Introduce type sugar for InlineArray

docs/ABI/Mangling.rst

@@ -954,6 +954,7 @@ productions:
   type ::= base-type "XSq"                       // sugared Optional type
   type ::= base-type "XSa"                       // sugared Array type
   type ::= key-type value-type "XSD"             // sugared Dictionary type
+  type ::= count-type element-type "XSA"         // sugared InlineArray type
 
 Generics
 ~~~~~~~~

include/swift/AST/ASTBridging.h

@@ -2702,6 +2702,11 @@ BridgedImplicitlyUnwrappedOptionalTypeRepr_createParsed(
     BridgedASTContext cContext, BridgedTypeRepr base,
     BridgedSourceLoc cExclamationLoc);
 
+SWIFT_NAME("BridgedInlineArrayTypeRepr.createParsed(_:count:element:brackets:)")
+BridgedInlineArrayTypeRepr BridgedInlineArrayTypeRepr_createParsed(
+    BridgedASTContext cContext, BridgedTypeRepr cCountType,
+    BridgedTypeRepr cElementType, BridgedSourceRange cBracketsRange);
+
 SWIFT_NAME("BridgedInverseTypeRepr.createParsed(_:tildeLoc:constraint:)")
 BridgedInverseTypeRepr
 BridgedInverseTypeRepr_createParsed(BridgedASTContext cContext,

include/swift/AST/ASTDemangler.h

@@ -248,6 +248,8 @@ class ASTBuilder {
 
   Type createArrayType(Type base);
 
+  Type createInlineArrayType(Type count, Type element);
+
   Type createDictionaryType(Type key, Type value);
 
   Type createIntegerType(intptr_t value);

include/swift/AST/DiagnosticsParse.def

@@ -878,6 +878,10 @@ NOTE(subscript_array_element_fix_it_add_comma, none, "add a separator between "
 NOTE(subscript_array_element_fix_it_remove_space, none,
      "remove the space between the elements to silence this warning", ())
 
+// Inline Array
+ERROR(expected_rsquare_inline_array,none,
+      "expected ']' in inline array type", ())
+
 // Tuple Types
 ERROR(expected_rparen_tuple_type_list,none,
       "expected ')' at end of tuple list", ())

include/swift/AST/DiagnosticsSema.def

@@ -6069,7 +6069,7 @@ NOTE(note_recursive_enum_case_here,none,
 
 ERROR(sugar_type_not_found,none,
       "broken standard library: cannot find "
-      "%select{Array|Optional|ImplicitlyUnwrappedOptional|Dictionary|"
+      "%select{Array|Optional|InlineArray|Dictionary|"
       "Error}0 type", (unsigned))
 ERROR(optional_intrinsics_not_found,none,
       "broken standard library: cannot find intrinsic operations on "
@@ -8334,6 +8334,9 @@ ERROR(invalid_value_for_type_same_type,none,
 ERROR(inlinearray_literal_incorrect_count,none,
       "expected %0 elements in inline array literal, but got %1", (Type, Type))
 
+ERROR(inline_array_type_backwards,none,
+      "element count must precede inline array element type", ())
+
 //===----------------------------------------------------------------------===//
 // MARK: @abi Attribute
 //===----------------------------------------------------------------------===//

include/swift/AST/PrintOptions.h

@@ -590,6 +590,10 @@ struct PrintOptions {
   /// Whether to always desugar array types from `[base_type]` to `Array<base_type>`
   bool AlwaysDesugarArraySliceTypes = false;
 
+  /// Whether to always desugar inline array types from
+  /// `[<count> x <element>]` to `InlineArray<count, element>`
+  bool AlwaysDesugarInlineArrayTypes = false;
+
   /// Whether to always desugar dictionary types
   /// from `[key_type:value_type]` to `Dictionary<key_type,value_type>`
   bool AlwaysDesugarDictionaryTypes = false;

include/swift/AST/TypeNodes.def

@@ -217,6 +217,7 @@ ABSTRACT_SUGARED_TYPE(Sugar, Type)
       SUGARED_TYPE(Optional, UnarySyntaxSugarType)
       SUGARED_TYPE(VariadicSequence, UnarySyntaxSugarType)
       TYPE_RANGE(UnarySyntaxSugar, ArraySlice, VariadicSequence)
+    SUGARED_TYPE(InlineArray, SyntaxSugarType)
     SUGARED_TYPE(Dictionary, SyntaxSugarType)
     TYPE_RANGE(SyntaxSugar, ArraySlice, Dictionary)
   TYPE_RANGE(Sugar, TypeAlias, Dictionary)

include/swift/AST/TypeRepr.h

@@ -641,6 +641,35 @@ class ArrayTypeRepr : public TypeRepr {
   friend class TypeRepr;
 };
 
+/// An InlineArray type e.g `[2 x Foo]`, sugar for `InlineArray<2, Foo>`.
+class InlineArrayTypeRepr : public TypeRepr {
+  TypeRepr *Count;
+  TypeRepr *Element;
+  SourceRange Brackets;
+
+  InlineArrayTypeRepr(TypeRepr *count, TypeRepr *element, SourceRange brackets)
+      : TypeRepr(TypeReprKind::InlineArray), Count(count), Element(element),
+        Brackets(brackets) {}
+
+public:
+  static InlineArrayTypeRepr *create(ASTContext &ctx, TypeRepr *count,
+                                     TypeRepr *element, SourceRange brackets);
+
+  TypeRepr *getCount() const { return Count; }
+  TypeRepr *getElement() const { return Element; }
+  SourceRange getBrackets() const { return Brackets; }
+
+  static bool classof(const TypeRepr *T) {
+    return T->getKind() == TypeReprKind::InlineArray;
+  }
+
+private:
+  SourceLoc getStartLocImpl() const { return Brackets.Start; }
+  SourceLoc getEndLocImpl() const { return Brackets.End; }
+  void printImpl(ASTPrinter &Printer, const PrintOptions &Opts) const;
+  friend class TypeRepr;
+};
+
 /// A dictionary type.
 /// \code
 ///   [K : V]
@@ -1626,6 +1655,7 @@ inline bool TypeRepr::isSimple() const {
   case TypeReprKind::Fixed:
   case TypeReprKind::Self:
   case TypeReprKind::Array:
+  case TypeReprKind::InlineArray:
   case TypeReprKind::SILBox:
   case TypeReprKind::Isolated:
   case TypeReprKind::Sending:

include/swift/AST/TypeReprNodes.def

@@ -49,6 +49,7 @@ ABSTRACT_TYPEREPR(DeclRef, TypeRepr)
   TYPEREPR(UnqualifiedIdent, DeclRefTypeRepr)
   TYPEREPR(QualifiedIdent, DeclRefTypeRepr)
 TYPEREPR(Function, TypeRepr)
+TYPEREPR(InlineArray, TypeRepr)
 TYPEREPR(Array, TypeRepr)
 TYPEREPR(Dictionary, TypeRepr)
 TYPEREPR(Optional, TypeRepr)

include/swift/AST/TypeTransform.h

@@ -894,6 +894,25 @@ case TypeKind::Id:
       return ArraySliceType::get(baseTy);
     }
 
+    case TypeKind::InlineArray: {
+      auto ty = cast<InlineArrayType>(base);
+      auto countTy = doIt(ty->getCountType(), TypePosition::Invariant);
+      if (!countTy)
+        return Type();
+
+      // Currently the element type is invariant for InlineArray.
+      // FIXME: Should we allow covariance?
+      auto eltTy = doIt(ty->getElementType(), TypePosition::Invariant);
+      if (!eltTy)
+        return Type();
+
+      if (countTy.getPointer() == ty->getCountType().getPointer() &&
+          eltTy.getPointer() == ty->getElementType().getPointer())
+        return t;
+
+      return InlineArrayType::get(countTy, eltTy);
+    }
+
     case TypeKind::Optional: {
       auto optional = cast<OptionalType>(base);
       auto baseTy = doIt(optional->getBaseType(), pos);

include/swift/AST/Types.h

@@ -6197,6 +6197,27 @@ class ArraySliceType : public UnarySyntaxSugarType {
   }
 };
 
+/// An InlineArray type e.g `[2 x Foo]`, sugar for `InlineArray<2, Foo>`.
+class InlineArrayType : public SyntaxSugarType {
+  Type Count;
+  Type Elt;
+
+  InlineArrayType(const ASTContext &ctx, Type count, Type elt,
+                  RecursiveTypeProperties properties)
+      : SyntaxSugarType(TypeKind::InlineArray, ctx, properties), Count(count),
+        Elt(elt) {}
+
+public:
+  static InlineArrayType *get(Type count, Type elt);
+
+  Type getCountType() const { return Count; }
+  Type getElementType() const { return Elt; }
+
+  static bool classof(const TypeBase *T) {
+    return T->getKind() == TypeKind::InlineArray;
+  }
+};
+
 /// The type T?, which is always sugar for a library type.
 class OptionalType : public UnarySyntaxSugarType {
   OptionalType(const ASTContext &ctx,Type base,

include/swift/Basic/Features.def

@@ -509,6 +509,9 @@ EXPERIMENTAL_FEATURE(SwiftSettings, false)
 /// Syntax sugar features for concurrency.
 EXPERIMENTAL_FEATURE(ConcurrencySyntaxSugar, true)
 
+/// Enable syntax sugar type '[3 x Int]' for Inline Array
+EXPERIMENTAL_FEATURE(InlineArrayTypeSugar, false)
+
 /// Allow declaration of compile-time values
 EXPERIMENTAL_FEATURE(CompileTimeValues, true)
 

include/swift/Demangling/DemangleNodes.def

@@ -330,6 +330,7 @@ NODE(AssociatedTypeGenericParamRef)
 NODE(SugaredOptional)
 NODE(SugaredArray)
 NODE(SugaredDictionary)
+NODE(SugaredInlineArray)
 NODE(SugaredParen) // Removed in Swift 6.TBD
 
 // Added in Swift 5.1

include/swift/Demangling/TypeDecoder.h

@@ -1466,6 +1466,22 @@ class TypeDecoder {
 
       return Builder.createArrayType(base.getType());
     }
+    case NodeKind::SugaredInlineArray: {
+      if (Node->getNumChildren() < 2) {
+        return MAKE_NODE_TYPE_ERROR(Node,
+                                    "fewer children (%zu) than required (2)",
+                                    Node->getNumChildren());
+      }
+      auto count = decodeMangledType(Node->getChild(0), depth + 1);
+      if (count.isError())
+        return count;
+
+      auto element = decodeMangledType(Node->getChild(1), depth + 1);
+      if (element.isError())
+        return element;
+
+      return Builder.createInlineArrayType(count.getType(), element.getType());
+    }
     case NodeKind::SugaredDictionary: {
       if (Node->getNumChildren() < 2)
         return MAKE_NODE_TYPE_ERROR(Node,

include/swift/Parse/Parser.h

@@ -1458,6 +1458,14 @@ class Parser {
   ParserResult<TypeRepr> parseTypeTupleBody();
   ParserResult<TypeRepr> parseTypeArray(ParserResult<TypeRepr> Base);
 
+  /// Whether the parser is at the start of an InlineArray type body.
+  bool isStartOfInlineArrayTypeBody();
+
+  /// Parse an InlineArray type '[' integer 'x' type ']'.
+  ///
+  /// NOTE: 'isStartOfInlineArrayTypeBody' must be true.
+  ParserResult<TypeRepr> parseTypeInlineArray(SourceLoc lSquare);
+
   /// Parse a collection type.
   ///   type-simple:
   ///     '[' type ']'
@@ -1691,8 +1699,14 @@ class Parser {
   /// and the expression will parse with the '<' as an operator.
   bool canParseAsGenericArgumentList();
 
+  bool canParseTypeSimple();
+  bool canParseTypeSimpleOrComposition();
+  bool canParseTypeScalar();
   bool canParseType();
 
+  bool canParseStartOfInlineArrayType();
+  bool canParseCollectionType();
+
   /// Returns true if a simple type identifier can be parsed.
   ///
   /// \verbatim

include/swift/RemoteInspection/TypeRefBuilder.h

@@ -917,6 +917,12 @@ class TypeRefBuilder {
     return nullptr;
   }
 
+  const TypeRef *createInlineArrayType(const TypeRef *count,
+                                       const TypeRef *element) {
+    // TypeRefs don't contain sugared types
+    return nullptr;
+  }
+
   const TypeRef *createDictionaryType(const TypeRef *key,
                                       const TypeRef *value) {
     // TypeRefs don't contain sugared types

lib/AST/ASTContext.cpp

@@ -547,6 +547,7 @@ struct ASTContext::Implementation {
     llvm::DenseMap<llvm::PointerIntPair<TypeBase*, 3, unsigned>,
                    ExistentialMetatypeType*> ExistentialMetatypeTypes;
     llvm::DenseMap<Type, ArraySliceType*> ArraySliceTypes;
+    llvm::DenseMap<std::pair<Type, Type>, InlineArrayType *> InlineArrayTypes;
     llvm::DenseMap<Type, VariadicSequenceType*> VariadicSequenceTypes;
     llvm::DenseMap<std::pair<Type, Type>, DictionaryType *> DictionaryTypes;
     llvm::DenseMap<Type, OptionalType*> OptionalTypes;
@@ -5427,6 +5428,21 @@ ArraySliceType *ArraySliceType::get(Type base) {
   return entry = new (C, arena) ArraySliceType(C, base, properties);
 }
 
+InlineArrayType *InlineArrayType::get(Type count, Type elt) {
+  auto properties =
+      count->getRecursiveProperties() | elt->getRecursiveProperties();
+  auto arena = getArena(properties);
+
+  const ASTContext &C = count->getASTContext();
+
+  auto *&entry = C.getImpl().getArena(arena).InlineArrayTypes[{count, elt}];
+  if (entry)
+    return entry;
+
+  entry = new (C, arena) InlineArrayType(C, count, elt, properties);
+  return entry;
+}
+
 VariadicSequenceType *VariadicSequenceType::get(Type base) {
   auto properties = base->getRecursiveProperties();
   auto arena = getArena(properties);

lib/AST/ASTDemangler.cpp

@@ -1054,6 +1054,10 @@ Type ASTBuilder::createArrayType(Type base) {
   return ArraySliceType::get(base);
 }
 
+Type ASTBuilder::createInlineArrayType(Type count, Type element) {
+  return InlineArrayType::get(count, element);
+}
+
 Type ASTBuilder::createDictionaryType(Type key, Type value) {
   return DictionaryType::get(key, value);
 }

lib/AST/ASTDumper.cpp

@@ -4544,6 +4544,13 @@ class PrintTypeRepr : public TypeReprVisitor<PrintTypeRepr, void, Label>,
     printFoot();
   }
 
+  void visitInlineArrayTypeRepr(InlineArrayTypeRepr *T, Label label) {
+    printCommon("type_inline_array", label);
+    printRec(T->getCount(), Label::always("count"));
+    printRec(T->getElement(), Label::always("element"));
+    printFoot();
+  }
+
   void visitDictionaryTypeRepr(DictionaryTypeRepr *T, Label label) {
     printCommon("type_dictionary", label);
     printRec(T->getKey(), Label::optional("key"));
@@ -6388,6 +6395,13 @@ namespace {
       printFoot();
     }
 
+    void visitInlineArrayType(InlineArrayType *T, Label label) {
+      printCommon("inline_array_type", label);
+      printRec(T->getCountType(), Label::always("count"));
+      printRec(T->getElementType(), Label::always("element"));
+      printFoot();
+    }
+
     void visitOptionalType(OptionalType *T, Label label) {
       printCommon("optional_type", label);
       printRec(T->getBaseType(), Label::optional("base_type"));

lib/AST/ASTMangler.cpp

@@ -1574,6 +1574,18 @@ void ASTMangler::appendType(Type type, GenericSignature sig,
       appendOperator("XSa");
       return;
 
+    case TypeKind::InlineArray: {
+      assert(DWARFMangling && "sugared types are only legal for the debugger");
+      auto *T = cast<InlineArrayType>(tybase);
+      appendType(T->getCountType(), sig, forDecl);
+      appendType(T->getElementType(), sig, forDecl);
+      // Note we don't have a known-type mangling for InlineArray, we can
+      // use 'A' since it's incredibly unlikely
+      // AutoreleasingUnsafeMutablePointer will ever receive type sugar.
+      appendOperator("XSA");
+      return;
+    }
+
     case TypeKind::VariadicSequence:
       assert(DWARFMangling && "sugared types are only legal for the debugger");
       appendType(cast<VariadicSequenceType>(tybase)->getBaseType(), sig, forDecl);

lib/AST/ASTPrinter.cpp

@@ -7066,6 +7066,18 @@ class TypePrinter : public TypeVisitor<TypePrinter> {
     }
   }
 
+  void visitInlineArrayType(InlineArrayType *T) {
+    if (Options.AlwaysDesugarInlineArrayTypes) {
+      visit(T->getDesugaredType());
+    } else {
+      Printer << "[";
+      visit(T->getCountType());
+      Printer << " x ";
+      visit(T->getElementType());
+      Printer << "]";
+    }
+  }
+
   void visitDictionaryType(DictionaryType *T) {
     if (Options.AlwaysDesugarDictionaryTypes) {
       visit(T->getDesugaredType());

lib/AST/ASTWalker.cpp

@@ -2248,6 +2248,10 @@ bool Traversal::visitArrayTypeRepr(ArrayTypeRepr *T) {
   return doIt(T->getBase());
 }
 
+bool Traversal::visitInlineArrayTypeRepr(InlineArrayTypeRepr *T) {
+  return doIt(T->getCount()) || doIt(T->getElement());
+}
+
 bool Traversal::visitDictionaryTypeRepr(DictionaryTypeRepr *T) {
   return doIt(T->getKey()) || doIt(T->getValue());
 }