Better errors for wrong or missing allowed field on forms

[edwardloveall]

I had a situation like this:

class Shard < BaseModel
  table :shards do
    # other fields
    belongs_to category : Category?
  end
end

class Shards::New < BrowserAction
  action do
    render NewPage, shard_form: ShardForm.new
  end
end

class ShardForm < Shard::BaseForm
  allow category_id
  allow_virtual repo_name : String
  # other fields
end

class Shard::NewPage < MainLayout
  private def render(f : ShardForm)
    form_for Create do
      # other fields
      select_input f.category_id do
        options_for_select(f.category_id, categories_for_select)
      end

      submit "Add"
    end
  end
end

At various times, I had the category_id field in the ShardForm labeled incorrectly (allow category_id : Int32?) or missing. I got an error like this:

no overload matches 'Shards::NewPage#select_input' with type LuckyRecord::Field(Int32 | Nil)
Overloads are:
- Lucky::SelectHelpers#select_input(field : LuckyRecord::AllowedField, **html_options, &block)

It took me a while to figure out that category_id didn't need a type along with it. Perhaps a better error message would have led me in the right direction sooner.