AST/Sema: Retire SemanticAvailableAttr::getVersionAvailability().

Query for availability constraints instead of calling getVersionAvailability().

NFC.

Author: tshortli

include/swift/AST/Attr.h

@@ -704,23 +704,6 @@ class SwiftNativeObjCRuntimeBaseAttr : public DeclAttribute {
   }
 };
 
-/// Determine the result of comparing an availability attribute to a specific
-/// platform or language version.
-enum class AvailableVersionComparison {
-  /// The entity is guaranteed to be available.
-  Available,
-
-  /// The entity is never available.
-  Unavailable,
-
-  /// The entity might be unavailable at runtime, because it was introduced
-  /// after the requested minimum platform version.
-  PotentiallyUnavailable,
-
-  /// The entity has been obsoleted.
-  Obsoleted,
-};
-
 /// Defines the @available attribute.
 class AvailableAttr : public DeclAttribute {
 public:
@@ -3395,12 +3378,6 @@ class SemanticAvailableAttr final {
   /// version for PackageDescription version-specific availability.
   llvm::VersionTuple getActiveVersion(const ASTContext &ctx) const;
 
-  /// Compare this attribute's version information against the platform or
-  /// language version (assuming the this attribute pertains to the active
-  /// platform).
-  AvailableVersionComparison
-  getVersionAvailability(const ASTContext &ctx) const;
-
   /// Returns true if this attribute is considered active in the current
   /// compilation context.
   bool isActive(ASTContext &ctx) const;

lib/AST/Attr.cpp

@@ -2309,50 +2309,6 @@ SemanticAvailableAttr::getActiveVersion(const ASTContext &ctx) const {
   }
 }
 
-AvailableVersionComparison
-SemanticAvailableAttr::getVersionAvailability(const ASTContext &ctx) const {
-
-  // Unconditional unavailability.
-  if (attr->isUnconditionallyUnavailable())
-    return AvailableVersionComparison::Unavailable;
-
-  llvm::VersionTuple queryVersion = getActiveVersion(ctx);
-  std::optional<llvm::VersionTuple> ObsoletedVersion = getObsoleted();
-
-  StringRef ObsoletedPlatform;
-  llvm::VersionTuple RemappedObsoletedVersion;
-  if (AvailabilityInference::updateObsoletedPlatformForFallback(
-          *this, ctx, ObsoletedPlatform, RemappedObsoletedVersion))
-    ObsoletedVersion = RemappedObsoletedVersion;
-
-  // If this entity was obsoleted before or at the query platform version,
-  // consider it obsolete.
-  if (ObsoletedVersion && *ObsoletedVersion <= queryVersion)
-    return AvailableVersionComparison::Obsoleted;
-
-  std::optional<llvm::VersionTuple> IntroducedVersion = getIntroduced();
-  StringRef IntroducedPlatform;
-  llvm::VersionTuple RemappedIntroducedVersion;
-  if (AvailabilityInference::updateIntroducedPlatformForFallback(
-          *this, ctx, IntroducedPlatform, RemappedIntroducedVersion))
-    IntroducedVersion = RemappedIntroducedVersion;
-
-  // If this entity was introduced after the query version and we're doing a
-  // platform comparison, true availability can only be determined dynamically;
-  // if we're doing a _language_ version check, the query version is a
-  // static requirement, so we treat "introduced later" as just plain
-  // unavailable.
-  if (IntroducedVersion && *IntroducedVersion > queryVersion) {
-    if (isSwiftLanguageModeSpecific() || isPackageDescriptionVersionSpecific())
-      return AvailableVersionComparison::Unavailable;
-    else
-      return AvailableVersionComparison::PotentiallyUnavailable;
-  }
-
-  // The entity is available.
-  return AvailableVersionComparison::Available;
-}
-
 SpecializeAttr::SpecializeAttr(SourceLoc atLoc, SourceRange range,
                                TrailingWhereClause *clause, bool exported,
                                SpecializationKind kind,

lib/Sema/TypeCheckAttr.cpp

@@ -2418,9 +2418,8 @@ void AttributeChecker::visitAvailableAttr(AvailableAttr *parsedAttr) {
   }
 
   SourceLoc attrLoc = parsedAttr->getLocation();
-  auto versionAvailability = attr->getVersionAvailability(Ctx);
-  if (versionAvailability == AvailableVersionComparison::Obsoleted ||
-      versionAvailability == AvailableVersionComparison::Unavailable) {
+  if (attr->isUnconditionallyUnavailable() || attr->getObsoleted() ||
+      (attr->getIntroduced() && !attr->isPlatformSpecific())) {
     if (auto cannotBeUnavailable =
             TypeChecker::diagnosticIfDeclCannotBeUnavailable(D)) {
       diagnose(attrLoc, cannotBeUnavailable.value());

lib/Sema/TypeCheckDeclOverride.cpp

@@ -245,15 +245,21 @@ bool swift::isOverrideBasedOnType(const ValueDecl *decl, Type declTy,
 
 static bool isUnavailableInAllVersions(ValueDecl *decl) {
   ASTContext &ctx = decl->getASTContext();
-  auto attr = decl->getUnavailableAttr();
-  if (!attr)
-    return false;
 
-  if (attr->isUnconditionallyUnavailable())
-    return true;
+  auto deploymentContext = AvailabilityContext::forDeploymentTarget(ctx);
+  auto constraints = getAvailabilityConstraintsForDecl(decl, deploymentContext);
+  for (auto constraint : constraints) {
+    switch (constraint.getReason()) {
+    case AvailabilityConstraint::Reason::UnconditionallyUnavailable:
+    case AvailabilityConstraint::Reason::IntroducedInLaterVersion:
+      return true;
+    case AvailabilityConstraint::Reason::Obsoleted:
+    case AvailabilityConstraint::Reason::IntroducedInLaterDynamicVersion:
+      break;
+    }
+  }
 
-  return attr->getVersionAvailability(ctx) ==
-         AvailableVersionComparison::Unavailable;
+  return false;
 }
 
 /// Perform basic checking to determine whether a declaration can override a