Debug print AST tree #276

[Konstantin8105]

See #276

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This change is 

[codecov]

Codecov Report

Merging #306 into master will decrease coverage by 0.02%.
The diff coverage is 76.92%.

@@            Coverage Diff             @@
##           master     #306      +/-   ##
==========================================
- Coverage   81.85%   81.83%   -0.03%     
==========================================
  Files         136      136              
  Lines        5588     5614      +26     
==========================================
+ Hits         4574     4594      +20     
- Misses        815      818       +3     
- Partials      199      202       +3

Impacted Files	Coverage Δ
ast/util.go	71.42% <76.92%> (+8.92%)	⬆️

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[elliotchance]

Reviewed 2 of 2 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved.

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