class SimpleForm::FormBuilder

def find_mapping(input_type)

3) If not, fallbacks to SimpleForm::Inputs::#{input_type}Input
2) If not, fallbacks to #{input_type}Input
b) Or use the found mapping
a) Try to find an alternative with the same name in the Object scope
1) It tries to find a registered mapping, if succeeds:

Attempts to find a mapping. It follows the following rules: 
def find_mapping(input_type)
  discovery_cache[input_type] ||=
    if mapping = self.class.mappings[input_type]
      mapping_override(mapping) || mapping
    else
      camelized = "#{input_type.to_s.camelize}Input"
      attempt_mapping_with_custom_namespace(camelized) ||
        attempt_mapping(camelized, Object) ||
        attempt_mapping(camelized, self.class) ||
        raise("No input found for #{input_type}")
    end
end