[AST] Remove @_typeSequence attribute

This is no longer needed now that we have the
ellipsis spelling.

Author: hamishknight

include/swift/AST/ASTContext.h

@@ -1357,7 +1357,7 @@ class ASTContext final {
   /// Get a generic signature where the generic parameter τ_d_i represents
   /// the element of the pack generic parameter τ_d_i… in \p baseGenericSig.
   ///
-  /// This drops the @_typeSequence attribute from each generic parameter,
+  /// This drops the parameter pack bit from each generic parameter,
   /// and converts same-element requirements to same-type requirements.
   CanGenericSignature getOpenedElementSignature(CanGenericSignature baseGenericSig);
 

include/swift/AST/Attr.h

@@ -2190,20 +2190,6 @@ class NonSendableAttr : public DeclAttribute {
   }
 };
 
-/// The @_typeSequence attribute, which treats a generic param decl as a variadic
-/// sequence of value/type pairs.
-class TypeSequenceAttr : public DeclAttribute {
-  TypeSequenceAttr(SourceLoc atLoc, SourceRange Range);
-
-public:
-  static TypeSequenceAttr *create(ASTContext &Ctx, SourceLoc atLoc,
-                                  SourceRange Range);
-
-  static bool classof(const DeclAttribute *DA) {
-    return DA->getKind() == DAK_TypeSequence;
-  }
-};
-
 /// The @_unavailableFromAsync attribute, used to make function declarations
 /// unavailable from async contexts.
 class UnavailableFromAsyncAttr : public DeclAttribute {

include/swift/AST/DiagnosticsSema.def

@@ -6482,14 +6482,6 @@ ERROR(noimplicitcopy_attr_valid_only_on_local_let_params,
 ERROR(noimplicitcopy_attr_invalid_in_generic_context,
       none, "'@_noImplicitCopy' attribute cannot be applied to entities in generic contexts", ())
 
-//------------------------------------------------------------------------------
-// MARK: variadics
-//------------------------------------------------------------------------------
-
-ERROR(type_sequence_on_non_generic_param, none,
-      "'@_typeSequence' must appear on a generic parameter",
-      ())
-
 //------------------------------------------------------------------------------
 // MARK: Type inference from default expressions
 //------------------------------------------------------------------------------

lib/AST/ASTContext.cpp

@@ -352,7 +352,7 @@ struct ASTContext::Implementation {
       ExistentialSignatures;
 
   /// The element signature for a generic signature, constructed by dropping
-  /// @_typeSequence attributes from generic parameters.
+  /// the parameter pack bit from generic parameters.
   llvm::DenseMap<const GenericSignatureImpl *,
                  CanGenericSignature> ElementSignatures;
 

lib/AST/Attr.cpp

@@ -1264,11 +1264,6 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
     break;
   }
 
-  case DAK_TypeSequence: {
-    Printer.printAttrName("@_typeSequence");
-    break;
-  }
-
   case DAK_UnavailableFromAsync: {
     Printer.printAttrName("@_unavailableFromAsync");
     const UnavailableFromAsyncAttr *attr = cast<UnavailableFromAsyncAttr>(this);
@@ -1454,8 +1449,6 @@ StringRef DeclAttribute::getAttrName() const {
     return "derivative";
   case DAK_Transpose:
     return "transpose";
-  case DAK_TypeSequence:
-    return "_typeSequence";
   case DAK_UnavailableFromAsync:
     return "_unavailableFromAsync";
   case DAK_BackDeploy:
@@ -2289,15 +2282,6 @@ bool CustomAttr::isArgUnsafe() const {
   return isArgUnsafeBit;
 }
 
-TypeSequenceAttr::TypeSequenceAttr(SourceLoc atLoc, SourceRange range)
-    : DeclAttribute(DAK_TypeSequence, atLoc, range, /*Implicit=*/false) {}
-
-TypeSequenceAttr *TypeSequenceAttr::create(ASTContext &Ctx, SourceLoc atLoc,
-                                           SourceRange range) {
-  void *mem = Ctx.Allocate(sizeof(TypeSequenceAttr), alignof(TypeSequenceAttr));
-  return new (mem) TypeSequenceAttr(atLoc, range);
-}
-
 const DeclAttribute *
 DeclAttributes::getEffectiveSendableAttr() const {
   const NonSendableAttr *assumedAttr = nullptr;

lib/Parse/ParseDecl.cpp

@@ -3050,15 +3050,6 @@ bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
         *name, AtLoc, range, /*implicit*/ false));
     break;
   }
-  case DAK_TypeSequence: {
-    if (Context.LangOpts.hasFeature(Feature::VariadicGenerics)) {
-      auto range = SourceRange(Loc, Tok.getRange().getStart());
-      Attributes.add(TypeSequenceAttr::create(Context, AtLoc, range));
-    } else {
-      DiscardAttribute = true;
-    }
-    break;
-  }
 
   case DAK_UnavailableFromAsync: {
     StringRef message;

lib/Parse/ParseGeneric.cpp

@@ -107,9 +107,7 @@ Parser::parseGenericParametersBeforeWhere(SourceLoc LAngleLoc,
         Inherited.push_back({Ty.get()});
     }
 
-    const bool isParameterPack =
-        attributes.getAttribute<TypeSequenceAttr>() != nullptr ||
-        EllipsisLoc.isValid();
+    const bool isParameterPack = EllipsisLoc.isValid();
     auto *Param = GenericTypeParamDecl::createParsed(
         CurDeclContext, Name, NameLoc, EllipsisLoc,
         /*index*/ GenericParams.size(), isParameterPack);

lib/Sema/TypeCheckAttr.cpp

@@ -287,7 +287,6 @@ class AttributeChecker : public AttributeVisitor<AttributeChecker> {
   void visitDynamicReplacementAttr(DynamicReplacementAttr *attr);
   void visitTypeEraserAttr(TypeEraserAttr *attr);
   void visitImplementsAttr(ImplementsAttr *attr);
-  void visitTypeSequenceAttr(TypeSequenceAttr *attr);
   void visitNoMetadataAttr(NoMetadataAttr *attr);
 
   void visitFrozenAttr(FrozenAttr *attr);
@@ -4065,13 +4064,6 @@ AttributeChecker::visitSPIOnlyAttr(SPIOnlyAttr *attr) {
   }
 }
 
-void AttributeChecker::visitTypeSequenceAttr(TypeSequenceAttr *attr) {
-  if (!isa<GenericTypeParamDecl>(D)) {
-    attr->setInvalid();
-    diagnoseAndRemoveAttr(attr, diag::type_sequence_on_non_generic_param);
-  }
-}
-
 void AttributeChecker::visitNoMetadataAttr(NoMetadataAttr *attr) {
   if (!Ctx.LangOpts.hasFeature(Feature::LayoutPrespecialization)) {
     auto error =

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1610,7 +1610,6 @@ namespace  {
     UNINTERESTING_ATTR(NoImplicitCopy)
     UNINTERESTING_ATTR(UnavailableFromAsync)
 
-    UNINTERESTING_ATTR(TypeSequence)
     UNINTERESTING_ATTR(NoMetadata)
     UNINTERESTING_ATTR(CompileTimeConst)
 

lib/Serialization/ModuleFormat.h

@@ -58,8 +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 =
-    715; // New test_specification instruction
+const uint16_t SWIFTMODULE_VERSION_MINOR = 716; // remove @_typeSequence
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -2064,8 +2063,6 @@ namespace decls_block {
     BCArray<BCFixed<1>> // Transposed parameter indices' bitvector.
   >;
 
-  using TypeSequenceDeclAttrLayout = BCRecordLayout<TypeSequence_DECL_ATTR>;
-
 #define SIMPLE_DECL_ATTR(X, CLASS, ...)         \
   using CLASS##DeclAttrLayout = BCRecordLayout< \
     CLASS##_DECL_ATTR, \

lib/Serialization/Serialization.cpp

@@ -2857,12 +2857,6 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
       return;
     }
 
-    case DAK_TypeSequence: {
-      auto abbrCode = S.DeclTypeAbbrCodes[TypeSequenceDeclAttrLayout::Code];
-      TypeSequenceDeclAttrLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode);
-      return;
-    }
-
     case DAK_UnavailableFromAsync: {
       auto abbrCode =
           S.DeclTypeAbbrCodes[UnavailableFromAsyncDeclAttrLayout::Code];