Merge branch 'feature/expansion_statements' into 'develop'

Reduce errors and compiletime in tree traversal

See merge request !93
4 jobs for develop in 25 minutes and 12 seconds (queued for 32 seconds)
Status Job ID Name Coverage
  Test
passed #8757
debian:10 clang-6-libcpp-17

00:25:12

passed #8756
debian:10 gcc-8-17

00:17:39

passed #8758
debian:9 gcc-6-14

00:18:09

passed #8759
ubuntu:18.04 clang-6-17

00:23:05