Parse unknown attributes as "custom" attributes.

Parse custom attributes with the grammar:

```
'@' type-identifier expr-paren?
```

Author: DougGregor

include/swift/AST/ASTTypeIDZone.def

@@ -0,0 +1,19 @@
+//===--- ASTTypeIDZone.def - Define the AST TypeID Zone ---------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+//  This definition file describes the types in the "AST" TypeID zone,
+//  for use with the TypeID template.
+//
+//===----------------------------------------------------------------------===//
+SWIFT_TYPEID_NAMED(NominalTypeDecl *, NominalTypeDecl)
+SWIFT_TYPEID_NAMED(VarDecl *, VarDecl)
+SWIFT_TYPEID(PropertyBehaviorTypeInfo)

include/swift/AST/ASTTypeIDs.h

@@ -0,0 +1,36 @@
+//===--- ASTTypeIDs.h - AST Type Ids ----------------------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines TypeID support for AST types.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_AST_ASTTYPEIDS_H
+#define SWIFT_AST_ASTTYPEIDS_H
+
+#include "swift/Basic/TypeID.h"
+namespace swift {
+
+class NominalTypeDecl;
+struct PropertyBehaviorTypeInfo;
+class VarDecl;
+
+#define SWIFT_AST_TYPEID_ZONE 1
+
+// Define the AST type zone (zone 1)
+#define SWIFT_TYPEID_ZONE SWIFT_AST_TYPEID_ZONE
+#define SWIFT_TYPEID_HEADER "swift/AST/ASTTypeIDZone.def"
+#include "swift/Basic/DefineTypeIDZone.h"
+
+} // end namespace swift
+
+#endif /* SWIFT_AST_ASTTYPEIDS_H */

include/swift/AST/Attr.def

@@ -393,6 +393,9 @@ SIMPLE_DECL_ATTR(_alwaysEmitIntoClient, AlwaysEmitIntoClient,
 SIMPLE_DECL_ATTR(_implementationOnly, ImplementationOnly,
   OnImport | UserInaccessible,
   84)
+DECL_ATTR(_custom, Custom,
+  OnAnyDecl | UserInaccessible,
+  85)
 
 #undef TYPE_ATTR
 #undef DECL_ATTR_ALIAS

include/swift/AST/Attr.h

@@ -32,6 +32,7 @@
 #include "swift/AST/Ownership.h"
 #include "swift/AST/PlatformKind.h"
 #include "swift/AST/Requirement.h"
+#include "swift/AST/TrailingCallArguments.h"
 #include "swift/AST/TypeLoc.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
@@ -49,6 +50,7 @@ class FuncDecl;
 class ClassDecl;
 class GenericFunctionType;
 class LazyConformanceLoader;
+class PatternBindingInitializer;
 class TrailingWhereClause;
 
 /// TypeAttributes - These are attributes that may be applied to types.
@@ -1408,6 +1410,54 @@ class ClangImporterSynthesizedTypeAttr : public DeclAttribute {
   }
 };
 
+/// Defines a custom attribute.
+class CustomAttr final : public DeclAttribute,
+                         public TrailingCallArguments<CustomAttr> {
+  TypeLoc type;
+  Expr *arg;
+  PatternBindingInitializer *initContext;
+
+  unsigned hasArgLabelLocs : 1;
+  unsigned numArgLabels : 16;
+
+  CustomAttr(SourceLoc atLoc, SourceRange range, TypeLoc type,
+             PatternBindingInitializer *initContext, Expr *arg,
+             ArrayRef<Identifier> argLabels, ArrayRef<SourceLoc> argLabelLocs,
+             bool implicit);
+
+public:
+  static CustomAttr *create(ASTContext &ctx, SourceLoc atLoc, TypeLoc type,
+                            bool implicit = false) {
+    return create(ctx, atLoc, type, false, nullptr, SourceLoc(), { }, { }, { },
+                  SourceLoc(), implicit);
+  }
+
+  static CustomAttr *create(ASTContext &ctx, SourceLoc atLoc, TypeLoc type,
+                            bool hasInitializer,
+                            PatternBindingInitializer *initContext,
+                            SourceLoc lParenLoc,
+                            ArrayRef<Expr *> args,
+                            ArrayRef<Identifier> argLabels,
+                            ArrayRef<SourceLoc> argLabelLocs,
+                            SourceLoc rParenLoc,
+                            bool implicit = false);
+
+  unsigned getNumArguments() const { return numArgLabels; }
+  bool hasArgumentLabelLocs() const { return hasArgLabelLocs; }
+
+  TypeLoc &getTypeLoc() { return type; }
+  const TypeLoc &getTypeLoc() const { return type; }
+
+  Expr *getArg() const { return arg; }
+  void setArg(Expr *newArg) { arg = newArg; }
+
+  PatternBindingInitializer *getInitContext() const { return initContext; }
+
+  static bool classof(const DeclAttribute *DA) {
+    return DA->getKind() == DAK_Custom;
+  }
+};
+
 /// Attributes that may be applied to declarations.
 class DeclAttributes {
   /// Linked list of declaration attributes.
@@ -1584,6 +1634,8 @@ class DeclAttributes {
   SourceLoc getStartLoc(bool forModifiers = false) const;
 };
 
+void simple_display(llvm::raw_ostream &out, const DeclAttribute *attr);
+
 } // end namespace swift
 
 #endif

include/swift/AST/DiagnosticsSema.def

@@ -1104,6 +1104,9 @@ ERROR(attribute_requires_operator_identifier,none,
 ERROR(attribute_requires_single_argument,none,
       "'%0' requires a function with one argument", (StringRef))
 
+ERROR(nominal_type_not_attribute,none,
+      "%0 %1 cannot be used as an attribute", (DescriptiveDeclKind, DeclName))
+
 ERROR(mutating_invalid_global_scope,none, "%0 is only valid on methods",
       (SelfAccessKind))
 ERROR(mutating_invalid_classes,none, "%0 isn't valid on methods in "

include/swift/AST/Expr.h

@@ -22,6 +22,7 @@
 #include "swift/AST/DeclNameLoc.h"
 #include "swift/AST/FunctionRefKind.h"
 #include "swift/AST/ProtocolConformanceRef.h"
+#include "swift/AST/TrailingCallArguments.h"
 #include "swift/AST/TypeAlignments.h"
 #include "swift/AST/TypeLoc.h"
 #include "swift/AST/TypeRepr.h"
@@ -570,105 +571,6 @@ class alignas(8) Expr {
   }
 };
 
-/// Helper class to capture trailing call argument labels and related
-/// information, for expression nodes that involve argument labels, trailing
-/// closures, etc.
-template<typename Derived>
-class TrailingCallArguments
-    : private llvm::TrailingObjects<Derived, Identifier, SourceLoc> {
-  // We need to friend TrailingObjects twice here to work around an MSVC bug.
-  // If we have two functions of the same name with the parameter
-  // typename TrailingObjectsIdentifier::template OverloadToken<T> where T is
-  // different for each function, then MSVC reports a "member function already
-  // defined or declared" error, which is incorrect.
-  using TrailingObjectsIdentifier = llvm::TrailingObjects<Derived, Identifier>;
-  friend TrailingObjectsIdentifier;
-
-  using TrailingObjects = llvm::TrailingObjects<Derived, Identifier, SourceLoc>;
-  friend TrailingObjects;
-
-  Derived &asDerived() {
-    return *static_cast<Derived *>(this);
-  }
-
-  const Derived &asDerived() const {
-    return *static_cast<const Derived *>(this);
-  }
-
-  size_t numTrailingObjects(
-      typename TrailingObjectsIdentifier::template OverloadToken<Identifier>)
-      const {
-    return asDerived().getNumArguments();
-  }
-
-  size_t numTrailingObjects(
-      typename TrailingObjectsIdentifier::template OverloadToken<SourceLoc>)
-      const {
-    return asDerived().hasArgumentLabelLocs() ? asDerived().getNumArguments()
-                                              : 0;
-  }
-
-  /// Retrieve the buffer containing the argument labels.
-  MutableArrayRef<Identifier> getArgumentLabelsBuffer() {
-    return { this->template getTrailingObjects<Identifier>(),
-             asDerived().getNumArguments() };
-  }
-
-  /// Retrieve the buffer containing the argument label locations.
-  MutableArrayRef<SourceLoc> getArgumentLabelLocsBuffer() {
-    if (!asDerived().hasArgumentLabelLocs())
-      return { };
-    
-    return { this->template getTrailingObjects<SourceLoc>(),
-             asDerived().getNumArguments() };
-  }
-
-protected:
-  /// Determine the total size to allocate.
-  static size_t totalSizeToAlloc(ArrayRef<Identifier> argLabels,
-                                 ArrayRef<SourceLoc> argLabelLocs,
-                                 bool hasTrailingClosure) {
-    return TrailingObjects::template totalSizeToAlloc<Identifier, SourceLoc>(
-        argLabels.size(), argLabelLocs.size());
-  }
-
-  /// Initialize the actual call arguments.
-  void initializeCallArguments(ArrayRef<Identifier> argLabels,
-                               ArrayRef<SourceLoc> argLabelLocs,
-                               bool hasTrailingClosure) {
-    if (!argLabels.empty()) {
-      std::uninitialized_copy(argLabels.begin(), argLabels.end(),
-                              this->template getTrailingObjects<Identifier>());
-    }
-    
-    if (!argLabelLocs.empty())
-      std::uninitialized_copy(argLabelLocs.begin(), argLabelLocs.end(),
-                              this->template getTrailingObjects<SourceLoc>());
-  }
-
-public:
-  /// Retrieve the argument labels provided at the call site.
-  ArrayRef<Identifier> getArgumentLabels() const {
-    return { this->template getTrailingObjects<Identifier>(),
-             asDerived().getNumArguments() };
-  }
-
-  /// Retrieve the buffer containing the argument label locations.
-  ArrayRef<SourceLoc> getArgumentLabelLocs() const {
-    if (!asDerived().hasArgumentLabelLocs())
-      return { };
-    
-    return { this->template getTrailingObjects<SourceLoc>(),
-             asDerived().getNumArguments() };
-  }
-
-  /// Retrieve the location of the ith argument label.
-  SourceLoc getArgumentLabelLoc(unsigned i) const {
-    auto locs = getArgumentLabelLocs();
-    return i < locs.size() ? locs[i] : SourceLoc();
-  }
-};
-
 /// ErrorExpr - Represents a semantically erroneous subexpression in the AST,
 /// typically this will have an ErrorType.
 class ErrorExpr : public Expr {
@@ -5448,7 +5350,27 @@ inline const SourceLoc *CollectionExpr::getTrailingSourceLocs() const {
 }
 
 #undef SWIFT_FORWARD_SOURCE_LOCS_TO
-  
+
+/// Pack the argument information into a single argument, to match the
+/// representation expected by the AST.
+///
+/// \param argLabels The argument labels, which might be updated by this
+/// function.
+///
+/// \param argLabelLocs The argument label locations, which might be updated by
+/// this function.
+Expr *packSingleArgument(ASTContext &ctx, SourceLoc lParenLoc,
+                         ArrayRef<Expr *> args,
+                         ArrayRef<Identifier> &argLabels,
+                         ArrayRef<SourceLoc> &argLabelLocs,
+                         SourceLoc rParenLoc,
+                         Expr *trailingClosure, bool implicit,
+                         SmallVectorImpl<Identifier> &argLabelsScratch,
+                         SmallVectorImpl<SourceLoc> &argLabelLocsScratch,
+                         llvm::function_ref<Type(const Expr *)> getType =
+                              [](const Expr *E) -> Type {
+                                return E->getType();
+                              });
 } // end namespace swift
 
 #endif

include/swift/AST/NameLookupRequests.h

@@ -17,6 +17,7 @@
 #define SWIFT_NAME_LOOKUP_REQUESTS_H
 
 #include "swift/AST/SimpleRequest.h"
+#include "swift/AST/ASTTypeIDs.h"
 #include "swift/Basic/Statistic.h"
 #include "llvm/ADT/TinyPtrVector.h"
 
@@ -238,6 +239,33 @@ class TypeDeclsFromWhereClauseRequest :
   void noteCycleStep(DiagnosticEngine &diags) const;
 };
 
+/// Request the nominal type declaration to which the given custom attribute
+/// refers.
+class CustomAttrNominalRequest :
+    public SimpleRequest<CustomAttrNominalRequest,
+                         CacheKind::Cached,
+                         NominalTypeDecl *,
+                         CustomAttr *,
+                         DeclContext *> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  // Evaluation.
+  llvm::Expected<NominalTypeDecl *>
+  evaluate(Evaluator &evaluator, CustomAttr *attr, DeclContext *dc) const;
+
+public:
+  // Caching
+  bool isCached() const { return true; }
+
+  // Cycle handling
+  void diagnoseCycle(DiagnosticEngine &diags) const;
+  void noteCycleStep(DiagnosticEngine &diags) const;
+};
+
 /// The zone number for name-lookup requests.
 #define SWIFT_NAME_LOOKUP_REQUESTS_TYPEID_ZONE 9
 

include/swift/AST/NameLookupTypeIDZone.def

@@ -20,3 +20,4 @@ SWIFT_TYPEID(SuperclassDeclRequest)
 SWIFT_TYPEID(ExtendedNominalRequest)
 SWIFT_TYPEID(SelfBoundsFromWhereClauseRequest)
 SWIFT_TYPEID(TypeDeclsFromWhereClauseRequest)
+SWIFT_TYPEID(CustomAttrNominalRequest)