What is the reasoning behind the lack of conversions when passing parameters

[Walter Bright]

On 2/13/2024 4:38 PM, Carl Sturtivant wrote:
> Variant is important to some of us because of its universality. If all 
> conversions are blocked for parameter passing, can a replacement of Variant (say 
> Any) be added to the list to be a part of the language?
> 
> This would be so that any literal or value of any type can be passed to a 
> parameter of type Any, enabling naive scripting and experimenting in any context 
> without an import.

Isn't that what a sumtype is?