Support pack expansion types in term rewriting, maintaining shape invariants and not
throwing assertions unnecessarily.
Additional tests added for an inifinite case and a concrete case.
Adding abstractions to check terms for shape symbol and remove the shape
symbol from the end of the sequence of symbols, rather than manually
manipulating the end() sequence externally.
The flow was such that we recorded subtype constraints regardless of the
subject type's nature. Extract value generics handling out of the
devious `else if` chain, and never record any subtype constraints if the
subject type is a non-type parameter.
While we're here, generalize the diagnostic message for user-written
subtype constraints on value generic parameters and emit it
consistently, not just if the right-hand side contains a protocol type.
If we failed to construct a rewrite system for a protocol, either because
the Knuth-Bendix algorithm failed or because of a request cycle while
resolving requirements, we would end up in a situation where the resulting
rewrite system didn't include all conformance requirements and associated
types, so name lookup would find declarations whose interface types are
not valid type parameters.
Fix this by propagating failure better and just doing nothing in
getReducedTypeParameter().
Fixes rdar://147277543.
We would crash in some cases, or produce a slightly misleading
diagnostic about same-element requirements, which are related but
not quite the same.
In the fullness of time, we should figure out this corner of the
language. Until then, add a new diagnostic since this is really
about same-type requirements between concrete types and packs.
Fixes rdar://159790557.
While the intent behind this functor was noble, it has grown in complexity
considerably over the years, and it seems to be nothing but a source of
crashes in practice. I don't want to deal with it anymore, so I've decided
to just subsume all usages with LookUpConformanceInModule instead.
The implementation of Knuth-Bendix completion has had a subtle
bookkeeping bug since I first wrote the code in 2021.
It is possible for two rules to overlap in more than one position,
but the ResolvedOverlaps set was a set of pairs (i, j), where
i and j are the index of the two rules. So overlaps other than
the first were not considered. Fix this by changing ResolvedOverlaps
to a set of triples (i, j, k), where k is the position in the
left-hand side of the first rule.
The end result is that we would incorrectly accept the protocol M3
shown in the test case. I'm pretty sure the monoid that M3 encodes
does not have a complete presentation over any alphabet, so of
course it should not be accepted here.
The concrete nesting limit, which defaults to 30, catches
things like A == G<A>. However, with something like
A == (A, A), you end up with an exponential problem size
before you hit the limit.
Add two new limits.
The first is the total size of the concrete type, counting
all leaves, which defaults to 4000. It can be set with the
-requirement-machine-max-concrete-size= frontend flag.
The second avoids an assertion in addTypeDifference() which
can be hit if a certain counter overflows before any other
limit is breached. This also defaults to 4000 and can be set
with the -requirement-machine-max-type-differences= frontend flag.
Convert a bunch of places where we're dumping to stderr and calling
`abort` over to using `ABORT` such that the message gets printed to
the pretty stack trace. This ensures it gets picked up by
CrashReporter.
Enhance the logic in `applyInverses` to also take into account same-type constraints spelled in
the generic signature, so that same-type-constraining a type parameter to a type that is itself
not `Copyable` or `Escapable` suppresses the default application of those constraints on the
type parameter. Fixes rdar://147757973.
`extension G<Int>` introduces a same-type requirement, and
this isn't supported for variadic generic types yet.
Make sure we pass a valid source location here to diagnose
instead of dropping the error.
- Fixes https://github.com/apple/swift/issues/70432
- Fixes rdar://119613080
In the below, 'Self.A.A' is not a type parameter; rather, since
'Self.A' is concretely known to be 'S', we resolve it as 'S.A',
which performs a name lookup and finds the concrete type alias 'A':
public struct S {
public typealias A = Int
}
public protocol P {
typealias A = S
}
public struct G<T> {}
public protocol Q: P {
typealias B = G<Self.A.A>
}
This is fine, but such a type alias should not participate in
the rewrite system. Let's exclude them like any other invalid
requirement.
The type alias itself is not an error; however, it is an error
to use it from a 'where' clause requirement. This is not
diagnosed yet, though.
Fixes rdar://136686001.
As specified by the SE-0446 acceptance, extensions that declare a type's
conditional `Copyable` or `Escapable` ability must reiterate explicitly all
of the `Copyable` and/or `Escapable` requirements, whether required or not
required (by e.g. `~Copyable`) that were suppressed in the original
type declaration.
