Introduce a simple request evaluator.

CHANGELOG.md

@@ -57,6 +57,24 @@ Swift 5.0
 Swift 4.2
 ---------
 
+* [SE-0194][]
+
+  The new CaseIterable protocol describes types which have a static
+  “allCases” property that is used to describe all of the cases of the
+  type. Swift will synthesize this “allCases” property for enums that
+  have no associated values. For example:
+
+  ```swift
+  enum Suit: CaseIterable {
+    case heart
+    case club
+    case diamond
+    case spade
+  }
+
+  print(Suit.allCases) // prints [Suit.heart, Suit.club, Suit.diamond, Suit.spade]
+  ```
+
 * [SE-0185][]
 
   Protocol conformances are now able to be synthesized in extensions in the same

include/swift/AST/AnyRequest.h

@@ -0,0 +1,248 @@
+//===--- AnyRequest.h - Requests Instances ----------------------*- 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 file defines the AnyRequest class, which describes a stored request.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_AST_ANYREQUEST_H
+#define SWIFT_AST_ANYREQUEST_H
+
+#include "swift/Basic/TypeID.h"
+#include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/Hashing.h"
+#include <string>
+
+namespace llvm {
+class raw_ostream;
+}
+
+namespace swift {
+
+using llvm::hash_code;
+using llvm::hash_value;
+
+class DiagnosticEngine;
+
+/// Stores a request (for the \c Evaluator class) of any kind.
+///
+/// Requests must be value types and provide the following API to be stored in
+/// an \c AnyRequest instance:
+///
+///   - Copy constructor
+///   - Equality operator (==)
+///   - Hashing support (hash_value)
+///   - TypeID support (see swift/Basic/TypeID.h)
+///   - Display support (free function):
+///       void simple_display(llvm::raw_ostream &, const T &);
+///   - Cycle diagnostics operations:
+///       void diagnoseCycle(DiagnosticEngine &diags) const;
+///       void noteCycleStep(DiagnosticEngine &diags) const;
+///
+class AnyRequest {
+  /// Abstract base class used to hold the specific request kind.
+  class HolderBase {
+  public:
+    /// The type ID of the request being stored.
+    const uint64_t typeID;
+
+    /// Hash value for the request itself.
+    const hash_code hash;
+
+  protected:
+    /// Initialize base with type ID and hash code.
+    HolderBase(uint64_t typeID, hash_code hash)
+      : typeID(typeID), hash(hash_combine(hash_value(typeID), hash)) { }
+
+  public:
+    virtual ~HolderBase();
+
+    /// Determine whether this request is equivalent to the \c other
+    /// request.
+    virtual bool equals(const HolderBase &other) const = 0;
+
+    /// Display.
+    virtual void display(llvm::raw_ostream &out) const = 0;
+
+    /// Diagnose a cycle detected for this request.
+    virtual void diagnoseCycle(DiagnosticEngine &diags) const = 0;
+
+    /// Note that this request is part of a cycle.
+    virtual void noteCycleStep(DiagnosticEngine &diags) const = 0;
+  };
+
+  /// Holds a value that can be used as a request input/output.
+  template<typename Request>
+  class Holder final : public HolderBase {
+  public:
+    const Request request;
+
+    Holder(const Request &request)
+      : HolderBase(TypeID<Request>::value, hash_value(request)),
+        request(request) { }
+
+    Holder(Request &&request)
+      : HolderBase(TypeID<Request>::value, hash_value(request)),
+        request(std::move(request)) { }
+
+    virtual ~Holder() { }
+
+    /// Determine whether this request is equivalent to another.
+    ///
+    /// The caller guarantees that the typeIDs are the same.
+    virtual bool equals(const HolderBase &other) const override {
+      assert(typeID == other.typeID && "Caller should match typeIDs");
+      return request == static_cast<const Holder<Request> &>(other).request;
+    }
+
+    /// Display.
+    virtual void display(llvm::raw_ostream &out) const override {
+      simple_display(out, request);
+    }
+
+    /// Diagnose a cycle detected for this request.
+    virtual void diagnoseCycle(DiagnosticEngine &diags) const override {
+      request.diagnoseCycle(diags);
+    }
+
+    /// Note that this request is part of a cycle.
+    virtual void noteCycleStep(DiagnosticEngine &diags) const override {
+      request.noteCycleStep(diags);
+    }
+  };
+
+  /// FIXME: Inefficient. Use the low bits.
+  enum class StorageKind {
+    Normal,
+    Empty,
+    Tombstone,
+  } storageKind = StorageKind::Normal;
+
+  /// The data stored in this value.
+  std::shared_ptr<HolderBase> stored;
+
+  AnyRequest(StorageKind storageKind) : storageKind(storageKind) {
+    assert(storageKind != StorageKind::Normal);
+  }
+
+public:
+  AnyRequest(const AnyRequest &other) = default;
+  AnyRequest(AnyRequest &&other) = default;
+  AnyRequest &operator=(const AnyRequest &other) = default;
+  AnyRequest &operator=(AnyRequest &&other) = default;
+
+  AnyRequest(AnyRequest &other)
+    : storageKind(other.storageKind), stored(other.stored) { }
+
+  AnyRequest(const AnyRequest &&other)
+    : storageKind(other.storageKind), stored(other.stored) { }
+
+  /// Construct a new instance with the given value.
+  template<typename T>
+  AnyRequest(T&& value) : storageKind(StorageKind::Normal) {
+    using ValueType =
+      typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+    stored.reset(new Holder<ValueType>(std::forward<T>(value)));
+  }
+
+  /// Cast to a specific (known) type.
+  template<typename Request>
+  const Request &castTo() const {
+    assert(stored->typeID == TypeID<Request>::value && "wrong type in cast");
+    return static_cast<const Holder<Request> *>(stored.get())->value;
+  }
+
+  /// Try casting to a specific (known) type, returning \c nullptr on
+  /// failure.
+  template<typename Request>
+  const Request *getAs() const {
+    if (stored->typeID != TypeID<Request>::value)
+      return nullptr;
+
+    return &static_cast<const Holder<Request> *>(stored.get())->value;
+  }
+
+  /// Diagnose a cycle detected for this request.
+  void diagnoseCycle(DiagnosticEngine &diags) const {
+    stored->diagnoseCycle(diags);
+  }
+
+  /// Note that this request is part of a cycle.
+  void noteCycleStep(DiagnosticEngine &diags) const {
+    stored->noteCycleStep(diags);
+  }
+
+  /// Compare two instances for equality.
+  friend bool operator==(const AnyRequest &lhs, const AnyRequest &rhs) {
+    if (lhs.storageKind != rhs.storageKind) {
+      return false;
+    }
+
+    if (lhs.storageKind != StorageKind::Normal)
+      return true;
+
+    if (lhs.stored->typeID != rhs.stored->typeID)
+      return false;
+
+    return lhs.stored->equals(*rhs.stored);
+  }
+
+  friend bool operator!=(const AnyRequest &lhs, const AnyRequest &rhs) {
+    return !(lhs == rhs);
+  }
+
+  friend hash_code hash_value(const AnyRequest &any) {
+    if (any.storageKind != StorageKind::Normal)
+      return 1;
+
+    return any.stored->hash;
+  }
+
+  friend void simple_display(llvm::raw_ostream &out, const AnyRequest &any) {
+    any.stored->display(out);
+  }
+
+  /// Return the result of calling simple_display as a string.
+  std::string getAsString() const;
+
+  static AnyRequest getEmptyKey() {
+    return AnyRequest(StorageKind::Empty);
+  }
+
+  static AnyRequest getTombstoneKey() {
+    return AnyRequest(StorageKind::Tombstone);
+  }
+};
+
+} // end namespace swift
+
+namespace llvm {
+  template<>
+  struct DenseMapInfo<swift::AnyRequest> {
+    static inline swift::AnyRequest getEmptyKey() {
+      return swift::AnyRequest::getEmptyKey();
+    }
+    static inline swift::AnyRequest getTombstoneKey() {
+      return swift::AnyRequest::getTombstoneKey();
+    }
+    static unsigned getHashValue(const swift::AnyRequest &request) {
+      return hash_value(request);
+    }
+    static bool isEqual(const swift::AnyRequest &lhs,
+                        const swift::AnyRequest &rhs) {
+      return lhs == rhs;
+    }
+  };
+
+} // end namespace llvm
+
+#endif // SWIFT_AST_ANYREQUEST_H