function signature requiring methods on past in type

[modest elk]

is there a way to tell a function that a passed in type requires certain methods to be defined?

[slow eagle]

could do some vallidation with stuff like if (!@hasField(T, "name")) @compileError("Invalid type passed in");

i dont think there is a better way of expressing "any type that matches this criteria"

[modest elk]

from what i see the documentation @hasFiels does not work for fuctions so it would need to be @hasCecl

but that is not really what i want as it only checks if a method with the name is defined and not for the signature of that method

well i could just call the methods with comp-time known values i expect and the compile will tell me if the expectation is wrong

[slow eagle]

true, Decl.... and you can check the signature later by doing @typeInfo(T.name).@"fn"

i would just assume correct types are passed in, and let the compiler emit the (maybe cryptic) errors when methods don't exist or don't match the expectation, though

[modest elk]

hmm yeah would work
i just wanted to see if there is a more elegant way then passing additional funtions in
as one of my function signatures has become uncomfortably long

[slow eagle]

could do something like Django's Meta class too

const Meta = struct {
    foo: *const fn (u8, usize) !void,
    // ... whatever ...
}

// types passed in must contain one of these, under a particular name
pub fn theFunc(T: type) void {
    if (!@hasDecl(T, "meta") or @TypeOf(T.meta) != Meta) @compileError("Wrong type");
}

by having a struct with known fields (names) and those fields having the arg/return info of your function, you will get good error messages by compiler already, without manually doing checking on your function

that's not viable for types that are out of user control (eg: imported from another project) though

[modest elk]

the type is under my control
just wanted to prevent having to refactor the function just because i change something little on the type that does not require a logic change in the function