Fix GFM autolink literals after tabs

Closes GH-18.

Co-authored-by: Christian Murphy <christian.murphy.42@gmail.com>

Author: wooorm

src/event.rs

@@ -3512,8 +3512,11 @@ impl Point {
                 b'\n' | b'\r' => unreachable!("cannot move past line endings"),
                 b'\t' => {
                     let remainder = next.column % TAB_SIZE;
-                    debug_assert_ne!(remainder, 0, "expected remainder larger than `0`");
-                    let vs = TAB_SIZE - remainder;
+                    let vs = if remainder == 0 {
+                        0
+                    } else {
+                        TAB_SIZE - remainder
+                    };
                     next.index += 1;
                     next.column += 1 + vs;
                 }

tests/fuzz.rs

@@ -74,5 +74,29 @@ fn fuzz() -> Result<(), String> {
         "7: lazy container lines almost starting fenced code (GH-19)"
     );
 
+    assert_eq!(
+        to_html_with_options("a\tb@c.d", &Options::gfm()),
+        Ok("<p>a\t<a href=\"mailto:b@c.d\">b@c.d</a></p>".into()),
+        "8-a: autolink literals after tabs (GH-18)"
+    );
+
+    assert_eq!(
+        to_html_with_options("aa\tb@c.d", &Options::gfm()),
+        Ok("<p>aa\t<a href=\"mailto:b@c.d\">b@c.d</a></p>".into()),
+        "8-b: autolink literals after tabs (GH-18)"
+    );
+
+    assert_eq!(
+        to_html_with_options("aaa\tb@c.d", &Options::gfm()),
+        Ok("<p>aaa\t<a href=\"mailto:b@c.d\">b@c.d</a></p>".into()),
+        "8-c: autolink literals after tabs (GH-18)"
+    );
+
+    assert_eq!(
+        to_html_with_options("aaaa\tb@c.d", &Options::gfm()),
+        Ok("<p>aaaa\t<a href=\"mailto:b@c.d\">b@c.d</a></p>".into()),
+        "8-d: autolink literals after tabs (GH-18)"
+    );
+
     Ok(())
 }