In Elixir you can pattern match on the struct’s type so for example:

defmodule StructTest do
    defstruct name: "Foo!"
end

defmodule TestStruct do
    def takesStruct(struct = %StructTest{}) do
        IO.puts(inspect struct)
    end
end

The takesStruct function will only match for instances of the %StructTest{} structure.

def takesStruct(%StructTest{} = struct) do, means:

1. this function will be invoked only when you pass to it one argument which is %StructTest{} struct, otherwise it will not be invoked
2. when you invoke it with proper struct, this struct will be bound to struct variable, which you can use later in the function body.

You can see more information at the Typespecs page in the Documentation.
To match a Struct inside a typespec, use the normal %StructName{} syntax.

EDIT: The documentation moved to a new location.

As far as I can see Dialyzer likens structs to any general map %{}, which means you lose the specificity…

1.3 rc0 was just released today.