Add notes to the code

Author: josevalim

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

@@ -15,6 +15,7 @@ defmodule Module.Types.Expr do
   list_of_modules = list(atom())
 
   @try_catch atom([:error, :exit, :throw])
+  @atom_true atom([true])
 
   @caller closed_map(
             __struct__: atom([Macro.Env]),
@@ -34,9 +35,12 @@ defmodule Module.Types.Expr do
             versioned_vars: open_map()
           )
 
-  # An annotation for terms where the reverse arrow is not yet fully defined
+  # An annotation for terms where the reverse arrow is not yet fully defined.
+  # Also revisit all users of dynamic() in this module in a later date.
   @pending term()
-  @atom_true atom([true])
+
+  # We do not make exception dynamic on purpose. If you do a blank rescue,
+  # then we will assume you need to statically handle all possible exceptions.
   @exception open_map(__struct__: atom(), __exception__: @atom_true)
 
   args_or_arity = union(list(term()), integer())
@@ -346,7 +350,7 @@ defmodule Module.Types.Expr do
 
     if stack.mode == :traversal do
       {_acc, context} = of_clauses(clauses, domain, @pending, nil, :fn, stack, context, none())
-      {dynamic(fun(length(patterns))), context}
+      {dynamic(), context}
     else
       {acc, context} =
         of_clauses_fun(clauses, domain, @pending, nil, :fn, stack, context, [], fn

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

@@ -146,8 +146,10 @@ defmodule Module.Types.Of do
   end
 
   def impl(struct) do
-    # Elixir did not strictly require the implementation to be available, so we need a fallback.
+    # Elixir did not strictly require the implementation to be available,
+    # so we need to deal with such cases accordingly.
     # TODO: Assume implementation is available on Elixir v2.0.
+    # A warning is emitted since v1.19+.
     if info = Code.ensure_loaded?(struct) && struct.__info__(:struct) do
       struct_type(struct, info)
     else