feat: better error reporting for missing link alt text

this can only really happen using a position as a link target

crates/typst-layout/src/rules.rs

@@ -216,13 +216,19 @@ const TERMS_RULE: ShowFn<TermsElem> = |elem, _, styles| {
 const LINK_MARKER_RULE: ShowFn<LinkMarker> = |elem, _, _| Ok(elem.body.clone());
 
 const LINK_RULE: ShowFn<LinkElem> = |elem, engine, styles| {
+    let span = elem.span();
     let body = elem.body.clone();
     let dest = elem.dest.resolve(engine.introspector).at(elem.span())?;
     let alt = match elem.alt.get_cloned(styles) {
         Some(alt) => Some(alt),
         None => dest.alt_text(engine, styles)?,
     };
-    Ok(body.linked(dest, alt))
+    // Manually construct link marker that spans the whole link elem, not just
+    // the body.
+    Ok(LinkMarker::new(body, dest.clone(), alt)
+        .pack()
+        .spanned(span)
+        .set(LinkElem::current, Some(dest)))
 };
 
 const HEADING_RULE: ShowFn<HeadingElem> = |elem, engine, styles| {

crates/typst-library/src/foundations/content/mod.rs

@@ -479,7 +479,7 @@ impl Content {
     /// Link the content somewhere.
     pub fn linked(self, dest: Destination, alt: Option<EcoString>) -> Self {
         let span = self.span();
-        LinkMarker::new(self, dest.clone(), alt, span)
+        LinkMarker::new(self, dest.clone(), alt)
             .pack()
             .spanned(span)
             .set(LinkElem::current, Some(dest))
@@ -797,9 +797,6 @@ pub struct LinkMarker {
     #[internal]
     #[required]
     pub alt: Option<EcoString>,
-    #[internal]
-    #[required]
-    pub span: Span,
 }
 
 impl Construct for LinkMarker {

crates/typst-pdf/src/convert.rs

@@ -617,7 +617,7 @@ fn convert_error(
             let span = to_span(*loc);
             error!(
                 span, "{prefix} missing annotation alt text";
-                hint: "please report this as a bug"
+                hint: "manually add alt text to your links"
             )
         }
         ValidationError::MissingAltText(loc) => {

crates/typst-pdf/src/link.rs

@@ -71,7 +71,7 @@ pub(crate) fn handle_link(
             let (alt, span) = if let Some((link, nodes)) = tagging_ctx {
                 nodes.push(TagNode::Placeholder(placeholder));
                 let alt = link.alt.as_ref().map(EcoString::to_string);
-                (alt, link.span)
+                (alt, link.span())
             } else {
                 (None, Span::detached())
             };

crates/typst-pdf/src/tags/mod.rs

@@ -535,10 +535,10 @@ impl TagStack {
 
     pub(crate) fn find_parent_link(
         &mut self,
-    ) -> Option<(LinkId, &LinkMarker, &mut Vec<TagNode>)> {
+    ) -> Option<(LinkId, &Packed<LinkMarker>, &mut Vec<TagNode>)> {
         self.0.iter_mut().rev().find_map(|e| {
             let (link_id, link) = e.kind.as_link()?;
-            Some((link_id, link.as_ref(), &mut e.nodes))
+            Some((link_id, link, &mut e.nodes))
         })
     }