Coverage gaps on match and some function argument lines.

[scouten]

I am seeing some lines of code marked as executable, but not reached, when it is logically impossible for those lines to have been missed.

This codecov.io report demonstrates some examples of that with a match expression and a function with arguments spilling across multiple lines.

[xd009642]

Closing this issue as the llvm coverage backend is now released --engine llvm with increased accuracy due to compile time instrumentation instead of runtime