For the most part, the differences between the diagnostics introduced
by the C++ implementation and the new SwiftIfConfig implementation are
cosmetic, so these are only wording changes.
The one major difference is that we've dropped the warnings about
potential typos in os/arch checks. For example, if one writes:
#if os(bisionos)
// ...
#endif
The C++ implementation will produce a warning "unknown operating system
for build configuration 'os'" with a note asking "did you mean
'visionOS'"? These warnings rely on a static list of known operating
systems and architectures, which is somewhat unfortunate: the whole
point of these checks is that the Swift you're dealing with might not
have support for those operating systems/architectures, so while these
warnings can be helpful in a few cases, they also cause false
positives when porting. Therefore, I chose not to bring them forward.
Previously, diagnostics for arguments of platform conditions (e.g.
'os(macOS)') used to point the condition name position instead of the
argument position.
Adjust the position to the start of the argument.
rdar://124160048
Until now, only ">=" was supported in #if swift() expressions, for example:
```#if swift(>=2.1)
```#endif
This means that if we want to evaluate code only when the language version is
less than a particular version we need to do the following:
```#if !swift(>=2.1)
```#endif
An alernative to make this more readable (the "!" can be easily missed in a code
review) is to introduce another supported unary operator, "<". The previous
example could be rewritten like this:
```#if swift(<2.1)
```#endif
This commit adds support for that unary operator, along with some tests.
* Narrow allowance of 3+ components numeric literal to condition part of the
directive.
* Allow 3+ components in '#if' directive in decl list position as well.
There are two similar but separate code paths for conditionally
compiling declarations and statements. Previously, only statements were
properly covered with a diagnostic transaction.
rdar://problem/24844513
