Remove deprecated passing string to define callback

And raise `ArgumentError` when passing string to define callback.

1 files changed, 4 insertions, 6 deletions

diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index e6c79f2a38..16455c8b93 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -286,9 +286,8 @@ module ActiveSupport
       class Callback #:nodoc:#
         def self.build(chain, filter, kind, options)
           if filter.is_a?(String)
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing string to define callback is deprecated and will be removed
-              in Rails 5.1 without replacement.
+            raise ArgumentError, <<-MSG.squish
+              Passing string to define callback is not supported. Use proc instead.
             MSG
           end
 
@@ -643,9 +642,8 @@ module ActiveSupport
         #   set_callback :save, :before_method
         #
         # The callback can be specified as a symbol naming an instance method; as a
-        # proc, lambda, or block; as a string to be instance evaluated(deprecated); or as an
-        # object that responds to a certain method determined by the <tt>:scope</tt>
-        # argument to +define_callbacks+.
+        # proc, lambda, or block; or as an object that responds to a certain method
+        # determined by the <tt>:scope</tt> argument to +define_callbacks+.
         #
         # If a proc, lambda, or block is given, its body is evaluated in the context
         # of the current object. It can also optionally accept the current object as