Merge 01f73c35ed279d26678fe9c991ef55a0e44a1b76 into b036fd97ab2c1cdc003b50eea7850279a1a7601f

Haste is the enemy of correctness

crates/typst-eval/src/code.rs

@@ -7,6 +7,7 @@ use typst_library::foundations::{
 };
 use typst_library::introspection::{Counter, State};
 use typst_syntax::ast::{self, AstNode};
+use typst_syntax::Span;
 use typst_utils::singleton;
 
 use crate::{CapturesVisitor, Eval, FlowEvent, Vm};
@@ -284,8 +285,19 @@ impl Eval for ast::CodeBlock<'_> {
     type Output = Value;
 
     fn eval(self, vm: &mut Vm) -> SourceResult<Self::Output> {
+        let body = self.body();
+        match body.exprs().next_back() {
+            Some(expr @ ast::Expr::ShowRule(_)) => {
+                warn_for_useless_rule(&mut vm.engine, expr.span(), "show")
+            }
+            Some(expr @ ast::Expr::SetRule(_)) => {
+                warn_for_useless_rule(&mut vm.engine, expr.span(), "set")
+            }
+            _ => {}
+        }
+
         vm.scopes.enter();
-        let output = self.body().eval(vm)?;
+        let output = body.eval(vm)?;
         vm.scopes.exit();
         Ok(output)
     }
@@ -389,3 +401,12 @@ fn warn_for_discarded_content(engine: &mut Engine, event: &FlowEvent, joined: &V
 
     engine.sink.warn(warning);
 }
+
+/// Emits a warning when a set or show rule has no effect.
+fn warn_for_useless_rule(engine: &mut Engine, span: Span, kind: &str) {
+    engine.sink.warn(warning!(
+        span,
+        "{kind} rule has no effect";
+        hint: "a {kind} rule is only in effect until the end of the surrounding code block"
+    ));
+}

tests/suite/foundations/context.typ

@@ -48,4 +48,5 @@
   let n = query(<a>).len()
   let fonts = ("nope", "Roboto")
   set text(font: fonts.at(n))
+  []
 }

tests/suite/model/document.typ

@@ -51,4 +51,5 @@ Hello
 #context {
   set document(author: "Changed") if "Normal" in document.author
   set document(title: "Changed") if document.title ==  "Normal"
+  []
 }

tests/suite/styling/in-block.typ

@@ -0,0 +1,12 @@
+--- warn-show-set-last-in-block ---
+#{
+  // Warning: 3-16 show rule has no effect
+  // Hint: 3-16 a show rule is only in effect until the end of the surrounding code block
+  show "a": "b"
+}
+
+#{
+  // Warning: 3-17 set rule has no effect
+  // Hint: 3-17 a set rule is only in effect until the end of the surrounding code block
+  set text(blue)
+}