Adopt warnUntilSwiftVersion for diag::witness_not_usable_from_inline_warn

This changes the wording of some diagnostics in Swift 4.2 and Swift 4 modes.

Author: beccadax

include/swift/AST/DiagnosticsSema.def

@@ -2637,11 +2637,7 @@ ERROR(type_witness_not_accessible_type,none,
 ERROR(witness_not_usable_from_inline,none,
       "%kind0 must be declared '@usableFromInline' "
       "because it matches a requirement in protocol %1",
-      (const ValueDecl *, Identifier))
-WARNING(witness_not_usable_from_inline_warn,none,
-        "%kind0 should be declared '@usableFromInline' "
-        "because it matches a requirement in protocol %1",
-        (const ValueDecl *, Identifier))
+      (const ValueDecl *, const ProtocolDecl *))
 ERROR(type_witness_objc_generic_parameter,none,
       "type %0 involving Objective-C type parameter%select{| %1}2 cannot be "
       "used for associated type %3 of protocol %4",

lib/Sema/TypeCheckProtocol.cpp

@@ -3310,14 +3310,10 @@ class DiagnoseUsableFromInline {
     auto proto = conformance->getProtocol();
     ASTContext &ctx = proto->getASTContext();
 
-    auto diagID = diag::witness_not_usable_from_inline;
-    if (!ctx.isSwiftVersionAtLeast(5))
-      diagID = diag::witness_not_usable_from_inline_warn;
-
     SourceLoc diagLoc = getLocForDiagnosingWitness(conformance, witness);
-    ctx.Diags.diagnose(diagLoc, diagID,
-                       witness,
-                       proto->getName());
+    ctx.Diags.diagnose(diagLoc, diag::witness_not_usable_from_inline, witness,
+                       proto)
+      .warnUntilSwiftVersion(5);
     emitDeclaredHereIfNeeded(ctx.Diags, diagLoc, witness);
   }
 };

test/Compatibility/attr_usableFromInline_protocol.swift

@@ -7,8 +7,8 @@ public protocol PublicProtoWithReqs {
 }
 
 @usableFromInline struct UFIAdopter<T> : PublicProtoWithReqs {}
-// expected-warning@-1 {{type alias 'Assoc' should be declared '@usableFromInline' because it matches a requirement in protocol 'PublicProtoWithReqs'}} {{none}}
-// expected-warning@-2 {{instance method 'foo()' should be declared '@usableFromInline' because it matches a requirement in protocol 'PublicProtoWithReqs'}} {{none}}
+// expected-warning@-1 {{type alias 'Assoc' must be declared '@usableFromInline' because it matches a requirement in protocol 'PublicProtoWithReqs'; this is an error in Swift 5}} {{none}}
+// expected-warning@-2 {{instance method 'foo()' must be declared '@usableFromInline' because it matches a requirement in protocol 'PublicProtoWithReqs'; this is an error in Swift 5}} {{none}}
 extension UFIAdopter {
   typealias Assoc = Int
   // expected-note@-1 {{'Assoc' declared here}}
@@ -18,9 +18,9 @@ extension UFIAdopter {
 
 @usableFromInline struct UFIAdopterAllInOne<T> : PublicProtoWithReqs {
   typealias Assoc = Int
-  // expected-warning@-1 {{type alias 'Assoc' should be declared '@usableFromInline' because it matches a requirement in protocol 'PublicProtoWithReqs'}} {{none}}
+  // expected-warning@-1 {{type alias 'Assoc' must be declared '@usableFromInline' because it matches a requirement in protocol 'PublicProtoWithReqs'; this is an error in Swift 5}} {{none}}
   func foo() {}
-  // expected-warning@-1 {{instance method 'foo()' should be declared '@usableFromInline' because it matches a requirement in protocol 'PublicProtoWithReqs'}} {{none}}
+  // expected-warning@-1 {{instance method 'foo()' must be declared '@usableFromInline' because it matches a requirement in protocol 'PublicProtoWithReqs'; this is an error in Swift 5}} {{none}}
 }
 
 internal struct InternalAdopter<T> : PublicProtoWithReqs {}
@@ -36,8 +36,8 @@ extension InternalAdopter {
 }
 
 public struct PublicAdopter<T> : UFIProtoWithReqs {}
-// expected-warning@-1 {{type alias 'Assoc' should be declared '@usableFromInline' because it matches a requirement in protocol 'UFIProtoWithReqs'}} {{none}}
-// expected-warning@-2 {{instance method 'foo()' should be declared '@usableFromInline' because it matches a requirement in protocol 'UFIProtoWithReqs'}} {{none}}
+// expected-warning@-1 {{type alias 'Assoc' must be declared '@usableFromInline' because it matches a requirement in protocol 'UFIProtoWithReqs'; this is an error in Swift 5}} {{none}}
+// expected-warning@-2 {{instance method 'foo()' must be declared '@usableFromInline' because it matches a requirement in protocol 'UFIProtoWithReqs'; this is an error in Swift 5}} {{none}}
 extension PublicAdopter {
   typealias Assoc = Int
   // expected-note@-1 {{'Assoc' declared here}}