[Macros] Use the external module/type name in lieu of macro registration.

A macro declaration contains the external module and type name of the
macro's implementation. Use that information to find the macro type
(via its type metadata accessor) in a loaded plugin, so we no longer
require the "allMacros" array. Instead, each macro implementation type
must be a public struct.

Since we are now fully dependent on the macro declaration for
everything about a macro except its kind, remove most of the query
infrastructure for compiler plugins.

Replace the macro registration scheme based on the allMacros array with

Author: DougGregor

include/swift/AST/ASTContext.h

@@ -1439,12 +1439,6 @@ class ASTContext final {
   /// The declared interface type of Builtin.TheTupleType.
   BuiltinTupleType *getBuiltinTupleType();
 
-  /// 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.
   void *getAddressOfSymbol(const char *name, void *libraryHandleHint = nullptr);

include/swift/AST/CompilerPlugin.h

@@ -54,21 +54,10 @@ class CompilerPlugin {
   // stdlib/toolchain/CompilerPluginSupport.swift.
   enum class WitnessTableEntry: unsigned {
     ConformanceDescriptor = 0,
-    // static func _name() -> (UnsafePointer<UInt8>, count: Int8)
-    Name = 1,
     // static func _kind() -> _CompilerPluginKind
-    Kind = 2,
+    Kind = 1,
     // static func _rewrite(...) -> (UnsafePointer<UInt8>?, count: Int)
-    Rewrite = 3,
-    // static func _genericSignature(...) -> (UnsafePointer<UInt8>?, count: Int)
-    GenericSignature = 4,
-    // static func _typeSignature(...) -> (UnsafePointer<UInt8>, count: Int)
-    TypeSignature = 5,
-    // static func _owningModule(...) -> (UnsafePointer<UInt8>, count: Int)
-    OwningModule = 6,
-    // static func _supplementalSignatureModules(...)
-    //     -> (UnsafePointer<UInt8>, count: Int)
-    SupplementalSignatureModules = 7,
+    Rewrite = 2,
   };
 
   /// The plugin type metadata.
@@ -77,8 +66,6 @@ class CompilerPlugin {
   void *parentLibrary;
   /// The witness table proving that the plugin conforms to `_CompilerPlugin`.
   const void *witnessTable;
-  /// The plugin name, aka. result of the `_name()` method.
-  StringRef name;
   /// The plugin's kind, aka. result of the `_kind()` method.
   Kind kind;
 
@@ -87,14 +74,10 @@ class CompilerPlugin {
     return reinterpret_cast<const Func *const *>(witnessTable)[(unsigned)entry];
   }
 
-protected:
+public:
   CompilerPlugin(const void *metadata, void *parentLibrary, ASTContext &ctx);
 
 private:
-  /// Invoke the `_name` method. The caller assumes ownership of the result
-  /// string buffer.
-  StringRef invokeName() const;
-
   /// Invoke the `_kind` method.
   Kind invokeKind() const;
 
@@ -110,26 +93,6 @@ class CompilerPlugin {
       CharSourceRange range, ASTContext &ctx,
       SmallVectorImpl<Diagnostic> &diagnostics) const;
 
-  /// Invoke the `_genericSignature` method. The caller assumes ownership of the
-  /// result string buffer.
-  Optional<StringRef> invokeGenericSignature() const;
-
-  /// Invoke the `_typeSignature` method. The caller assumes ownership of the
-  /// result string buffer.
-  StringRef invokeTypeSignature() const;
-
-  /// Invoke the `_owningModule` method. The caller assumes ownership of the
-  /// result string buffer.
-  StringRef invokeOwningModule() const;
-
-  /// Invoke the `_supplementalSignatureModules` method. The caller assumes
-  /// ownership of the result string buffer.
-  StringRef invokeSupplementalSignatureModules() const;
-
-  StringRef getName() const {
-    return name;
-  }
-
   Kind getKind() const {
     return kind;
   }

include/swift/AST/DiagnosticsFrontend.def

@@ -478,10 +478,6 @@ REMARK(warning_in_access_notes_file,none,
 
 WARNING(compiler_plugin_not_loaded,none,
         "compiler plugin not loaded: %0; loader error: %1", (StringRef, StringRef))
-WARNING(compiler_plugin_missing_macro_declaration,none,
-        "compiler plugin module '%0' (in %1) is missing a top-level computed "
-        "property 'public var %2: [Any.Type]' to declare all macros; "
-        "undeclared macros will be ignored", (StringRef, StringRef, StringRef))
 
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

include/swift/AST/DiagnosticsSema.def

@@ -6742,12 +6742,16 @@ ERROR(expected_macro_expansion_expr,PointsToFirstBadToken,
 ERROR(macro_undefined,PointsToFirstBadToken,
       "macro %0 is undefined; use `-load-plugin-library` to specify dynamic "
       "libraries that contain this macro", (Identifier))
+ERROR(external_macro_not_found,none,
+      "external implementation struct '%0.%1' could not be found in for "
+      "macro %2; the type must be public and provided via "
+      "'-load-plugin-library'", (StringRef, StringRef, DeclName))
 NOTE(macro_note, none,
-     "macro %0: %1", (Identifier, StringRef))
+     "%1 (in macro %0)", (DeclName, StringRef))
 WARNING(macro_warning, none,
-        "macro %0: %1", (Identifier, StringRef))
+        "%1 (in macro %0)", (DeclName, StringRef))
 ERROR(macro_error, none,
-      "macro %0: %1", (Identifier, StringRef))
+      "%1 (in macro %0)", (DeclName, StringRef))
 
 //------------------------------------------------------------------------------
 // MARK: Move Only Errors

lib/AST/ASTContext.cpp

@@ -22,6 +22,7 @@
 #include "swift/AST/CompilerPlugin.h"
 #include "swift/AST/ConcreteDeclRef.h"
 #include "swift/AST/DiagnosticEngine.h"
+#include "swift/AST/DiagnosticsFrontend.h"
 #include "swift/AST/DiagnosticsSema.h"
 #include "swift/AST/DistributedDecl.h"
 #include "swift/AST/ExistentialLayout.h"
@@ -514,11 +515,8 @@ 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;
+  /// Record of loaded plugin modules.
+  std::vector<std::pair<std::string, void *>> LoadedPluginPaths;
 
   /// Cache of loaded symbols.
   llvm::StringMap<void *> LoadedSymbols;
@@ -584,12 +582,6 @@ ASTContext::Implementation::Implementation()
 ASTContext::Implementation::~Implementation() {
   for (auto &cleanup : Cleanups)
     cleanup();
-
-  for (const auto &pluginsByName : LoadedPlugins) {
-    for (auto plugin : pluginsByName.second) {
-      delete plugin;
-    }
-  }
 }
 
 ConstraintCheckerArenaRAII::
@@ -6103,16 +6095,24 @@ BuiltinTupleType *ASTContext::getBuiltinTupleType() {
   return result;
 }
 
-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::loadCompilerPlugins() {
+  for (auto &path : SearchPathOpts.getCompilerPluginLibraryPaths()) {
+    void *lib = nullptr;
+#if !defined(_WIN32)
+    lib = dlopen(path.c_str(), RTLD_LAZY|RTLD_LOCAL);
+#endif
+    if (!lib) {
+      const char *errorMsg = "Unsupported platform";
+#if !defined(_WIN32)
+      errorMsg = dlerror();
+#endif
+      Diags.diagnose(SourceLoc(), diag::compiler_plugin_not_loaded, path,
+                     errorMsg);
+      continue;
+    }
 
-void ASTContext::addLoadedPlugin(StringRef name, CompilerPlugin *plugin) {
-  getImpl().LoadedPlugins[name].push_back(plugin);
+    getImpl().LoadedPluginPaths.push_back({path, lib});
+  }
 }
 
 void *ASTContext::getAddressOfSymbol(const char *name,
@@ -6123,6 +6123,15 @@ void *ASTContext::getAddressOfSymbol(const char *name,
   if (lookup.second) {
     auto *handle = libraryHandleHint ? libraryHandleHint : RTLD_DEFAULT;
     address = dlsym(handle, name);
+
+    // If we didn't know where to look, look specifically in each plugin.
+    if (!address && !libraryHandleHint) {
+      for (const auto &plugin: getImpl().LoadedPluginPaths) {
+        address = dlsym(plugin.second, name);
+        if (address)
+          break;
+      }
+    }
   }
 #endif
   return address;