Promote a bunch of Swift 3 compatibility access warnings to errors.

This was done back in Swift 3.0.1 or 3.0.2. Let's finally make them
errors in Swift 4!

I also fixed up a number of '%error' entries in diagnostics that can
actually happen in invalid code. These are the ones that were already
present in the warnings.

Author: jrose-apple

include/swift/AST/DiagnosticsSema.def

@@ -1196,7 +1196,8 @@ ERROR(pattern_type_access,none,
       "%select{%select{variable|constant}0|property}1 "
       "%select{must be declared %select{"
       "%select{private|fileprivate|internal|%error|%error}3|private or fileprivate}4"
-      "|cannot be declared %select{%error|fileprivate|internal|public|open}3}2 "
+      "|cannot be declared "
+      "%select{in this context|fileprivate|internal|public|open}3}2 "
       "because its type uses "
       "%select{a private|a fileprivate|an internal|%error|%error}5 type",
       (bool, bool, bool, Accessibility, bool, Accessibility))
@@ -1211,7 +1212,8 @@ ERROR(pattern_type_access_inferred,none,
       "%select{%select{variable|constant}0|property}1 "
       "%select{must be declared %select{"
       "%select{private|fileprivate|internal|%error|%error}3|private or fileprivate}4"
-      "|cannot be declared %select{%error|fileprivate|internal|public|open}3}2 "
+      "|cannot be declared "
+      "%select{in this context|fileprivate|internal|public|open}3}2 "
       "because its type %6 uses "
       "%select{a private|a fileprivate|an internal|%error|%error}5 type",
       (bool, bool, bool, Accessibility, bool, Accessibility, Type))
@@ -1271,14 +1273,16 @@ ERROR(unsupported_nested_protocol,none,
 ERROR(type_alias_underlying_type_access,none,
       "type alias %select{must be declared %select{"
       "%select{private|fileprivate|internal|%error|%error}2|private or fileprivate}3"
-      "|cannot be declared %select{%error|fileprivate|internal|public|open}1}0 "
+      "|cannot be declared "
+      "%select{in this context|fileprivate|internal|public|open}1}0 "
       "because its underlying type uses "
       "%select{a private|a fileprivate|an internal|%error|%error}2 type",
       (bool, Accessibility, Accessibility, bool))
 WARNING(type_alias_underlying_type_access_warn,none,
         "type alias %select{should be declared "
         "%select{private|fileprivate|internal|%error|%error}2"
-        "|should not be declared %select{%error|fileprivate|internal|public|open}1}0 "
+        "|should not be declared "
+        "%select{in this context|fileprivate|internal|public|open}1}0 "
         "because its underlying type uses "
         "%select{a private|a fileprivate|an internal|%error|%error}2 type",
         (bool, Accessibility, Accessibility, bool))
@@ -1287,7 +1291,8 @@ WARNING(type_alias_underlying_type_access_warn,none,
 ERROR(subscript_type_access,none,
       "subscript %select{must be declared "
       "%select{private|fileprivate|internal|%error|%error}1"
-      "|cannot be declared %select{%error|fileprivate|internal|public|open}1}0 "
+      "|cannot be declared "
+      "%select{in this context|fileprivate|internal|public|open}1}0 "
       "because its %select{index|element type}3 uses "
       "%select{a private|a fileprivate|an internal|%error|%error}2 type",
       (bool, Accessibility, Accessibility, bool))
@@ -1304,7 +1309,8 @@ ERROR(function_type_access,none,
       "%select{function|method|initializer}4 "
       "%select{must be declared %select{"
       "%select{private|fileprivate|internal|%error|%error}1|private or fileprivate}2"
-      "|cannot be declared %select{%error|fileprivate|internal|public|open}1}0 "
+      "|cannot be declared "
+      "%select{in this context|fileprivate|internal|public|open}1}0 "
       "because its %select{parameter|result}5 uses "
       "%select{a private|a fileprivate|an internal|%error|%error}3 type",
       (bool, Accessibility, bool, Accessibility, unsigned, bool))
@@ -1462,8 +1468,9 @@ ERROR(protocol_refine_access,none,
       "%select{protocol must be declared %select{"
       "%select{private|fileprivate|internal|%error|%error}2"
       "|private or fileprivate}3 because it refines"
-      "|%select{%error|fileprivate|internal|public|%error}1 protocol cannot "
-      "refine}0 %select{a private|a fileprivate|an internal|%error|%error}2 protocol",
+      "|%select{in this context|fileprivate|internal|public|%error}1 "
+      "protocol cannot refine}0 "
+      "%select{a private|a fileprivate|an internal|%error|%error}2 protocol",
       (bool, Accessibility, Accessibility, bool))
 WARNING(protocol_refine_access_warn,none,
         "%select{protocol should be declared "
@@ -1502,7 +1509,8 @@ NOTE(default_associated_type_req_fail,none,
      (Type, DeclName, Type, Type, bool))
 ERROR(associated_type_access,none,
       "associated type in "
-      "%select{%error|a fileprivate|an internal|a public|%error}0 protocol uses "
+      "%select{a private|a fileprivate|an internal|a public|%error}0 protocol "
+      "uses "
       "%select{a private|a fileprivate|an internal|%error|%error}1 type in its "
       "%select{default definition|requirement}2 ",
       (Accessibility, Accessibility, unsigned))
@@ -1732,7 +1740,8 @@ WARNING(typealias_override_associated_type,none,
 ERROR(generic_param_access,none,
       "%0 %select{must be declared %select{"
       "%select{private|fileprivate|internal|%error|%error}3|private or fileprivate}4"
-      "|cannot be declared %select{%error|fileprivate|internal|public|open}2}1 "
+      "|cannot be declared "
+      "%select{in this context|fileprivate|internal|public|open}2}1 "
       "because its generic %select{parameter|requirement}5 uses "
       "%select{a private|a fileprivate|an internal|%error|%error}3 type",
       (DescriptiveDeclKind, bool, Accessibility, Accessibility, bool, bool))
@@ -1954,7 +1963,7 @@ WARNING(class_inherits_anyobject,none,
 
 // Enums
 ERROR(enum_case_access,none,
-      "enum case in %select{%error|a fileprivate|an internal|a public|%error}0 enum "
+      "enum case in %select{a private|a fileprivate|an internal|a public|%error}0 enum "
       "uses %select{a private|a fileprivate|an internal|%error|%error}1 type",
       (Accessibility, Accessibility))
 WARNING(enum_case_access_warn,none,
@@ -1985,7 +1994,8 @@ NOTE(enum_declares_rawrep_with_raw_type,none,
 ERROR(enum_raw_type_access,none,
       "enum %select{must be declared %select{"
       "%select{private|fileprivate|internal|%error|%error}2|private or fileprivate}3"
-      "|cannot be declared %select{%error|fileprivate|internal|public|open}1}0 "
+      "|cannot be declared "
+      "%select{in this context|fileprivate|internal|public|open}1}0 "
       "because its raw type uses "
       "%select{a private|a fileprivate|an internal|%error|%error}2 type",
       (bool, Accessibility, Accessibility, bool))
@@ -3032,7 +3042,8 @@ ERROR(bool_intrinsics_not_found,none,
 ERROR(class_super_access,none,
       "class %select{must be declared %select{"
       "%select{private|fileprivate|internal|%error|%error}2|private or fileprivate}3"
-      "|cannot be declared %select{%error|fileprivate|internal|public|open}1}0 "
+      "|cannot be declared "
+      "%select{in this context|fileprivate|internal|public|open}1}0 "
       "because its superclass is "
       "%select{private|fileprivate|internal|%error|%error}2",
       (bool, Accessibility, Accessibility, bool))

lib/Sema/TypeCheckDecl.cpp

@@ -1751,11 +1751,12 @@ static void checkTypeAccessibility(
 
   AccessScope contextAccessScope = context->getFormalAccessScope();
   checkTypeAccessibilityImpl(TC, TL, contextAccessScope, DC,
-                             [=](AccessScope requiredAccessScope,
-                                 const TypeRepr *offendingTR,
-                                 DowngradeToWarning downgradeToWarning) {
+                             [=, &TC](AccessScope requiredAccessScope,
+                                      const TypeRepr *offendingTR,
+                                      DowngradeToWarning downgradeToWarning) {
     if (!contextAccessScope.isPublic() &&
-        !isa<ModuleDecl>(contextAccessScope.getDeclContext())) {
+        !isa<ModuleDecl>(contextAccessScope.getDeclContext()) &&
+        TC.getLangOpts().isSwiftVersion3()) {
       // Swift 3.0.0 mistakenly didn't diagnose any issues when the context
       // access scope represented a private or fileprivate level.
       downgradeToWarning = DowngradeToWarning::Yes;
@@ -1868,10 +1869,10 @@ static void checkGenericParamAccessibility(TypeChecker &TC,
 
   // Swift 3.0.0 mistakenly didn't diagnose any issues when the context access
   // scope represented a private or fileprivate level.
-  // FIXME: Conditionalize this on Swift 3 mode.
   if (downgradeToWarning == DowngradeToWarning::No) {
     if (!accessScope.isPublic() &&
-        !isa<ModuleDecl>(accessScope.getDeclContext())) {
+        !isa<ModuleDecl>(accessScope.getDeclContext()) &&
+        TC.getLangOpts().isSwiftVersion3()) {
       downgradeToWarning = DowngradeToWarning::Yes;
     }
   }

test/Sema/accessibility_private.swift

@@ -163,51 +163,51 @@ extension Container {
   }
 }
 
-// All of these should be errors, but didn't have the correct behavior in Swift 
-// 3.0GM.
+// All of these are errors in Swift 4, but didn't have the correct behavior in 
+// Swift 3.0GM.
 extension Container {
   private struct VeryPrivateStruct { // expected-note * {{type declared here}}
     private typealias VeryPrivateType = Int // expected-note * {{type declared here}}
-    var privateVar: VeryPrivateType { fatalError() } // expected-warning {{property should be declared private because its type uses a private type}}
-    var privateVar2 = VeryPrivateType() // expected-warning {{property should be declared private because its type 'Container.VeryPrivateStruct.VeryPrivateType' (aka 'Int') uses a private type}}
-    typealias PrivateAlias = VeryPrivateType // expected-warning {{type alias should be declared private because its underlying type uses a private type}}
-    subscript(_: VeryPrivateType) -> Void { return () } // expected-warning {{subscript should be declared private because its index uses a private type}}
-    func privateMethod(_: VeryPrivateType) -> Void {} // expected-warning {{method should be declared private because its parameter uses a private type}} {{none}}
-    enum PrivateRawValue: VeryPrivateType { // expected-warning {{enum should be declared private because its raw type uses a private type}} {{none}}
+    var privateVar: VeryPrivateType { fatalError() } // expected-error {{property must be declared private because its type uses a private type}}
+    var privateVar2 = VeryPrivateType() // expected-error {{property must be declared private because its type 'Container.VeryPrivateStruct.VeryPrivateType' (aka 'Int') uses a private type}}
+    typealias PrivateAlias = VeryPrivateType // expected-error {{type alias must be declared private because its underlying type uses a private type}}
+    subscript(_: VeryPrivateType) -> Void { return () } // expected-error {{subscript must be declared private because its index uses a private type}}
+    func privateMethod(_: VeryPrivateType) -> Void {} // expected-error {{method must be declared private because its parameter uses a private type}} {{none}}
+    enum PrivateRawValue: VeryPrivateType { // expected-error {{enum must be declared private because its raw type uses a private type}} {{none}}
       case A
     }
     enum PrivatePayload {
-      case A(VeryPrivateType) // expected-warning {{enum case in an internal enum uses a private type}} {{none}}
+      case A(VeryPrivateType) // expected-error {{enum case in an internal enum uses a private type}} {{none}}
     }
 
     private class PrivateInnerClass {} // expected-note * {{declared here}}
-    class PrivateSuper: PrivateInnerClass {} // expected-warning {{class should be declared private because its superclass is private}} {{none}}
+    class PrivateSuper: PrivateInnerClass {} // expected-error {{class must be declared private because its superclass is private}} {{none}}
   }
 
-  fileprivate var privateVar: VeryPrivateStruct { fatalError() } // expected-warning {{property should not be declared fileprivate because its type uses a private type}} {{none}}
-  fileprivate typealias PrivateAlias = VeryPrivateStruct // expected-warning {{type alias should not be declared fileprivate because its underlying type uses a private type}} {{none}}
-  fileprivate subscript(_: VeryPrivateStruct) -> Void { return () } // expected-warning {{subscript should not be declared fileprivate because its index uses a private type}} {{none}}
-  fileprivate func privateMethod(_: VeryPrivateStruct) -> Void {} // expected-warning {{method should not be declared fileprivate because its parameter uses a private type}} {{none}}
-  fileprivate enum PrivateRawValue: VeryPrivateStruct {} // expected-warning {{enum should not be declared fileprivate because its raw type uses a private type}} {{none}}
+  fileprivate var privateVar: VeryPrivateStruct { fatalError() } // expected-error {{property cannot be declared fileprivate because its type uses a private type}} {{none}}
+  fileprivate typealias PrivateAlias = VeryPrivateStruct // expected-error {{type alias cannot be declared fileprivate because its underlying type uses a private type}} {{none}}
+  fileprivate subscript(_: VeryPrivateStruct) -> Void { return () } // expected-error {{subscript cannot be declared fileprivate because its index uses a private type}} {{none}}
+  fileprivate func privateMethod(_: VeryPrivateStruct) -> Void {} // expected-error {{method cannot be declared fileprivate because its parameter uses a private type}} {{none}}
+  fileprivate enum PrivateRawValue: VeryPrivateStruct {} // expected-error {{enum cannot be declared fileprivate because its raw type uses a private type}} {{none}}
   // expected-error@-1 {{raw type 'Container.VeryPrivateStruct' is not expressible by any literal}}
   // expected-error@-2 {{'Container.PrivateRawValue' declares raw type 'Container.VeryPrivateStruct', but does not conform to RawRepresentable and conformance could not be synthesized}}
   // expected-error@-3 {{RawRepresentable conformance cannot be synthesized because raw type 'Container.VeryPrivateStruct' is not Equatable}}
   fileprivate enum PrivatePayload {
-    case A(VeryPrivateStruct) // expected-warning {{enum case in an internal enum uses a private type}} {{none}}
+    case A(VeryPrivateStruct) // expected-error {{enum case in an internal enum uses a private type}} {{none}}
   }
 
   private class PrivateInnerClass {} // expected-note * {{declared here}}
-  fileprivate class PrivateSuperClass: PrivateInnerClass {} // expected-warning {{class should not be declared fileprivate because its superclass is private}} {{none}}
-  fileprivate class PrivateGenericUser<T> where T: PrivateInnerClass {} // expected-warning {{generic class should not be declared fileprivate because its generic requirement uses a private type}} {{none}}
+  fileprivate class PrivateSuperClass: PrivateInnerClass {} // expected-error {{class cannot be declared fileprivate because its superclass is private}} {{none}}
+  fileprivate class PrivateGenericUser<T> where T: PrivateInnerClass {} // expected-error {{generic class cannot be declared fileprivate because its generic requirement uses a private type}} {{none}}
 }
 
 fileprivate struct SR2579 {
   private struct Inner {
     private struct InnerPrivateType {}
-    var innerProperty = InnerPrivateType() // expected-warning {{property should be declared private because its type 'SR2579.Inner.InnerPrivateType' uses a private type}}
+    var innerProperty = InnerPrivateType() // expected-error {{property must be declared private because its type 'SR2579.Inner.InnerPrivateType' uses a private type}}
   }
   // FIXME: We need better errors when one access violation results in more
   // downstream.
-  private var outerProperty = Inner().innerProperty // expected-warning {{property should not be declared in this context because its type 'SR2579.Inner.InnerPrivateType' uses a private type}}
-  var outerProperty2 = Inner().innerProperty // expected-warning {{property should be declared private because its type 'SR2579.Inner.InnerPrivateType' uses a private type}}
+  private var outerProperty = Inner().innerProperty // expected-error {{property cannot be declared in this context because its type 'SR2579.Inner.InnerPrivateType' uses a private type}}
+  var outerProperty2 = Inner().innerProperty // expected-error {{property must be declared private because its type 'SR2579.Inner.InnerPrivateType' uses a private type}}
 }