This blog is part of our Ruby 2.5 series.

Ruby 2.4

irb > class Project irb > end => nil irb > class Category irb > end => nil irb > Project :: Category ( irb ): 5 : warning: toplevel constant Category referenced by Project :: Category => Category

Ruby 2.4 returns the top level constant with a warning if it is unable to find a constant in the specified scope.

This does not work well in cases where we need constants to be defined with same name at top level and also in the same scope.

Ruby 2.5.0-preview1

irb > class Project irb > end => nil irb > class Category irb > end => nil irb > Project :: Category NameError : uninitialized constant Project :: Category Did you mean? Category from ( irb ): 5

Ruby 2.5 throws an error if it is unable to find a constant in the specified scope.

Here is the relevant commit and discussion.