[Diagnostics] Use warnUntilSwiftVersion for the ownership_invalid_in_protocols

diagnostic and remove ownership_invalid_in_protocols_compat_warning.

Author: hborla

include/swift/AST/DiagnosticsSema.def

@@ -4728,10 +4728,6 @@ ERROR(invalid_ownership_is_let,none,
 ERROR(ownership_invalid_in_protocols,none,
       "%0 cannot be applied to a property declaration in a protocol",
       (ReferenceOwnership))
-WARNING(ownership_invalid_in_protocols_compat_warning,none,
-      "%0 should not be applied to a property declaration "
-      "in a protocol and will be disallowed in future versions",
-      (ReferenceOwnership))
 
 // required
 ERROR(required_initializer_nonclass,none,

lib/Sema/TypeCheckAttr.cpp

@@ -3354,10 +3354,9 @@ Type TypeChecker::checkReferenceOwnershipAttr(VarDecl *var, Type type,
   if (PDC && !PDC->isObjC()) {
     // Ownership does not make sense in protocols, except for "weak" on
     // properties of Objective-C protocols.
-    auto D = var->getASTContext().isSwiftVersionAtLeast(5)
-                 ? diag::ownership_invalid_in_protocols
-                 : diag::ownership_invalid_in_protocols_compat_warning;
+    auto D = diag::ownership_invalid_in_protocols;
     Diags.diagnose(attr->getLocation(), D, ownershipKind)
+        .warnUntilSwiftVersion(5)
         .fixItRemove(attr->getRange());
     attr->setInvalid();
   }

test/Compatibility/ownership_protocol.swift

@@ -4,14 +4,14 @@
 class SomeClass {}
 
 protocol P {
-  // expected-warning@+1 {{'weak' should not be applied to a property declaration in a protocol and will be disallowed in future versions}}
+  // expected-warning@+1 {{'weak' cannot be applied to a property declaration in a protocol; this is an error in Swift 5}}
   weak var foo: SomeClass? { get set }
-  // expected-warning@+1 {{'unowned' should not be applied to a property declaration in a protocol and will be disallowed in future versions}}
+  // expected-warning@+1 {{'unowned' cannot be applied to a property declaration in a protocol; this is an error in Swift 5}}
   unowned var foo2: SomeClass { get set }
-  // expected-warning@+2 {{'weak' should not be applied to a property declaration in a protocol and will be disallowed in future versions}}
+  // expected-warning@+2 {{'weak' cannot be applied to a property declaration in a protocol; this is an error in Swift 5}}
   // expected-error@+1 {{'weak' may only be applied to class and class-bound protocol types, not 'Int'}}
   weak var foo3: Int? { get set }
-  // expected-warning@+2 {{'unowned' should not be applied to a property declaration in a protocol and will be disallowed in future versions}}
+  // expected-warning@+2 {{'unowned' cannot be applied to a property declaration in a protocol; this is an error in Swift 5}}
   // expected-error@+1 {{'unowned' may only be applied to class and class-bound protocol types, not 'Int'}}
   unowned var foo4: Int { get set }
 }

test/decl/protocol/protocols.swift

@@ -467,7 +467,7 @@ protocol ShouldntCrash {
 
 // rdar://problem/18168866
 protocol FirstProtocol {
-    // expected-warning@+1 {{'weak' should not be applied to a property declaration in a protocol and will be disallowed in future versions}}
+    // expected-warning@+1 {{'weak' cannot be applied to a property declaration in a protocol; this is an error in Swift 5}}
     weak var delegate : SecondProtocol? { get } // expected-error{{'weak' must not be applied to non-class-bound 'SecondProtocol'; consider adding a protocol conformance that has a class bound}}
 }