Add warning

crates/typst-eval/src/math.rs

@@ -1,5 +1,5 @@
 use ecow::eco_format;
-use typst_library::diag::{At, SourceResult};
+use typst_library::diag::{warning, At, SourceResult};
 use typst_library::foundations::{Content, NativeElement, Symbol, SymbolElem, Value};
 use typst_library::math::{
     AlignPointElem, AttachElem, FracElem, LrElem, PrimesElem, RootElem,
@@ -80,7 +80,14 @@ impl Eval for ast::MathAttach<'_> {
         let mut elem = AttachElem::new(base);
 
         if let Some(expr) = self.top() {
-            elem.t.set(Some(expr.eval_display(vm)?));
+            let top = expr.eval(vm)?;
+            if let Value::Func(_) = top {
+                vm.engine.sink.warn(warning!(
+                    expr.span(), "function literal used as superscript";
+                    hint: "wrap the entire function call in parentheses",
+                ));
+            }
+            elem.t.set(Some(top.display().spanned(self.span())));
         }
 
         // Always attach primes in scripts style (not limits style),
@@ -90,7 +97,14 @@ impl Eval for ast::MathAttach<'_> {
         }
 
         if let Some(expr) = self.bottom() {
-            elem.b.set(Some(expr.eval_display(vm)?));
+            let bottom = expr.eval(vm)?;
+            if let Value::Func(_) = bottom {
+                vm.engine.sink.warn(warning!(
+                    expr.span(), "function literal used as subscript";
+                    hint: "wrap the entire function call in parentheses",
+                ));
+            }
+            elem.b.set(Some(bottom.display().spanned(self.span())));
         }
 
         Ok(elem.pack())

tests/suite/math/attach.typ

@@ -45,6 +45,10 @@ $
 // Test function call after subscripts and superscripts.
 #set page(width: auto)
 $a_1(x), a^10(x), a_f(x), a^zeta(x), a_"text"(x),
+// Warning: 22-25 function literal used as subscript
+// Hint: 22-25 wrap the entire function call in parentheses
+// Warning: 32-36 function literal used as superscript
+// Hint: 32-36 wrap the entire function call in parentheses
  a_∂(x), a^cos(x), a_abs(x), a^root(2, x), a_subset.eq(x) \
  a_(1(x)), a^(10(x)), a_(f(x)), a^(zeta(x)), a_("text"(x)),
  a_(∂(x)), a^(cos(x)), a_(abs(x)), a^(root(2, x)), a_(subset.eq(x))$
@@ -52,14 +56,28 @@ $a_1(x), a^10(x), a_f(x), a^zeta(x), a_"text"(x),
 --- math-attach-followed-by-func-call-complex ---
 // Test function call with named arguments after scripts.
 #let cross = $c$
+// Warning: 4-10 function literal used as subscript
+// Hint: 4-10 wrap the entire function call in parentheses
 $a_cancel(x, cross: #true)$
 
 --- math-attach-followed-by-func-call-error ---
 // Error: 14-19 unknown variable: cross
 // Hint: 14-19 if you meant to display multiple letters as is, try adding spaces between each letter: `c r o s s`
 // Hint: 14-19 or if you meant to display this as text, try placing it in quotes: `"cross"`
+// Warning: 4-10 function literal used as subscript
+// Hint: 4-10 wrap the entire function call in parentheses
 $a_cancel(x, cross: #true)$
 
+--- math-attach-followed-by-func-call-warning ---
+// Test warning for function literal as subscripts and superscripts.
+#let myfunc(arg) = $arg$
+// Warning: 4-10 function literal used as subscript
+// Hint: 4-10 wrap the entire function call in parentheses
+$a_myfunc(x) a_(myfunc(x))$
+// Warning: 4-10 function literal used as subscript
+// Hint: 4-10 wrap the entire function call in parentheses
+$a_myfunc a_(myfunc)$
+
 --- math-attach-nested ---
 // Test associativity and scaling.
 $ 1/(V^2^3^4^5),