Unlock Parameterized Existentials Behind 'any'

Author: CodaFi

lib/Sema/TypeCheckType.h

@@ -282,12 +282,12 @@ class TypeResolutionOptions {
     case Context::Inherited:
     case Context::ExtensionBinding:
     case Context::GenericRequirement:
+    case Context::ExistentialConstraint:
       return true;
     case Context::None:
     case Context::TypeAliasDecl:
     case Context::GenericTypeAliasDecl:
     case Context::MetatypeBase:
-    case Context::ExistentialConstraint:
     case Context::InExpression:
     case Context::ExplicitCastExpr:
     case Context::ForEachStmt:

test/type/parameterized_protocol.swift

@@ -158,10 +158,8 @@ func returnsSequenceOfInt1() -> Sequence<Int> {}
 // expected-error@-1 {{protocol type with generic arguments can only be used as a generic constraint}}
 
 func takesSequenceOfInt2(_: any Sequence<Int>) {}
-// expected-error@-1 {{protocol type with generic arguments can only be used as a generic constraint}}
 
 func returnsSequenceOfInt2() -> any Sequence<Int> {}
-// expected-error@-1 {{protocol type with generic arguments can only be used as a generic constraint}}
 
 func typeExpr() {
   _ = Sequence<Int>.self