NOTE all these questions are related to my use of dialyxir . Type variables From the erlang documentation . Type variables can be used in specifications to specify relations for the input and output arguments of a function. For example, the following specification defines the type of a polymorphic …

[image] Crowdhailer: @spec id(T) :: T Maybe @spec id(t) :: t. T seems to be considered as an atom :"Elixir.T" by dializer, and not a variable.

Is the error the same? What about @spec id(t) :: t when t: any

Close… when a: var, or t :wink:

Thanks, I know longer get a compiler error but i’m not sure what it’s doing. I would have expected the following to give an error defmodule TypeVariables do @spec id(t) :: t when t: var def id(x) do Atom.to_string(x) end def run() do id(:foo) end end It’s a function taking an a…

[image] NobbZ: Close… when a: var, or t :wink: Defining a specification Type variables with no restriction can also be defined. That reads as if it is simply unconstrained rather than unified. In my experience dialyzer wants specifics, e.g. @type my_t(t) :: list(t) @type my_int_t ::…

Does equivalent Erlang code produce the same not-warning?

Even in Erlang the error isn’t detected on id/1 - it is only caught if you spec run/0 -spec id(T) -> T. id(X) -> X, 10. -spec run() -> atom(). run() -> id(foo). $ dialyzer frequency.erl Checking whether the PLT /Users/wheatley/.dialyzer_plt is up-to-date... yes Proceeding with ana…

Type variables are not unified by dialyzer. In the spec @spec id(t) :: t when t: var, the t as arg and t as return may as well be different type variables entirely.

Does anyone do this or similar. Here I am using a spec’d identity function to “cast” a binary to an opaque type which will instruct dialyzer to warn when I try to use it in normal strip operation. defmodule MyID do @opaque t(x) :: x @spec id(binary) :: t(binary) def id(x) do x end …

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How to declare type variables using elixir/dialyixir?

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NobbZ April 29, 2018, 4:55pm 5

Close… when a: var, or t