Fix inconsistency in whether locations are opaque in sexps

[WardBrian]

This was mostly a simple case of some missing parenthesis changing the meaning of annotations, or annotations being misnamed.

Submission Checklist

• Run unit tests
• Documentation
  • If a user-facing facing change was made, the documentation PR is here:
  • OR, no user-facing changes were made

Release notes

Copyright and Licensing

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the BSD 3-clause license (https://opensource.org/licenses/BSD-3-Clause)

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.14%. Comparing base (dee6786) to head (861e74e).
⚠️ Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
src/frontend/Ast.ml	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1547      +/-   ##
==========================================
+ Coverage   90.09%   90.14%   +0.05%     
==========================================
  Files          64       64              
  Lines        9861     9855       -6     
==========================================
  Hits         8884     8884              
+ Misses        977      971       -6     

Files with missing lines	Coverage Δ
src/middle/Program.ml	88.88% <ø> (-0.45%)	⬇️
src/frontend/Ast.ml	76.67% <66.66%> (+2.07%)	⬆️

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[nhuurre]

I didn't find a related test. What does this do exactly?

[WardBrian]

I just added an extra Parse_test -- removing the parenthesis will change the output of this new test to include the location, rather than omit <opaque> as elsewhere.

I couldn't find much about the fact that these annotations for deriving are so sensitive, but it seems like they're ignored if they're not precisely as expected, meaning it's easy to miss