puppetlabs/puppet · error · Puppet::ParseError

'%{pn}' is not a known type parameter for %{label}-Type

Error message

'%{pn}' is not a known type parameter for %{label}-Type

What it means

When an Object type is parameterized with a single Hash argument that is not itself assignable to the first type parameter, the hash is treated as named arguments: each key must be a declared type parameter name of the base type. An unknown key raises Puppet::ParseError naming the key and the type.

Source

Thrown at lib/puppet/pops/types/p_object_type_extension.rb:71

  def initialize(base_type, init_parameters)
    pts = base_type.type_parameters(true)
    raise Puppet::ParseError, _('The %{label}-Type cannot be parameterized using []') % { label: base_type.label } if pts.empty?

    @base_type = base_type

    named_args = init_parameters.size == 1 && init_parameters[0].is_a?(Hash)
    if named_args
      # Catch case when first parameter is an assignable Hash
      named_args = pts.size >= 1 && !pts.values[0].type.instance?(init_parameters[0])
    end

    by_name = {}
    if named_args
      hash = init_parameters[0]
      hash.each_pair do |pn, pv|
        tp = pts[pn]
        if tp.nil?
          raise Puppet::ParseError, _("'%{pn}' is not a known type parameter for %{label}-Type") % { pn: pn, label: base_type.label }
        end

        by_name[pn] = check_param(tp, pv) unless pv == :default
      end
    else
      pts.values.each_with_index do |tp, idx|
        if idx < init_parameters.size
          pv = init_parameters[idx]
          by_name[tp.name] = check_param(tp, pv) unless pv == :default
        end
      end
    end
    if by_name.empty?
      raise Puppet::ParseError, _('The %{label}-Type cannot be parameterized using an empty parameter list') % { label: base_type.label }
    end

    @parameters = by_name
  end

View on GitHub (pinned to e227c27540)

Solutions

1. Use exactly the declared type parameter names as hash keys: MyApp::Color[{channel => 3}]
2. If the name is right but undefined, declare it under type_parameters in the Object definition
3. Remember each value is type-checked against the parameter's declared type (check_param), so also verify the value kind

Example fix

# before
type MyApp::Color = Object[{ type_parameters => { channel => Integer } }]
$bad = MyApp::Color[{colour => 3}]   # 'colour' is not a type parameter

# after
$good = MyApp::Color[{channel => 3}]

# named-argument keys must all be declared type parameter names
known = base_type.type_parameters(true).keys
unknown = arg_hash.keys - known
raise "unknown type parameters: #{unknown.inspect}; known: #{known.inspect}" unless unknown.empty?

def valid_type_param_keys?(base_type, hash)
  (hash.keys - base_type.type_parameters(true).keys).empty?
end

begin
  Puppet::Pops::Types::PObjectTypeExtension.create(base_type, [hash])
rescue Puppet::ParseError => e
  raise unless e.message =~ /is not a known type parameter/
  raise  # e.message names the bad key and the type
end

When it happens

Trigger: MyApp::Color[{colour => 3}] when the declared type parameter is channel; also triggered by hash keys matching only an attribute name instead of a type parameter name. Note that a hash assignable to the first type parameter's type is instead bound positionally as that parameter's value.

Common situations: Typos or spelling differences (colour vs channel, UK/US variants); using attribute names in the parameterization hash; renaming a type parameter without updating call sites.

Related errors

• The %{label}-Type cannot be parameterized using []
• The %{label}-Type cannot be parameterized using an empty par
• The attribute '%{name}' is reserved and cannot be used
• Initializer for class #{impl_class.name} does not match the
• Initializer for class #{impl_class.name} parameter '#{ip}' d

AI-assisted analysis of puppetlabs/puppet@e227c27540 (2026-08-21). Data as JSON: /api/errors/6e5b2e50a30c8e0c. Report an issue: GitHub.