Type Inference for Struct/Enum Literals

[IchorDev]

On Monday, 8 July 2024 at 10:41:39 UTC, Nick Treleaven wrote:
> Vladimir's idea is for an identifier to have its own type. When 
> omitting the struct type, there is no identifier. So that idea 
> doesn't have a bearing on being able to do that.
> ```d
> MyStruct x;
> x = _(args); // type identifier not present
> ```

I see what you mean, but `_` is actually an identifier. ;) I know 
a lot of us would like to deprecate it favour of pattern matching 
discards/etc., but it would still be a considerable syntax break.
To solve the issue you mentioned about there being no identifier, 
instead of having a type for an identifier, we make another 
similar type that stores just a list of parameters.

> BTW it would be nice to be able to omit the class type in a 
> NewExpression too:
> ```d
> MyClass obj;
> obj = new _(args);
> ```

Absolutely, that's a great idea! Now, this presents an 
interesting question:
Can `new`+type inference only be used for classes, or can `new 
MyStruct(args)` also be shortened to `new _(args)`? Personally I 
think allowing structs makes sense.
Class type inference would certainly grant a bit less benefit 
than for other aggregates due to polymorphism, but as long it's 
doable I'm down for it. I guess I should mention that I think 
union literals should get type inference too before someone 
brings those up. One really cool way of inferring their type 
would be via named parameters.