Misslead error message, when function ist not found

[mbihn]

if a function is missed sass does complain about it, but complains that the variables are not a valid CSS value.
Typically, this leads to misunderstandings when one of the parameterizers is a map.

Example (from Bootstrap 5.2):

$theme-colors: (
      "primary":    $primary,
      "secondary":  $secondary,
      "success":    $success,
      "info":       $info,
      "warning":    $warning,
      "danger":     $danger,
      "light":      $light,
      "dark":       $dark
    ) !default;

$theme-colors-rgb: map-loop($theme-colors, to-rgb, "$value") !default;](url)

End up in Error:

    Error: ("primary": #007bff, "secondary": #6c757d, "success": #28a745, "info": #17a2b8, "warning": #ffc107, "danger": #dc3545, "light": #f8f9fa, "dark": #343a40) isn't a valid CSS value.
      ╷
    6 │ $theme-colors-rgb: map-loop($theme-colors, to-rgb, "$value") !default;
      │                             ^^^^^^^^^^^^^

because

@function map-loop($map, $func, $args...) {
      $_map: ();
    
      @each $key, $value in $map {
        // allow to pass the $key and $value of the map as an function argument
        $_args: ();
        @each $arg in $args {
          $_args: append($_args, if($arg == "$key", $key, if($arg == "$value", $value, $arg)));
        }
    
        $_map: map-merge($_map, ($key: call(get-function($func), $_args...)));
      }
    
      @return $_map;
    }

is missing.

The error message is clearly wrong and confuses the user.

This happens often, if someone mix versions (e.g. Bootstrap) or forget to include all partials or just made a small typing error.

[nex3]

Yeah, it would probably be worth highlighting the function name as well in this case and saying something like "This is interpreted as a plain CSS function. If you intended it to be a Sass function, the definition could not be found."