Invalid parser function breaks catalog compilation in all environments

Puppet Version: 6.20.0
Puppet Server Version: 6.15.0
OS Name/Version: CentOS Linux 7.9

Crafting a parser function file in a particular way causes most future catalog compilations to fail across all environments after the function is executed once, until puppetserver is restarted. 

To reproduce, create a file in lib/puppet/parser/functions/bork.rb with the following contents:

module Puppet
  module Parser
    module Functions
      newfunction(
        :bork,
        type: :rvalue,
        doc: 'B0rks the puppetserver'
      ) do |args|
        return true
      end
    end
  end
end

Then have an agent manifest call the `bork()` function. 

Observe most future puppet runs fail, even for other nodes in other environments that previously worked before.  

The error frequently seen is:

Error 500 on SERVER: Server Error: Evaluation Error: Error while evaluating a Function Call, undefined method `[]' for Puppet::Pops::Loader::RubyLegacyFunctionInstantiator::Puppet:Module

Desired Behavior:

Catalog fails for the invalid parser function, and other catalogs work fine. 

Actual Behavior:

Most future catalog compilations fail, even for unrelated nodes in other environments that previously worked before the `bork()` function was called.

The following simple catalog is known to fail, where it previous works:

include stdlib

$test = pick($puppetmaster, $::fqdn)