Sema: Replace TypeChecker::checkConformanceAvailability().

Adopt `getUnmetDeclAvailabilityRequirement()` instead.

Author: tshortli

lib/Sema/TypeCheckAvailability.cpp

@@ -1513,13 +1513,6 @@ checkDeclarationAvailability(const Decl *D, const ExportContext &Where) {
   return std::nullopt;
 }
 
-std::optional<AvailabilityRange>
-TypeChecker::checkConformanceAvailability(const RootProtocolConformance *conf,
-                                          const ExtensionDecl *ext,
-                                          const ExportContext &where) {
-  return checkDeclarationAvailability(ext, where);
-}
-
 /// A class that walks the AST to find the innermost (i.e., deepest) node that
 /// contains a target SourceRange and matches a particular criterion.
 /// This class finds the innermost nodes of interest by walking
@@ -4625,6 +4618,7 @@ swift::diagnoseConformanceAvailability(SourceLoc loc,
   // Diagnose "missing" conformances where we needed a conformance but
   // didn't have one.
   auto *DC = where.getDeclContext();
+  auto &ctx = DC->getASTContext();
   if (auto builtinConformance = dyn_cast<BuiltinProtocolConformance>(rootConf)){
     if (builtinConformance->isMissing()) {
       diagnoseMissingConformance(loc, builtinConformance->getType(),
@@ -4638,7 +4632,6 @@ swift::diagnoseConformanceAvailability(SourceLoc loc,
 
     Type selfTy = rootConf->getProtocol()->getSelfInterfaceType();
     if (!depTy->isEqual(selfTy)) {
-      auto &ctx = DC->getASTContext();
       ctx.Diags.diagnose(
           loc,
           diag::assoc_conformance_from_implementation_only_module,
@@ -4653,20 +4646,24 @@ swift::diagnoseConformanceAvailability(SourceLoc loc,
       return true;
     }
 
-    if (diagnoseExplicitUnavailability(loc, rootConf, ext, where,
-                                       warnIfConformanceUnavailablePreSwift6)) {
-      maybeEmitAssociatedTypeNote();
-      return true;
-    }
+    auto unmetRequirement = getUnmetDeclAvailabilityRequirement(
+        ext, where.getDeclContext(), where.getAvailability());
+    if (unmetRequirement) {
+      // FIXME: diagnoseExplicitUnavailability() should take unmet requirement
+      if (diagnoseExplicitUnavailability(
+              loc, rootConf, ext, where,
+              warnIfConformanceUnavailablePreSwift6)) {
+        maybeEmitAssociatedTypeNote();
+        return true;
+      }
 
-    // Diagnose (and possibly signal) for potential unavailability
-    auto maybeUnavail = TypeChecker::checkConformanceAvailability(
-        rootConf, ext, where);
-    if (maybeUnavail.has_value()) {
-      diagnosePotentialUnavailability(rootConf, ext, loc, DC,
-                                      maybeUnavail.value());
-      maybeEmitAssociatedTypeNote();
-      return true;
+      // Diagnose (and possibly signal) for potential unavailability
+      if (auto requiredRange =
+              unmetRequirement->getRequiredNewerAvailabilityRange(ctx)) {
+        diagnosePotentialUnavailability(rootConf, ext, loc, DC, *requiredRange);
+        maybeEmitAssociatedTypeNote();
+        return true;
+      }
     }
 
     // Diagnose for deprecation

lib/Sema/TypeChecker.h

@@ -1032,14 +1032,6 @@ diagnosticIfDeclCannotBePotentiallyUnavailable(const Decl *D);
 /// is allowed.
 std::optional<Diagnostic> diagnosticIfDeclCannotBeUnavailable(const Decl *D);
 
-/// Checks whether a conformance should be considered unavailable when
-/// referred to at the given location and, if so, returns the unmet required
-/// version range. Returns None is the declaration is definitely available.
-std::optional<AvailabilityRange>
-checkConformanceAvailability(const RootProtocolConformance *Conf,
-                             const ExtensionDecl *Ext,
-                             const ExportContext &Where);
-
 bool checkAvailability(
     SourceRange ReferenceRange, AvailabilityRange RequiredAvailability,
     const DeclContext *ReferenceDC,