Compiler Validator Pass

[ScottCarda-MS]

Added a Validator pass to check that the submitted code does not contain:

• Adj/Ctl operations that return non-Unit
• Partial applications
• Lambda expressions
• Callable type parameters on callables
• Type holes

Issue #71

[swernli]

I think it would make sense to include calls to the validator in the compile function in compiler/qsc_frontend/src/compile.rs. That way you can collect errors and surface them up in a way consistent with how parsing and symbol resolution errors work. That will involve introducing a new ErrorKind alongside the existing ErrorKind::Parse and ErrorKind::Resolve, and then updating the new code in validate.rs to collect errors into an internal structure instead of using panic. We chat more about the details here, but I think this is a good foundation so far.

[swernli]

One minor formatting comment, otherwise this looks good!

[ScottCarda-MS]

/azp run

[azure-pipelines]

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.