..2] == "/*") {
+                               .any(|s| s.len() >= 2 && &s[0..2] == "/*") {
                             // Add a newline after line comments
                             self.buffer.push_str("\n");
                         }

tests/target/issue-1598.rs

@@ -0,0 +1,6 @@
+fn main() {
+    //foo
+    /*
+     */
+    format!("hello");
+}