closes #16654; add a test case (#21478)

tests/errmsgs/t16654.nim

@@ -0,0 +1,12 @@
+discard """
+  cmd: "nim check $options $file"
+  errormsg: "type mismatch: got <int> but expected 'float'"
+"""
+
+when true: # bug #16654
+  func fn[T](a: T, op: proc(a: T): float) = discard
+  proc main() =
+    let v = 1
+    proc bar(r: auto): auto = v
+    fn(1, bar)
+  main()