Prevent silent swallowing of return expressions trailing arguments (#2545)

Fixes #2104

crates/typst-syntax/src/parser.rs

@@ -605,6 +605,7 @@ fn embedded_code_expr(p: &mut Parser) {
             | SyntaxKind::Show
             | SyntaxKind::Import
             | SyntaxKind::Include
+            | SyntaxKind::Return
     );
 
     let prev = p.prev_end();

tests/typ/compiler/return.typ

@@ -80,3 +80,10 @@
 ]
 
 #test(f(), "nope")
+
+---
+// Test rejection of extra value
+#let f() = [
+  // Error: 16-16 expected semicolon or line break
+  #return a + b Hello World
+]