Fix missing capturing of assignments

The previous commit was a bit overambitious. The left-hand side of assignments should actually be fully captured: Argument lists in `at` calls can contain captured variables. And if the assigned variable itself is captured, then the function is faulty anyway. (And we ensure the correct error message by capturing it.)

Fixes #2169

1 files changed, 18 insertions, 0 deletions

diff --git a/tests/typ/compiler/closure.typ b/tests/typ/compiler/closure.typ
index 92d01446..85e9dbe2 100644
--- a/tests/typ/compiler/closure.typ
+++ b/tests/typ/compiler/closure.typ
@@ -132,6 +132,24 @@
 }
 
 ---
+// Mutable method with capture in argument.
+#let x = "b"
+#let f() = {
+  let a = (b: 5)
+  a.at(x) = 10
+  a
+}
+#f()
+
+---
+#let x = ()
+#let f() = {
+  // Error: 3-4 variables from outside the function are read-only and cannot be modified
+  x.at(1) = 2
+}
+#f()
+
+---
 // Named arguments.
 #{
   let greet(name, birthday: false) = {