Sema: Refactor "cannot be marked unavailable" diagnostics.

Make it possible to share the diagnostics string for common case.

Author: tshortli

include/swift/AST/DiagnosticsSema.def

@@ -6757,12 +6757,13 @@ WARNING(availability_query_useless_enclosing_scope, none,
 NOTE(availability_query_useless_enclosing_scope_here, none,
      "enclosing scope here", ())
 
-ERROR(availability_deinit_no_potential, none,
-      "deinitializer cannot be marked potentially unavailable with "
-      "'@available'", ())
+ERROR(availability_decl_no_potential, none,
+      "%kindonly0 cannot be marked potentially unavailable with '@available'",
+      (const Decl *))
 
-ERROR(availability_deinit_no_unavailable, none,
-      "deinitializer cannot be marked unavailable with '@available'", ())
+ERROR(availability_decl_no_unavailable, none,
+      "%kindonly0 cannot be marked unavailable with '@available'",
+      (const Decl *))
 
 ERROR(availability_global_script_no_potential,
       none, "global variable cannot be marked potentially "

lib/Sema/TypeCheckAttr.cpp

@@ -2220,7 +2220,7 @@ void AttributeChecker::visitAvailableAttr(AvailableAttr *attr) {
     }
   }
 
-  std::optional<Diag<>> MaybeNotAllowed =
+  std::optional<Diagnostic> MaybeNotAllowed =
       TypeChecker::diagnosticIfDeclCannotBePotentiallyUnavailable(D);
   if (MaybeNotAllowed.has_value()) {
     AvailabilityContext DeploymentRange
@@ -4924,13 +4924,13 @@ Type TypeChecker::checkReferenceOwnershipAttr(VarDecl *var, Type type,
   return ReferenceStorageType::get(type, ownershipKind, var->getASTContext());
 }
 
-std::optional<Diag<>>
+std::optional<Diagnostic>
 TypeChecker::diagnosticIfDeclCannotBePotentiallyUnavailable(const Decl *D) {
   auto *DC = D->getDeclContext();
 
   // A destructor is always called if declared.
   if (auto *DD = dyn_cast<DestructorDecl>(D))
-    return diag::availability_deinit_no_potential;
+    return Diagnostic(diag::availability_decl_no_potential, D);
 
   if (auto *VD = dyn_cast<VarDecl>(D)) {
     if (!VD->hasStorageOrWrapsStorage())
@@ -4964,7 +4964,7 @@ TypeChecker::diagnosticIfDeclCannotBePotentiallyUnavailable(const Decl *D) {
   return std::nullopt;
 }
 
-std::optional<Diag<>>
+std::optional<Diagnostic>
 TypeChecker::diagnosticIfDeclCannotBeUnavailable(const Decl *D) {
   auto parentIsUnavailable = [](const Decl *D) -> bool {
     if (auto *parent =
@@ -4979,7 +4979,7 @@ TypeChecker::diagnosticIfDeclCannotBeUnavailable(const Decl *D) {
     if (parentIsUnavailable(D))
       return std::nullopt;
 
-    return diag::availability_deinit_no_unavailable;
+    return Diagnostic(diag::availability_decl_no_unavailable, D);
   }
 
   if (auto *VD = dyn_cast<VarDecl>(D)) {

lib/Sema/TypeChecker.h

@@ -1020,13 +1020,13 @@ TypeRefinementContext *getOrBuildTypeRefinementContext(SourceFile *SF);
 /// Returns a diagnostic indicating why the declaration cannot be annotated
 /// with an @available() attribute indicating it is potentially unavailable
 /// or None if this is allowed.
-std::optional<Diag<>>
+std::optional<Diagnostic>
 diagnosticIfDeclCannotBePotentiallyUnavailable(const Decl *D);
 
 /// Returns a diagnostic indicating why the declaration cannot be annotated
 /// with an @available() attribute indicating it is unavailable or None if this
 /// is allowed.
-std::optional<Diag<>> diagnosticIfDeclCannotBeUnavailable(const Decl *D);
+std::optional<Diagnostic> diagnosticIfDeclCannotBeUnavailable(const Decl *D);
 
 /// Same as \c checkDeclarationAvailability but doesn't give a reason for
 /// unavailability.