From 53d13bae369ec3a186e2a7e3a340cb0032c48e1a Mon Sep 17 00:00:00 2001
From: mkorje <max@mkor.je>
Date: Wed, 25 Jun 2025 16:03:00 +1000
Subject: [PATCH] Add warning

---
 crates/typst-eval/src/math.rs                 |  20 +++++++++++++++---
 ...h-attach-followed-by-func-call-warning.png | Bin 0 -> 630 bytes
 tests/suite/math/attach.typ                   |  18 ++++++++++++++++
 3 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 tests/ref/math-attach-followed-by-func-call-warning.png

diff --git a/crates/typst-eval/src/math.rs b/crates/typst-eval/src/math.rs
index c2325a8c5..9712b2b81 100644
--- a/crates/typst-eval/src/math.rs
+++ b/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())
diff --git a/tests/ref/math-attach-followed-by-func-call-warning.png b/tests/ref/math-attach-followed-by-func-call-warning.png
new file mode 100644
index 0000000000000000000000000000000000000000..1b05ef8416c0622a1e27af466852a540ffb28b55
GIT binary patch
literal 630
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zU|$z*h&4;WHuUg~gS$AK-c&D32bV-Yi!+jXi9e<d&ph{?Wupw6UH~6E=PWF5OF`x<
z-VOZ@+PUVj&%<nz2fu#a4nYw^PveLT=BU8fP^4d0hjT)gGFO+xwd`HV{Bs}Qcam9;
z!!g*K?E?Wwg6&B6WbPI6beF{J6&VD%{+Ap9`RJ)89{=pa#Y>4YEU*M*a~Plp2cpsW
zQY+vEET$DNUf_wbP)@?pWj`*K6T4;MU*a+;bRUqRNWHczpgoxytig59AE+lirv`E-
QM*si-07*qoM6N<$g2*-_xc~qF

literal 0
HcmV?d00001

diff --git a/tests/suite/math/attach.typ b/tests/suite/math/attach.typ
index bac0417c5..994355652 100644
--- a/tests/suite/math/attach.typ
+++ b/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),