Implement an analysis check that statically validates a string literal pattern argument to find, matches, and sub is a valid regex.

[peterhuene]

If the pattern argument to the find, matches, and sub WDL standard library functions are string literals, we can easily check to see that the pattern compiles as a regex and, if not, emit a diagnostic. It's quite common to use a string literal for the pattern too.

I'm leaning towards doing that in a lint rather than analysis, although a lint warning seems wrong as it could lead to a runtime evaluation error.

[peterhuene]

Another reason I don't want this in analysis itself is that compiling regular expressions can be expensive depending on their complexity; as we must compile it for evaluation, I don't want to compile it twice either (once for analysis and then once again for evaluation).

[a-frantz]

This makes more sense in analysis to me. IMO evaluating it twice is an acceptable redundancy. Main reason for me is that I would want it emitted during a run of sprocket check when lints aren't active.

[peterhuene]

I guess we could implement a cache in each analyzed document where you can ask it for an already-compiled regex for a particular expression (which would need to be a string literal expression).

Ok, makes sense to stick this in analysis then.