Typing of basic arithmetic operators

Author: josevalim

lib/elixir/lib/module/types.ex

@@ -74,27 +74,28 @@ defmodule Module.Types do
       no_warn_undefined: no_warn_undefined,
       # A list of cached modules received from the parallel compiler
       cache: cache,
-      # The mode control what happens on function application when
+      # The mode controls what happens on function application when
       # there are gradual arguments. Non-gradual arguments always
       # perform subtyping and return its output (OUT).
       #
-      # The mode may also control exhaustiveness checks in the future
-      # (to be decided).
-      #
       #   * :strict - Requires types signatures (not implemented).
       #     * Strong arrows with gradual performs subtyping and returns OUT
       #     * Weak arrows with gradual performs subtyping and returns OUT
       #
       #   * :static - Type signatures have been given.
       #     * Strong arrows with gradual performs compatibility and returns OUT
-      #     * Weak arrows with gradual performs compatibility and returns OUT
+      #     * Weak arrows with gradual performs compatibility and returns dynamic()
       #
       #   * :dynamic - Type signatures have not been given.
       #     * Strong arrows with gradual performs compatibility and returns dynamic(OUT)
       #     * Weak arrows with gradual performs compatibility and returns dynamic()
       #
       #   * :infer - Same as :dynamic but skips remote calls.
       #
+      # The mode may also control exhaustiveness checks in the future (to be decided).
+      # We may also want for applications with subtyping in dynamic mode to always
+      # intersect with dynamic, but this mode may be too lax (to be decided based on
+      # feedback).
       mode: mode
     }
   end

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

@@ -328,11 +328,21 @@ defmodule Module.Types.Of do
     |> union(atom())
     |> union(tuple([atom(), atom()]))
 
+  basic_arith_2_args_clauses = [
+    {[integer(), integer()], integer()},
+    {[integer(), float()], float()},
+    {[float(), integer()], float()},
+    {[float(), float()], float()}
+  ]
+
   for {mod, fun, clauses} <- [
         # :binary
         {:binary, :copy, [{[binary(), integer()], binary()}]},
 
         # :erlang
+        {:erlang, :+, basic_arith_2_args_clauses},
+        {:erlang, :-, basic_arith_2_args_clauses},
+        {:erlang, :*, basic_arith_2_args_clauses},
         {:erlang, :"/=", [{[term(), term()], boolean()}]},
         {:erlang, :"=/=", [{[term(), term()], boolean()}]},
         {:erlang, :<, [{[term(), term()], boolean()}]},
@@ -869,9 +879,8 @@ defmodule Module.Types.Of do
 
               #{args_to_quoted_string(mod, fun, args_types) |> indent(4)}
 
-          but expected types:
-
-              #{clauses_args_to_quoted_string(mod, fun, clauses, args_types) |> indent(4)}
+          but expected one of:
+          #{clauses_args_to_quoted_string(mod, fun, clauses, args_types)}
           """,
           format_traces(traces)
         ])
@@ -1020,6 +1029,18 @@ defmodule Module.Types.Of do
   alias Inspect.Algebra, as: IA
 
   defp clauses_args_to_quoted_string(mod, fun, [{args, _return}], args_types) do
+    "\n    " <> (clause_args_to_quoted_string(mod, fun, args, args_types) |> indent(4))
+  end
+
+  defp clauses_args_to_quoted_string(mod, fun, clauses, args_types) do
+    clauses
+    |> Enum.with_index(fn {args, _return}, index ->
+      "\n##{index + 1}\n#{clause_args_to_quoted_string(mod, fun, args, args_types)}" |> indent(4)
+    end)
+    |> Enum.join("\n")
+  end
+
+  defp clause_args_to_quoted_string(mod, fun, args, args_types) do
     ansi? = IO.ANSI.enabled?()
 
     docs =

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

@@ -55,7 +55,7 @@ defmodule Module.Types.ExprTest do
 
                    empty_list()
 
-               but expected types:
+               but expected one of:
 
                    non_empty_list(term(), term())
                """
@@ -70,7 +70,7 @@ defmodule Module.Types.ExprTest do
 
                    integer()
 
-               but expected types:
+               but expected one of:
 
                    non_empty_list(term(), term())
                """
@@ -92,7 +92,7 @@ defmodule Module.Types.ExprTest do
 
                    empty_list()
 
-               but expected types:
+               but expected one of:
 
                    non_empty_list(term(), term())
                """
@@ -107,7 +107,7 @@ defmodule Module.Types.ExprTest do
 
                    integer()
 
-               but expected types:
+               but expected one of:
 
                    non_empty_list(term(), term())
                """
@@ -327,7 +327,7 @@ defmodule Module.Types.ExprTest do
 
                    integer(), integer()
 
-               but expected types:
+               but expected one of:
 
                    integer(), {...}
 
@@ -372,7 +372,7 @@ defmodule Module.Types.ExprTest do
 
                    integer(), integer(), binary()
 
-               but expected types:
+               but expected one of:
 
                    integer(), {...}, term()
 
@@ -411,7 +411,7 @@ defmodule Module.Types.ExprTest do
 
                    integer(), integer()
 
-               but expected types:
+               but expected one of:
 
                    integer(), {...}
 
@@ -673,6 +673,45 @@ defmodule Module.Types.ExprTest do
   end
 
   describe ":erlang rewrites" do
+    test "Kernel.+/2" do
+      assert typeerror!([x = :foo, y = 123], x + y) |> strip_ansi() ==
+               ~l"""
+               incompatible types given to Kernel.+/2:
+
+                   x + y
+
+               given types:
+
+                   dynamic(:foo), integer()
+
+               but expected one of:
+
+                   #1
+                   integer(), integer()
+
+                   #2
+                   integer(), float()
+
+                   #3
+                   float(), integer()
+
+                   #4
+                   float(), float()
+
+               where "x" was given the type:
+
+                   # type: dynamic(:foo)
+                   # from: types_test.ex:677
+                   x = :foo
+
+               where "y" was given the type:
+
+                   # type: integer()
+                   # from: types_test.ex:677
+                   y = 123
+               """
+    end
+
     test "Integer.to_string/1" do
       assert typecheck!([x = 123], Integer.to_string(x)) == binary()
       assert typedyn!([x = 123], Integer.to_string(x)) == dynamic(binary())
@@ -687,7 +726,7 @@ defmodule Module.Types.ExprTest do
 
                    dynamic(:foo)
 
-               but expected types:
+               but expected one of:
 
                    integer()
 
@@ -713,7 +752,7 @@ defmodule Module.Types.ExprTest do
 
                    dynamic(:foo)
 
-               but expected types:
+               but expected one of:
 
                    integer()
 

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

@@ -36,7 +36,7 @@ defmodule Module.Types.PatternTest do
 
                    empty_list() or non_empty_list(integer())
 
-               but expected types:
+               but expected one of:
 
                    non_empty_list(term(), term())