Ensure that buffers containing Clang swift_attr attributes are parsed as attributes

Previously, they were being parsed as top-level code, which would cause
errors because there are no definitions. Introduce a new
GeneratedSourceInfo kind to mark the purpose of these buffers so the
parser can handle them appropriately.

Author: DougGregor

include/swift/Basic/BasicBridging.h

@@ -445,6 +445,7 @@ enum ENUM_EXTENSIBILITY_ATTR(closed) BridgedGeneratedSourceFileKind {
   BridgedGeneratedSourceFileKindReplacedFunctionBody,
   BridgedGeneratedSourceFileKindPrettyPrinted,
   BridgedGeneratedSourceFileKindDefaultArgument,
+  BridgedGeneratedSourceFileKindAttribute,
 
   BridgedGeneratedSourceFileKindNone,
 };

include/swift/Basic/SourceManager.h

@@ -65,6 +65,9 @@ class GeneratedSourceInfo {
 
     /// The expansion of default argument at caller side
     DefaultArgument,
+
+    /// A Swift attribute expressed in C headers.
+    Attribute,
   } kind;
 
   static StringRef kindToString(GeneratedSourceInfo::Kind kind) {
@@ -80,6 +83,8 @@ class GeneratedSourceInfo {
       return "PrettyPrinted";
     case DefaultArgument:
       return "DefaultArgument";
+    case Attribute:
+      return "Attribute";
     }
     llvm_unreachable("Invalid kind");
   }

lib/AST/ASTMangler.cpp

@@ -4535,6 +4535,7 @@ void ASTMangler::appendMacroExpansionContext(
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::ReplacedFunctionBody:
   case GeneratedSourceInfo::DefaultArgument:
+  case GeneratedSourceInfo::Attribute:
     return appendMacroExpansionLoc();
   }
 
@@ -4586,6 +4587,7 @@ void ASTMangler::appendMacroExpansionContext(
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::ReplacedFunctionBody:
   case GeneratedSourceInfo::DefaultArgument:
+  case GeneratedSourceInfo::Attribute:
     llvm_unreachable("Exited above");
   }
 

lib/AST/Decl.cpp

@@ -12075,6 +12075,7 @@ MacroDiscriminatorContext MacroDiscriminatorContext::getParentOf(
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::ReplacedFunctionBody:
   case GeneratedSourceInfo::DefaultArgument:
+  case GeneratedSourceInfo::Attribute:
     return origDC;
   }
 }

lib/AST/DiagnosticEngine.cpp

@@ -1336,6 +1336,7 @@ DiagnosticEngine::diagnosticInfoForDiagnostic(const Diagnostic &diagnostic) {
 #include "swift/Basic/MacroRoles.def"
       case GeneratedSourceInfo::PrettyPrinted:
       case GeneratedSourceInfo::DefaultArgument:
+      case GeneratedSourceInfo::Attribute:
         fixIts = {};
         break;
       case GeneratedSourceInfo::ReplacedFunctionBody:
@@ -1381,6 +1382,7 @@ getGeneratedSourceInfoMacroName(const GeneratedSourceInfo &info) {
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::ReplacedFunctionBody:
   case GeneratedSourceInfo::DefaultArgument:
+  case GeneratedSourceInfo::Attribute:
     return DeclName();
   }
 }
@@ -1438,6 +1440,7 @@ DiagnosticEngine::getGeneratedSourceBufferNotes(SourceLoc loc) {
     }
 
     case GeneratedSourceInfo::PrettyPrinted:
+    case GeneratedSourceInfo::Attribute:
       break;
 
     case GeneratedSourceInfo::DefaultArgument:

lib/AST/Module.cpp

@@ -862,6 +862,7 @@ ModuleDecl::getOriginalLocation(SourceLoc loc) const {
       // replaced function bodies. The body is actually different code to the
       // original file.
     case GeneratedSourceInfo::PrettyPrinted:
+    case GeneratedSourceInfo::Attribute:
       // No original location, return the original buffer/location
       return {startBufferID, startLoc};
     }
@@ -1148,6 +1149,7 @@ std::optional<MacroRole> SourceFile::getFulfilledMacroRole() const {
   case GeneratedSourceInfo::ReplacedFunctionBody:
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::DefaultArgument:
+  case GeneratedSourceInfo::Attribute:
     return std::nullopt;
   }
 }

lib/ASTGen/Sources/ASTGen/SourceFile.swift

@@ -122,7 +122,8 @@ public func parseSourceFile(
       .preambleMacroExpansion,
       .replacedFunctionBody,
       .prettyPrinted,
-      .defaultArgument:
+      .defaultArgument,
+      .attribute:
     parsed = Syntax(SourceFileSyntax.parse(from: &parser))
 
   case .declarationMacroExpansion,

lib/Basic/SourceLoc.cpp

@@ -306,7 +306,8 @@ StringRef SourceManager::getIdentifierForBuffer(
       // We only care about macros, so skip everything else.
       if (generatedInfo->kind == GeneratedSourceInfo::ReplacedFunctionBody ||
           generatedInfo->kind == GeneratedSourceInfo::PrettyPrinted ||
-          generatedInfo->kind == GeneratedSourceInfo::DefaultArgument)
+          generatedInfo->kind == GeneratedSourceInfo::DefaultArgument ||
+          generatedInfo->kind == GeneratedSourceInfo::Attribute)
         return buffer->getBufferIdentifier();
 
       if (generatedInfo->onDiskBufferCopyFileName.empty()) {
@@ -400,6 +401,7 @@ void SourceManager::setGeneratedSourceInfo(
 #include "swift/Basic/MacroRoles.def"
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::DefaultArgument:
+  case GeneratedSourceInfo::Attribute:
     break;
 
   case GeneratedSourceInfo::ReplacedFunctionBody:

lib/ClangImporter/ImportDecl.cpp

@@ -8205,6 +8205,16 @@ unsigned ClangImporter::Implementation::getClangSwiftAttrSourceBuffer(
   auto &sourceMgr = SwiftContext.SourceMgr;
   auto bufferID = sourceMgr.addMemBufferCopy(attributeText);
   ClangSwiftAttrSourceBuffers.insert({attributeText, bufferID});
+
+  // Note that this is for an attribute.
+  sourceMgr.setGeneratedSourceInfo(
+      bufferID,
+      {
+        GeneratedSourceInfo::Attribute,
+        CharSourceRange(),
+        sourceMgr.getRangeForBuffer(bufferID)
+      }
+  );
   return bufferID;
 }
 

lib/IDE/Utils.cpp

@@ -661,6 +661,7 @@ adjustMacroExpansionWhitespace(GeneratedSourceInfo::Kind kind,
   case GeneratedSourceInfo::ReplacedFunctionBody:
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::DefaultArgument:
+  case GeneratedSourceInfo::Attribute:
     return expandedCode;
   }
 }