semantic: test constraints

[shramee]

chore: clippy/fmt
semantic: test constraints

Minor updates to add semantic test constraints like get! should return a tail and correct inputs should not result in diagnostic errors.

Helps to enforce the constraints are met and CAIRO_FIX_TESTS with incorrect semantics doesn't make failing tests pass.

[tarrencev]

Hmm I think these cases should actually be explicitly tested in the semantics test. We should have test cases in the test_data that result in expected diagnostics

[shramee]

That does happen, but it can be easily changed to potentially incorrect ones with CAIRO_FIX_TESTS.

[tarrencev]

Hm but the generated outputs should be verified in the pull request, thats the point of the snapshot tests