Rewrite std_links

This rewrites std_links for two major changes:

- Uses pulldown_cmark to parse the markdown instead of using regular
  expressions. The RegEx approach was just too unreliable.
- Call rustdoc only once, instead of once per chapter. The overhead of
  calling rustdoc is significant, and calling it for each chapter was
  extremely slow.

  Unfortunately the error messages are a little worse now, since it
  doesn't show which chapter a bad link came from. I'm uncertain how to
  make that better.

Author: ehuss

mdbook-spec/Cargo.lock

@@ -13,6 +13,8 @@ anyhow = "1.0.79"
 mdbook = { version = "0.4.36", default-features = false }
 once_cell = "1.19.0"
 pathdiff = "0.2.1"
+# Try to keep in sync with mdbook.
+pulldown-cmark = { version = "0.10.3", default-features = false }
 regex = "1.9.4"
 semver = "1.0.21"
 serde_json = "1.0.113"

mdbook-spec/Cargo.toml

@@ -154,7 +154,6 @@ impl Preprocessor for Spec {
             }
             ch.content = self.rule_definitions(&ch, &mut found_rules);
             ch.content = self.admonitions(&ch);
-            ch.content = std_links::std_links(&ch);
         });
         // This is a separate pass because it relies on the modifications of
         // the previous passes.
@@ -167,6 +166,10 @@ impl Preprocessor for Spec {
             }
             ch.content = self.auto_link_references(&ch, &found_rules);
         });
+        // Final pass will resolve everything as a std link (or error if the
+        // link is unknown).
+        std_links::std_links(&mut book);
+
         Ok(book)
     }
 }