swift-module-digester: refactor the ABI/API diagnostics to use DiagnosticEngine. NFC (#18957)

Before this patch, we used to define tooling-specific diagnostics. With adding more
checking logics, we found this mechanism hard to extend. This patch
eliminates the home-made diagnostics model to use the one from compiler, which provides
several benefits: less boiler-templates, better integration with DiagnosticConsumer,
and easy ordering of detected issues.

include/swift/AST/DiagnosticEngine.h

@@ -672,6 +672,19 @@ namespace swift {
       return diagnose(Loc, Diagnostic(ID, std::move(Args)...));
     }
 
+    /// \brief Emit a diagnostic with the given set of diagnostic arguments.
+    ///
+    /// \param ID The diagnostic to be emitted.
+    ///
+    /// \param Args The diagnostic arguments, which will be converted to
+    /// the types expected by the diagnostic \p ID.
+    template<typename ...ArgTypes>
+    InFlightDiagnostic
+    diagnose(Diag<ArgTypes...> ID,
+             typename detail::PassArgument<ArgTypes>::type... Args) {
+      return diagnose(SourceLoc(), ID, std::move(Args)...);
+    }
+
     /// \brief Emit a diagnostic with the given set of diagnostic arguments.
     ///
     /// \param Loc The declaration name location to which the

include/swift/AST/DiagnosticsAll.def

@@ -49,6 +49,7 @@
 #include "DiagnosticsFrontend.def"
 #include "DiagnosticsDriver.def"
 #include "DiagnosticsRefactoring.def"
+#include "DiagnosticsModuleDiffer.def"
 
 #undef DIAG_NO_UNDEF
 

include/swift/AST/DiagnosticsModuleDiffer.def

@@ -0,0 +1,62 @@
+//===--- DiagnosticsModuleDiffer.def - Diagnostics Text ---------*- 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 diagnostics emitted during diffing two Swift modules.
+//  Each diagnostic is described using one of three kinds (error, warning, or
+//  note) along with a unique identifier, category, options, and text, and is
+//  followed by a signature describing the diagnostic argument kinds.
+//
+//===----------------------------------------------------------------------===//
+
+#if !(defined(DIAG) || (defined(ERROR) && defined(WARNING) && defined(NOTE)))
+#  error Must define either DIAG or the set {ERROR,WARNING,NOTE}
+#endif
+
+#ifndef ERROR
+#  define ERROR(ID,Options,Text,Signature)   \
+  DIAG(ERROR,ID,Options,Text,Signature)
+#endif
+
+#ifndef WARNING
+#  define WARNING(ID,Options,Text,Signature) \
+  DIAG(WARNING,ID,Options,Text,Signature)
+#endif
+
+#ifndef NOTE
+#  define NOTE(ID,Options,Text,Signature) \
+  DIAG(NOTE,ID,Options,Text,Signature)
+#endif
+
+ERROR(generic_sig_change,none,"%0 has generic signature change from %1 to %2", (StringRef, StringRef, StringRef))
+
+ERROR(raw_type_change,none,"%0(%1) is now %2 representable", (StringRef, StringRef, StringRef))
+
+ERROR(removed_decl,none,"%0 has been removed%select{| (deprecated)}1", (StringRef, bool))
+
+ERROR(moved_decl,none,"%0 has been moved to %1", (StringRef, StringRef))
+
+ERROR(renamed_decl,none,"%0 has been renamed to %1", (StringRef, StringRef))
+
+ERROR(decl_type_change,none,"%0 has %1 type change from %2 to %3", (StringRef, StringRef, StringRef, StringRef))
+
+ERROR(decl_attr_change,none,"%0 changes from %1 to %2", (StringRef, StringRef, StringRef))
+
+ERROR(decl_new_attr,none,"%0 is now %1", (StringRef, StringRef))
+
+#ifndef DIAG_NO_UNDEF
+# if defined(DIAG)
+#  undef DIAG
+# endif
+# undef NOTE
+# undef WARNING
+# undef ERROR
+#endif

include/swift/AST/DiagnosticsModuleDiffer.h

@@ -0,0 +1,32 @@
+//===--- DiagnosticsModuleDiffer.h - Diagnostic Definitions ----*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// \brief This file defines diagnostics for the Swift module differ.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_DIAGNOSTICS_MODULE_DIFFER_H
+#define SWIFT_DIAGNOSTICS_MODULE_DIFFER_H
+
+#include "swift/AST/DiagnosticsCommon.h"
+
+namespace swift {
+  namespace diag {
+  // Declare common diagnostics objects with their appropriate types.
+#define DIAG(KIND,ID,Options,Text,Signature) \
+  extern detail::DiagWithArguments<void Signature>::type ID;
+#include "DiagnosticsModuleDiffer.def"
+  }
+}
+
+#endif

include/swift/IDE/APIDigesterData.h

@@ -60,6 +60,11 @@ raw_ostream &operator<<(raw_ostream &Out, const NodeAnnotation Value);
 // Redefine << so that we can output the name of the node kind.
 raw_ostream &operator<<(raw_ostream &Out, const SDKNodeKind Value);
 
+StringRef getDeclKindStr(const DeclKind Value);
+
+// Redefine << so that we can output the name of decl kind.
+raw_ostream &operator<<(raw_ostream &Out, const DeclKind Value);
+
 struct APIDiffItem {
   virtual void streamDef(llvm::raw_ostream &S) const = 0;
   virtual APIDiffItemKind getKind() const = 0;

lib/IDE/APIDigesterData.cpp

@@ -23,7 +23,7 @@ using namespace swift;
 using namespace ide;
 using namespace api;
 
-inline raw_ostream &swift::ide::api::
+raw_ostream &swift::ide::api::
 operator<<(raw_ostream &Out, const SDKNodeKind Value) {
   switch (Value) {
 #define NODE_KIND(Name, Value) case SDKNodeKind::Name: return Out << #Value;
@@ -32,13 +32,26 @@ operator<<(raw_ostream &Out, const SDKNodeKind Value) {
   llvm_unreachable("Undefined SDK node kind.");
 }
 
-inline raw_ostream &swift::ide::api::
+raw_ostream &swift::ide::api::
 operator<<(raw_ostream &Out, const NodeAnnotation Value) {
 #define NODE_ANNOTATION(X) if (Value == NodeAnnotation::X) { return Out << #X; }
 #include "swift/IDE/DigesterEnums.def"
   llvm_unreachable("Undefined SDK node kind.");
 }
 
+StringRef swift::ide::api::getDeclKindStr(const DeclKind Value)  {
+  switch (Value) {
+#define DECL(X, PARENT) case DeclKind::X: return #X;
+#include "swift/AST/DeclNodes.def"
+  } 
+  llvm_unreachable("Unhandled DeclKind in switch.");
+}
+
+raw_ostream &swift::ide::api::operator<<(raw_ostream &Out,
+    const DeclKind Value) {
+  return Out << getDeclKindStr(Value);
+}
+
 Optional<SDKNodeKind> swift::ide::api::parseSDKNodeKind(StringRef Content) {
   return llvm::StringSwitch<Optional<SDKNodeKind>>(Content)
 #define NODE_KIND(NAME, VALUE) .Case(#VALUE, SDKNodeKind::NAME)

test/api-digester/Outputs/Cake-abi.txt

@@ -11,8 +11,8 @@ cake1: Func C4.foo() has been removed
 /* Moved Decls */
 
 /* Renamed Decls */
-cake1: Struct Somestruct2 has been renamed to Struct NSSomestruct2
 cake1: Func S1.foo5(x:y:) has been renamed to Func S1.foo5(x:y:z:)
+cake1: Struct Somestruct2 has been renamed to Struct NSSomestruct2
 
 /* Type Changes */
 cake1: Constructor S1.init(_:) has parameter 0 type change from Int to Double
@@ -20,12 +20,12 @@ cake1: Func C1.foo2(_:) has parameter 0 type change from Int to () -> ()
 cake1: Func Somestruct2.foo1(_:) has parameter 0 type change from C3 to C1
 
 /* Decl Attribute changes */
-cake1: Enum IceKind is now without @_frozen
-cake1: Struct C6 is now with @_fixed_layout
 cake1: Class C5 is now without @objc
-cake1: Var C1.CIIns1 changes from weak to strong
-cake1: Var C1.CIIns2 changes from strong to weak
+cake1: Enum IceKind is now without @_frozen
 cake1: Func C1.foo1() is now not static
 cake1: Func C5.dy_foo() is now with dynamic
 cake1: Func S1.foo1() is now mutating
 cake1: Func S1.foo3() is now static
+cake1: Struct C6 is now with @_fixed_layout
+cake1: Var C1.CIIns1 changes from weak to strong
+cake1: Var C1.CIIns2 changes from strong to weak

test/api-digester/Outputs/Cake.txt

@@ -11,16 +11,16 @@ cake1: Func C4.foo() has been removed
 /* Moved Decls */
 
 /* Renamed Decls */
-cake1: Struct Somestruct2 has been renamed to Struct NSSomestruct2
 cake1: Func S1.foo5(x:y:) has been renamed to Func S1.foo5(x:y:z:)
+cake1: Struct Somestruct2 has been renamed to Struct NSSomestruct2
 
 /* Type Changes */
 cake1: Constructor S1.init(_:) has parameter 0 type change from Int to Double
 cake1: Func C1.foo2(_:) has parameter 0 type change from Int to () -> ()
 
 /* Decl Attribute changes */
-cake1: Var C1.CIIns1 changes from weak to strong
-cake1: Var C1.CIIns2 changes from strong to weak
 cake1: Func C1.foo1() is now not static
 cake1: Func S1.foo1() is now mutating
 cake1: Func S1.foo3() is now static
+cake1: Var C1.CIIns1 changes from weak to strong
+cake1: Var C1.CIIns2 changes from strong to weak

test/api-digester/source-stability.swift.expected

@@ -4,17 +4,6 @@
 /* RawRepresentable Changes */
 
 /* Removed Decls */
-TypeAlias AbsoluteValuable has been removed
-TypeAlias BitwiseOperations has been removed (deprecated)
-TypeAlias IntMax has been removed
-TypeAlias Integer has been removed
-TypeAlias IntegerArithmetic has been removed
-TypeAlias SignedNumber has been removed
-TypeAlias StringProtocol.UTF16Index has been removed (deprecated)
-TypeAlias StringProtocol.UTF8Index has been removed (deprecated)
-TypeAlias StringProtocol.UnicodeScalarIndex has been removed (deprecated)
-TypeAlias UIntMax has been removed
-Var FixedWidthInteger.allZeros has been removed (deprecated)
 Constructor Int.init(truncatingBitPattern:) has been removed
 Constructor Int16.init(truncatingBitPattern:) has been removed
 Constructor Int32.init(truncatingBitPattern:) has been removed
@@ -64,6 +53,17 @@ Func UInt32.toIntMax() has been removed
 Func UInt64.toIntMax() has been removed
 Func UInt8.toIntMax() has been removed
 Func UnsignedInteger.toUIntMax() has been removed
+TypeAlias AbsoluteValuable has been removed
+TypeAlias BitwiseOperations has been removed (deprecated)
+TypeAlias IntMax has been removed
+TypeAlias Integer has been removed
+TypeAlias IntegerArithmetic has been removed
+TypeAlias SignedNumber has been removed
+TypeAlias StringProtocol.UTF16Index has been removed (deprecated)
+TypeAlias StringProtocol.UTF8Index has been removed (deprecated)
+TypeAlias StringProtocol.UnicodeScalarIndex has been removed (deprecated)
+TypeAlias UIntMax has been removed
+Var FixedWidthInteger.allZeros has been removed (deprecated)
 
 /* Moved Decls */
 
@@ -72,12 +72,13 @@ Func Dictionary.filter(_:obsoletedInSwift4:) has been renamed to Func Dictionary
 Func Set.filter(_:obsoletedInSwift4:) has been renamed to Func Set.filter(_:)
 
 /* Type Changes */
-Var Dictionary.keys has declared type change from LazyMapCollection<[Key : Value], Key> to Dictionary<Key, Value>.Keys
-Var Dictionary.values has declared type change from LazyMapCollection<[Key : Value], Value> to Dictionary<Key, Value>.Values
 Constructor String.init(_:) has return type change from String? to String
 Func Dictionary.filter(_:obsoletedInSwift4:) has return type change from [Dictionary<Key, Value>.Element] to [Dictionary<Key, Value>.Key : Dictionary<Key, Value>.Value]
 Func Dictionary.makeIterator() has return type change from DictionaryIterator<Dictionary<Key, Value>.Key, Dictionary<Key, Value>.Value> to Dictionary<Key, Value>.Iterator
 Func Set.filter(_:obsoletedInSwift4:) has return type change from [Set<Element>.Element] to Set<Element>
 Func Set.makeIterator() has return type change from SetIterator<Element> to Set<Element>.Iterator
+Var Dictionary.keys has declared type change from LazyMapCollection<[Key : Value], Key> to Dictionary<Key, Value>.Keys
+Var Dictionary.values has declared type change from LazyMapCollection<[Key : Value], Value> to Dictionary<Key, Value>.Values
+
 
 /* Decl Attribute changes */

tools/swift-api-digester/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_swift_host_tool(swift-api-digester
   swift-api-digester.cpp
   ModuleAnalyzerNodes.cpp
+  ModuleDiagsConsumer.cpp
   LINK_LIBRARIES swiftFrontend swiftIDE
   SWIFT_COMPONENT tools
 )

tools/swift-api-digester/ModuleAnalyzerNodes.cpp

@@ -293,6 +293,22 @@ SDKNode *SDKNodeRoot::getInstance(SDKContext &Ctx) {
   return Info.createSDKNode(SDKNodeKind::Root);
 }
 
+StringRef SDKNodeDecl::getScreenInfo() const {
+  auto ModuleName = getModuleName();
+  auto HeaderName = getHeaderName();
+  auto &Ctx = getSDKContext();
+  llvm::SmallString<64> SS;
+  llvm::raw_svector_ostream OS(SS);
+  if (Ctx.getOpts().PrintModule)
+    OS << ModuleName;
+  if (!HeaderName.empty())
+    OS << "(" << HeaderName << ")";
+  if (!OS.str().empty())
+    OS << ": ";
+  OS << getDeclKind() << " " << getFullyQualifiedName();
+  return Ctx.buffer(OS.str());
+}
+
 bool SDKNodeDecl::isSDKPrivate() const {
   if (getName().startswith("__"))
     return true;

tools/swift-api-digester/ModuleAnalyzerNodes.h

@@ -139,6 +139,7 @@ struct CheckerOptions {
   bool ABI;
   bool Verbose;
   bool AbortOnModuleLoadFailure;
+  bool PrintModule;
   StringRef LocationFilter;
 };
 
@@ -303,6 +304,7 @@ public:
   bool hasDeclAttribute(DeclAttrKind DAKind) const;
   bool isStatic() const { return IsStatic; };
   StringRef getGenericSignature() const { return GenericSig; }
+  StringRef getScreenInfo() const;
 };
 
 class SDKNodeRoot: public SDKNode {

tools/swift-api-digester/ModuleDiagsConsumer.cpp

@@ -0,0 +1,94 @@
+//===--- ModuleDiagsConsumer.cpp - Print module differ diagnostics --*- 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 implements the ModuleDifferDiagsConsumer class, which displays
+//  diagnostics from the module differ as text to an output.
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/AST/DiagnosticEngine.h"
+#include "swift/AST/DiagnosticsModuleDiffer.h"
+#include "ModuleDiagsConsumer.h"
+
+using namespace swift;
+
+namespace {
+// Reproduce the DiagIDs, as we want both the size and access to the raw ids
+// themselves.
+enum LocalDiagID : uint32_t {
+#define DIAG(KIND, ID, Options, Text, Signature) ID,
+#include "swift/AST/DiagnosticsAll.def"
+  NumDiags
+};
+
+static StringRef getCategoryName(uint32_t ID) {
+  switch(ID) {
+  case LocalDiagID::removed_decl:
+    return "/* Removed Decls */";
+  case LocalDiagID::moved_decl:
+    return "/* Moved Decls */";
+  case LocalDiagID::renamed_decl:
+    return "/* Renamed Decls */";
+  case LocalDiagID::decl_attr_change:
+  case LocalDiagID::decl_new_attr:
+    return "/* Decl Attribute changes */";
+  case LocalDiagID::decl_type_change:
+    return "/* Type Changes */";
+  case LocalDiagID::raw_type_change:
+    return "/* RawRepresentable Changes */";
+  case LocalDiagID::generic_sig_change:
+    return "/* Generic Signature Changes */";
+  default:
+    return StringRef();
+  }
+}
+}
+
+swift::ide::api::
+ModuleDifferDiagsConsumer::ModuleDifferDiagsConsumer():
+    PrintingDiagnosticConsumer(llvm::errs()) {
+#define DIAG(KIND, ID, Options, Text, Signature)                              \
+  auto ID = getCategoryName(LocalDiagID::ID);                                 \
+  assert(!ID.empty());                                                        \
+  AllDiags[ID] = std::set<std::string>();
+#include "swift/AST/DiagnosticsModuleDiffer.def"
+}
+
+void swift::ide::api::
+ModuleDifferDiagsConsumer::handleDiagnostic(SourceManager &SM, SourceLoc Loc,
+                        DiagnosticKind Kind,
+                        StringRef FormatString,
+                        ArrayRef<DiagnosticArgument> FormatArgs,
+                        const DiagnosticInfo &Info) {
+  auto Category = getCategoryName((uint32_t)Info.ID);
+  if (Category.empty()) {
+    PrintingDiagnosticConsumer::handleDiagnostic(SM, Loc, Kind, FormatString,
+      FormatArgs, Info);
+    return;
+  }
+  llvm::SmallString<256> Text;
+  {
+    llvm::raw_svector_ostream Out(Text);
+    DiagnosticEngine::formatDiagnosticText(Out, FormatString, FormatArgs);
+  }
+  AllDiags[Category].insert(Text.str().str());
+}
+
+swift::ide::api::ModuleDifferDiagsConsumer::~ModuleDifferDiagsConsumer() {
+  for (auto &Pair: AllDiags) {
+    llvm::outs() << "\n";
+    llvm::outs() << Pair.first << "\n";
+    for (auto &Item: Pair.second) {
+      llvm::outs() << Item << "\n";
+    }
+  }
+}

tools/swift-api-digester/ModuleDiagsConsumer.h

@@ -0,0 +1,49 @@
+//===--- ModuleDiagsConsumer.h - Print module differ diagnostics --*- 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 ModuleDifferDiagsConsumer class, which displays
+//  diagnostics from the module differ as text to an output.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __SWIFT_MODULE_DIFFER_DIAGS_CONSUMER_H__
+#define __SWIFT_MODULE_DIFFER_DIAGS_CONSUMER_H__
+
+#include "llvm/ADT/MapVector.h"
+#include "swift/Basic/LLVM.h"
+#include "swift/AST/DiagnosticConsumer.h"
+#include "swift/Frontend/PrintingDiagnosticConsumer.h"
+
+#include "llvm/Support/raw_ostream.h"
+#include <set>
+
+namespace swift {
+namespace ide {
+namespace api {
+
+/// \brief Diagnostic consumer that displays diagnostics to standard output.
+class ModuleDifferDiagsConsumer: public PrintingDiagnosticConsumer {
+  llvm::MapVector<StringRef, std::set<std::string>> AllDiags;
+public:
+  ModuleDifferDiagsConsumer();
+  ~ModuleDifferDiagsConsumer();
+  void handleDiagnostic(SourceManager &SM, SourceLoc Loc,
+                        DiagnosticKind Kind,
+                        StringRef FormatString,
+                        ArrayRef<DiagnosticArgument> FormatArgs,
+                        const DiagnosticInfo &Info) override;
+};
+}
+}
+}
+
+#endif

tools/swift-api-digester/swift-api-digester.cpp

@@ -26,8 +26,11 @@
 // can be reflected as source-breaking changes for API users. If they are,
 // the output of api-digester will include such changes.
 
+#include "swift/AST/DiagnosticsModuleDiffer.h"
+#include "swift/IDE/APIDigesterData.h"
 #include <functional>
-#include <ModuleAnalyzerNodes.h>
+#include "ModuleAnalyzerNodes.h"
+#include "ModuleDiagsConsumer.h"
 
 using namespace swift;
 using namespace ide;
@@ -1478,16 +1481,6 @@ public:
   }
 };
 
-// Redefine << so that we can output the name of decl kind.
-raw_ostream &operator<<(raw_ostream &Out, const DeclKind Value) {
-  switch (Value) {
-#define DECL(X, PARENT) case DeclKind::X: return Out << #X;
-#include "swift/AST/DeclNodes.def"
-  }
-
-  llvm_unreachable("Unhandled DeclKind in switch.");
-}
-
 class DiagnosisEmitter : public SDKNodeVisitor {
   void handle(const SDKNodeDecl *D, NodeAnnotation Anno);
   void visitType(SDKNodeType *T);
@@ -1495,182 +1488,18 @@ class DiagnosisEmitter : public SDKNodeVisitor {
   void visit(NodePtr Node) override;
   SDKNodeDecl *findAddedDecl(const SDKNodeDecl *Node);
   bool findTypeAliasDecl(const SDKNodeDecl *Node);
-  static StringRef printName(StringRef Name);
-  static StringRef printDiagKeyword(StringRef Name);
   static void collectAddedDecls(NodePtr Root, std::set<SDKNodeDecl*> &Results);
 
-  template<typename T>
-  struct DiagBag {
-    std::vector<T> Diags;
-    ~DiagBag() {
-      llvm::outs() << "\n/* ";
-      T::theme(llvm::outs());
-      llvm::outs() << " */\n";
-      removeRedundantAndSort(Diags);
-      std::for_each(Diags.begin(), Diags.end(), [](T &Diag) {
-        if (Diag.isABISpecific() && !options::Abi)
-          return;
-        Diag.outputModule();
-        Diag.output();
-      });
-    }
-  };
-
-  struct MetaInfo {
-    StringRef ModuleName;
-    StringRef HeaderName;
-    DeclKind Kind;
-    StringRef Name;
-    bool IsABISpecific;
-    MetaInfo(const SDKNodeDecl *Node, bool IsABISpecific):
-      ModuleName(Node->getModuleName()), HeaderName(Node->getHeaderName()),
-      Kind(Node->getDeclKind()), Name(Node->getFullyQualifiedName()),
-      IsABISpecific(IsABISpecific) {}
-    int compare(MetaInfo &Other) const {
-      if (ModuleName != Other.ModuleName)
-        return ModuleName.compare(Other.ModuleName);
-      if (HeaderName != Other.HeaderName)
-        return HeaderName.compare(Other.HeaderName);
-      if (Kind != Other.Kind)
-        return (uint8_t)Kind - (uint8_t)Other.Kind;
-      return Name.compare(Other.Name);
-    }
-  };
-
-  class DiagBase {
-  protected:
-    MetaInfo Info;
-    DiagBase(MetaInfo Info): Info(Info) {}
-    virtual ~DiagBase() = default;
-    raw_ostream &outputName() const {
-      return llvm::outs() << Info.Kind << " " << printName(Info.Name);
-    }
-  public:
-    void outputModule() const {
-      if (options::PrintModule) {
-        llvm::outs() << Info.ModuleName;
-        if (!Info.HeaderName.empty())
-          llvm::outs() << "(" << Info.HeaderName << ")";
-        llvm::outs() << ": ";
-      }
-    }
-    virtual void output() const = 0;
-    bool isABISpecific() const { return Info.IsABISpecific; }
-  };
-
-  struct RemovedDeclDiag: public DiagBase  {
-    DeclKind Kind;
-    StringRef Name;
-    bool IsDeprecated;
-    RemovedDeclDiag(MetaInfo Info, bool IsDeprecated): DiagBase(Info),
-      IsDeprecated(IsDeprecated) {}
-    bool operator<(RemovedDeclDiag Other) const {
-       return Info.compare(Other.Info) < 0;
-    }
-    void output() const override;
-    static void theme(raw_ostream &OS) { OS << "Removed Decls"; };
-  };
-
-  struct MovedDeclDiag: public DiagBase {
-    DeclKind AddedKind;
-    StringRef AddedName;
-    MovedDeclDiag(MetaInfo Info, DeclKind AddedKind, StringRef AddedName):
-      DiagBase(Info), AddedKind(AddedKind), AddedName(AddedName) {}
-    bool operator<(MovedDeclDiag Other) const {
-       return Info.compare(Other.Info) < 0;
-    }
-    void output() const override;
-    static void theme(raw_ostream &OS) { OS << "Moved Decls"; };
-  };
-
-  struct RenamedDeclDiag: public DiagBase  {
-    DeclKind KindAfter;
-    StringRef NameAfter;
-    RenamedDeclDiag(MetaInfo Info, DeclKind KindAfter, StringRef NameAfter):
-                      DiagBase(Info), KindAfter(KindAfter), NameAfter(NameAfter) {}
-    bool operator<(RenamedDeclDiag Other) const {
-      return Info.compare(Other.Info) < 0;
-    };
-    void output() const override;
-    static void theme(raw_ostream &OS) { OS << "Renamed Decls"; };
-  };
-
-  struct DeclAttrDiag: public DiagBase {
-    StringRef AttrBefore;
-    StringRef AttrAfter;
-    DeclAttrDiag(MetaInfo Info, StringRef AttrBefore, StringRef AttrAfter):
-                 DiagBase(Info), AttrBefore(AttrBefore), AttrAfter(AttrAfter) {}
-    DeclAttrDiag(MetaInfo Info, StringRef AttrAfter): DeclAttrDiag(Info,
-                 StringRef(), AttrAfter) {}
-    bool operator<(DeclAttrDiag Other) const;
-    void output() const override;
-    static void theme(raw_ostream &OS) { OS << "Decl Attribute changes"; };
-  };
-
-  struct DeclTypeChangeDiag: public DiagBase {
-    StringRef TypeNameBefore;
-    StringRef TypeNameAfter;
-    StringRef Description;
-    DeclTypeChangeDiag(MetaInfo Info, StringRef TypeNameBefore,
-                       StringRef TypeNameAfter,
-                       StringRef Description): DiagBase(Info),
-      TypeNameBefore(TypeNameBefore), TypeNameAfter(TypeNameAfter),
-      Description(Description) {}
-    bool operator<(DeclTypeChangeDiag Other) const {
-      return Info.compare(Other.Info) < 0;
-    };
-    void output() const override;
-    static void theme(raw_ostream &OS) { OS << "Type Changes"; };
-  };
-
-  struct RawRepresentableChangeDiag: public DiagBase {
-    StringRef UnderlyingType;
-    StringRef RawTypeName;
-    RawRepresentableChangeDiag(MetaInfo Info, StringRef UnderlyingType,
-      StringRef RawTypeName): DiagBase(Info), UnderlyingType(UnderlyingType),
-      RawTypeName(RawTypeName) {}
-    bool operator<(RawRepresentableChangeDiag Other) const {
-      return Info.compare(Other.Info) < 0;
-    }
-    void output() const override {
-      outputName() << "(" << UnderlyingType << ")"
-        << " is now " << RawTypeName << " representable\n";
-    }
-    static void theme(raw_ostream &OS) { OS << "RawRepresentable Changes"; };
-  };
-
-  struct GenericSignatureChangeDiag: public DiagBase {
-    StringRef GSBefore;
-    StringRef GSAfter;
-    GenericSignatureChangeDiag(MetaInfo Info, StringRef GSBefore,
-      StringRef GSAfter): DiagBase(Info),
-      GSBefore(GSBefore), GSAfter(GSAfter) {}
-    bool operator<(GenericSignatureChangeDiag Other) const {
-      return Info.compare(Other.Info) < 0;
-    }
-    void output() const override {
-      outputName() << " has generic signature change from " << GSBefore << " to "
-        << GSAfter << "\n";
-    }
-    static void theme(raw_ostream &OS) { OS << "Generic Signature Changes"; };
-  };
-
   std::set<SDKNodeDecl*> AddedDecls;
-  DiagBag<DeclAttrDiag> AttrChangedDecls;
-  DiagBag<DeclTypeChangeDiag> TypeChangedDecls;
-  DiagBag<RenamedDeclDiag> RenamedDecls;
-  DiagBag<MovedDeclDiag> MovedDecls;
-  DiagBag<RemovedDeclDiag> RemovedDecls;
-  DiagBag<RawRepresentableChangeDiag> RawRepresentableDecls;
-  DiagBag<GenericSignatureChangeDiag> GSChangeDecls;
 
   UpdatedNodesMap &UpdateMap;
   NodeMap &TypeAliasUpdateMap;
   TypeMemberDiffVector &MemberChanges;
+  DiagnosticEngine &Diags;
   DiagnosisEmitter(SDKContext &Ctx):
     UpdateMap(Ctx.getNodeUpdateMap()),
     TypeAliasUpdateMap(Ctx.getTypeAliasUpdateMap()),
-    MemberChanges(Ctx.getTypeMemberDiffs()){}
+    MemberChanges(Ctx.getTypeMemberDiffs()), Diags(Ctx.getDiags()) {}
 
 public:
   static void diagnosis(NodePtr LeftRoot, NodePtr RightRoot,
@@ -1707,58 +1536,6 @@ bool DiagnosisEmitter::findTypeAliasDecl(const SDKNodeDecl *Node) {
   });
 }
 
-StringRef DiagnosisEmitter::printName(StringRef Name) {
-  OSColor Color(llvm::outs(), llvm::raw_ostream::CYAN);
-  Color << Name;
-  return StringRef();
-}
-
-StringRef DiagnosisEmitter::printDiagKeyword(StringRef Name) {
-  OSColor Color(llvm::outs(), llvm::raw_ostream::YELLOW);
-  Color << Name;
-  return StringRef();
-}
-
-void DiagnosisEmitter::RemovedDeclDiag::output() const {
-  outputName() << " has been " << printDiagKeyword("removed");
-  if (IsDeprecated)
-    llvm::outs() << " (deprecated)";
-  llvm::outs() << "\n";
-}
-
-void DiagnosisEmitter::MovedDeclDiag::output() const {
-  outputName() << " has been " << printDiagKeyword("moved") << " to "
-    << AddedKind << " " << printName(AddedName) << "\n";
-}
-
-void DiagnosisEmitter::RenamedDeclDiag::output() const {
-  outputName() << " has been " << printDiagKeyword("renamed") << " to "
-    << KindAfter << " " << printName(NameAfter) << "\n";
-}
-
-void DiagnosisEmitter::DeclTypeChangeDiag::output() const {
-  outputName() << " has "
-               << Description << " type change from "
-               << printName(TypeNameBefore) << " to "
-               << printName(TypeNameAfter) << "\n";
-}
-
-
-bool DiagnosisEmitter::DeclAttrDiag::operator<(DeclAttrDiag Other) const {
-  auto result = Info.compare(Other.Info);
-  if (result)
-    return result < 0;
-  return AttrAfter.compare(Other.AttrAfter) < 0;
-}
-
-void DiagnosisEmitter::DeclAttrDiag::output() const {
-  if (AttrBefore.empty())
-    outputName() << " is now " << printDiagKeyword(AttrAfter)<< "\n";
-  else
-    outputName() << " changes from " << printDiagKeyword(AttrBefore)
-      << " to "<< printDiagKeyword(AttrAfter)<< "\n";
-}
-
 void DiagnosisEmitter::diagnosis(NodePtr LeftRoot, NodePtr RightRoot,
                                  SDKContext &Ctx) {
   DiagnosisEmitter Emitter(Ctx);
@@ -1771,16 +1548,15 @@ void DiagnosisEmitter::handle(const SDKNodeDecl *Node, NodeAnnotation Anno) {
   auto &Ctx = Node->getSDKContext();
   switch(Anno) {
   case NodeAnnotation::Removed: {
-    MetaInfo ScreenInfo(Node, false);
     // If we can find a type alias decl with the same name of this type, we
     // consider the type is not removed.
     if (findTypeAliasDecl(Node))
       return;
     if (auto *Added = findAddedDecl(Node)) {
       if (Node->getDeclKind() != DeclKind::Constructor) {
-        MovedDecls.Diags.emplace_back(ScreenInfo,
-                                      Added->getDeclKind(),
-                                      Added->getFullyQualifiedName());
+        Diags.diagnose(diag::moved_decl, Node->getScreenInfo(),
+          Ctx.buffer((Twine(getDeclKindStr(Added->getDeclKind())) + " " +
+            Added->getFullyQualifiedName()).str()));
         return;
       }
     }
@@ -1790,8 +1566,9 @@ void DiagnosisEmitter::handle(const SDKNodeDecl *Node, NodeAnnotation Anno) {
     auto It = std::find_if(MemberChanges.begin(), MemberChanges.end(),
       [&](TypeMemberDiffItem &Item) { return Item.usr == Node->getUsr(); });
     if (It != MemberChanges.end()) {
-      RenamedDecls.Diags.emplace_back(ScreenInfo, Node->getDeclKind(),
-        Ctx.buffer((Twine(It->newTypeName) + "." + It->newPrintedName).str()));
+      Diags.diagnose(diag::renamed_decl, Node->getScreenInfo(),
+        Ctx.buffer((Twine(getDeclKindStr(Node->getDeclKind())) + " " +
+          It->newTypeName + "." + It->newPrintedName).str()));
       return;
     }
 
@@ -1800,7 +1577,7 @@ void DiagnosisEmitter::handle(const SDKNodeDecl *Node, NodeAnnotation Anno) {
     // refine diagnostics message instead of showing the type alias has been
     // removed.
     if (TypeAliasUpdateMap.find((SDKNode*)Node) != TypeAliasUpdateMap.end()) {
-      RawRepresentableDecls.Diags.emplace_back(ScreenInfo,
+      Diags.diagnose(diag::raw_type_change, Node->getScreenInfo(),
         Node->getAs<SDKNodeDeclTypeAlias>()->getUnderlyingType()->getPrintedName(),
         TypeAliasUpdateMap[(SDKNode*)Node]->getAs<SDKNodeDeclType>()->
           getRawValueType()->getPrintedName());
@@ -1822,53 +1599,47 @@ void DiagnosisEmitter::handle(const SDKNodeDecl *Node, NodeAnnotation Anno) {
     }
     if (FoundInSuperclass)
       return;
-    RemovedDecls.Diags.emplace_back(ScreenInfo,
-                                    Node->isDeprecated());
+    Diags.diagnose(diag::removed_decl, Node->getScreenInfo(), Node->isDeprecated());
     return;
   }
   case NodeAnnotation::Rename: {
-    MetaInfo ScreenInfo(Node, false);
     auto *Count = UpdateMap.findUpdateCounterpart(Node)->getAs<SDKNodeDecl>();
-    RenamedDecls.Diags.emplace_back(ScreenInfo,
-                                    Count->getDeclKind(),
-                                    Count->getFullyQualifiedName());
+    Diags.diagnose(diag::renamed_decl, Node->getScreenInfo(),
+        Ctx.buffer((Twine(getDeclKindStr(Count->getDeclKind())) + " " +
+          Count->getFullyQualifiedName()).str()));
     return;
   }
   case NodeAnnotation::NowMutating: {
-    MetaInfo ScreenInfo(Node, false);
-    AttrChangedDecls.Diags.emplace_back(ScreenInfo, Ctx.buffer("mutating"));
+    Diags.diagnose(diag::decl_new_attr, Node->getScreenInfo(),
+      Ctx.buffer("mutating"));
     return;
   }
   case NodeAnnotation::NowThrowing: {
-    MetaInfo ScreenInfo(Node, false);
-    AttrChangedDecls.Diags.emplace_back(ScreenInfo, Ctx.buffer("throwing"));
+    Diags.diagnose(diag::decl_new_attr, Node->getScreenInfo(),
+      Ctx.buffer("throwing"));
     return;
   }
   case NodeAnnotation::StaticChange: {
-    MetaInfo ScreenInfo(Node, false);
-    AttrChangedDecls.Diags.emplace_back(ScreenInfo,
-                        Ctx.buffer(Node->isStatic() ? "not static" : "static"));
+    Diags.diagnose(diag::decl_new_attr, Node->getScreenInfo(),
+      Ctx.buffer(Node->isStatic() ? "not static" : "static"));
     return;
   }
   case NodeAnnotation::OwnershipChange: {
-    MetaInfo ScreenInfo(Node, false);
     auto getOwnershipDescription = [&](swift::ReferenceOwnership O) {
       if (O == ReferenceOwnership::Strong)
         return Ctx.buffer("strong");
       return keywordOf(O);
     };
     auto *Count = UpdateMap.findUpdateCounterpart(Node)->getAs<SDKNodeDecl>();
-    AttrChangedDecls.Diags.emplace_back(
-        ScreenInfo,
-        getOwnershipDescription(Node->getReferenceOwnership()),
-        getOwnershipDescription(Count->getReferenceOwnership()));
+    Diags.diagnose(diag::decl_attr_change, Node->getScreenInfo(),
+      getOwnershipDescription(Node->getReferenceOwnership()),
+      getOwnershipDescription(Count->getReferenceOwnership()));
     return;
   }
   case NodeAnnotation::ChangeGenericSignature: {
-    MetaInfo ScreenInfo(Node, false);
-    GSChangeDecls.Diags.emplace_back(ScreenInfo, Node->getGenericSignature(),
-      UpdateMap.findUpdateCounterpart(Node)->getAs<SDKNodeDecl>()->
-                                     getGenericSignature());
+    Diags.diagnose(diag::generic_sig_change, Node->getScreenInfo(),
+      Node->getGenericSignature(), UpdateMap.findUpdateCounterpart(Node)->
+        getAs<SDKNodeDecl>()->getGenericSignature());
     return;
   }
 
@@ -1879,11 +1650,11 @@ void DiagnosisEmitter::handle(const SDKNodeDecl *Node, NodeAnnotation Anno) {
       [&](const ABIAttributeInfo &I) { return I.Annotation == Anno; });
     if (It == Infos.end())
       return;
-    MetaInfo ScreenInfo(Node, true);
     auto Desc = Node->hasDeclAttribute(It->Kind) ?
       Ctx.buffer((llvm::Twine("without ") + It->Content).str()):
       Ctx.buffer((llvm::Twine("with ") + It->Content).str());
-    AttrChangedDecls.Diags.emplace_back(ScreenInfo, Desc);
+    if (options::Abi)
+      Diags.diagnose(diag::decl_new_attr, Node->getScreenInfo(), Desc);
     return;
   }
   }
@@ -1901,7 +1672,6 @@ void DiagnosisEmitter::visitType(SDKNodeType *Node) {
   auto *Parent = dyn_cast<SDKNodeDecl>(Node->getParent());
   if (!Parent || Parent->isSDKPrivate())
     return;
-  MetaInfo ScreenInfo(Parent, false);
   SDKContext &Ctx = Node->getSDKContext();
   if (Node->isAnnotatedAs(NodeAnnotation::Updated)) {
     auto *Count = UpdateMap.findUpdateCounterpart(Node)->getAs<SDKNodeType>();
@@ -1914,10 +1684,8 @@ void DiagnosisEmitter::visitType(SDKNodeType *Node) {
         SDKNodeDeclAbstractFunc::getTypeRoleDescription(Ctx, Parent->getChildIndex(Node)) :
         Ctx.buffer("declared");
       if (Node->getPrintedName() != Count->getPrintedName())
-        TypeChangedDecls.Diags.emplace_back(ScreenInfo,
-                                            Node->getPrintedName(),
-                                            Count->getPrintedName(),
-                                            Descriptor);
+        Diags.diagnose(diag::decl_type_change, Parent->getScreenInfo(),
+          Descriptor, Node->getPrintedName(), Count->getPrintedName());
       break;
     default:
       break;
@@ -2043,7 +1811,7 @@ static int diagnoseModuleChange(StringRef LeftPath, StringRef RightPath,
     llvm::errs() << RightPath << " does not exist\n";
     return 1;
   }
-  PrintingDiagnosticConsumer PDC;
+  ModuleDifferDiagsConsumer PDC;
   SDKContext Ctx(Opts);
   Ctx.getDiags().addConsumer(PDC);
 
@@ -2061,6 +1829,7 @@ static int diagnoseModuleChange(StringRef LeftPath, StringRef RightPath,
   RefinementPass.pass(LeftModule, RightModule);
   // Find member hoist changes to help refine diagnostics.
   findTypeMemberDiffs(LeftModule, RightModule, Ctx.getTypeMemberDiffs());
+
   DiagnosisEmitter::diagnosis(LeftModule, RightModule, Ctx);
   return 0;
 }
@@ -2099,7 +1868,7 @@ static int compareSDKs(StringRef LeftPath, StringRef RightPath,
   }
   llvm::errs() << "Diffing: " << LeftPath << " and " << RightPath << "\n";
 
-  PrintingDiagnosticConsumer PDC;
+  ModuleDifferDiagsConsumer PDC;
   SDKContext Ctx(Opts);
   Ctx.getDiags().addConsumer(PDC);
 
@@ -2319,6 +2088,7 @@ static CheckerOptions getCheckOpts() {
   Opts.Verbose = options::Verbose;
   Opts.AbortOnModuleLoadFailure = options::AbortOnModuleLoadFailure;
   Opts.LocationFilter = options::LocationFilter;
+  Opts.PrintModule = options::PrintModule;
   return Opts;
 }