method_owner.rb

hash_instance_methods = %w(
<
  <=
  ==
  ===
  >
  >=
  []
[]=
  assoc
clear
clone
compact
compact!
compare_by_identity
compare_by_identity?
default
default=
  default_proc
default_proc=
  delete
delete_if
dig
dup
each
each_key
each_pair
each_value
empty?
eql?
equal?
fetch
fetch_values
filter
filter!
flatten
has_key?
has_value?
hash
include?
index
inspect
invert
keep_if
key
key?
keys
length
member?
merge
merge!
rassoc
rehash
reject
reject!
replace
select
select!
shift
size
slice
sort
store
to_a
to_h
to_hash
to_proc
to_s
transform_keys
transform_keys!
transform_values
transform_values!
update
value?
values
values_at
)

hash_instance_methods.each do |m|
  result = {}.method(m).owner
  puts "#{m}: #{result}" unless result.to_s == 'Hash'
end

result.txt

===: Kernel
clone: Kernel
dup: Kernel
equal?: BasicObject
sort: Enumerable