Fix block spacing

library/src/layout/mod.rs

@@ -466,8 +466,12 @@ impl<'a> FlowBuilder<'a> {
                 self.0.push(spacing.pack(), styles);
             }
 
-            let above = BlockElem::above_in(styles);
-            let below = BlockElem::below_in(styles);
+            let (above, below) = if let Some(block) = content.to::<BlockElem>() {
+                (block.above(styles), block.below(styles))
+            } else {
+                (BlockElem::above_in(styles), BlockElem::below_in(styles))
+            };
+
             self.0.push(above.pack(), styles);
             self.0.push(content.clone(), styles);
             self.0.push(below.pack(), styles);

tests/typ/layout/block-spacing.typ

@@ -0,0 +1,9 @@
+// Test block spacing.
+
+---
+#set block(spacing: 10pt)
+Hello
+
+There
+
+#block(spacing: 20pt)[Further down]