AST: Remove Decl::isSemanticallyUnavailable().

It can be replaced by querying the `AvailabilityContext` for a declaration
directly.

Author: tshortli

include/swift/AST/Decl.h

@@ -1475,11 +1475,6 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl>, public Swi
   /// extension) that makes it unavailable.
   std::optional<SemanticAvailableAttr> getUnavailableAttr() const;
 
-  /// Returns true if the decl is effectively always unavailable in the current
-  /// compilation context. This query differs from \c isUnavailable() because it
-  /// takes the availability of parent declarations into account.
-  bool isSemanticallyUnavailable() const;
-
   /// Returns true if code associated with this declaration should be considerd
   /// unreachable at runtime because the declaration is unavailable in all
   /// execution contexts in which the code may run. This result takes the

lib/AST/Availability.cpp

@@ -645,13 +645,6 @@ SemanticDeclAvailabilityRequest::evaluate(Evaluator &evaluator,
   return SemanticDeclAvailability::PotentiallyAvailable;
 }
 
-bool Decl::isSemanticallyUnavailable() const {
-  auto availability = evaluateOrDefault(
-      getASTContext().evaluator, SemanticDeclAvailabilityRequest{this},
-      SemanticDeclAvailability::PotentiallyAvailable);
-  return availability != SemanticDeclAvailability::PotentiallyAvailable;
-}
-
 bool Decl::isUnreachableAtRuntime() const {
   auto availability = evaluateOrDefault(
       getASTContext().evaluator, SemanticDeclAvailabilityRequest{this},

lib/SIL/IR/SILProfiler.cpp

@@ -12,6 +12,7 @@
 
 #include "swift/SIL/SILProfiler.h"
 #include "swift/AST/ASTWalker.h"
+#include "swift/AST/AvailabilityContext.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/Expr.h"
 #include "swift/AST/Module.h"
@@ -117,7 +118,7 @@ static bool shouldProfile(SILDeclRef Constant) {
 
   if (auto *D = DC->getInnermostDeclarationDeclContext()) {
     // Do not profile AST nodes in unavailable contexts.
-    if (D->isSemanticallyUnavailable()) {
+    if (AvailabilityContext::forDeclSignature(D).isUnavailable()) {
       LLVM_DEBUG(llvm::dbgs() << "Skipping ASTNode: unavailable context\n");
       return false;
     }

lib/Sema/TypeCheckAttr.cpp

@@ -5455,7 +5455,7 @@ TypeChecker::diagnosticIfDeclCannotBeUnavailable(const Decl *D,
   auto parentIsUnavailable = [](const Decl *D) -> bool {
     if (auto *parent =
             AvailabilityInference::parentDeclForInferredAvailability(D)) {
-      return parent->isSemanticallyUnavailable();
+      return AvailabilityContext::forDeclSignature(parent).isUnavailable();
     }
     return false;
   };

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1933,7 +1933,7 @@ checkOverrideUnavailability(ValueDecl *override, ValueDecl *base) {
   if (auto *overrideParent = override->getDeclContext()->getAsDecl()) {
     // If the parent of the override is unavailable, then the unavailability of
     // the override decl is irrelevant.
-    if (overrideParent->isSemanticallyUnavailable())
+    if (AvailabilityContext::forDeclSignature(overrideParent).isUnavailable())
       return {OverrideUnavailabilityStatus::Ignored, std::nullopt};
   }
 

lib/Sema/TypeCheckProtocol.cpp

@@ -1885,7 +1885,8 @@ RequirementCheck WitnessChecker::checkWitness(ValueDecl *requirement,
       }
 
       if (auto adoptingNominal = DC->getSelfNominalTypeDecl()) {
-        if (adoptingNominal->isSemanticallyUnavailable())
+        if (AvailabilityContext::forDeclSignature(adoptingNominal)
+                .isUnavailable())
           return true;
       }