Introduce callables.

include/swift/AST/Attr.def

@@ -117,7 +117,7 @@ DECL_ATTR(available, Available,
   AllowMultipleAttributes | LongAttribute,
   1)
 CONTEXTUAL_SIMPLE_DECL_ATTR(final, Final,
-  OnClass | OnFunc | OnAccessor | OnVar | OnSubscript |
+  OnClass | OnFunc | OnAccessor | OnCall | OnVar | OnSubscript |
   DeclModifier,
   2)
 DECL_ATTR(objc, ObjC,
@@ -129,7 +129,7 @@ CONTEXTUAL_SIMPLE_DECL_ATTR(required, Required,
   DeclModifier,
   4)
 CONTEXTUAL_SIMPLE_DECL_ATTR(optional, Optional,
-  OnConstructor | OnFunc | OnAccessor | OnVar | OnSubscript |
+  OnConstructor | OnFunc | OnAccessor | OnCall | OnVar | OnSubscript |
   DeclModifier,
   5)
 SIMPLE_DECL_ATTR(dynamicCallable, DynamicCallable,
@@ -183,7 +183,7 @@ DECL_ATTR(_semantics, Semantics,
   AllowMultipleAttributes | UserInaccessible,
   21)
 CONTEXTUAL_SIMPLE_DECL_ATTR(dynamic, Dynamic,
-  OnFunc | OnAccessor | OnVar | OnSubscript | OnConstructor |
+  OnFunc | OnAccessor | OnCall | OnVar | OnSubscript | OnConstructor |
   DeclModifier,
   22)
 CONTEXTUAL_SIMPLE_DECL_ATTR(infix, Infix,
@@ -199,13 +199,14 @@ CONTEXTUAL_SIMPLE_DECL_ATTR(postfix, Postfix,
   DeclModifier,
   25)
 SIMPLE_DECL_ATTR(_transparent, Transparent,
-  OnFunc | OnAccessor | OnConstructor | OnVar | UserInaccessible,
+  OnFunc | OnAccessor | OnCall | OnConstructor | OnVar | UserInaccessible,
   26)
 SIMPLE_DECL_ATTR(requires_stored_property_inits, RequiresStoredPropertyInits,
   OnClass,
   27)
 SIMPLE_DECL_ATTR(nonobjc, NonObjC,
-  OnExtension | OnFunc | OnAccessor | OnVar | OnSubscript | OnConstructor,
+  OnExtension | OnFunc | OnAccessor | OnCall | OnVar | OnSubscript |
+  OnConstructor,
   30)
 SIMPLE_DECL_ATTR(_fixed_layout, FixedLayout,
   OnVar | OnClass | OnStruct |
@@ -215,40 +216,41 @@ SIMPLE_DECL_ATTR(inlinable, Inlinable,
   OnVar | OnSubscript | OnAbstractFunction,
   32)
 DECL_ATTR(_specialize, Specialize,
-  OnConstructor | OnFunc | OnAccessor |
+  OnConstructor | OnFunc | OnAccessor | OnCall |
   AllowMultipleAttributes | LongAttribute | UserInaccessible,
   33)
 SIMPLE_DECL_ATTR(objcMembers, ObjCMembers,
   OnClass,
   34)
 CONTEXTUAL_SIMPLE_DECL_ATTR(__consuming, Consuming,
-  OnFunc | OnAccessor |
+  OnFunc | OnAccessor | OnCall |
   DeclModifier |
   UserInaccessible |
   NotSerialized, 40)
 CONTEXTUAL_SIMPLE_DECL_ATTR(mutating, Mutating,
-  OnFunc | OnAccessor |
+  OnFunc | OnAccessor | OnCall |
   DeclModifier |
   NotSerialized, 41)
 CONTEXTUAL_SIMPLE_DECL_ATTR(nonmutating, NonMutating,
-  OnFunc | OnAccessor |
+  OnFunc | OnAccessor | OnCall |
   DeclModifier |
   NotSerialized, 42)
 CONTEXTUAL_SIMPLE_DECL_ATTR(convenience, Convenience,
   OnConstructor |
   DeclModifier |
   NotSerialized, 43)
 CONTEXTUAL_SIMPLE_DECL_ATTR(override, Override,
-  OnFunc | OnAccessor | OnVar | OnSubscript | OnConstructor | OnAssociatedType |
+  OnFunc | OnAccessor | OnCall | OnVar | OnSubscript | OnConstructor |
+  OnAssociatedType |
   DeclModifier |
   NotSerialized, 44)
 SIMPLE_DECL_ATTR(_hasStorage, HasStorage,
   OnVar |
   UserInaccessible |
   NotSerialized, 45)
 DECL_ATTR(private, AccessControl,
-  OnFunc | OnAccessor | OnExtension | OnGenericType | OnVar | OnSubscript |
-  OnConstructor |
+  OnFunc | OnAccessor | OnCall | OnExtension | OnGenericType | OnVar |
+  OnSubscript | OnConstructor |
   DeclModifier |
   NotSerialized, 46)
 DECL_ATTR_ALIAS(fileprivate, AccessControl)
@@ -296,7 +298,7 @@ DECL_ATTR(_alignment, Alignment,
   UserInaccessible,
   56)
 SIMPLE_DECL_ATTR(rethrows, Rethrows,
-  OnFunc | OnAccessor | OnConstructor |
+  OnFunc | OnAccessor | OnCall | OnConstructor |
   RejectByParser,
   57)
 DECL_ATTR(_swift_native_objc_runtime_base, SwiftNativeObjCRuntimeBase,
@@ -307,30 +309,30 @@ CONTEXTUAL_SIMPLE_DECL_ATTR(indirect, Indirect, DeclModifier |
   OnEnum | OnEnumElement,
   60)
 SIMPLE_DECL_ATTR(warn_unqualified_access, WarnUnqualifiedAccess,
-  OnFunc | OnAccessor /*| OnVar*/ |
+  OnFunc | OnAccessor | /*OnVar |*/
   LongAttribute,
   61)
 SIMPLE_DECL_ATTR(_show_in_interface, ShowInInterface,
   OnProtocol |
   UserInaccessible,
   62)
 DECL_ATTR(_cdecl, CDecl,
-  OnFunc | OnAccessor |
+  OnFunc | OnAccessor | OnCall |
   LongAttribute | UserInaccessible,
   63)
 SIMPLE_DECL_ATTR(usableFromInline, UsableFromInline,
   OnAbstractFunction | OnVar | OnSubscript | OnNominalType | OnTypeAlias |
   LongAttribute,
   64)
 SIMPLE_DECL_ATTR(discardableResult, DiscardableResult,
-  OnFunc | OnAccessor | OnConstructor |
+  OnFunc | OnAccessor | OnCall | OnConstructor |
   LongAttribute,
   65)
 SIMPLE_DECL_ATTR(GKInspectable, GKInspectable,
   OnVar,
   66)
 DECL_ATTR(_implements, Implements,
-  OnFunc | OnAccessor | OnVar | OnSubscript | OnTypeAlias |
+  OnFunc | OnAccessor | OnCall | OnVar | OnSubscript | OnTypeAlias |
   UserInaccessible |
   NotSerialized, 67)
 DECL_ATTR(_objcRuntimeName, ObjCRuntimeName,
@@ -346,7 +348,7 @@ DECL_ATTR(_restatedObjCConformance, RestatedObjCConformance,
   NotSerialized, 70)
 // NOTE: 71 is unused
 SIMPLE_DECL_ATTR(_implicitly_unwrapped_optional, ImplicitlyUnwrappedOptional,
-  OnFunc | OnAccessor | OnVar | OnParam | OnSubscript | OnConstructor |
+  OnFunc | OnAccessor | OnCall | OnVar | OnParam | OnSubscript | OnConstructor |
   RejectByParser,
   72)
 DECL_ATTR(_optimize, Optimize,
@@ -358,7 +360,7 @@ DECL_ATTR(_clangImporterSynthesizedType, ClangImporterSynthesizedType,
   LongAttribute | RejectByParser | UserInaccessible |
   NotSerialized, 74)
 SIMPLE_DECL_ATTR(_weakLinked, WeakLinked,
-  OnNominalType | OnAssociatedType | OnFunc | OnAccessor | OnVar |
+  OnNominalType | OnAssociatedType | OnFunc | OnAccessor | OnCall | OnVar |
   OnSubscript | OnConstructor | OnEnumElement | OnExtension | UserInaccessible,
   75)
 SIMPLE_DECL_ATTR(_frozen, Frozen,
@@ -374,7 +376,8 @@ SIMPLE_DECL_ATTR(_hasInitialValue, HasInitialValue,
   UserInaccessible,
   78)
 SIMPLE_DECL_ATTR(_nonoverride, NonOverride,
-  OnFunc | OnAccessor | OnVar | OnSubscript | OnConstructor | OnAssociatedType |
+  OnFunc | OnAccessor | OnCall | OnVar | OnSubscript | OnConstructor |
+  OnAssociatedType |
   UserInaccessible | NotSerialized,
   79)
 DECL_ATTR(_dynamicReplacement, DynamicReplacement,

include/swift/AST/Decl.h

@@ -54,6 +54,7 @@ namespace swift {
   struct ASTNode;
   class ASTPrinter;
   class ASTWalker;
+  class CallDecl;
   class ConstructorDecl;
   class DestructorDecl;
   class DiagnosticEngine;
@@ -137,6 +138,7 @@ enum class DescriptiveDeclKind : uint8_t {
   GenericStruct,
   GenericClass,
   GenericType,
+  Call,
   Subscript,
   Constructor,
   Destructor,
@@ -5758,7 +5760,8 @@ class FuncDecl : public AbstractFunctionDecl {
 
   static bool classof(const Decl *D) {
     return D->getKind() == DeclKind::Func ||
-           D->getKind() == DeclKind::Accessor;
+           D->getKind() == DeclKind::Accessor ||
+           D->getKind() == DeclKind::Call;
   }
   static bool classof(const AbstractFunctionDecl *D) {
     return classof(static_cast<const Decl*>(D));
@@ -5911,7 +5914,53 @@ AbstractStorageDecl::AccessorRecord::getAccessor(AccessorKind kind) const {
   }
   return nullptr;
 }
-
+
+/// CallDecl - Declares a callable method for a type. For example:
+///
+/// \code
+/// struct Adder {
+///   var base: Int
+///   call(_ x: Int) -> Int {
+///      return base + x
+///   }
+/// }
+/// \endcode
+class CallDecl final : public FuncDecl {
+  CallDecl(DeclName fullName, SourceLoc declLoc, bool throws,
+           SourceLoc throwsLoc, unsigned numParameterLists,
+           GenericParamList *genericParams, DeclContext *parent)
+    : FuncDecl(DeclKind::Call,
+               /*staticLoc*/ SourceLoc(), StaticSpellingKind::None,
+               /*func loc*/ declLoc, /*name*/ fullName, /*name loc*/ declLoc,
+               throws, throwsLoc, numParameterLists, genericParams, parent) {}
+
+  static CallDecl *createImpl(ASTContext &ctx, DeclName fullName,
+                              SourceLoc declLoc, bool throws,
+                              SourceLoc throwsLoc,
+                              GenericParamList *genericParams,
+                              DeclContext *parent, ClangNode clangNode);
+
+public:
+  static CallDecl *create(ASTContext &ctx, DeclName fullName, SourceLoc declLoc,
+                          bool throws, SourceLoc throwsLoc,
+                          GenericParamList *genericParams,
+                          ParameterList *parameterList,
+                          TypeLoc fnRetType, DeclContext *parent,
+                          ClangNode clangNode = ClangNode());
+
+  static bool classof(const Decl *D) {
+    return D->getKind() == DeclKind::Call;
+  }
+  static bool classof(const AbstractFunctionDecl *D) {
+    return classof(static_cast<const Decl*>(D));
+  }
+  static bool classof(const DeclContext *DC) {
+    if (auto D = DC->getAsDecl())
+      return classof(D);
+    return false;
+  }
+};
+
 /// This represents a 'case' declaration in an 'enum', which may declare
 /// one or more individual comma-separated EnumElementDecls.
 class EnumCaseDecl final : public Decl,
@@ -6834,6 +6883,7 @@ inline ParamDecl **AbstractFunctionDecl::getImplicitSelfDeclStorage() {
     return cast<DestructorDecl>(this)->getImplicitSelfDeclStorage();
   case DeclKind::Func:
   case DeclKind::Accessor:
+  case DeclKind::Call:
     return cast<FuncDecl>(this)->getImplicitSelfDeclStorage();
   }
 }
@@ -6842,11 +6892,12 @@ inline ParamDecl **FuncDecl::getImplicitSelfDeclStorage() {
   if (!hasImplicitSelfDecl())
     return nullptr;
 
-  if (!isa<AccessorDecl>(this)) {
-    assert(getKind() == DeclKind::Func && "no new kinds of functions");
-    return reinterpret_cast<ParamDecl **>(this+1);
-  }
-  return reinterpret_cast<ParamDecl **>(static_cast<AccessorDecl*>(this)+1);
+  if (isa<AccessorDecl>(this))
+    return reinterpret_cast<ParamDecl **>(static_cast<AccessorDecl *>(this)+1);
+  else if (isa<CallDecl>(this))
+    return reinterpret_cast<ParamDecl **>(static_cast<CallDecl *>(this)+1);
+  assert(getKind() == DeclKind::Func && "no new kinds of functions");
+  return reinterpret_cast<ParamDecl **>(this+1);
 }
 
 inline DeclIterator &DeclIterator::operator++() {

include/swift/AST/DeclNodes.def

@@ -170,7 +170,8 @@ ABSTRACT_DECL(Value, Decl)
     ABSTRACT_FUNCTION_DECL(Destructor, AbstractFunctionDecl)
     ABSTRACT_FUNCTION_DECL(Func, AbstractFunctionDecl)
       ABSTRACT_FUNCTION_DECL(Accessor, FuncDecl)
-    DECL_RANGE(AbstractFunction, Constructor, Accessor)
+      ABSTRACT_FUNCTION_DECL(Call, FuncDecl)
+    DECL_RANGE(AbstractFunction, Constructor, Call)
   CONTEXT_VALUE_DECL(EnumElement, ValueDecl)
   DECL_RANGE(Value, Enum, EnumElement)
 

include/swift/AST/DiagnosticsParse.def

@@ -395,6 +395,16 @@ ERROR(subscript_without_get,none,
 ERROR(subscript_static,none,
       "subscript cannot be marked %0", (StaticSpellingKind))
 
+// `call` member
+ERROR(call_decl_static,none,
+      "'call' member cannot be marked %0", (StaticSpellingKind))
+ERROR(call_decl_wrong_scope,none,
+      "'call' members may only be declared within a type", ())
+ERROR(expected_lparen_call,PointsToFirstBadToken,
+      "expected '(' for 'call' member parameters", ())
+ERROR(call_decl_cannot_have_name,PointsToFirstBadToken,
+      "'call' member cannot have a name", ())
+
 // initializer
 ERROR(invalid_nested_init,none,
       "missing '%select{super.|self.}0' at initializer invocation", (bool))

include/swift/AST/DiagnosticsSema.def

@@ -1051,6 +1051,9 @@ NOTE(archetype_declared_in_type,none,
 NOTE(unbound_generic_parameter_explicit_fix,none,
      "explicitly specify the generic arguments to fix this issue", ())
 
+ERROR(missing_call_decl,none,
+      "%0 does not define 'call' declaration of type", (Type))
+
 ERROR(invalid_dynamic_callable_type,none,
       "@dynamicCallable attribute requires %0 to have either a valid "
       "'dynamicallyCall(withArguments:)' method or "
@@ -1687,15 +1690,15 @@ ERROR(witness_requires_class_implementation,none,
       (DeclName, Type))
 ERROR(witness_not_accessible_proto,none,
       "%select{initializer %1|method %1|%select{|setter for }2property %1"
-      "|subscript%select{| setter}2}0 must be declared "
+      "|subscript%select{| setter}2|'call' member}0 must be declared "
       "%select{%error|fileprivate|internal|public|%error}3 because it matches a "
       "requirement in %select{private|fileprivate|internal|public|%error}4 protocol "
       "%5",
       (RequirementKind, DeclName, bool, AccessLevel, AccessLevel, DeclName))
 ERROR(witness_not_accessible_type,none,
       "%select{initializer %1|method %1|%select{|setter for }2property %1"
-      "|subscript%select{| setter}2}0 must be as accessible as its enclosing "
-      "type because it matches a requirement in protocol %5",
+      "|subscript%select{| setter}2|'call' member}0 must be as accessible as "
+      "its enclosing type because it matches a requirement in protocol %5",
       (RequirementKind, DeclName, bool, AccessLevel, AccessLevel, DeclName))
 ERROR(type_witness_not_accessible_proto,none,
       "%0 %1 must be declared %select{%error|fileprivate|internal|public|%error}2 "
@@ -1763,19 +1766,21 @@ NOTE(inherited_protocol_does_not_conform,none,
      "type %0 does not conform to inherited protocol %1", (Type, Type))
 NOTE(no_witnesses,none,
      "protocol requires "
-     "%select{initializer %1|function %1|property %1|subscript}0 with type %2"
-     "%select{|; do you want to add a stub?}3",
+     "%select{initializer %1|function %1|property %1|subscript|'call' member}0 "
+     "with type %2%select{|; do you want to add a stub?}3",
      (RequirementKind, DeclName, Type, bool))
 NOTE(missing_witnesses_general,none, "do you want to add protocol stubs?",
      ())
 NOTE(ambiguous_witnesses,none,
      "multiple matching "
      "%select{initializers named %1|functions named %1|properties named %1|"
-     "subscript operators}0 with type %2", (RequirementKind, DeclName, Type))
+     "subscript operators|'call' member}0 with type %2",
+     (RequirementKind, DeclName, Type))
 NOTE(ambiguous_witnesses_wrong_name,none,
      "multiple matching "
      "%select{initializers named %1|functions named %1|properties named %1|"
-     "subscript operators}0 with type %2", (RequirementKind, DeclName, Type))
+     "subscript operators|'call' member}0 with type %2",
+     (RequirementKind, DeclName, Type))
 NOTE(no_witnesses_type,none,
      "protocol requires nested type %0; do you want to add it?", (Identifier))
 NOTE(default_associated_type_req_fail,none,
@@ -1839,7 +1844,7 @@ NOTE(protocol_witness_renamed,none,
      "rename to %0 to satisfy this requirement%1", (DeclName, StringRef))
 NOTE(protocol_witness_kind_conflict,none,
      "candidate is not %select{an initializer|a function|a variable|"
-     "a subscript}0", (RequirementKind))
+     "a subscript|a 'call' member}0", (RequirementKind))
 NOTE(protocol_witness_type_conflict,none,
      "candidate has non-matching type %0%1", (Type, StringRef))
 NOTE(protocol_witness_missing_requirement,none,

include/swift/AST/DiagnosticsSema.h

@@ -29,7 +29,8 @@ namespace swift {
       Constructor,
       Func,
       Var,
-      Subscript
+      Subscript,
+      Call
     };
 
   // Declare common diagnostics objects with their appropriate types.

include/swift/AST/Identifier.h

@@ -221,8 +221,8 @@ class DeclBaseName {
   };
 
 private:
-  /// In a special DeclName represenenting a subscript, this opaque pointer
-  /// is used as the data of the base name identifier.
+  /// In a special DeclName representing a subscript, this opaque pointer is
+  /// used as the data of the base name identifier.
   /// This is an implementation detail that should never leak outside of
   /// DeclName.
   static void *SubscriptIdentifierData;

include/swift/Demangling/DemangleNodes.def

@@ -43,6 +43,7 @@ NODE(BoundGenericOtherNominalType)
 NODE(BoundGenericTypeAlias)
 NODE(BoundGenericFunction)
 NODE(BuiltinTypeName)
+CONTEXT_NODE(CallDeclaration)
 NODE(CFunctionPointer)
 CONTEXT_NODE(Class)
 NODE(ClassMetadataBaseOffset)

include/swift/IDE/CodeCompletion.h

@@ -398,6 +398,7 @@ enum class CodeCompletionDeclKind {
   Constructor,
   Destructor,
   Subscript,
+  Call,
   StaticMethod,
   InstanceMethod,
   PrefixOperatorFunction,