This reverts commit c725660cc9. It
uncovered a use-after-free in the GenericSignatureBuilder. Apologies
for the lack of a test case here; I'm still looking for something
small enough to commit.
Fixes rdar://problem/46772328.
Instead of trying to order based on the "nested depth", let's
always prefer canonical ordering of type parameters when it comes
to picking representative equivalence class.
Resolves: rdar://problem/45957015
Associated type inference can synthesize type aliases with the same name
as a generic parameter. This is all fine since the underlying type of
the alias is the generic parameter type, however it might have been
synthesized in a constrained extension, resulting in bogus diagnostics
that depend on the order in which declarations are type checked, which
can vary between WMO and non-WMO, different batch mode settings, etc.
Instead, let's just check the generic parameter list first.
Fixes <rdar://problem/22587551>, <rdar://problem/44777661>.
We can use a cheaper check; instead of transforming both types and
replacing any type parameters with their anchors, instead just
check if both map to the same equivalence class.
This also fixes a bug, even though it shouldn't, but I'll take it.
Fixes <rdar://problem/35756206>.
In structural lookup mode, let's resolve protocol typealiases to
dependent member types also. This is because areSameType() has
no way to see if a type alias is going to be equal to another
associated type with the same name, and so it would return false,
which produced ambiguity errors when there should not be any.
This exposes a deficiency in how we diagnose same-type constraints
where both sides are concrete. Instead of performing the check on
the requirement types, which might be dependent member types that
later on resolve to concrete types, do the check on the actual
equivalence classes further down in the GSB instead.
However, this in turn produces bogus diagnostics in some recursive
cases where we add same-type constraints twice for some reason,
resulting in a warning the second time around. Refine the check by
adding a new predicate to FloatingRequirementSource for requirements
that are explicitly written in source... which is not what
isExplicit() currently means.
These two declarations are now equivalent:
protocol P : SomeClass { ... }
protocol P where Self : SomeClass { ... }
There's a long, complicated story here:
- Swift 4.2 rejected classes in the inheritance clause of a
protocol, but it accepted the 'where' clause form, even
though it didn't always work and would sometimes crash
- Recently we got the inheritance clause form working, and
added a diagnostic to ban the 'where' clause form, because
we thought it would simplify name lookup to not have to
consider the 'where' clause
- However, we already had to support looking at the 'where'
clause from name lookup anyway, because you could write
extension P where Self : SomeClass { ... }
- It turns out that despite the crashes, protocols with
'Self' constraints were already common enough that it was
worth supporting the existing behavior, instead of banning
it
Fixes <rdar://problem/43028442>.
There's no need to instantiate archetypes in the generic environment
of the declaration being opened.
A couple of diagnostics changed. They were already misleading, and the
new diagnostics, while different, are not any more misleading than
before.
This makes diagnostics more verbose and accurate, because
it's possible to distinguish how many parameters there are
based on the message itself.
Also there are multiple diagnostic messages in a format of
`<descriptive-kind> <decl-name> ...` that get printed as
e.g. `subscript 'subscript'` if empty labels are omitted.
For explicit abstract protocol floating requirement sources, get the source location from the protocol requirement rather than delegating to the parent `RequirementSource`.
These will never work properly because of phase ordering issues with
the current declaration checker design. Since we can always express
the same thing with the protocol inheritance clause instead, just
diagnose this as an error instead of trying to hack around it.
Fixes <rdar://problem/38077232>, <https://bugs.swift.org/browse/SR-5581>.
This is fix for a source compat regression from:
commit 790625ab5b
Author: Doug Gregor <dgregor@apple.com>
Date: Mon Mar 19 15:29:32 2018 -0700
Allow a witness's noescape parameter to match a requirement's escaping parameter
The regression is not severe but its easy enough to fix.
With the above change, it was possible for an optional requirement that did
not have a witness in Swift 4.1 to pick up a witness in Swift 4.2, because
the escaping/noescape mismatch prevented it from being considered in Swift 4.1.
If the new witness was not sufficiently visible, this caused a source
compatibility regression.
Work around this by discarding the witness if its not sufficiently
visible. In -swift-version 5, the hack expires, and we revert to the
stricter, more consistent behavior.
Fixes <rdar://problem/39614880>.
Allow witnesses to protocols in a copyable context to elide explicit
ownership conventions. This allows clients like the standard library to
standardize on one ownership convention without an ABI or API breaking
change in 3rd party code.
In the future, moveonly contexts must disallow this default behavior
else the witness thunks could silently transfer ownership.
rdar://40774922
protocol P {
__consuming func implicit(x: __shared String)
__consuming func explicit(x: __owned String)
__consuming func mismatch(x: __shared String)
}
class C : P {
// C.implicit(x:) takes self and x '@guaranteed' thru the witness thunk
func implicit(x: String) {}
// C.explicit(x:) takes self and x @owned with no convention changes
__consuming func explicit(x: __owned String) {}
// Would inherit __consuming, but x has been spelled __owned so the requirement match fails.
func mismatch(x: __owned String) {}
}
That is, if there's a problem with a witness, and the witness comes
from a different extension from the conformance (or the original type,
when the conformance is on an extension), put the main diagnostic on
the conformance, with a note on the witness. This involves some
shuffling and rephrasing of existing diagnostics too.
There's a few reasons for this change:
- More context. It may not be obvious why a declaration in file
A.swift needs to be marked 'public' if you can't see the conformance
in B.swift.
- Better locations for imported declarations. If you're checking a
conformance in a source file but the witness came from an imported
module, it's better to put the diagnostic on the part you have
control over. (This is especially true in Xcode, which can't display
diagnostics on imported declarations in the source editor.)
- Plays better with batch mode. Without this change, you can have
diagnostics being reported in file A.swift that are tied to a
conformance declared in file B.swift. Of course the contents of
A.swift also affect the diagnostic, but compiling A.swift on its
own wouldn't produce the diagnostic, and so putting it there is
problematic.
The change does in some cases make for a worse user experience,
though; if you just want to apply the changes and move on, the main
diagnostic isn't in the "right place". It's the note that has the info
and possible fix-it. It's also a slightly more complicated
implementation.
The diagnostic change is harmless. The diagnostic that is no longer being
emitted was intended for multi-file conformance checking only, and we still
emit a diagnostic for the overall conformance failure with missing witnesses.
Typealiases in protocol extensions can be used to satisfy
associated type requirements. However, when they don’t meet all
of the requirements placed on the associated type, fall back to
the normal inference path rather than failing outright.
Fixes SR-6609 / rdar://problem/36038033.
Introduce an ugly hack where a typealias in a protocol extension that
has the name `_Default_Foo` can be found by associated type inference for
an associated type named `Foo`, respecting the constrains of the protocol
extension in which that typealias resides.
When a protocol closes off an associated type by tying it to a concrete
type (e.g., via a same-type constraint), allow associated type inference
to use that information to infer the associated type rather than
requiring the user to restate the obvious.
Fixes SR-6640.
During associated type inference, also look for default associated type
witnesses from overridden associated types, so that one need not
redeclare default associated types at every level in a protocol hierarchy.
Within the compiler, we use the term "layout constraint" for any
constraint that affects the layout of a type parameter that has that
constraint. However, the only user-visible constraint is "AnyObject",
and calling that a layout constraint is confusing. Drop the term
"layout" from diagnostics.
Fixes rdar://problem/35295372.
As part of type witness inference, allow us to infer a generic parameter
as the type witness for an associated type, when the associated type has
the same name as the generic parameter.
We likely want the more-general rule that generic parameters are always
visible as members of their enclosing type, but I'll tackle that separately.
This works around an order dependency that affected the source
compatibility suite.
If unqualified name lookup finds an associated type, but resolution to
the type witness fails, produce a diagnostic rather than silently
failing. Fixes the crash in SR-5825, SR-5881, and SR-5905.
It's conceivable that we could resolve this with suitably global
associated type inference... but that's far off and it's best not to
crash until then.
The base mutability of storage is part of the signature, so be sure
to compute that during validation. Also, serialize it as part of
the storage declaration, and fix some places that synthesize
declarations to set it correctly.
We had two slightly different codepaths to diagnose ': class'
in an inheritance clause where it is not supported.
For generic parameters, we would fix the 'class' to 'AnyObject',
but for associated types we didn't do this. Perform the fix in
all cases where it makes sense and remove one of the two
diagnostics.
