Define a feature for _specialize with availability

rdar://84782342

Author: aschwaighofer

include/swift/AST/ASTPrinter.h

@@ -386,7 +386,9 @@ void getInheritedForPrinting(
 StringRef getAccessorKindString(AccessorKind value);
 
 bool printCompatibilityFeatureChecksPre(ASTPrinter &printer, Decl *decl);
-void printCompatibilityFeatureChecksPost(ASTPrinter &printer);
+void printCompatibilityFeatureChecksPost(
+    ASTPrinter &printer,
+    llvm::function_ref<void()> printElse = []() -> void {});
 
 } // namespace swift
 

include/swift/AST/PrintOptions.h

@@ -477,6 +477,10 @@ struct PrintOptions {
   /// compilers that might parse the result.
   bool PrintCompatibilityFeatureChecks = false;
 
+  /// Whether to print @_specialize attributes that have an availability
+  /// parameter.
+  bool PrintSpecializeAttributeWithAvailability = true;
+
   /// \see ShouldQualifyNestedDeclarations
   enum class QualifyNestedDeclarations {
     Never,

include/swift/Basic/Features.def

@@ -56,5 +56,6 @@ LANGUAGE_FEATURE(BuiltinBuildMainExecutor, 0, "MainActor executor building built
 LANGUAGE_FEATURE(BuiltinCreateAsyncTaskInGroup, 0, "MainActor executor building builtin", true)
 LANGUAGE_FEATURE(BuiltinMove, 0, "Builtin.move()", true)
 LANGUAGE_FEATURE(BuiltinCopy, 0, "Builtin.copy()", true)
+LANGUAGE_FEATURE(SpecializeAttributeWithAvailability, 0, "@_specialize attribute with availability", true)
 
 #undef LANGUAGE_FEATURE

lib/AST/ASTPrinter.cpp

@@ -534,6 +534,7 @@ static bool willUseTypeReprPrinting(TypeLoc tyLoc,
           (tyLoc.getType().isNull() && tyLoc.getTypeRepr()));
 }
 
+static std::vector<Feature> getUniqueFeaturesUsed(Decl *decl);
 namespace {
 /// AST pretty-printer.
 class PrintAST : public ASTVisitor<PrintAST> {
@@ -1003,7 +1004,22 @@ class PrintAST : public ASTVisitor<PrintAST> {
     ASTVisitor::visit(D);
 
     if (haveFeatureChecks) {
-      printCompatibilityFeatureChecksPost(Printer);
+
+      printCompatibilityFeatureChecksPost(Printer, [&]() -> void {
+        auto features = getUniqueFeaturesUsed(D);
+        assert(!features.empty());
+        if (std::find_if(features.begin(), features.end(),
+                         [](Feature feature) -> bool {
+                           return getFeatureName(feature).equals(
+                               "SpecializeAttributeWithAvailability");
+                         }) != features.end()) {
+          Printer << "#else\n";
+          Options.PrintSpecializeAttributeWithAvailability = false;
+          ASTVisitor::visit(D);
+          Options.PrintSpecializeAttributeWithAvailability = true;
+          Printer.printNewline();
+        }
+      });
     }
 
     if (Synthesize) {
@@ -2818,6 +2834,16 @@ static bool usesFeatureBuiltinMove(Decl *decl) {
 
 static bool usesFeatureBuiltinCopy(Decl *decl) { return false; }
 
+static bool usesFeatureSpecializeAttributeWithAvailability(Decl *decl) {
+  if (auto func = dyn_cast<AbstractFunctionDecl>(decl)) {
+    for (auto specialize : func->getAttrs().getAttributes<SpecializeAttr>()) {
+      if (!specialize->getAvailabeAttrs().empty())
+        return true;
+    }
+  }
+  return false;
+}
+
 static bool usesFeatureInheritActorContext(Decl *decl) {
   if (auto func = dyn_cast<AbstractFunctionDecl>(decl)) {
     for (auto param : *func->getParameters()) {
@@ -2926,12 +2952,13 @@ bool swift::printCompatibilityFeatureChecksPre(
   return true;
 }
 
-void swift::printCompatibilityFeatureChecksPost(ASTPrinter &printer) {
+void swift::printCompatibilityFeatureChecksPost(
+    ASTPrinter &printer, llvm::function_ref<void()> printElse) {
   printer.printNewline();
+  printElse();
   printer << "#endif\n";
 }
 
-
 void PrintAST::visitExtensionDecl(ExtensionDecl *decl) {
   if (Options.TransformContext &&
       Options.TransformContext->isPrintingSynthesizedExtension()) {

lib/AST/Attr.cpp

@@ -982,6 +982,12 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
     if (!Options.PrintSPIs && !attr->getSPIGroups().empty())
       return false;
 
+    // Don't print the _specialize attribute if we are asked to skip the ones
+    // with availability parameters.
+    if (!Options.PrintSpecializeAttributeWithAvailability &&
+        !attr->getAvailabeAttrs().empty())
+      return false;
+
     Printer << "@" << getAttrName() << "(";
     auto exported = attr->isExported() ? "true" : "false";
     auto kind = attr->isPartialSpecialization() ? "partial" : "full";