If we encounter an error prior to 'initialize-static-globals', this pass will not run, and will not convert globals to be statically-initialized at all, regardless of whether or not it would have been possible. This means that diagnostics on failure to do so would then always be emitted, likely as false-positives.
Avoid emitting these diagnostics in a context that contains a prior error.
As a future alternative, we could refine the conditions that make `initialize-static-globals` give up on a given function/value, but for now we need to ensure we do not emit spurious diagnostics.
Resolves rdar://172195372
* move it from the SIL to the AST module (where it belongs)
* change the signature of `diagnose` from `diagnose(location, .some_error)` to `diagnose(.some_error, at: location)`
* add an overload to allow passing a `SIL.Location` directly to `diagnose`
* add a `Diagnostic : Error` utility struct which allows throwing a `Diagnostic`
Artem Chikin
Erik Eckstein