Validate that self must be the first parameter in impl method

[dsocolobsky]

I think this solves #216 ?
Let me know if I need to change anything.

[github-actions]

Benchmarking (macOS) factorial

Compiling factorial (factorial.con)
Finished release in 1.871051667s
Running 5000000 iterations
Using input value: 20
Concrete Result = 2432902008176640000 Time taken : 39.05 ms
Rust Result = 2432902008176640000 Time taken : 33.91 ms

Benchmarking (macOS) fib

Compiling fib (fib.con)
Finished release in 168.960291ms
Running 5000 iterations
Using input value: 20
Concrete Result = 6765 Time taken : 100.83 ms
Rust Result = 6765 Time taken : 109.89 ms

[github-actions]

Benchmarking (Linux) factorial

Compiling factorial (factorial.con)
Finished release in 32.892612ms
Running 5000000 iterations
Using input value: 20
Concrete Result = 2432902008176640000 Time taken : 96.89 ms
Rust Result = 2432902008176640000 Time taken : 60.43 ms

Benchmarking (Linux) fib

Compiling fib (fib.con)
Finished release in 26.116232ms
Running 5000 iterations
Using input value: 20
Concrete Result = 6765 Time taken : 136.93 ms
Rust Result = 6765 Time taken : 85.86 ms

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.16%. Comparing base (4802a28) to head (73fbbae).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/check/mod.rs	0.00%	12 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #236      +/-   ##
==========================================
- Coverage   56.29%   56.16%   -0.13%     
==========================================
  Files          25       25              
  Lines        5516     5528      +12     
==========================================
  Hits         3105     3105              
- Misses       2411     2423      +12     

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