Plumb Through Parameterized Protocol Existentials #41743
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Add deep equality typing rules for
P =~= Q, T == X, U == Y, V == Z, ...
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P<T, U, V, ...> == Q<X, Y, Z, ...>
Also add existential matching rules to discharge the constraints on parameterized protocols against concrete types. e.g.
class C: P { typealias T = Int }
func foo<T>(_ x: P<T>) {}
foo(C())
Should cause T to unify against C.T = Int
Represent this in much the same way that collections do by creating an opaque value representing the source argument, and a conversion expression representing the destination argument.
CodaFi
changed the title
The problem is that we currenly cannot represent the generic signature of values of type `any P<some P>`. This is because we wind up producing <Self where Self : P, Self.T == (some P)> What we'd like to do in the future is erase the errant (some P) with a fresh generic parameter and keep a substitution map on the side that records the opaque type constraint. Something like <Self, Opaque1 where Self : P, Opaque1 : P, Self.T == Opaque1> where Opaque1 == (some P)
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@swift-ci smoke test |
slavapestov
reviewed
Mar 9, 2022
| @@ -635,6 +635,7 @@ Types | |||
| type ::= protocol-list 'p' // existential type | |||
| type ::= protocol-list superclass 'Xc' // existential type with superclass | |||
| type ::= protocol-list 'Xl' // existential type with AnyObject | |||
| type ::= protocol-list 'y' (type* '_')* type* retroactive-conformance* 'Xp' // parameterized protocol type | |||
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I would prefer a more general mangling that could accommodate arbitrary requirements in the future.
| @@ -3253,6 +3259,22 @@ NodePointer Demangler::demangleSpecialType() { | |||
| return createType(createWithChildren(Node::Kind::ExistentialMetatype, | |||
| MTR, Type)); | |||
| } | |||
| case 'P': { | |||
| NodePointer RetroactiveConformances; | |||
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What are the retroactive conformances here for? any P<some Q>?
| @@ -1445,7 +1445,7 @@ static const TypeInfo *createExistentialTypeInfo(IRGenModule &IGM, CanType T) { | |||
| T = existential->getConstraintType()->getCanonicalType(); | |||
| } | |||
| llvm::StructType *type; | |||
| if (isa<ProtocolType>(T)) | |||
| if (isa<ProtocolType>(T) || isa<ParameterizedProtocolType>(T)) | |||
| type = IGM.createNominalType(T); | |||
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Add a FIXME here or an assert, since this is wrong; the parametrized protocol type does not share metadata with the protocol type
| @@ -1464,9 +1464,10 @@ class SubstFunctionTypePatternVisitor | |||
| if (auto gp = handleTypeParameterInAbstractionPattern(pattern, t)) | |||
| return gp; | |||
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| assert(!pattern.getType()->hasTypeParameter() | |||
| assert(pattern.getType()->isExistentialType() || | |||
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| // Use the requirements of any parameterized protocols to build out fake | ||
| // argument conversions that can be used to infer opaque types. | ||
| SmallVector<CollectionUpcastConversionExpr::ConversionPair, 4> argConversions; |
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Maybe CollectionUpcastConversionExpr::ConversionPair should be moved out?
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Unblock most of the statics and the lowering for the static side of parameterized protocol existentials. Practically, this implements
any P<T>forPa parameterized protocol type (as in #41640). It also unblocksany P<some Q>, though there's some representational issues that are not resolved in this PR - I will tackle them when opened existentials and their signatures are refactored to use a side substitution map.