Add typespec syntax for records

Author: ericmj

lib/elixir/lib/kernel/typespec.ex

@@ -77,9 +77,11 @@ defmodule Kernel.Typespec do
            | %{Keyword}
            | %{Pairs}
 
-      Tuple :: tuple     # a tuple of any size
-             | {}        # empty tuple
+      Tuple :: tuple                 # a tuple of any size
+             | {}                    # empty tuple
              | {TList}
+             | record(Atom)          # record (see Record)
+             | record(Atom, Keyword)
 
       Keyword :: ElixirAtom: Type
                | ElixirAtom: Type, Keyword
@@ -851,6 +853,34 @@ defmodule Kernel.Typespec do
     typespec({:%{}, meta, fields}, vars, caller)
   end
 
+  # Handle records
+  defp typespec({:record, meta, [atom]}, vars, caller) do
+    typespec({:record, meta, [atom, []]}, vars, caller)
+  end
+
+  defp typespec({:record, meta, [atom, fields]}, vars, caller) do
+    case Macro.expand({atom, [], [{atom, [], []}]}, caller) do
+      keyword when is_list(keyword) ->
+        keyword =
+          :lists.map(fn {field, _} ->
+            {field, quote do: term()}
+          end, keyword)
+
+        :lists.foreach(fn {field, _} ->
+          unless Keyword.has_key?(keyword, field) do
+            compile_error(caller, "undefined field #{field} on record #{inspect atom}")
+          end
+        end, fields)
+
+        fields = Keyword.merge(keyword, fields)
+        types = Keyword.values(fields)
+
+        typespec({:{}, meta, [atom|types]}, vars, caller)
+      _ ->
+        compile_error(caller, "unknown record #{inspect atom}")
+    end
+  end
+
   # Handle ranges
   defp typespec({:.., meta, args}, vars, caller) do
     typespec({:range, meta, args}, vars, caller)

lib/elixir/lib/record.ex

@@ -20,6 +20,20 @@ defmodule Record do
   The macros `defrecord/3` and `defrecordp/3` can be used to create
   records while `extract/2` can be used to extract records from Erlang
   files.
+
+  ## Types
+
+  Types can be defined for tuples with the `record/2` macro (only available
+  in typespecs). Like with the generated record macros it will expand to
+  a tuple.
+
+      defmodule MyModule do
+        require Record
+        Record.defrecord :user name: "José", age: 25
+
+        @type user :: record(:user, name: String.t, age: integer)
+        # expands to: `@type user :: {:user, String.t, integer}`
+      end
   """
 
   @doc """

lib/elixir/test/elixir/kernel/typespec_test.exs

@@ -214,6 +214,52 @@ defmodule Kernel.TypespecTest do
     end
   end
 
+  test "@type with public record" do
+    module = test_module do
+      require Record
+      Record.defrecord :timestamp, [date: 1, time: 2]
+      @type mytype :: record(:timestamp, time: :foo)
+    end
+
+    assert [type: {:mytype,
+             {:type, _, :tuple, [
+               {:atom, 0, :timestamp}, {:atom, 0, :foo}, {:type, 0, :term, []}
+             ]},
+            []}] = types(module)
+  end
+
+  test "@type with private record" do
+    module = test_module do
+      require Record
+      Record.defrecordp :timestamp, [date: 1, time: 2]
+      @type mytype :: record(:timestamp, time: :foo)
+    end
+
+    assert [type: {:mytype,
+             {:type, _, :tuple, [
+               {:atom, 0, :timestamp}, {:atom, 0, :foo}, {:type, 0, :term, []}
+             ]},
+            []}] = types(module)
+  end
+
+  test "@type with undefined record" do
+    assert_raise CompileError, ~r"unknown record :this_record_does_not_exist", fn ->
+      test_module do
+        @type mytype :: record(:this_record_does_not_exist, [])
+      end
+    end
+  end
+
+  test "@type with a record with undefined field" do
+    assert_raise CompileError, ~r"undefined field no_field on record :timestamp", fn ->
+      test_module do
+        require Record
+        Record.defrecord :timestamp, [date: 1, time: 2]
+        @type mytype :: record(:timestamp, no_field: :foo)
+      end
+    end
+  end
+
   test "@type with list shortcuts" do
     module = test_module do
       @type mytype :: []