diff --git a/gems/activesupport/6.0/_test/test.rb b/gems/activesupport/6.0/_test/test.rb
index 392495a4..4f8d2c69 100644
--- a/gems/activesupport/6.0/_test/test.rb
+++ b/gems/activesupport/6.0/_test/test.rb
@@ -42,6 +42,15 @@ class TestAttrInternal
   attr_internal_writer 'internal_variable_accessor_2'
 end
 
+"yukihiro_matz".constantize
+"yukihiro_matz".safe_constantize
+"string_ending_with_id".titleize(keep_id_suffix: true).titleize
+"::Net::HTTP".deconstantize.demodulize
+"Donald E. Knuth".parameterize(separator: ":", preserve_case: true, locale: :en).parameterize
+"ham_and_egg".tableize.classify
+"author_id".humanize(capitalize: false, keep_id_suffix: true).humanize
+"iD".upcase_first
+"User".foreign_key(false).foreign_key
 "yukihiro_matz".camelize.underscore.dasherize
 "rabbit".pluralize.singularize
 "rabbit".pluralize(2).pluralize(:en).pluralize(2, :en)
diff --git a/gems/activesupport/6.0/activesupport-generated.rbs b/gems/activesupport/6.0/activesupport-generated.rbs
index 7624bfa2..dc615fab 100644
--- a/gems/activesupport/6.0/activesupport-generated.rbs
+++ b/gems/activesupport/6.0/activesupport-generated.rbs
@@ -5263,156 +5263,6 @@ class String
   def indent: (untyped amount, ?untyped? indent_string, ?bool indent_empty_lines) -> untyped
 end
 
-# String inflections define new methods on the String class to transform names for different purposes.
-# For instance, you can figure out the name of a table from the name of a class.
-#
-#   'ScaleScore'.tableize # => "scale_scores"
-#
-class String
-  # +constantize+ tries to find a declared constant with the name specified
-  # in the string. It raises a NameError when the name is not in CamelCase
-  # or is not initialized.  See ActiveSupport::Inflector.constantize
-  #
-  #   'Module'.constantize  # => Module
-  #   'Class'.constantize   # => Class
-  #   'blargle'.constantize # => NameError: wrong constant name blargle
-  def constantize: () -> untyped
-
-  # +safe_constantize+ tries to find a declared constant with the name specified
-  # in the string. It returns +nil+ when the name is not in CamelCase
-  # or is not initialized.  See ActiveSupport::Inflector.safe_constantize
-  #
-  #   'Module'.safe_constantize  # => Module
-  #   'Class'.safe_constantize   # => Class
-  #   'blargle'.safe_constantize # => nil
-  def safe_constantize: () -> untyped
-
-  alias camelcase camelize
-
-  # Capitalizes all the words and replaces some characters in the string to create
-  # a nicer looking title. +titleize+ is meant for creating pretty output. It is not
-  # used in the Rails internals.
-  #
-  # The trailing '_id','Id'.. can be kept and capitalized by setting the
-  # optional parameter +keep_id_suffix+ to true.
-  # By default, this parameter is false.
-  #
-  # +titleize+ is also aliased as +titlecase+.
-  #
-  #   'man from the boondocks'.titleize                       # => "Man From The Boondocks"
-  #   'x-men: the last stand'.titleize                        # => "X Men: The Last Stand"
-  #   'string_ending_with_id'.titleize(keep_id_suffix: true)  # => "String Ending With Id"
-  def titleize: (?keep_id_suffix: bool keep_id_suffix) -> untyped
-
-  alias titlecase titleize
-
-  # Removes the module part from the constant expression in the string.
-  #
-  #   'ActiveSupport::Inflector::Inflections'.demodulize # => "Inflections"
-  #   'Inflections'.demodulize                           # => "Inflections"
-  #   '::Inflections'.demodulize                         # => "Inflections"
-  #   ''.demodulize                                      # => ''
-  #
-  # See also +deconstantize+.
-  def demodulize: () -> untyped
-
-  # Removes the rightmost segment from the constant expression in the string.
-  #
-  #   'Net::HTTP'.deconstantize   # => "Net"
-  #   '::Net::HTTP'.deconstantize # => "::Net"
-  #   'String'.deconstantize      # => ""
-  #   '::String'.deconstantize    # => ""
-  #   ''.deconstantize            # => ""
-  #
-  # See also +demodulize+.
-  def deconstantize: () -> untyped
-
-  # Replaces special characters in a string so that it may be used as part of a 'pretty' URL.
-  #
-  # If the optional parameter +locale+ is specified,
-  # the word will be parameterized as a word of that language.
-  # By default, this parameter is set to <tt>nil</tt> and it will use
-  # the configured <tt>I18n.locale</tt>.
-  #
-  #   class Person
-  #     def to_param
-  #       "#{id}-#{name.parameterize}"
-  #     end
-  #   end
-  #
-  #   @person = Person.find(1)
-  #   # => #<Person id: 1, name: "Donald E. Knuth">
-  #
-  #   <%= link_to(@person.name, person_path) %>
-  #   # => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
-  #
-  # To preserve the case of the characters in a string, use the +preserve_case+ argument.
-  #
-  #   class Person
-  #     def to_param
-  #       "#{id}-#{name.parameterize(preserve_case: true)}"
-  #     end
-  #   end
-  #
-  #   @person = Person.find(1)
-  #   # => #<Person id: 1, name: "Donald E. Knuth">
-  #
-  #   <%= link_to(@person.name, person_path) %>
-  #   # => <a href="/person/1-Donald-E-Knuth">Donald E. Knuth</a>
-  def parameterize: (?locale: untyped? locale, ?preserve_case: bool preserve_case, ?separator: ::String separator) -> untyped
-
-  # Creates the name of a table like Rails does for models to table names. This method
-  # uses the +pluralize+ method on the last word in the string.
-  #
-  #   'RawScaledScorer'.tableize # => "raw_scaled_scorers"
-  #   'ham_and_egg'.tableize     # => "ham_and_eggs"
-  #   'fancyCategory'.tableize   # => "fancy_categories"
-  def tableize: () -> untyped
-
-  # Creates a class name from a plural table name like Rails does for table names to models.
-  # Note that this returns a string and not a class. (To convert to an actual class
-  # follow +classify+ with +constantize+.)
-  #
-  #   'ham_and_eggs'.classify # => "HamAndEgg"
-  #   'posts'.classify        # => "Post"
-  def classify: () -> untyped
-
-  # Capitalizes the first word, turns underscores into spaces, and (by default)strips a
-  # trailing '_id' if present.
-  # Like +titleize+, this is meant for creating pretty output.
-  #
-  # The capitalization of the first word can be turned off by setting the
-  # optional parameter +capitalize+ to false.
-  # By default, this parameter is true.
-  #
-  # The trailing '_id' can be kept and capitalized by setting the
-  # optional parameter +keep_id_suffix+ to true.
-  # By default, this parameter is false.
-  #
-  #   'employee_salary'.humanize                    # => "Employee salary"
-  #   'author_id'.humanize                          # => "Author"
-  #   'author_id'.humanize(capitalize: false)       # => "author"
-  #   '_id'.humanize                                # => "Id"
-  #   'author_id'.humanize(keep_id_suffix: true)    # => "Author Id"
-  def humanize: (?keep_id_suffix: bool keep_id_suffix, ?capitalize: bool capitalize) -> untyped
-
-  # Converts just the first character to uppercase.
-  #
-  #   'what a Lovely Day'.upcase_first # => "What a Lovely Day"
-  #   'w'.upcase_first                 # => "W"
-  #   ''.upcase_first                  # => ""
-  def upcase_first: () -> untyped
-
-  # Creates a foreign key name from a class name.
-  # +separate_class_name_and_id_with_underscore+ sets whether
-  # the method should put '_' between the name and 'id'.
-  #
-  #   'Message'.foreign_key        # => "message_id"
-  #   'Message'.foreign_key(false) # => "messageid"
-  #   'Admin::Post'.foreign_key    # => "post_id"
-  def foreign_key: (?bool separate_class_name_and_id_with_underscore) -> untyped
-end
-
 class String
   # Wraps the current string in the <tt>ActiveSupport::StringInquirer</tt> class,
   # which gives you a prettier way to test for equality.
diff --git a/gems/activesupport/6.0/activesupport.rbs b/gems/activesupport/6.0/activesupport.rbs
index aa028bab..91b8fe95 100644
--- a/gems/activesupport/6.0/activesupport.rbs
+++ b/gems/activesupport/6.0/activesupport.rbs
@@ -392,10 +392,23 @@ end
 
 class String
   def camelize: (?Symbol first_letter) -> String
+  alias camelcase camelize
   def underscore: () -> String
   def dasherize: () -> String
   def pluralize: (?Integer | Symbol? count, ?Symbol locale) -> String
   def singularize: (?Symbol locale) -> String
+  def constantize: () -> untyped
+  def safe_constantize: () -> untyped
+  def titleize: (?keep_id_suffix: boolish) -> String
+  alias titlecase titleize
+  def demodulize: () -> String
+  def deconstantize: () -> String
+  def parameterize: (?separator: String, ?preserve_case: boolish, ?locale: Symbol) -> String
+  def tableize: () -> String
+  def classify: () -> String
+  def humanize: (?capitalize: boolish, ?keep_id_suffix: boolish) -> String
+  def upcase_first: () -> String
+  def foreign_key: (?boolish separate_class_name_and_id_with_underscore) -> String
 end
 
 module ActiveSupport
diff --git a/gems/activesupport/7.0/_test/test.rb b/gems/activesupport/7.0/_test/test.rb
index 1c5354b0..d77e2c4f 100644
--- a/gems/activesupport/7.0/_test/test.rb
+++ b/gems/activesupport/7.0/_test/test.rb
@@ -17,3 +17,5 @@
 nil.try(:tap) { |n| p n }
 nil.try { p 'hello' }
 nil.try { |n| p n }
+
+"Id".downcase_first
diff --git a/gems/activesupport/7.0/activesupport-7.0.rbs b/gems/activesupport/7.0/activesupport-7.0.rbs
index b3ce4444..702386a0 100644
--- a/gems/activesupport/7.0/activesupport-7.0.rbs
+++ b/gems/activesupport/7.0/activesupport-7.0.rbs
@@ -89,3 +89,8 @@ class Array[unchecked out Elem]
   #   # =>  [1, 2, true]
   def compact_blank!: () -> Array[Elem]
 end
+
+# active_support/core_ext/string/inflections.rb
+class String
+  def downcase_first: () -> String
+end