Link to label

8 files changed, 109 insertions, 38 deletions

diff --git a/docs/src/general/changelog.md b/docs/src/general/changelog.md
index 958c3e4a..cbd6b039 100644
--- a/docs/src/general/changelog.md
+++ b/docs/src/general/changelog.md
@@ -7,9 +7,12 @@ description: |
 # Changelog
 ## Unreleased
 - Added [`polygon`]($func/polygon) function
-- Reduced maximum function call depth from 256 to 64
+- The [`link`]($func/link) function now accepts [labels]($func/label)
+- Fixed styling of text operators in math
+- Fixed invalid parsing of language tag in raw block with a single backtick
 - CLI now returns with non-zero status code if there is an error
 - CLI now watches the root directory instead of the current one
+- Reduced maximum function call depth from 256 to 64
 
 ## March 28, 2023
 - **Breaking:** Enumerations now require a space after their marker, that is,
diff --git a/library/src/meta/bibliography.rs b/library/src/meta/bibliography.rs
index 2a0a96b1..c9532915 100644
--- a/library/src/meta/bibliography.rs
+++ b/library/src/meta/bibliography.rs
@@ -614,7 +614,8 @@ fn format_display_string(
                 Formatting::Bold => content.strong(),
                 Formatting::Italic => content.emph(),
                 Formatting::Link(link) => {
-                    LinkElem::new(Destination::Url(link.as_str().into()), content).pack()
+                    LinkElem::new(Destination::Url(link.as_str().into()).into(), content)
+                        .pack()
                 }
             };
         }
diff --git a/library/src/meta/link.rs b/library/src/meta/link.rs
index d8cb779a..135ce0af 100644
--- a/library/src/meta/link.rs
+++ b/library/src/meta/link.rs
@@ -13,6 +13,7 @@ use crate::text::{Hyphenate, TextElem};
 /// #show link: underline
 ///
 /// https://example.com \
+///
 /// #link("https://example.com") \
 /// #link("https://example.com")[
 ///   See example.com
@@ -25,7 +26,7 @@ use crate::text::{Hyphenate, TextElem};
 ///
 /// Display: Link
 /// Category: meta
-#[element(Show, Finalize)]
+#[element(Show)]
 pub struct LinkElem {
     /// The destination the link points to.
     ///
@@ -34,33 +35,42 @@ pub struct LinkElem {
     ///   omitted, the email address or phone number will be the link's body,
     ///   without the scheme.
     ///
-    /// - To link to another part of the document, `dest` can take one of two
-    ///   forms: A [`location`]($func/locate) or a dictionary with a `page` key
-    ///   of type `integer` and `x` and `y` coordinates of type `length`. Pages
-    ///   are counted from one, and the coordinates are relative to the page's
-    ///   top left corner.
+    /// - To link to another part of the document, `dest` can take one of three
+    ///   forms:
+    ///   - A [label]($func/label) attached to an element. If you also want
+    ///     automatic text for the link based on the element, consider using
+    ///     a [reference]($func/ref) instead.
+    ///
+    ///   - A [location]($func/locate) resulting from a [`locate`]($func/locate)
+    ///     call or [`query`]($func/query).
+    ///
+    ///   - A dictionary with a `page` key of type [integer]($type/integer) and
+    ///     `x` and `y` coordinates of type [length]($type/length). Pages are
+    ///     counted from one, and the coordinates are relative to the page's top
+    ///     left corner.
     ///
     /// ```example
+    /// = Introduction <intro>
     /// #link("mailto:hello@typst.app") \
+    /// #link(<intro>)[Go to intro] \
     /// #link((page: 1, x: 0pt, y: 0pt))[
     ///   Go to top
     /// ]
     /// ```
     #[required]
     #[parse(
-        let dest = args.expect::<Destination>("destination")?;
+        let dest = args.expect::<LinkTarget>("destination")?;
         dest.clone()
     )]
-    pub dest: Destination,
+    pub dest: LinkTarget,
 
-    /// How the link is represented.
+    /// The content that should become a link.
     ///
-    /// The content that should become a link. If `dest` is an URL string, the
-    /// parameter can be omitted. In this case, the URL will be shown as the
-    /// link.
+    /// If `dest` is an URL string, the parameter can be omitted. In this case,
+    /// the URL will be shown as the link.
     #[required]
     #[parse(match &dest {
-        Destination::Url(url) => match args.eat()? {
+        LinkTarget::Dest(Destination::Url(url)) => match args.eat()? {
             Some(body) => body,
             None => body_from_url(url),
         },
@@ -73,21 +83,28 @@ impl LinkElem {
     /// Create a link element from a URL with its bare text.
     pub fn from_url(url: EcoString) -> Self {
         let body = body_from_url(&url);
-        Self::new(Destination::Url(url), body)
+        Self::new(LinkTarget::Dest(Destination::Url(url)), body)
     }
 }
 
 impl Show for LinkElem {
-    fn show(&self, _: &mut Vt, _: StyleChain) -> SourceResult<Content> {
-        Ok(self.body())
-    }
-}
+    fn show(&self, vt: &mut Vt, _: StyleChain) -> SourceResult<Content> {
+        let body = self.body();
+        let dest = match self.dest() {
+            LinkTarget::Dest(dest) => dest,
+            LinkTarget::Label(label) => {
+                if !vt.introspector.init() {
+                    return Ok(body);
+                }
+
+                let elem = vt.introspector.query_label(&label).at(self.span())?;
+                Destination::Location(elem.location().unwrap())
+            }
+        };
 
-impl Finalize for LinkElem {
-    fn finalize(&self, realized: Content, _: StyleChain) -> Content {
-        realized
-            .linked(self.dest())
-            .styled(TextElem::set_hyphenate(Hyphenate(Smart::Custom(false))))
+        Ok(body
+            .linked(dest)
+            .styled(TextElem::set_hyphenate(Hyphenate(Smart::Custom(false)))))
     }
 }
 
@@ -99,3 +116,29 @@ fn body_from_url(url: &EcoString) -> Content {
     let shorter = text.len() < url.len();
     TextElem::packed(if shorter { text.into() } else { url.clone() })
 }
+
+/// A target where a link can go.
+#[derive(Debug, Clone)]
+pub enum LinkTarget {
+    Dest(Destination),
+    Label(Label),
+}
+
+cast_from_value! {
+    LinkTarget,
+    v: Destination => Self::Dest(v),
+    v: Label => Self::Label(v),
+}
+
+cast_to_value! {
+    v: LinkTarget => match v {
+        LinkTarget::Dest(v) => v.into(),
+        LinkTarget::Label(v) => v.into(),
+    }
+}
+
+impl From<Destination> for LinkTarget {
+    fn from(dest: Destination) -> Self {
+        Self::Dest(dest)
+    }
+}
diff --git a/library/src/meta/reference.rs b/library/src/meta/reference.rs
index 14246436..0b317db0 100644
--- a/library/src/meta/reference.rs
+++ b/library/src/meta/reference.rs
@@ -11,6 +11,9 @@ use crate::text::TextElem;
 ///
 /// Reference syntax can also be used to [cite]($func/cite) from a bibliography.
 ///
+/// If you just want to link to a labelled element and not get an automatic
+/// textual reference, consider using the [`link`]($func/link) function instead.
+///
 /// # Example
 /// ```example
 /// #set heading(numbering: "1.")
@@ -93,24 +96,17 @@ impl Show for RefElem {
         }
 
         let target = self.target();
-        let matches = vt.introspector.query(Selector::Label(self.target()));
+        let elem = vt.introspector.query_label(&self.target());
 
         if BibliographyElem::has(vt, &target.0) {
-            if !matches.is_empty() {
+            if elem.is_ok() {
                 bail!(self.span(), "label occurs in the document and its bibliography");
             }
 
             return Ok(self.to_citation(styles).pack());
         }
 
-        let [elem] = matches.as_slice() else {
-            bail!(self.span(), if matches.is_empty() {
-                "label does not exist in the document"
-            } else {
-                "label occurs multiple times in the document"
-            });
-        };
-
+        let elem = elem.at(self.span())?;
         if !elem.can::<dyn Locatable>() {
             bail!(self.span(), "cannot reference {}", elem.func().name());
         }
diff --git a/src/model/introspect.rs b/src/model/introspect.rs
index f0ff1169..31786d5b 100644
--- a/src/model/introspect.rs
+++ b/src/model/introspect.rs
@@ -3,9 +3,11 @@ use std::hash::Hash;
 use std::num::NonZeroUsize;
 
 use super::{Content, Selector};
+use crate::diag::StrResult;
 use crate::doc::{Frame, FrameItem, Meta, Position};
 use crate::eval::cast_from_value;
 use crate::geom::{Point, Transform};
+use crate::model::Label;
 use crate::util::NonZeroExt;
 
 /// Stably identifies an element in the document across multiple layout passes.
@@ -160,6 +162,18 @@ impl Introspector {
             .collect()
     }
 
+    /// Query for a unique element with the label.
+    pub fn query_label(&self, label: &Label) -> StrResult<Content> {
+        let mut found = None;
+        for elem in self.all().filter(|elem| elem.label() == Some(label)) {
+            if found.is_some() {
+                return Err("label occurs multiple times in the document".into());
+            }
+            found = Some(elem.clone());
+        }
+        found.ok_or_else(|| "label does not exist in the document".into())
+    }
+
     /// The total number pages.
     pub fn pages(&self) -> NonZeroUsize {
         NonZeroUsize::new(self.pages).unwrap_or(NonZeroUsize::ONE)
diff --git a/src/model/realize.rs b/src/model/realize.rs
index 10e1b0e2..e96e0dc1 100644
--- a/src/model/realize.rs
+++ b/src/model/realize.rs
@@ -176,9 +176,8 @@ pub trait Show {
 
 /// Post-process an element after it was realized.
 pub trait Finalize {
-    /// Finalize the fully realized form of the element. Use this for effects that
-    /// should work even in the face of a user-defined show rule, for example
-    /// the linking behaviour of a link element.
+    /// Finalize the fully realized form of the element. Use this for effects
+    /// that should work even in the face of a user-defined show rule.
     fn finalize(&self, realized: Content, styles: StyleChain) -> Content;
 }
 
diff --git a/tests/ref/meta/link.png b/tests/ref/meta/link.png
index d80acc6f..4e182e9b 100644
--- a/tests/ref/meta/link.png
+++ b/tests/ref/meta/link.png
diff --git a/tests/typ/meta/link.typ b/tests/typ/meta/link.typ
index 3ceb261d..de4c91c9 100644
--- a/tests/typ/meta/link.typ
+++ b/tests/typ/meta/link.typ
@@ -44,3 +44,18 @@ My cool #box(move(dx: 0.7cm, dy: 0.7cm, rotate(10deg, scale(200%, mylink))))
 ---
 // Link to page one.
 #link((page: 1, x: 10pt, y: 20pt))[Back to the start]
+
+---
+// Test link to label.
+Text <hey>
+#link(<hey>)[Go to text.]
+
+---
+// Error: 2-20 label does not exist in the document
+#link(<hey>)[Nope.]
+
+---
+Text <hey>
+Text <hey>
+// Error: 2-20 label occurs multiple times in the document
+#link(<hey>)[Nope.]