Collapse structs in type warnings by default

Author: josevalim

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

@@ -1982,7 +1982,7 @@ defmodule Module.Types.Descr do
              [_ | _] = info <- maybe_struct(struct),
              true <- map_size(fields) == length(info) + 1,
              true <- Enum.all?(info, &is_map_key(fields, &1.field)) do
-          collapse? = Keyword.get(opts, :collapse_structs, false)
+          collapse? = Keyword.get(opts, :collapse_structs, true)
 
           fields =
             for %{field: field} <- info,

lib/elixir/lib/module/types/expr.ex

@@ -806,11 +806,11 @@ defmodule Module.Types.Expr do
           """
           expected a map with key #{inspect(key)} in map update syntax:
 
-              #{expr_to_string(expr) |> indent(4)}
+              #{expr_to_string(expr, collapse_structs: false) |> indent(4)}
 
           but got type:
 
-              #{to_quoted_string(type) |> indent(4)}
+              #{to_quoted_string(type, collapse_structs: false) |> indent(4)}
           """,
           format_traces(traces)
         ])

lib/elixir/lib/module/types/helpers.ex

@@ -251,8 +251,8 @@ defmodule Module.Types.Helpers do
 
   We also undo some macro expressions done by the Kernel module.
   """
-  def expr_to_string(expr) do
-    string = prewalk_expr_to_string(expr)
+  def expr_to_string(expr, opts \\ []) do
+    string = prewalk_expr_to_string(expr, opts)
 
     case expr do
       {_, meta, _} ->
@@ -275,7 +275,9 @@ defmodule Module.Types.Helpers do
     end
   end
 
-  defp prewalk_expr_to_string(expr) do
+  defp prewalk_expr_to_string(expr, opts) do
+    collapse_structs? = Keyword.get(opts, :collapse_structs, true)
+
     expr
     |> Macro.prewalk(fn
       {:%, _, [Range, {:%{}, _, fields}]} = node ->
@@ -289,6 +291,26 @@ defmodule Module.Types.Helpers do
             node
         end
 
+      {:%, struct_meta, [struct, {:%{}, map_meta, fields}]} = node
+      when collapse_structs? ->
+        try do
+          struct.__info__(:struct)
+        rescue
+          _ -> node
+        else
+          infos ->
+            filtered =
+              for {field, value} <- fields, not matches_default?(infos, field, value) do
+                {field, value}
+              end
+
+            if length(fields) != length(filtered) do
+              {:%, struct_meta, [struct, {:%{}, map_meta, [{:..., [], []} | filtered]}]}
+            else
+              node
+            end
+        end
+
       {{:., _, [Elixir.String.Chars, :to_string]}, meta, [arg]} ->
         {:to_string, meta, [arg]}
 
@@ -340,6 +362,13 @@ defmodule Module.Types.Helpers do
     |> Macro.to_string()
   end
 
+  defp matches_default?(infos, field, value) do
+    case Enum.find(infos, &(&1.field == field)) do
+      %{default: default} -> Macro.escape(default) == value
+      _ -> false
+    end
+  end
+
   defp erl_to_ex(
          :erlang,
          :error,

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

@@ -615,11 +615,11 @@ defmodule Module.Types.Of do
           """
           unknown key .#{key} in expression:
 
-              #{expr_to_string(expr) |> indent(4)}
+              #{expr_to_string(expr, collapse_structs: false) |> indent(4)}
 
           the given type does not have the given key:
 
-              #{to_quoted_string(type) |> indent(4)}
+              #{to_quoted_string(type, collapse_structs: false) |> indent(4)}
           """,
           format_traces(traces)
         ])

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

@@ -1557,15 +1557,15 @@ defmodule Module.Types.DescrTest do
                "%{__struct__: Another or URI}"
 
       assert closed_map(__struct__: atom([Decimal]), coef: term(), exp: term(), sign: term())
-             |> to_quoted_string() ==
+             |> to_quoted_string(collapse_structs: false) ==
                "%Decimal{sign: term(), coef: term(), exp: term()}"
 
       assert closed_map(__struct__: atom([Decimal]), coef: term(), exp: term(), sign: term())
-             |> to_quoted_string(collapse_structs: true) ==
+             |> to_quoted_string() ==
                "%Decimal{}"
 
       assert closed_map(__struct__: atom([Decimal]), coef: term(), exp: term(), sign: integer())
-             |> to_quoted_string(collapse_structs: true) ==
+             |> to_quoted_string() ==
                "%Decimal{sign: integer()}"
 
       # Does not fuse structs

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

@@ -940,6 +940,34 @@ defmodule Module.Types.ExprTest do
 
       assert [%{type: :variable, name: :x}] = diagnostic.details.typing_traces
     end
+
+    test "inspect struct definition" do
+      assert typeerror!(
+               (
+                 p = %Point{x: 123}
+                 Integer.to_string(p)
+               )
+             )
+             |> strip_ansi() == ~l"""
+             incompatible types given to Integer.to_string/1:
+
+                 Integer.to_string(p)
+
+             given types:
+
+                 %Point{x: integer(), y: nil, z: integer()}
+
+             but expected one of:
+
+                 integer()
+
+             where "p" was given the type:
+
+                 # type: %Point{x: integer(), y: nil, z: integer()}
+                 # from: types_test.ex:947
+                 p = %Point{..., x: 123}
+             """
+    end
   end
 
   describe "comparison" do

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

@@ -443,7 +443,7 @@ defmodule Module.Types.IntegrationTest do
 
             because it is expected to receive type:
 
-                dynamic(%Range{first: term(), last: term(), step: term()})
+                dynamic(%Range{})
 
             typing violation found at:
             │
@@ -475,7 +475,7 @@ defmodule Module.Types.IntegrationTest do
 
             it has type:
 
-                -dynamic(%Range{first: term(), last: term(), step: term()})-
+                -dynamic(%Range{})-
 
             but expected a type that implements the String.Chars protocol, it must be one of:
 
@@ -499,7 +499,7 @@ defmodule Module.Types.IntegrationTest do
 
             given types:
 
-                -dynamic(%Range{first: term(), last: term(), step: term()})-
+                -dynamic(%Range{})-
 
             but expected a type that implements the String.Chars protocol, it must be one of:
 
@@ -538,7 +538,7 @@ defmodule Module.Types.IntegrationTest do
 
             it has type:
 
-                -dynamic(%Date{year: term(), month: term(), day: term(), calendar: term()})-
+                -dynamic(%Date{})-
 
             but expected a type that implements the Enumerable protocol, it must be one of: