From a517a08d2fc50706654bb649db496b21b47f421b Mon Sep 17 00:00:00 2001
From: T0mstone <realt0mstone@gmail.com>
Date: Sat, 22 Mar 2025 22:31:51 +0100
Subject: [PATCH] Warn on last show/set rule in block

---
 crates/typst-eval/src/code.rs    | 13 +++++++++++++
 tests/suite/styling/in-block.typ | 12 ++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 tests/suite/styling/in-block.typ

diff --git a/crates/typst-eval/src/code.rs b/crates/typst-eval/src/code.rs
index 9078418e4..56c96a071 100644
--- a/crates/typst-eval/src/code.rs
+++ b/crates/typst-eval/src/code.rs
@@ -285,6 +285,19 @@ impl Eval for ast::CodeBlock<'_> {
 
     fn eval(self, vm: &mut Vm) -> SourceResult<Self::Output> {
         vm.scopes.enter();
+        if let Some((span, kind)) =
+            self.body().exprs().next_back().and_then(|x| match x {
+                ast::Expr::ShowRule(_) => Some((x.span(), "show")),
+                ast::Expr::SetRule(_) => Some((x.span(), "set")),
+                _ => None,
+            })
+        {
+            vm.engine.sink.warn(typst_library::diag::warning!(
+                span,
+                "{kind} rule has no effect";
+                hint: "See https://typst.app/docs/tutorial/making-a-template/#set-and-show-rules"
+            ));
+        }
         let output = self.body().eval(vm)?;
         vm.scopes.exit();
         Ok(output)
diff --git a/tests/suite/styling/in-block.typ b/tests/suite/styling/in-block.typ
new file mode 100644
index 000000000..e13a2d3a8
--- /dev/null
+++ b/tests/suite/styling/in-block.typ
@@ -0,0 +1,12 @@
+--- warn-show-set-last-in-block ---
+#{
+// Warning: 1-14 show rule has no effect
+// Hint: 1-14 See https://typst.app/docs/tutorial/making-a-template/#set-and-show-rules
+show "a": "b"
+}
+
+#{
+// Warning: 1-15 set rule has no effect
+// Hint: 1-15 See https://typst.app/docs/tutorial/making-a-template/#set-and-show-rules
+set text(blue)
+}