Fix line alignment

Fixes #1398. How this works for the other shapes is a hack, but the line was missing from that hack.

library/src/layout/flow.rs

@@ -6,7 +6,8 @@ use super::{
 use crate::meta::{FootnoteElem, FootnoteEntry};
 use crate::prelude::*;
 use crate::visualize::{
-    CircleElem, EllipseElem, ImageElem, PathElem, PolygonElem, RectElem, SquareElem,
+    CircleElem, EllipseElem, ImageElem, LineElem, PathElem, PolygonElem, RectElem,
+    SquareElem,
 };
 
 /// Arrange spacing, paragraphs and block-level elements into a flow.
@@ -45,7 +46,8 @@ impl Layout for FlowElem {
                 layouter.layout_spacing(vt, elem, styles)?;
             } else if let Some(elem) = child.to::<ParElem>() {
                 layouter.layout_par(vt, elem, styles)?;
-            } else if child.is::<RectElem>()
+            } else if child.is::<LineElem>()
+                || child.is::<RectElem>()
                 || child.is::<SquareElem>()
                 || child.is::<EllipseElem>()
                 || child.is::<CircleElem>()

library/src/layout/mod.rs

@@ -58,7 +58,8 @@ use crate::prelude::*;
 use crate::shared::BehavedBuilder;
 use crate::text::{LinebreakElem, SmartQuoteElem, SpaceElem, TextElem};
 use crate::visualize::{
-    CircleElem, EllipseElem, ImageElem, PathElem, PolygonElem, RectElem, SquareElem,
+    CircleElem, EllipseElem, ImageElem, LineElem, PathElem, PolygonElem, RectElem,
+    SquareElem,
 };
 
 /// Hook up all layout definitions.
@@ -248,6 +249,7 @@ fn realize_block<'a>(
     styles: StyleChain<'a>,
 ) -> SourceResult<(Content, StyleChain<'a>)> {
     if content.can::<dyn Layout>()
+        && !content.is::<LineElem>()
         && !content.is::<RectElem>()
         && !content.is::<SquareElem>()
         && !content.is::<EllipseElem>()

tests/typ/bugs/line-align.typ

@@ -0,0 +1,5 @@
+// Test right-aligning a line and a rectangle.
+
+---
+#align(right, line(length: 30%))
+#align(right, rect())