Improve deprecation messages (#1902)

* Improve deprecation messages

* Update ChangeLog.md

Author: menelaos

yesod-form/ChangeLog.md

@@ -1,5 +1,9 @@
 # ChangeLog for yesod-form
 
+## Unreleased
+
+* Improve deprecation messages for `radioField` and `checkboxesField` [#1902](https://github.com/yesodweb/yesod/pull/1902)
+
 ## 1.7.9.1
 
 * Set `base >= 4.11` for less CPP and imports [#1876](https://github.com/yesodweb/yesod/pull/1876)

yesod-form/Yesod/Form/Fields.hs

@@ -124,8 +124,8 @@ import Data.String (IsString)
 
 import Data.Char (isHexDigit)
 
-{-# DEPRECATED radioField "This function seems to have a bug (label could not be found with byLabel algorithm)" #-}
-{-# DEPRECATED checkboxesField "This function seems to have a bug (label could not be found with byLabel algorithm)" #-}
+{-# DEPRECATED radioField "This function seems to have a bug (label could not be found with byLabel algorithm). Use radioField' instead." #-}
+{-# DEPRECATED checkboxesField "This function seems to have a bug (label could not be found with byLabel algorithm). Use checkboxesField' instead." #-}
 
 defaultFormMessage :: FormMessage -> Text
 defaultFormMessage = englishFormMessage