Sema: Allow parameterized existential compositions

Author: slavapestov

lib/Sema/TypeCheckType.cpp

@@ -5680,11 +5680,7 @@ TypeResolver::resolveCompositionType(CompositionTypeRepr *repr,
       continue;
     }
 
-    // FIXME: Support compositions involving parameterized protocol types,
-    // like 'any Collection<String> & Sendable', etc.
-    if (ty->is<ParameterizedProtocolType>() &&
-        !options.isConstraintImplicitExistential() &&
-        options.getContext() != TypeResolverContext::ExistentialConstraint) {
+    if (ty->is<ParameterizedProtocolType>()) {
       checkMember(tyR->getStartLoc(), ty);
       Members.push_back(ty);
       continue;

test/Constraints/parameterized_existential_composition.swift

@@ -0,0 +1,33 @@
+// RUN: %target-typecheck-verify-swift
+
+func f1(_ s: any Sequence<Int> & Hashable) -> any Sequence<Int> {
+  return s
+}
+
+func f2(_ s: any Sequence<Int> & Hashable) -> any Hashable {
+  return s
+}
+
+func f3(_ s: any Sequence<Int> & Hashable) -> any Sequence {
+  return s
+}
+
+func f4(_ s: any Sequence<Int> & Hashable) -> any Sequence & Hashable {
+  return s
+}
+
+func f5(_ s: any Sequence<Int> & Hashable) -> any Sequence<Int> & Equatable {
+  return s
+}
+
+func f6(_ s: any Sequence<Int> & Hashable) -> any Sequence<String> & Hashable {
+  return s // expected-error {{cannot convert return expression of type 'Int' to return type 'String'}}
+}
+
+func f7(_ s: any Sequence<Int> & Hashable) -> any Sequence<String> {
+  return s // expected-error {{cannot convert return expression of type 'Int' to return type 'String'}}
+}
+
+func f8(_ s: any Collection<Int> & Hashable) -> any Sequence<Int> & Hashable {
+  return s
+}

test/decl/protocol/existential_member_accesses_self_assoctype.swift

@@ -81,8 +81,6 @@ protocol P1 {
   func invariantSelf11() -> Struct<Self>.InnerGeneric<Void>
   // https://github.com/apple/swift/issues/61934
   func invariantSelf12() -> any Sequence<Self>
-  // FIXME
-  // expected-error@+1 {{non-protocol, non-class type 'Sequence<Self>' cannot be used within a protocol-constrained type}}
   func invariantSelf13() -> any P1 & Sequence<Self>
   func invariantSelf14() -> (any Sequence<Self>).Type
   func invariantAssoc1(_: inout Q)
@@ -97,10 +95,8 @@ protocol P1 {
   func invariantAssoc10(_: any P1 & Class<Q>)
   func invariantAssoc11() -> Struct<Q>.InnerGeneric<Void>
   func invariantAssoc12() -> any Sequence<Q>
-  // FIXME
-  // expected-error@+1 {{non-protocol, non-class type 'Sequence<Self.Q>' cannot be used within a protocol-constrained type}}
   func invariantAssoc13() -> any P1 & Sequence<Q>
-func invariantAssoc14() -> (any Sequence<Q>).Type
+  func invariantAssoc14() -> (any Sequence<Q>).Type
 
   // Properties
   var covariantSelfProp1: Self { get }

test/type/parameterized_existential.swift

@@ -82,16 +82,6 @@ func typeExpr() {
   _ = (any Sequence<Int>).self
 }
 
-/// Not supported as a protocol composition term for now
-
-protocol SomeProto {}
-
-func protocolCompositionNotSupported1(_: SomeProto & Sequence<Int>) {}
-// expected-error@-1 {{non-protocol, non-class type 'Sequence<Int>' cannot be used within a protocol-constrained type}}
-
-func protocolCompositionNotSupported2(_: any SomeProto & Sequence<Int>) {}
-// expected-error@-1 {{non-protocol, non-class type 'Sequence<Int>' cannot be used within a protocol-constrained type}}
-
 func increment(_ n : any Collection<Float>) {
   for value in n {
       _ = value + 1