Add Orb.Stack.drop/1

lib/orb/ops.ex

@@ -58,6 +58,11 @@ defmodule Orb.Ops do
     Orb.CustomType.resolve!(mod) |> to_primitive_type()
   end
 
+  def type_stack_count(type) when is_primitive_type(type), do: 1
+  def type_stack_count(type) when is_effect(type), do: 0
+  def type_stack_count(type) when is_atom(type), do: 1
+  def type_stack_count(type) when is_tuple(type), do: tuple_size(type)
+
   def types_compatible?(Elixir.Integer, b),
     do: to_primitive_type(b) in @integer_types
 

lib/orb/stack.ex

@@ -0,0 +1,42 @@
+defmodule Orb.Stack do
+  @moduledoc false
+
+  defmodule Drop do
+    defstruct instruction: nil, count: 0
+
+    require alias Orb.Ops
+
+    def new(%{type: type} = instruction) do
+      count = Ops.typeof(instruction) |> Ops.type_stack_count()
+
+      %__MODULE__{
+        instruction: instruction,
+        count: count
+      }
+    end
+
+    def new(value) when is_number(value) do
+      %__MODULE__{
+        instruction: value,
+        count: 1
+      }
+    end
+
+    defimpl Orb.ToWat do
+      def to_wat(
+            %Orb.Stack.Drop{instruction: instruction, count: count},
+            indent
+          ) do
+        [
+          Orb.ToWat.to_wat(instruction, indent),
+          "\n",
+          for _ <- 1..count do
+            [indent, "drop", "\n"]
+          end
+        ]
+      end
+    end
+  end
+
+  def drop(instruction), do: Drop.new(instruction)
+end