activerecord: CollectionProxy#build can take Hash-like object

The current definition of `#build`, `#craete` and `#create!` methods of
`ActiveRecord::Associations::CollectionProxy#build` take a Hash object.

But they can also take Hash-like object.  Usually, Rails apps pass an
instance of `ActionController::Parameters`.  The technique is well known
as "Mass Assignment".

Internally, they expects the object should have `#each_pair` method.
Therefore, this changes the signature of these methods to take a
Hash-like object instead of Hash.

refs: https://github.com/rails/rails/blob/v7.0.0/activemodel/lib/active_model/attribute_assignment.rb#L29

gems/activerecord/6.0/_test/activerecord-generated.rb

@@ -2,6 +2,8 @@ class User < ActiveRecord::Base
   enum status: { active: 0, inactive: 1 }, _suffix: true
   enum role: { admin: 0, user: 1 }, _prefix: :user_role
 
+  has_many :articles
+
   validates :name, presence: true, if: -> { something }
   validates :age, presence: true, if: ->(user) { user.something }
 
@@ -12,7 +14,12 @@ def something
   end
 end
 
-_user = User.new
+class Article < ActiveRecord::Base
+end
+
+user = User.new
+user.articles.build(Hash.new)
+user.articles.build(ActionController::Parameters.new)
 
 User.eager_load(:address, friends: [:address, :followers])
 User.includes(:address, :friends).to_a

gems/activerecord/6.0/_test/activerecord-generated.rbs

@@ -2,7 +2,24 @@ class User < ActiveRecord::Base
   class ActiveRecord_Relation < ActiveRecord::Relation
   end
 
+  class ActiveRecord_Associations_CollectionProxy < ::ActiveRecord::Associations::CollectionProxy
+    include ActiveRecord::Relation::Methods[User, Integer]
+  end
+
   extend ActiveRecord::Base::ClassMethods[User, ActiveRecord_Relation, Integer]
 
+  def articles: () -> Article::ActiveRecord_Associations_CollectionProxy
+
   def something: () -> untyped
 end
+
+class Article < ActiveRecord::Base
+  class ActiveRecord_Relation < ActiveRecord::Relation
+  end
+
+  class ActiveRecord_Associations_CollectionProxy < ::ActiveRecord::Associations::CollectionProxy
+    include ActiveRecord::Relation::Methods[Article, Integer]
+  end
+
+  extend ActiveRecord::Base::ClassMethods[Article, ActiveRecord_Relation, Integer]
+end

gems/activerecord/6.0/_test/metadata.yaml

@@ -0,0 +1,2 @@
+additional_gems:
+  - actionpack

gems/activerecord/6.0/_test/steep_expectations.yml

@@ -0,0 +1,13 @@
+---
+- file: activerecord-generated.rb
+  diagnostics:
+  - range:
+      start:
+        line: 1
+        character: 6
+      end:
+        line: 1
+        character: 10
+    severity: ERROR
+    message: Cannot find implementation of method `::User#articles`
+    code: Ruby::MethodDefinitionMissing

gems/activerecord/6.0/activerecord.rbs

@@ -756,6 +756,10 @@ module ActiveRecord
     # is computed directly through SQL and does not trigger by itself the
     # instantiation of the actual post records.
     class CollectionProxy < Relation
+      interface _EachPair
+        def each_pair: () { ([untyped, untyped]) -> untyped } -> self
+      end
+
       def initialize: (untyped klass, untyped association) -> untyped
 
       def target: () -> untyped
@@ -876,7 +880,7 @@ module ActiveRecord
       #
       #   person.pets.size  # => 5 # size of the collection
       #   person.pets.count # => 0 # count from database
-      def build: (?::Hash[untyped, untyped] attributes) ?{ () -> untyped } -> untyped
+      def build: (?_EachPair attributes) ?{ () -> untyped } -> untyped
 
       alias new build
 
@@ -906,7 +910,7 @@ module ActiveRecord
       #   #       #<Pet id: 2, name: "Spook", person_id: 1>,
       #   #       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
       #   #    ]
-      def create: (?::Hash[untyped, untyped] attributes) ?{ () -> untyped } -> untyped
+      def create: (?_EachPair attributes) ?{ () -> untyped } -> untyped
 
       # Like #create, except that if the record is invalid, raises an exception.
       #
@@ -920,7 +924,7 @@ module ActiveRecord
       #
       #   person.pets.create!(name: nil)
       #   # => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank
-      def create!: (?::Hash[untyped, untyped] attributes) ?{ () -> untyped } -> untyped
+      def create!: (?_EachPair attributes) ?{ () -> untyped } -> untyped
 
       # Replaces this collection with +other_array+. This will perform a diff
       # and delete/add only records that have changed.