interrupt_styles: Check all potential style matches (#4345)

crates/typst/src/realize/behaviour.rs

@@ -231,7 +231,13 @@ impl<'a> Default for BehavedBuilder<'a> {
 /// A sequence of elements with associated styles.
 #[derive(Clone, PartialEq, Hash)]
 pub struct StyleVec {
+    /// The elements themselves.
     elements: EcoVec<Content>,
+    /// A run-length encoded list of style lists.
+    ///
+    /// Each element is a (styles, count) pair. Any elements whose
+    /// style falls after the end of this list is considered to
+    /// have an empty style list.
     styles: EcoVec<(Styles, usize)>,
 }
 

crates/typst/src/realize/mod.rs

@@ -220,16 +220,19 @@ impl<'a, 'v, 't> Builder<'a, 'v, 't> {
             {
                 bail!(span, "document set rules must appear before any content");
             }
-        } else if let Some(Some(span)) = local.interruption::<PageElem>() {
+        }
+        if let Some(Some(span)) = local.interruption::<PageElem>() {
             if self.doc.is_none() {
                 bail!(span, "page configuration is not allowed inside of containers");
             }
             self.interrupt_page(outer, false)?;
-        } else if local.interruption::<ParElem>().is_some()
+        }
+        if local.interruption::<ParElem>().is_some()
             || local.interruption::<AlignElem>().is_some()
         {
             self.interrupt_par()?;
-        } else if local.interruption::<ListElem>().is_some()
+        }
+        if local.interruption::<ListElem>().is_some()
             || local.interruption::<EnumElem>().is_some()
             || local.interruption::<TermsElem>().is_some()
         {

tests/suite/layout/page.typ

@@ -258,3 +258,11 @@ Default page numbers now.
 Hi
 #pagebreak()
 = Second
+
+--- issue-4340-set-document-and-page ---
+// Test custom page fields being applied on the last page
+// if the document has custom fields.
+#set document(author: "")
+#set page(fill: gray)
+text
+#pagebreak()