Type Tuple.duplicate/2

Author: josevalim

lib/elixir/lib/module/types/descr.ex

@@ -70,7 +70,7 @@ defmodule Module.Types.Descr do
   def non_empty_list(type, tail \\ @empty_list), do: list_descr(type, tail, false)
   def open_map(), do: %{map: @map_top}
   def open_map(pairs), do: map_descr(:open, pairs)
-  def open_tuple(elements), do: tuple_descr(:open, elements)
+  def open_tuple(elements, _fallback \\ term()), do: tuple_descr(:open, elements)
   def pid(), do: %{bitmap: @bit_pid}
   def port(), do: %{bitmap: @bit_port}
   def reference(), do: %{bitmap: @bit_reference}

lib/elixir/lib/module/types/of.ex

@@ -326,14 +326,7 @@ defmodule Module.Types.Of do
     end
   end
 
-  def apply(
-        :erlang,
-        :delete_element,
-        [_, tuple],
-        {_, meta, [index, _]} = expr,
-        stack,
-        context
-      )
+  def apply(:erlang, :delete_element, [_, tuple], {_, meta, [index, _]} = expr, stack, context)
       when is_integer(index) do
     case tuple_delete_at(tuple, index - 1) do
       value_type when is_descr(value_type) ->
@@ -344,6 +337,11 @@ defmodule Module.Types.Of do
     end
   end
 
+  def apply(:erlang, :make_tuple, [_, elem], {_, _meta, [size, _]}, _stack, context)
+      when is_integer(size) and size >= 0 do
+    {tuple(List.duplicate(elem, size)), context}
+  end
+
   def apply(:erlang, name, [left, right], expr, stack, context)
       when name in [:>=, :"=<", :>, :<, :min, :max] do
     result = if name in [:min, :max], do: union(left, right), else: boolean()

lib/elixir/test/elixir/module/types/expr_test.exs

@@ -364,6 +364,13 @@ defmodule Module.Types.ExprTest do
                     {:ok, integer()}
                 """}
     end
+
+    test "duplicate/2" do
+      assert typecheck!(Tuple.duplicate(123, 0)) == tuple([])
+      assert typecheck!(Tuple.duplicate(123, 1)) == tuple([integer()])
+      assert typecheck!(Tuple.duplicate(123, 2)) == tuple([integer(), integer()])
+      assert typecheck!([x], Tuple.duplicate(x, 2)) == dynamic(tuple([term(), term()]))
+    end
   end
 
   describe "maps/structs" do