...so that we don't have to keep coming back to update it every major
release. And also so we can actually put methods on it instead of
using free functions.
No intended behavior change (yet).
These work like next_or_end or prev_or_begin, except that instead of forcing the
default value to be the compared against the value, you can specify the value
used upon going out of range.
i.e., instead of:
(x, y) -> (x == y) ? y : std::next(x)
We have:
(x, y, z) -> (x == y) ? z : std::next(x)
This is a strict generalization of next_or_end and prev_or_begin so I
re-implemented both routines in terms of the new routines, so no source needed
to be updated.
We've found in practice that multiple different types of expressions
are still going to benefit from shrinking continuing even when it
couldn't simplify up to 10 sub-expressions.
This patch allows Parser to generate a refined token stream to satisfy tooling's need. For syntax coloring, token stream from lexer is insufficient because (1) we have contextual keywords like get and set; (2) we may allow keywords to be used as argument labels and names; and (3) we need to split tokens like "==<". In this patch, these refinements are directly fulfilled through parsing without additional heuristics. The refined token vector is optionally saved in SourceFile instance.
The etymology of these terms isn't about race, but "black" = "blocked"
and "white" = "allowed" isn't really a good look these days. In most
cases we weren't using these terms particularly precisely anyway, so
the rephrasing is actually an improvement.
This implementation required a compromise between parser
performance and AST structuring. On the one hand, Parse
must be fast in order to keep things in the IDE zippy, on
the other we must hit the disk to properly resolve 'canImport'
conditions and inject members of the active clause into the AST.
Additionally, a Parse-only pass may not provide platform-specific
information to the compiler invocation and so may mistakenly
activate or de-activate branches in the if-configuration decl.
The compromise is to perform condition evaluation only when
continuing on to semantic analysis. This keeps the parser quick
and avoids the unpacking that parse does for active conditions
while still retaining the ability to see through to an active
condition when we know we're moving on to semantic analysis anyways.
Recently support was added for '-swift-version 5' to the frontend.
Right now we only have an isSwiftVersion3() check which returns 'true'
if the version is 3, and returns 'false' if it is 4 or 5. This was used
during Swift 4.0 development to guard various legacy behaviors that we
wish to deprecate.
Going forward, when do not want to add isSwiftVersion4() and
isSwiftVersion5() checks, because they're too fragile; if a new
behavior is introduced in Swift 5 that we wish to disable in Swift 3
and Swift 4 mode, checking for isSwiftVersion5() is insufficient,
because eventually Swift 6 will roll around, and presumably one would
expect the new behavior to take effect in Swift 6 mode as well.
I think a better solution is a 'isSwiftVersionAtLeast()' check, which
checks if the major version number is greater than or equal to the
given value.
We could refactor the existing 'isSwiftVersion3()' checks to instead
do '!isSwiftVersionAtLeast(4)', but I'm going to hold off on doing that
for now.
