[Macros] Handle macro overloading.

Allow more than one macro plugin to introduce a macro with the same
name, and let the constraint solver figure out which one to call. Also
eliminates a potential use-after-free if we somehow find additional
compiler plugins to load after having expanded a macro.

include/swift/AST/ASTContext.h

@@ -352,12 +352,6 @@ public:
       llvm::SmallPtrSet<DerivativeAttr *, 1>>
       DerivativeAttrs;
 
-  /// Cache of compiler plugins keyed by their name.
-  llvm::StringMap<CompilerPlugin> LoadedPlugins;
-
-  /// Cache of loaded symbols.
-  llvm::StringMap<void *> LoadedSymbols;
-
 private:
   /// The current generation number, which reflects the number of
   /// times that external modules have been loaded.
@@ -1452,8 +1446,11 @@ public:
   /// The declared interface type of Builtin.TheTupleType.
   BuiltinTupleType *getBuiltinTupleType();
 
-  /// Finds the loaded compiler plugin given its name.
-  CompilerPlugin *getLoadedPlugin(StringRef name);
+  /// Finds the loaded compiler plugins with the given name.
+  TinyPtrVector<CompilerPlugin *> getLoadedPlugins(StringRef name);
+
+  /// Add a loaded plugin with the given name.
+  void addLoadedPlugin(StringRef name, CompilerPlugin *plugin);
 
   /// Finds the address of the given symbol. If `libraryHandleHint` is non-null,
   /// search within the library.

lib/AST/ASTContext.cpp

@@ -515,6 +515,15 @@ struct ASTContext::Implementation {
 
   llvm::StringMap<OptionSet<SearchPathKind>> SearchPathsSet;
 
+  /// Cache of compiler plugins keyed by their name.
+  ///
+  /// Names can be overloaded, so there can be multiple plugins with the same
+  /// name.
+  llvm::StringMap<TinyPtrVector<CompilerPlugin*>> LoadedPlugins;
+
+  /// Cache of loaded symbols.
+  llvm::StringMap<void *> LoadedSymbols;
+
   /// The permanent arena.
   Arena Permanent;
 
@@ -579,6 +588,12 @@ ASTContext::Implementation::Implementation()
 ASTContext::Implementation::~Implementation() {
   for (auto &cleanup : Cleanups)
     cleanup();
+
+  for (const auto &pluginsByName : LoadedPlugins) {
+    for (auto plugin : pluginsByName.second) {
+      delete plugin;
+    }
+  }
 }
 
 ConstraintCheckerArenaRAII::
@@ -6047,16 +6062,21 @@ BuiltinTupleType *ASTContext::getBuiltinTupleType() {
   return result;
 }
 
-CompilerPlugin *ASTContext::getLoadedPlugin(StringRef name) {
-  auto lookup = LoadedPlugins.find(name);
-  if (lookup == LoadedPlugins.end())
-    return nullptr;
-  return &lookup->second;
+TinyPtrVector<CompilerPlugin *> ASTContext::getLoadedPlugins(StringRef name) {
+  auto &loadedPlugins = getImpl().LoadedPlugins;
+  auto lookup = loadedPlugins.find(name);
+  if (lookup == loadedPlugins.end())
+    return { };
+  return lookup->second;
+}
+
+void ASTContext::addLoadedPlugin(StringRef name, CompilerPlugin *plugin) {
+  getImpl().LoadedPlugins[name].push_back(plugin);
 }
 
 void *ASTContext::getAddressOfSymbol(const char *name,
                                      void *libraryHandleHint) {
-  auto lookup = LoadedSymbols.try_emplace(name, nullptr);
+  auto lookup = getImpl().LoadedSymbols.try_emplace(name, nullptr);
   void *&address = lookup.first->getValue();
 #if !defined(_WIN32)
   if (lookup.second) {

lib/AST/CompilerPlugin.cpp

@@ -188,9 +188,9 @@ void ASTContext::loadCompilerPlugins() {
     swift_ASTGen_getMacroTypes(getter, &metatypesAddress, &metatypeCount);
     ArrayRef<const void *> metatypes(metatypesAddress, metatypeCount);
     for (const void *metatype : metatypes) {
-      CompilerPlugin plugin(metatype, lib, *this);
-      auto name = plugin.getName();
-      LoadedPlugins.try_emplace(name, std::move(plugin));
+      auto plugin = new CompilerPlugin(metatype, lib, *this);
+      auto name = plugin->getName();
+      addLoadedPlugin(name, plugin);
     }
     free(const_cast<void *>((const void *)metatypes.data()));
 #endif // SWIFT_SWIFT_PARSER

lib/Sema/TypeCheckMacros.cpp

@@ -317,7 +317,7 @@ ArrayRef<MacroDecl *> MacroLookupRequest::evaluate(
   // Look for a loaded plugin based on the macro name.
   // FIXME: This API needs to be able to return multiple plugins, because
   // several plugins could export a macro with the same name.
-  if (auto *plugin = ctx.getLoadedPlugin(macroName.str())) {
+  for (auto plugin: ctx.getLoadedPlugins(macroName.str())) {
     if (auto pluginMacro = createPluginMacro(mod, macroName, plugin)) {
       macros.push_back(pluginMacro);
     }

test/Macros/Inputs/macro_definition.swift

@@ -180,10 +180,95 @@ struct ColorLiteralMacro: _CompilerPlugin {
   }
 }
 
+struct HSVColorLiteralMacro: _CompilerPlugin {
+  static func _name() -> (UnsafePointer<UInt8>, count: Int) {
+    var name = "customColorLiteral"
+    return name.withUTF8 { buffer in
+      let result = UnsafeMutablePointer<UInt8>.allocate(capacity: buffer.count)
+      result.initialize(from: buffer.baseAddress!, count: buffer.count)
+      return (UnsafePointer(result), count: buffer.count)
+    }
+  }
+
+  static func _genericSignature() -> (UnsafePointer<UInt8>?, count: Int) {
+    var genSig = "<T>"
+    return genSig.withUTF8 { buffer in
+      let result = UnsafeMutablePointer<UInt8>.allocate(capacity: buffer.count)
+      result.initialize(from: buffer.baseAddress!, count: buffer.count)
+      return (UnsafePointer(result), count: buffer.count)
+    }
+  }
+
+  static func _typeSignature() -> (UnsafePointer<UInt8>, count: Int) {
+    var typeSig =
+      """
+      (
+       hue hue: Float, saturation saturation: Float, value value: Float
+      ) -> T
+      """
+    return typeSig.withUTF8 { buffer in
+      let result = UnsafeMutablePointer<UInt8>.allocate(capacity: buffer.count)
+      result.initialize(from: buffer.baseAddress!, count: buffer.count)
+      return (UnsafePointer(result), count: buffer.count)
+    }
+  }
+
+  static func _owningModule() -> (UnsafePointer<UInt8>, count: Int) {
+    var swiftModule = "Swift"
+    return swiftModule.withUTF8 { buffer in
+      let result = UnsafeMutablePointer<UInt8>.allocate(capacity: buffer.count)
+      result.initialize(from: buffer.baseAddress!, count: buffer.count)
+      return (UnsafePointer(result), count: buffer.count)
+    }
+  }
+
+  static func _supplementalSignatureModules() -> (UnsafePointer<UInt8>, count: Int) {
+    var nothing = ""
+    return nothing.withUTF8 { buffer in
+      let result = UnsafeMutablePointer<UInt8>.allocate(capacity: buffer.count)
+      result.initialize(from: buffer.baseAddress!, count: buffer.count)
+      return (UnsafePointer(result), count: buffer.count)
+    }
+  }
+
+  static func _kind() -> _CompilerPluginKind {
+    .expressionMacro
+  }
+
+  static func _rewrite(
+    targetModuleName: UnsafePointer<UInt8>,
+    targetModuleNameCount: Int,
+    filePath: UnsafePointer<UInt8>,
+    filePathCount: Int,
+    sourceFileText: UnsafePointer<UInt8>,
+    sourceFileTextCount: Int,
+    localSourceText: UnsafePointer<UInt8>,
+    localSourceTextCount: Int
+  ) -> (UnsafePointer<UInt8>?, count: Int) {
+    let meeTextBuffer = UnsafeBufferPointer(
+      start: localSourceText, count: localSourceTextCount)
+    let meeText = String(decoding: meeTextBuffer, as: UTF8.self)
+    let prefix = "#customColorLiteral(hue:"
+    guard meeText.starts(with: prefix), meeText.last == ")" else {
+      return (nil, 0)
+    }
+    let expr = meeText.dropFirst(prefix.count).dropLast()
+    var resultString = ".init(_colorLiteralHue:\(expr))"
+    return resultString.withUTF8 { buffer in
+      let result = UnsafeMutableBufferPointer<UInt8>.allocate(
+          capacity: buffer.count + 1)
+      _ = result.initialize(from: buffer)
+      result[buffer.count] = 0
+      return (UnsafePointer(result.baseAddress), buffer.count)
+    }
+  }
+}
+
 
 public var allMacros: [Any.Type] {
   [
     StringifyMacro.self,
-    ColorLiteralMacro.self
+    ColorLiteralMacro.self,
+    HSVColorLiteralMacro.self
   ]
 }

test/Macros/macro_plugin.swift

@@ -37,7 +37,12 @@ let _ = #customStringify(["a", "b", "c"] + ["d", "e", "f"])
 
 struct MyColor: _ExpressibleByColorLiteral {
   init(_colorLiteralRed red: Float, green: Float, blue: Float, alpha: Float) { }
+  init(_colorLiteralHue hue: Float, saturation: Float, value: Float) { }
 }
 
+// CHECK: (macro_expansion_expr type='MyColor' {{.*}} name=customColorLiteral
 let _: MyColor = #customColorLiteral(red: 0.5, green: 0.5, blue: 0.2, alpha: 0.9)
 
+// CHECK: (macro_expansion_expr type='MyColor' {{.*}} name=customColorLiteral
+let _: MyColor = #customColorLiteral(hue: 0.5, saturation: 0.5, value: 0.2)
+