Sema: Introduce an ExportabilityReason for availability attributes.

This allows diagnostics to be more precise and will also support logic that
allows for special cases for `@available` attributes in exportability checking.

Also fixes a bug where the exportability of `@available` attributes attached to
extensions were diagnosed twice for slightly differing reasons.

include/swift/AST/DiagnosticsSema.def

@@ -3826,7 +3826,8 @@ ERROR(decl_from_hidden_module,none,
       "as result builder here|"
       "in an extension with public or '@usableFromInline' members|"
       "in an extension with conditional conformances|"
-      "in a public or '@usableFromInline' conformance}1; "
+      "in a public or '@usableFromInline' conformance|"
+      "in an '@available' attribute here}1; "
       "%select{%2 has been imported as implementation-only|"
       "it is an SPI imported from %2|"
       "it is SPI|"
@@ -3841,7 +3842,8 @@ ERROR(typealias_desugars_to_type_from_hidden_module,none,
       "as result builder here|"
       "in an extension with public or '@usableFromInline' members|"
       "in an extension with conditional conformance|"
-      "in a public or '@usableFromInline' conformance}3 "
+      "in a public or '@usableFromInline' conformance|"
+      "<<ERROR>>}3 "
       "because %select{%4 has been imported as implementation-only|"
       "it is an SPI imported from %4|"
       "<<ERROR>>|"
@@ -3855,7 +3857,7 @@ ERROR(conformance_from_implementation_only_module,none,
       "as result builder here|"
       "in an extension with public or '@usableFromInline' members|"
       "in an extension with conditional conformances|"
-      "<<ERROR>>}2; "
+      "<<ERROR>>|<<ERROR>>}2; "
       "%select{%3 has been imported as implementation-only|"
       "the conformance is declared as SPI in %3|"
       "the conformance is declared as SPI|"

lib/Sema/ResilienceDiagnostics.cpp

@@ -257,6 +257,13 @@ static bool diagnoseValueDeclRefExportability(SourceLoc loc, const ValueDecl *D,
           return true;
         case ExportabilityReason::Inheritance:
           return isa<ProtocolDecl>(D);
+        case ExportabilityReason::AvailableAttribute:
+          // If the context is an extension and that extension has an explicit
+          // access level, then access has already been diagnosed for the
+          // @available attribute.
+          if (auto *ED = dyn_cast_or_null<ExtensionDecl>(DC->getAsDecl()))
+            return !ED->getAttrs().getAttribute<AccessControlAttr>();
+          return false;
         default:
           return false;
       }

lib/Sema/TypeCheckAccess.cpp

@@ -2261,11 +2261,13 @@ public:
 
   void checkAvailabilityDomains(const Decl *D) {
     D = D->getAbstractSyntaxDeclForAttributes();
+
+    auto where = Where.withReason(ExportabilityReason::AvailableAttribute);
     for (auto attr : D->getSemanticAvailableAttrs()) {
       if (auto *domainDecl = attr.getDomain().getDecl()) {
         diagnoseDeclAvailability(domainDecl,
                                  attr.getParsedAttr()->getDomainLoc(), nullptr,
-                                 Where, std::nullopt);
+                                 where, std::nullopt);
       }
     }
   }
@@ -2557,18 +2559,6 @@ public:
             : ExportabilityReason::ExtensionWithConditionalConformances;
     checkConstrainedExtensionRequirements(ED, reason);
 
-    // Diagnose the exportability of the availability domains referenced by the
-    // @available attributes attached to the extension.
-    if (Where.isExported()) {
-      for (auto availableAttr : ED->getSemanticAvailableAttrs()) {
-        if (auto *domainDecl = availableAttr.getDomain().getDecl()) {
-          TypeChecker::diagnoseDeclRefExportability(
-              availableAttr.getParsedAttr()->getDomainLoc(), domainDecl,
-              Where.withReason(reason));
-        }
-      }
-    }
-
     // If we haven't already visited the extended nominal visit it here.
     // This logic is too wide but prevents false reports of an unused public
     // import. We should instead check for public generic requirements

lib/Sema/TypeCheckAvailability.h

@@ -77,7 +77,8 @@ enum class ExportabilityReason : unsigned {
   ResultBuilder,
   ExtensionWithPublicMembers,
   ExtensionWithConditionalConformances,
-  Inheritance
+  Inheritance,
+  AvailableAttribute,
 };
 
 /// A description of the restrictions on what declarations can be referenced

test/ClangImporter/access-level-import-availability-custom-domains.swift

@@ -16,11 +16,11 @@
 
 private import Rivers // also re-exported by Oceans
 internal import Oceans
-// expected-note@-1 22 {{availability domain 'Arctic' imported as 'internal' from 'Oceans' here}}
+// expected-note@-1 23 {{availability domain 'Arctic' imported as 'internal' from 'Oceans' here}}
 // expected-swift5-note@-2 2 {{availability domain 'Arctic' imported as 'internal' from 'Oceans' here}}
-// expected-note@-3 23 {{availability domain 'Colorado' imported as 'internal' from 'Oceans' here}}
+// expected-note@-3 24 {{availability domain 'Colorado' imported as 'internal' from 'Oceans' here}}
 // expected-swift5-note@-4 2 {{availability domain 'Colorado' imported as 'internal' from 'Oceans' here}}
-// expected-note@-5 22 {{availability domain 'Grand' imported as 'internal' from 'Oceans' here}}
+// expected-note@-5 23 {{availability domain 'Grand' imported as 'internal' from 'Oceans' here}}
 // expected-swift5-note@-6 2 {{availability domain 'Grand' imported as 'internal' from 'Oceans' here}}
 public import Seas
 @_spiOnly import Lakes
@@ -31,7 +31,7 @@ public import Seas
 @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public global function 'publicFunc()'}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
 public func publicFunc() { }
 
 @available(Colorado) // expected-swift5-error {{availability domain 'Colorado' used in '@available' on global function 'usableFromInlineFunc()' must be '@usableFromInline' or public}}
@@ -40,7 +40,7 @@ public func publicFunc() { }
 @available(Arctic) // expected-swift5-error {{availability domain 'Arctic' used in '@available' on global function 'usableFromInlineFunc()' must be '@usableFromInline' or public}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
 @usableFromInline func usableFromInlineFunc() { }
 
 @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public global function 'spiFunc()'}}
@@ -74,7 +74,7 @@ private func privateFunc() { }
 @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public var 'publicGlobalVar'}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
 public var publicGlobalVar: Int {
   get { 0 }
   set { }
@@ -86,7 +86,7 @@ public var publicGlobalVar: Int {
 @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public struct 'PublicStruct'}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
 public struct PublicStruct { }
 
 public struct PublicGenericStruct<T> {
@@ -98,7 +98,7 @@ public struct PublicGenericStruct<T> {
   @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public initializer 'init(value:)'}}
   @available(Baltic)
   @available(BayBridge)
-  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
   public init(value: T) {
     self.value = value
   }
@@ -109,7 +109,7 @@ public struct PublicGenericStruct<T> {
   @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public property 'publicProperty'}}
   @available(Baltic)
   @available(BayBridge)
-  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
   public var publicProperty: T { value }
 
   @available(Colorado) // expected-swift5-error {{availability domain 'Colorado' used in '@available' on property 'usableFromInlineProperty' must be '@usableFromInline' or public}}
@@ -118,7 +118,7 @@ public struct PublicGenericStruct<T> {
   @available(Arctic) // expected-swift5-error {{availability domain 'Arctic' used in '@available' on property 'usableFromInlineProperty' must be '@usableFromInline' or public}}
   @available(Baltic)
   @available(BayBridge)
-  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
   @usableFromInline var usableFromInlineProperty: T { value }
 
   public var publicPropertyWithSetter: T {
@@ -130,7 +130,7 @@ public struct PublicGenericStruct<T> {
     @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public setter for property 'publicPropertyWithSetter'}}
     @available(Baltic)
     @available(BayBridge)
-    @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+    @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
     set { value = newValue }
   }
 
@@ -140,7 +140,7 @@ public struct PublicGenericStruct<T> {
   @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public instance method 'publicMethod()'}}
   @available(Baltic)
   @available(BayBridge)
-  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
   public func publicMethod() { }
 
   @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public subscript 'subscript(_:)'}}
@@ -150,7 +150,7 @@ public struct PublicGenericStruct<T> {
   @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public subscript 'subscript(_:)'}}
   @available(Baltic)
   @available(BayBridge)
-  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
   public subscript(indexForSubscriptInColorado: T) -> T { value }
 }
 
@@ -160,7 +160,7 @@ public struct PublicGenericStruct<T> {
 @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public enum 'PublicEnum'}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
 public enum PublicEnum { }
 
 public enum PublicEnumWithCase {
@@ -170,7 +170,7 @@ public enum PublicEnumWithCase {
   @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public enum case 'colorado'}}
   @available(Baltic)
   @available(BayBridge)
-  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
   case colorado
 }
 
@@ -180,7 +180,7 @@ public enum PublicEnumWithCase {
 @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public class 'PublicClass'}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
 public class PublicClass { }
 
 @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public protocol 'PublicProtocol'}}
@@ -189,7 +189,7 @@ public class PublicClass { }
 @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public protocol 'PublicProtocol'}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
 public protocol PublicProtocol { }
 
 public protocol PublicProtocolWithAssociatedType {
@@ -199,7 +199,7 @@ public protocol PublicProtocolWithAssociatedType {
   @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public associated type 'AssociatedType'}}
   @available(Baltic)
   @available(BayBridge)
-  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
   associatedtype AssociatedType
 
   @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public instance method 'requirement()'}}
@@ -208,7 +208,7 @@ public protocol PublicProtocolWithAssociatedType {
   @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public instance method 'requirement()'}}
   @available(Baltic)
   @available(BayBridge)
-  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
   func requirement() -> AssociatedType
 }
 
@@ -218,7 +218,7 @@ public protocol PublicProtocolWithAssociatedType {
 @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public type alias 'PublicTypealias'}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
 public typealias PublicTypealias = Int
 
 @available(Colorado)
@@ -235,9 +235,20 @@ extension PublicGenericStruct { }
 @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public extension of generic struct 'PublicGenericStruct'}}
 @available(Baltic)
 @available(BayBridge)
-@available(Salt) // FIXME: Should be diangosed
+@available(Salt)
 public extension PublicGenericStruct { }
 
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public extension of generic struct 'PublicGenericStruct'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public extension of generic struct 'PublicGenericStruct'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public extension of generic struct 'PublicGenericStruct'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
+public extension PublicGenericStruct {
+  func publicMemberOfPublicExtension() { }
+}
+
 @available(Colorado)
 @available(Grand) // expected-warning {{availability domain 'Grand' is deprecated: Use Colorado instead}}
 @available(Arctic)
@@ -248,15 +259,12 @@ extension PublicGenericStruct {
   func internalMethodInExtensionInColorado() { }
 }
 
-@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an extension with public or '@usableFromInline' members; 'Rivers' was not imported publicly}}
+@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an '@available' attribute here; 'Rivers' was not imported publicly}}
-@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an extension with public or '@usableFromInline' members; 'Rivers' was not imported publicly}}
+@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an '@available' attribute here; 'Rivers' was not imported publicly}}
-// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an '@available' attribute here; 'Oceans' was not imported publicly}}
-@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an extension with public or '@usableFromInline' members; 'Oceans' was not imported publicly}}
 @available(Baltic)
 @available(BayBridge)
-// FIXME: Duplicate error
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
-// expected-error@-1 {{cannot use availability domain 'Salt' in an extension with public or '@usableFromInline' members; 'Lakes' was imported for SPI only}}
 extension PublicGenericStruct {
   public func publicMethodInExtensionInColorado() { }
 }
@@ -269,26 +277,20 @@ extension PublicGenericStruct {
 @available(Salt)
 extension PublicGenericStruct where T: PublicProtocolWithAssociatedType { }
 
-@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an extension with conditional conformances; 'Rivers' was not imported publicly}}
+@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an '@available' attribute here; 'Rivers' was not imported publicly}}
-@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an extension with conditional conformances; 'Rivers' was not imported publicly}}
+@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an '@available' attribute here; 'Rivers' was not imported publicly}}
-// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an '@available' attribute here; 'Oceans' was not imported publicly}}
-@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an extension with conditional conformances; 'Oceans' was not imported publicly}}
 @available(Baltic)
 @available(BayBridge)
-// FIXME: Duplicate error
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an extension with conditional conformances; 'Lakes' was imported for SPI only}}
-// expected-error@-1 {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
 extension PublicGenericStruct: PublicProtocol {}
 
-@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an extension with public or '@usableFromInline' members; 'Rivers' was not imported publicly}}
+@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an '@available' attribute here; 'Rivers' was not imported publicly}}
-@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an extension with public or '@usableFromInline' members; 'Rivers' was not imported publicly}}
+@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an '@available' attribute here; 'Rivers' was not imported publicly}}
-// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an '@available' attribute here; 'Oceans' was not imported publicly}}
-@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an extension with public or '@usableFromInline' members; 'Oceans' was not imported publicly}}
 @available(Baltic)
 @available(BayBridge)
-// FIXME: Duplicate error
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an '@available' attribute here; 'Lakes' was imported for SPI only}}
-@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
-// expected-error@-1 {{cannot use availability domain 'Salt' in an extension with public or '@usableFromInline' members; 'Lakes' was imported for SPI only}}
 extension PublicGenericStruct: PublicProtocolWithAssociatedType {
   public func requirement() -> Int { 0 }
 }