Reported Syntax error when using conditional facts["${facts['factname']}"]

[Cinderhaze]

Describe the Bug

We are trying to use the value of a fact as a key for looking up another fact in a conditional. Inside the body of the conditional, we are trying to use the fact, and it is reporting as a syntax error, but it passes puppet parser validate

Initial example that caused it to fail

if $facts["file_${facts['some_custom_fact']}_yaml] {
  service: "${facts['some_custom_fact']}":
    ensure => running,
    enable => true
}

Error was on the line inside of the conditional where we were setting the service name.

I noticed that if I commented out the service line and made changes below it, I still got syntax errors on the commented line.

if $facts["file_${facts['some_custom_fact']}_yaml] {
  service: "$some_custom_fact}":
#  service: "${facts['some_custom_fact']}":
    ensure => running,
    enable => true
}

Expected Behavior

Given usage of using a facts[] lookup as part of a facts lookup is valid consistent with puppet parser validate

Steps to Reproduce

Steps to reproduce the behavior:

cat << 'EOF' > error.pp
if $facts["[]"] {
  #"${bar}"
}
EOF
puppet-lint error.pp

Environment

• Version [2.5.2, 4.0.0(pdk)]

Additional Context

Minimal example that still signals syntax error seems to occur if there are square brackets in the conditional string. Note that the line that it fails on is the comment inside the

if $facts["[]"] {
  #"${bar}"
}

This leads me to believe that there is some error in parsing the 'key' in the facts map, that causes some kind of downstream problems.

We can workaround this by storing the fact in a local variable, and using the local variable for any references within our class.