Fix check access of nested fields of object

[JSAbrahams]

Relevant issues

• Closes #297

Summary

Fix #297 by recursively for each inner call also generating a constraint.

An example

x.y.z is turned into:

• 'x'.y == 'x.y'
• 'x.y'.z == 'x.y.z'

Then in the unifcation stage:

• 'x'.y is a direct access so one can take the class of x, look at field y, and determine the of expression 'x.y'.
• One now knows what 'x.y' is in 'x.y'.z, so we lookup z in whatever type 'x.y' is to know the type of x.y.z.

Added Tests

• Operations on nested access
• Print of nested access

[JSAbrahams]

Perhaps we are missing a substitute rule for access somewhere, though that does seem unlikely. Also, it would be nice if we can get rid of all duplicate constraints before going into the unification stage, also for a more succinct trace. I've tried to check before adding but didn't work yet for some reason.

[codecov[bot]]

Codecov Report

Merging #339 (82bbaa1) into develop (28b4109) will increase coverage by 0.18%. The diff coverage is 95.23%.

@@             Coverage Diff             @@
##           develop     #339      +/-   ##
===========================================
+ Coverage    86.39%   86.57%   +0.18%     
===========================================
  Files          109      109              
  Lines        11649    11637      -12     
===========================================
+ Hits         10064    10075      +11     
+ Misses        1585     1562      -23