Add version to Binding deprecation warnings

This allows displaying a hint in which the version a binding may be
removed in. It helps to signal how urgent a package update may be to
package authors.

crates/typst-library/src/diag.rs

@@ -234,18 +234,23 @@ impl From<SyntaxError> for SourceDiagnostic {
 
 /// Destination for a deprecation message when accessing a deprecated value.
 pub trait DeprecationSink {
-    /// Emits the given deprecation message into this sink.
-    fn emit(self, message: &str);
+    /// Emits the given deprecation message into this sink alongside a version
+    /// in which the deprecated item is planned to be removed.
+    fn emit(self, message: &str, until: Option<&str>);
 }
 
 impl DeprecationSink for () {
-    fn emit(self, _: &str) {}
+    fn emit(self, _: &str, _: Option<&str>) {}
 }
 
 impl DeprecationSink for (&mut Engine<'_>, Span) {
     /// Emits the deprecation message as a warning.
-    fn emit(self, message: &str) {
-        self.0.sink.warn(SourceDiagnostic::warning(self.1, message));
+    fn emit(self, message: &str, version: Option<&str>) {
+        self.0.sink.warn(
+            SourceDiagnostic::warning(self.1, message).with_hints(
+                version.map(|v| eco_format!("this will be removed in {}", v)),
+            ),
+        );
     }
 }
 

crates/typst-library/src/foundations/scope.rs

@@ -255,6 +255,10 @@ pub struct Binding {
     category: Option<Category>,
     /// A deprecation message for the definition.
     deprecation: Option<&'static str>,
+    /// A version in which the deprecated binding is planned to be removed.
+    ///
+    /// This is ignored if `deprecation` is `None`.
+    until: Option<&'static str>,
 }
 
 /// The different kinds of slots.
@@ -275,6 +279,7 @@ impl Binding {
             kind: BindingKind::Normal,
             category: None,
             deprecation: None,
+            until: None,
         }
     }
 
@@ -289,6 +294,14 @@ impl Binding {
         self
     }
 
+    /// Set the version in which the binding is planned to be removed.
+    ///
+    /// This is ignored if [`Binding::deprecated`] isn't also set.
+    pub fn until(&mut self, version: &'static str) -> &mut Self {
+        self.until = Some(version);
+        self
+    }
+
     /// Read the value.
     pub fn read(&self) -> &Value {
         &self.value
@@ -301,7 +314,7 @@ impl Binding {
     /// - pass `(&mut engine, span)` to emit a warning into the engine.
     pub fn read_checked(&self, sink: impl DeprecationSink) -> &Value {
         if let Some(message) = self.deprecation {
-            sink.emit(message);
+            sink.emit(message, self.until);
         }
         &self.value
     }

crates/typst-library/src/foundations/symbol.rs

@@ -151,7 +151,7 @@ impl Symbol {
                 modifiers.best_match_in(list.variants().map(|(m, _, d)| (m, d)))
             {
                 if let Some(message) = deprecation {
-                    sink.emit(message)
+                    sink.emit(message, None)
                 }
                 return Ok(self);
             }