Always declare vars upfront

Author: josevalim

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

@@ -580,6 +580,7 @@ defmodule Module.Types.Expr do
         _ ->
           expected = if structs == [], do: @exception, else: Enum.reduce(structs, &union/2)
           expr = {:__block__, [type_check: info], [expr]}
+          context = Of.declare_var(var, context)
           {_ok?, _type, context} = Of.refine_head_var(var, expected, expr, stack, context)
           context
       end

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

@@ -103,8 +103,7 @@ defmodule Module.Types.Of do
   because we want to refine types. Otherwise we should
   use compatibility.
   """
-  def refine_head_var(var, type, expr, stack, context) do
-    {var_name, meta, var_context} = var
+  def refine_head_var({_, meta, _}, type, expr, stack, context) do
     version = Keyword.fetch!(meta, :version)
 
     case context.vars do
@@ -128,17 +127,6 @@ defmodule Module.Types.Of do
           context = %{context | vars: %{vars | version => data}}
           {:ok, new_type, context}
         end
-
-      %{} = vars ->
-        data = %{
-          type: type,
-          name: var_name,
-          context: var_context,
-          off_traces: new_trace(expr, type, stack, [])
-        }
-
-        context = %{context | vars: Map.put(vars, version, data)}
-        {:ok, type, context}
     end
   end
 

lib/elixir/lib/module/types/pattern.ex

@@ -406,6 +406,8 @@ defmodule Module.Types.Pattern do
   end
 
   def of_match_var(var, expected, expr, stack, context) when is_var(var) do
+    context = Of.declare_var(var, context)
+
     case Of.refine_head_var(var, expected, expr, stack, context) do
       {:ok, type, context} ->
         {type, context}