[cxx-interop] Generate safe overloads for non-escapable spans

A previous PR already added support to the SwiftifyImport macro to
generate safe wrappers. This PR makes ClangImporter emit the macro to do
the transformation.

Author: Gabor Horvath

lib/ClangImporter/ClangImporter.cpp

@@ -580,7 +580,8 @@ void importer::getNormalInvocationArguments(
     }
   }
 
-  if (LangOpts.hasFeature(Feature::SafeInteropWrappers))
+  if (LangOpts.hasFeature(Feature::SafeInteropWrappers) &&
+      !LangOpts.EnableCXXInterop)
     invocationArgStrs.push_back("-fexperimental-bounds-safety-attributes");
 
   // Set C language options.

lib/ClangImporter/ImportDecl.cpp

@@ -59,6 +59,7 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjCCommon.h"
+#include "clang/AST/PrettyPrinter.h"
 #include "clang/AST/Type.h"
 #include "clang/Basic/Specifiers.h"
 #include "clang/Basic/TargetInfo.h"
@@ -70,10 +71,12 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/Path.h"
 
 #include <algorithm>
+#include <utility>
 
 #define DEBUG_TYPE "Clang module importer"
 
@@ -129,6 +132,7 @@ createFuncOrAccessor(ClangImporter::Implementation &impl, SourceLoc funcLoc,
   impl.importSwiftAttrAttributes(decl);
   if (hasBoundsAnnotation)
     impl.importBoundsAttributes(decl);
+  impl.importSpanAttributes(decl);
 
   return decl;
 }
@@ -8684,11 +8688,7 @@ class SwiftifyInfoPrinter {
 
   void printCountedBy(const clang::CountAttributedType *CAT,
                       size_t pointerIndex) {
-    if (!firstParam) {
-      out << ", ";
-    } else {
-      firstParam = false;
-    }
+    printSeparator();
     clang::Expr *countExpr = CAT->getCountExpr();
     bool isSizedBy = CAT->isCountInBytes();
     out << ".";
@@ -8706,9 +8706,76 @@ class SwiftifyInfoPrinter {
         out, {}, {ctx.getLangOpts()}); // TODO: map clang::Expr to Swift Expr
     out << "\")";
   }
+
+  void printNonEscaping(int idx) {
+    printSeparator();
+    out << ".nonescaping(pointer: " << idx << ")";
+  }
+
+  void printTypeMapping(const llvm::StringMap<std::string> &mapping) {
+    printSeparator();
+    out << "typeMappings: [";
+    if (mapping.empty()) {
+      out << ":]";
+      return;
+    }
+    llvm::interleaveComma(mapping, out, [&](const auto &entry) {
+      out << '"' << entry.getKey() << "\" : \"" << entry.getValue() << '"';
+    });
+    out << "]";
+  }
+
+private:
+  void printSeparator() {
+    if (!firstParam) {
+      out << ", ";
+    } else {
+      firstParam = false;
+    }
+  }
 };
 } // namespace
 
+void ClangImporter::Implementation::importSpanAttributes(FuncDecl *MappedDecl) {
+  if (!SwiftContext.LangOpts.hasFeature(Feature::SafeInteropWrappers))
+    return;
+  auto ClangDecl =
+      dyn_cast_or_null<clang::FunctionDecl>(MappedDecl->getClangDecl());
+  if (!ClangDecl)
+    return;
+
+  llvm::SmallString<128> MacroString;
+  bool attachMacro = false;
+  {
+    llvm::raw_svector_ostream out(MacroString);
+    llvm::StringMap<std::string> typeMapping;
+
+    SwiftifyInfoPrinter printer(getClangASTContext(), out);
+    for (auto [index, param] : llvm::enumerate(ClangDecl->parameters())) {
+      auto paramTy = param->getType();
+      const auto *decl = paramTy->getAsTagDecl();
+      if (!decl || !decl->isInStdNamespace())
+        continue;
+      if (decl->getName() != "span")
+        continue;
+      if (param->hasAttr<clang::NoEscapeAttr>()) {
+        printer.printNonEscaping(index + 1);
+        clang::PrintingPolicy policy(param->getASTContext().getLangOpts());
+        policy.SuppressTagKeyword = true;
+        auto param = MappedDecl->getParameters()->get(index);
+        typeMapping.insert(std::make_pair(
+            paramTy.getAsString(policy),
+            param->getInterfaceType()->getDesugaredType()->getString()));
+        attachMacro = true;
+      }
+    }
+    printer.printTypeMapping(typeMapping);
+  }
+
+  if (attachMacro)
+    importNontrivialAttribute(MappedDecl, MacroString);
+}
+
 void ClangImporter::Implementation::importBoundsAttributes(
     FuncDecl *MappedDecl) {
   assert(SwiftContext.LangOpts.hasFeature(Feature::SafeInteropWrappers));

lib/ClangImporter/ImporterImpl.h

@@ -1746,6 +1746,7 @@ class LLVM_LIBRARY_VISIBILITY ClangImporter::Implementation
 
   void importSwiftAttrAttributes(Decl *decl);
   void importBoundsAttributes(FuncDecl *MappedDecl);
+  void importSpanAttributes(FuncDecl *MappedDecl);
 
   /// Find the lookup table that corresponds to the given Clang module.
   ///

lib/Macros/Sources/SwiftMacros/SwiftifyImportMacro.swift

@@ -156,6 +156,18 @@ func getPointerMutability(text: String) -> Mutability? {
   }
 }
 
+// Remove std. or std.__1. prefix
+func getUnqualifiedStdName(_ type: String) -> String? {
+  if (type.hasPrefix("std.")) {
+    var ty = type.dropFirst(4)
+    if (ty.hasPrefix("__1.")) {
+      ty = ty.dropFirst(4)
+    }
+    return String(ty)
+  }
+  return nil
+}
+
 func getSafePointerName(mut: Mutability, generateSpan: Bool, isRaw: Bool) -> TokenSyntax {
   switch (mut, generateSpan, isRaw) {
   case (.Immutable, true, true): return "RawSpan"
@@ -299,9 +311,10 @@ struct CxxSpanThunkBuilder: BoundsCheckedThunkBuilder {
         "unable to desugar type with name '\(typeName)'", node: node)
     }
 
-    let parsedDesugaredType = try TypeSyntax("\(raw: desugaredType)")
-    types[index] = TypeSyntax(IdentifierTypeSyntax(name: "Span",
-      genericArgumentClause: parsedDesugaredType.as(IdentifierTypeSyntax.self)!.genericArgumentClause))
+    let parsedDesugaredType = try TypeSyntax("\(raw: getUnqualifiedStdName(desugaredType)!)")
+    let genericArg = TypeSyntax(parsedDesugaredType.as(IdentifierTypeSyntax.self)!
+      .genericArgumentClause!.arguments.first!.argument)!
+    types[index] = TypeSyntax("Span<\(raw: try getTypeName(genericArg).text)>")
     return try base.buildFunctionSignature(types, variant)
   }
 
@@ -656,9 +669,11 @@ public struct SwiftifyImportMacro: PeerMacro {
     for (idx, param) in signature.parameterClause.parameters.enumerated() {
       let typeName = try getTypeName(param.type).text;
       if let desugaredType = typeMappings[typeName] {
-        if desugaredType.starts(with: "span") {
-          result.append(CxxSpan(pointerIndex: idx + 1, nonescaping: false,
-            original: param, typeMappings: typeMappings))
+        if let unqualifiedDesugaredType = getUnqualifiedStdName(desugaredType) {
+          if unqualifiedDesugaredType.starts(with: "span<") {
+            result.append(CxxSpan(pointerIndex: idx + 1, nonescaping: false,
+              original: param, typeMappings: typeMappings))
+          }
         }
       }
     }

test/Interop/Cxx/stdlib/Inputs/std-span.h

@@ -54,4 +54,6 @@ inline SpanOfInt initSpan(int arr[], size_t size) {
 
 inline struct SpanBox getStructSpanBox() { return {iarray, iarray, sarray, sarray}; }
 
+void funcWithSafeWrapper(SpanOfInt s [[clang::noescape]]) {}
+
 #endif // TEST_INTEROP_CXX_STDLIB_INPUTS_STD_SPAN_H

test/Interop/Cxx/stdlib/std-span-interface.swift

@@ -0,0 +1,14 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-ide-test -plugin-path %swift-plugin-dir -I %S/Inputs -enable-experimental-feature Span -enable-experimental-feature SafeInteropWrappers -print-module -module-to-print=StdSpan -source-filename=x -enable-experimental-cxx-interop -Xcc -std=c++20 -module-cache-path %t > %t/interface.swift
+// RUN: %FileCheck %s < %t/interface.swift
+
+// REQUIRES: swift_feature_SafeInteropWrappers
+// REQUIRES: swift_feature_Span
+
+#if !BRIDGING_HEADER
+import StdSpan
+#endif
+import CxxStdlib
+
+// CHECK: func funcWithSafeWrapper(_ s: SpanOfInt)
+// CHECK-NEXT: @_alwaysEmitIntoClient public func funcWithSafeWrapper(_ s: Span<CInt>)

test/Macros/SwiftifyImport/CxxSpan/NoEscapeSpan.swift

@@ -7,7 +7,7 @@ public struct SpanOfInt {
     init(_ x: Span<CInt>) {}
 }
 
-@_SwiftifyImport(.nonescaping(pointer: 1), typeMappings: ["SpanOfInt" : "span<CInt>"])
+@_SwiftifyImport(.nonescaping(pointer: 1), typeMappings: ["SpanOfInt" : "std.span<CInt>"])
 func myFunc(_ span: SpanOfInt, _ secondSpan: SpanOfInt) {
 }