All strings returned by `ImmutableString` should be frozen

I seriously don't even know why we handle booleans, but those strings
should technically be frozen. Additionally, we don't need to actually
check the class in the mutable string type, since the `cast_value`
function will always return a string.

2 files changed, 7 insertions, 11 deletions

diff --git a/activemodel/lib/active_model/type/immutable_string.rb b/activemodel/lib/active_model/type/immutable_string.rb
index cfa4b3fb4b..20b8ca0cc4 100644
--- a/activemodel/lib/active_model/type/immutable_string.rb
+++ b/activemodel/lib/active_model/type/immutable_string.rb
@@ -17,11 +17,12 @@ module ActiveModel
       private
 
       def cast_value(value)
-        case value
-        when true then "t"
-        when false then "f"
-        else value.to_s.freeze
-        end
+        result = case value
+                 when true then "t"
+                 when false then "f"
+                 else value.to_s
+                 end
+        result.freeze
       end
     end
   end
diff --git a/activemodel/lib/active_model/type/string.rb b/activemodel/lib/active_model/type/string.rb
index 4c8dc15778..8a91410998 100644
--- a/activemodel/lib/active_model/type/string.rb
+++ b/activemodel/lib/active_model/type/string.rb
@@ -12,12 +12,7 @@ module ActiveModel
       private
 
       def cast_value(value)
-        result = super
-        if ::String === result
-          ::String.new(result)
-        else
-          result
-        end
+        ::String.new(super)
       end
     end
   end