Struct vs. @type t

[hauleth]

@vrod

Is the @type t special? Or is that just a convention?

Convention.

@vrod

Is there any difference between using %MyStruct{} or MyStruct.t() in function specs?

Yes. If you will use just %MyStruct{} then the types specified in t() will not be used. So:

@type t :: %MyStruct{a: integer()}

@spec pass(%MyStruct{}) :: term()
def pass(t), do: t

@spec fail(t()) :: term()
def fail(t), do: t

s = %MyStruct{a: "bar"}

pass(s)
fail(s) # this will cause Dialyzer error

@vrod

Is there any case where you would use one and not the other?

If there is defined t() then you should always use that.

@vrod

Is the @type t more “specific” because it can declare the types of various keys in the struct? (Whereas the struct itself only defines the names of the keys, not their data types)

Yes, as shown above.