First Draft: Implicit Conversion of Template Instantiations

[Dukc]

On Saturday, 16 March 2024 at 15:50:27 UTC, Walter Bright wrote:
> https://github.com/WalterBright/documents/blob/9dba63a4c2887bdb2b988c354ebb0d6bb44c4968/templatecast.md

Thanks. Having a look:

> But `const X!(int*)` will instantiate `bar` as `void bar(int*)`.

Nope. It will instantiate it as `void bar(int*) const`.

> The template struct or template class will be treated as a list 
> of its members.

Three points.

1. Why wouldn't this apply only to templated structs? It'd make 
sense for the rules to apply to all structs/classes.

2. In the presented example, no fields are actually converted. 
The only field, `x`, is the same type in both cases 
(`const(int[])`). Please add an example where type of the 
field(s) differ, say converting `X!(immutable(int))` to 
`const(X!int)`.

3. Could allowing these casts break assumptions of a type that 
has `@system` fields (DIP1035)? I haven't thought it deeply 
enough to conclude one way pr another but the DIP should probably 
explain it.

> Only members that are fields or non-static functions are 
> considered.

I don't see why member functions would need to be considered, 
static or no. An instance of a struct doesn't contain it's member 
functions as fields.