René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Restrict method arguments by model getters","articleBody":"Just an idea.\r\n\r\n```crystal\r\nmodule Onyx::SQL\r\n  macro restrict(t, model, \u0026block)\r\n    {% for exp in block.body.expressions %}\r\n      {% unless exp.is_a?(Call) \u0026\u0026 exp.name == \"getter\" %}\r\n        {% raise \"Must be getter\" %}\r\n      {% end %}\r\n\r\n      {% found = false %}\r\n\r\n      {% for method in t.methods %}\r\n        {% if method.name == exp.args.first.var \u0026\u0026\r\n                method.return_type == exp.args.first.type %}\r\n          {% found = true %}\r\n        {% end %}\r\n      {% end %}\r\n\r\n      {% raise \"#{model} is restricted to have `#{exp.args.first.var}` getter with return type `#{exp.args.first.type}`\" unless found %}\r\n    {% end %}\r\n  end\r\nend\r\n\r\nclass User\r\n  property id : Int32?\r\n  property name : String?\r\n\r\n  def initialize(@id = nil, @name = nil)\r\n  end\r\nend\r\n\r\ndef foo(user : T) forall T\r\n  Onyx::SQL.restrict({{T}}, User) do\r\n    getter id : Int32\r\n    getter name : String?\r\n  end\r\n\r\n  pp user\r\nend\r\n\r\nrecord UserObject, id : Int32, name : String?\r\n\r\n# foo(UserObject.new(42, nil)) # OK\r\nfoo(User.new(42, nil)) # User is restricted to have `id` getter with return type `Int32`\r\n```","author":{"url":"https://github.com/vladfaust","@type":"Person","name":"vladfaust"},"datePublished":"2019-05-04T08:15:36.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/99/sql/issues/99"}