rustdoc: Fix generation of impl links. Closes #1953

Author: brson

Diff for: src/rustdoc/markdown_index_pass.rs

@@ -86,6 +86,12 @@ fn pandoc_header_id(header: str) -> str {
     fn remove_punctuation(s: str) -> str {
         let s = str::replace(s, "<", "");
         let s = str::replace(s, ">", "");
+        let s = str::replace(s, "[", "");
+        let s = str::replace(s, "]", "");
+        let s = str::replace(s, "(", "");
+        let s = str::replace(s, ")", "");
+        let s = str::replace(s, "@", "");
+        let s = str::replace(s, "~", "");
         ret s;
     }
     fn replace_with_hyphens(s: str) -> str {
@@ -97,8 +103,9 @@ fn pandoc_header_id(header: str) -> str {
 }
 
 #[test]
-fn should_remove_brackets_from_headers() {
+fn should_remove_punctuation_from_headers() {
     assert pandoc_header_id("impl foo of bar<A>") == "impl-foo-of-bara";
+    assert pandoc_header_id("fn@([~A])") == "fna";
 }
 
 #[test]