chore: Improve no instantiation error message

[jawoznia]

#98

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 85.17%. Comparing base (5888a88) to head (bc15684).

Files	Patch %	Lines
sylvia-derive/src/message.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #338      +/-   ##
==========================================
- Coverage   85.23%   85.17%   -0.07%     
==========================================
  Files          37       37              
  Lines        2702     2704       +2     
==========================================
  Hits         2303     2303              
- Misses        399      401       +2     

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[kulikthebird]

That looks promising!

[kulikthebird]

Only one thing bothers me - why the code coverage is not calculated properly here?

[jawoznia]

Only one thing bothers me - why the code coverage is not calculated properly here?

I think this is because trybuild invokes rustc on it's own per test file (otherwise tests would fail the original process run by us).
Then it makes sense that tarpaulin doesn't incorporate those runs into it's report since those are separate processes.

It's sad as I thought we will be able to cover error cases using trybuild.
Solution to this is not obvious to me at the moment so I will open a separate issue to track it.