fix: check for reserved names in let bindings

[obycode]

This change checks for reserved names in addition to checking for names previously defined by the user.

Fixes: #418

[codecov-commenter]

Codecov Report

Merging #420 (0a3f56a) into develop (3fc8ac2) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #420      +/-   ##
===========================================
+ Coverage    22.31%   22.33%   +0.01%     
===========================================
  Files          163      163              
  Lines        39186    39187       +1     
===========================================
+ Hits          8745     8753       +8     
+ Misses       30441    30434       -7     

Flag	Coverage Δ
unittests	22.33% <100.00%> (+0.01%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...repl/src/clarity/analysis/type_checker/contexts.rs	80.54% <100.00%> (+0.10%)	:arrow_up:
...ents/clarity-repl/src/repl/ast/parser/lexer/mod.rs	36.13% <0.00%> (+0.35%)	:arrow_up:
...larity-repl/src/clarity/ast/traits_resolver/mod.rs	64.28% <0.00%> (+0.79%)	:arrow_up:
...ponents/clarity-repl/src/clarity/util/secp256k1.rs	12.06% <0.00%> (+0.86%)	:arrow_up:
components/clarinet-files/src/project_manifest.rs	76.28% <0.00%> (+3.09%)	:arrow_up:

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[obycode]

• [ ] I should also add unit tests for this before merging

[moodmosaic]

• [ ] I should also add unit tests for this before merging

Yep! And depending on how the test(s) will look like, it might make sense to turn the test(s) into (a single?) proptest. (May be tackled on a separate PR.)

[lgalabru]

With the VM being pulled from the stacks-blockchain repo this approach does not seem to be viable anymore, so I'll close this PR.