[NFC] Add flag distinguishing @impl and @objcImpl

They will have slightly different enablement and diagnostic behavior in a future commit.

Author: beccadax

include/swift/AST/ASTBridging.h

@@ -625,10 +625,10 @@ BridgedObjCAttr BridgedObjCAttr_createParsedSelector(
     BridgedArrayRef cNameLocs, BridgedArrayRef cNames,
     BridgedSourceLoc cRParenLoc);
 
-SWIFT_NAME("BridgedObjCImplementationAttr.createParsed(_:atLoc:range:name:)")
+SWIFT_NAME("BridgedObjCImplementationAttr.createParsed(_:atLoc:range:name:isEarlyAdopter:)")
 BridgedObjCImplementationAttr BridgedObjCImplementationAttr_createParsed(
     BridgedASTContext cContext, BridgedSourceLoc cAtLoc,
-    BridgedSourceRange cRange, BridgedIdentifier cName);
+    BridgedSourceRange cRange, BridgedIdentifier cName, bool isEarlyAdopter);
 
 SWIFT_NAME("BridgedObjCRuntimeNameAttr.createParsed(_:atLoc:range:name:)")
 BridgedObjCRuntimeNameAttr BridgedObjCRuntimeNameAttr_createParsed(

include/swift/AST/Attr.h

@@ -184,8 +184,9 @@ class DeclAttribute : public AttributeBase {
       isUnchecked : 1
     );
 
-    SWIFT_INLINE_BITFIELD(ObjCImplementationAttr, DeclAttribute, 1,
-      isCategoryNameInvalid : 1
+    SWIFT_INLINE_BITFIELD(ObjCImplementationAttr, DeclAttribute, 2,
+      isCategoryNameInvalid : 1,
+      isEarlyAdopter : 1
     );
 
     SWIFT_INLINE_BITFIELD(NonisolatedAttr, DeclAttribute, 1,
@@ -2424,11 +2425,19 @@ class ObjCImplementationAttr final : public DeclAttribute {
   Identifier CategoryName;
 
   ObjCImplementationAttr(Identifier CategoryName, SourceLoc AtLoc,
-                         SourceRange Range, bool Implicit = false,
+                         SourceRange Range, bool isEarlyAdopter = false,
+                         bool Implicit = false,
                          bool isCategoryNameInvalid = false)
       : DeclAttribute(DeclAttrKind::ObjCImplementation, AtLoc, Range, Implicit),
         CategoryName(CategoryName) {
     Bits.ObjCImplementationAttr.isCategoryNameInvalid = isCategoryNameInvalid;
+    Bits.ObjCImplementationAttr.isEarlyAdopter = isEarlyAdopter;
+  }
+
+  /// Early adopters use the \c \@_objcImplementation spelling. For backwards
+  /// compatibility, issues with them are diagnosed as warnings, not errors.
+  bool isEarlyAdopter() const {
+    return Bits.ObjCImplementationAttr.isEarlyAdopter;
   }
 
   bool isCategoryNameInvalid() const {

lib/AST/ASTBridging.cpp

@@ -662,9 +662,10 @@ BridgedObjCAttr BridgedObjCAttr_createParsedSelector(
 
 BridgedObjCImplementationAttr BridgedObjCImplementationAttr_createParsed(
     BridgedASTContext cContext, BridgedSourceLoc cAtLoc,
-    BridgedSourceRange cRange, BridgedIdentifier cName) {
+    BridgedSourceRange cRange, BridgedIdentifier cName, bool isEarlyAdopter) {
   return new (cContext.unbridged()) ObjCImplementationAttr(
-      cName.unbridged(), cAtLoc.unbridged(), cRange.unbridged());
+      cName.unbridged(), cAtLoc.unbridged(), cRange.unbridged(),
+      isEarlyAdopter);
 }
 
 BridgedObjCRuntimeNameAttr BridgedObjCRuntimeNameAttr_createParsed(

lib/AST/Attr.cpp

@@ -1820,7 +1820,9 @@ StringRef DeclAttribute::getAttrName() const {
   case DeclAttrKind::ObjCRuntimeName:
     return "objc";
   case DeclAttrKind::ObjCImplementation:
-    return "_objcImplementation";
+    if (cast<ObjCImplementationAttr>(this)->isEarlyAdopter())
+      return "_objcImplementation";
+    return "implementation";
   case DeclAttrKind::MainType:
     return "main";
   case DeclAttrKind::DynamicReplacement:

lib/ASTGen/Sources/ASTGen/DeclAttrs.swift

@@ -732,19 +732,25 @@ extension ASTGenVisitor {
   }
 
   func generateObjCImplementationAttr(attribute node: AttributeSyntax) -> BridgedObjCImplementationAttr? {
-    let name: BridgedIdentifier? = self.generateSingleAttrOption(attribute: node) {
-      self.generateIdentifier($0)
-    }
+    let name: BridgedIdentifier? = self.generateSingleAttrOption(
+      attribute: node,
+      self.generateIdentifier,
+      valueIfOmitted: BridgedIdentifier()
+    )
     guard let name else {
-      // TODO: Diagnose.
+      // Should be diagnosed by `generateSingleAttrOption`.
       return nil
     }
 
+    let attrName = node.attributeName.as(IdentifierTypeSyntax.self)?.name.text
+    let isEarlyAdopter = attrName != "implementation"
+
     return .createParsed(
       self.ctx,
       atLoc: self.generateSourceLoc(node.atSign),
       range: self.generateSourceRange(node),
-      name: name
+      name: name,
+      isEarlyAdopter: isEarlyAdopter
     )
   }
 

lib/Parse/ParseDecl.cpp

@@ -3640,7 +3640,9 @@ ParserStatus Parser::parseNewDeclAttribute(DeclAttributes &Attributes,
     if (!name)
       return makeParserSuccess();
 
-    Attributes.add(new (Context) ObjCImplementationAttr(*name, AtLoc, range));
+    bool isEarlyAdopter = (AttrName != "implementation");
+    Attributes.add(new (Context) ObjCImplementationAttr(*name, AtLoc, range,
+                                                        isEarlyAdopter));
     break;
   }
   case DeclAttrKind::ObjCRuntimeName: {

lib/Serialization/Deserialization.cpp

@@ -6127,13 +6127,15 @@ llvm::Error DeclDeserializer::deserializeDeclCommon() {
       case decls_block::ObjCImplementation_DECL_ATTR: {
         bool isImplicit;
         bool isCategoryNameInvalid;
+        bool isEarlyAdopter;
         uint64_t categoryNameID;
         serialization::decls_block::ObjCImplementationDeclAttrLayout::
             readRecord(scratch, isImplicit, isCategoryNameInvalid,
-                       categoryNameID);
+                       isEarlyAdopter, categoryNameID);
         Identifier categoryName = MF.getIdentifier(categoryNameID);
         Attr = new (ctx) ObjCImplementationAttr(categoryName, SourceLoc(),
-                                                SourceRange(), isImplicit,
+                                                SourceRange(), isEarlyAdopter,
+                                                isImplicit,
                                                 isCategoryNameInvalid);
         break;
       }

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 867; // _distributed_get accessor for distributed thunks
+const uint16_t SWIFTMODULE_VERSION_MINOR = 868; // @implementation
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -2314,6 +2314,7 @@ namespace decls_block {
     ObjCImplementation_DECL_ATTR,
     BCFixed<1>,                // implicit flag
     BCFixed<1>,                // category name invalid
+    BCFixed<1>,                // is early adopter
     IdentifierIDField          // category name
   >;
 

lib/Serialization/Serialization.cpp

@@ -2947,7 +2947,7 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
           S.DeclTypeAbbrCodes[ObjCImplementationDeclAttrLayout::Code];
       ObjCImplementationDeclAttrLayout::emitRecord(S.Out, S.ScratchRecord,
           abbrCode, theAttr->isImplicit(), theAttr->isCategoryNameInvalid(),
-          categoryNameID);
+          theAttr->isEarlyAdopter(), categoryNameID);
       return;
     }