Swift lookup tables: translate DeclContext into something less tied to the AST.

We want to serialize this data structure, so make that easier.

Author: DougGregor

lib/ClangImporter/SwiftLookupTable.cpp

@@ -19,28 +19,6 @@
 #include "clang/AST/DeclObjC.h"
 using namespace swift;
 
-bool SwiftLookupTable::matchesContext(clang::DeclContext *foundContext,
-                                      clang::DeclContext *requestedContext) {
-  /// If the requested context was null, we match.
-  if (!requestedContext)
-    return true;
-
-  // If the contexts match, we match.
-  if (foundContext == requestedContext)
-    return true;
-
-  // If we found something in an Objective-C protocol to which a class
-  // conforms, we match.
-  if (auto objcProto = dyn_cast<clang::ObjCProtocolDecl>(foundContext)) {
-    if (auto objcClass = dyn_cast<clang::ObjCInterfaceDecl>(requestedContext)) {
-      return objcClass->ClassImplementsProtocol(objcProto,
-                                                /*lookupCategory=*/true);
-    }
-  }
-
-  return false;
-}
-
 /// Determine whether the new declarations matches an existing declaration.
 static bool matchesExistingDecl(clang::Decl *decl, clang::Decl *existingDecl) {
   // If the canonical declarations are equivalent, we have a match.
@@ -51,9 +29,38 @@ static bool matchesExistingDecl(clang::Decl *decl, clang::Decl *existingDecl) {
   return false;
 }
 
+Optional<std::pair<SwiftLookupTable::ContextKind, StringRef>>
+SwiftLookupTable::translateContext(clang::DeclContext *context) {
+  // Translation unit context.
+  if (context->isTranslationUnit())
+    return std::make_pair(ContextKind::TranslationUnit, StringRef());
+
+  // Tag declaration context.
+  if (auto tag = dyn_cast<clang::TagDecl>(context)) {
+    if (tag->getIdentifier())
+      return std::make_pair(ContextKind::Tag, tag->getName());
+    if (auto typedefDecl = tag->getTypedefNameForAnonDecl())
+      return std::make_pair(ContextKind::Tag, typedefDecl->getName());
+    return None;
+  }
+
+  // Objective-C class context.
+  if (auto objcClass = dyn_cast<clang::ObjCInterfaceDecl>(context))
+    return std::make_pair(ContextKind::ObjCClass, objcClass->getName());
+
+  // Objective-C protocol context.
+  if (auto objcProtocol = dyn_cast<clang::ObjCProtocolDecl>(context))
+    return std::make_pair(ContextKind::ObjCProtocol, objcProtocol->getName());
+
+  return None;
+}
+
 void SwiftLookupTable::addEntry(DeclName name, clang::NamedDecl *decl,
                                 clang::DeclContext *effectiveContext) {
-  clang::DeclContext *context = effectiveContext->getPrimaryContext();
+  // Translate the context.
+  auto contextOpt = translateContext(effectiveContext);
+  if (!contextOpt) return;
+  auto context = *contextOpt;
 
   // First, check whether there is already a full name entry.
   auto knownFull = FullNameTable.find(name);
@@ -86,7 +93,7 @@ void SwiftLookupTable::addEntry(DeclName name, clang::NamedDecl *decl,
 
   // This is a new context for this name. Add it.
   FullTableEntry newEntry;
-  newEntry.Context = context;
+  newEntry.Context = context;;
   newEntry.Decls.push_back(decl);
   fullEntries.push_back(newEntry);
 }
@@ -181,13 +188,15 @@ void SwiftLookupTable::dump() const {
     llvm::errs() << "  " << fullName << ":\n";
     const auto &fullEntries = FullNameTable.find(fullName)->second;
     for (const auto &fullEntry : fullEntries) {
-      llvm::errs() << "    ";
-      if (fullEntry.Context->isTranslationUnit()) {
+      switch (fullEntry.Context.first) {
+      case ContextKind::TranslationUnit:
         llvm::errs() << "TU";
-      } else if (auto named = dyn_cast<clang::NamedDecl>(fullEntry.Context)) {
-        printName(named, llvm::errs());
-      } else {
-        llvm::errs() << "<unknown>";
+        break;
+
+      case ContextKind::Tag:
+      case ContextKind::ObjCClass:
+      case ContextKind::ObjCProtocol:
+        llvm::errs() << fullEntry.Context.second;
       }
       llvm::errs() << ": ";
 

lib/ClangImporter/SwiftLookupTable.h

@@ -20,8 +20,10 @@
 #include "swift/Basic/LLVM.h"
 #include "swift/AST/Identifier.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/TinyPtrVector.h"
+#include <utility>
 
 namespace clang {
 class NamedDecl;
@@ -40,20 +42,32 @@ namespace swift {
 /// entities based on their Swift names, and is used by the Clang
 /// importer to satisfy the Swift compiler's queries.
 class SwiftLookupTable {
+public:
+  /// The kind of context in which a name occurs.
+  enum class ContextKind : uint8_t {
+    /// A translation unit.
+    TranslationUnit = 0,
+    /// A tag declaration (struct, enum, union, C++ class).
+    Tag,
+    /// An Objective-C class.
+    ObjCClass,
+    /// An Objective-C protocol.
+    ObjCProtocol,
+  };
+
   /// An entry in the table of C entities indexed by full Swift name.
   struct FullTableEntry {
     /// The context in which the entities with the given name occur, e.g.,
     /// a class, struct, translation unit, etc.
-    ///
-    /// Many Clang DeclContexts can have redeclarations, so this entry
     /// is always the canonical DeclContext for the entity.
-    clang::DeclContext *Context;
+    std::pair<ContextKind, StringRef> Context;
 
     /// The set of Clang declarations with this name and in this
     /// context.
     llvm::TinyPtrVector<clang::NamedDecl *> Decls;
   };
 
+private:
   /// A table mapping from the full name of Swift entities to all of
   /// the C entities that have that name, in all contexts.
   llvm::DenseMap<DeclName, SmallVector<FullTableEntry, 2>> FullNameTable;
@@ -62,11 +76,11 @@ class SwiftLookupTable {
   /// full Swift names based on that identifier.
   llvm::DenseMap<Identifier, SmallVector<DeclName, 2>> BaseNameTable;
 
-  /// Determine whether the given context we found matches the
-  /// requested context.
-  bool matchesContext(clang::DeclContext *foundContext,
-                      clang::DeclContext *requestedContext);
 public:
+  /// Translate a Clang DeclContext into a context kind and name.
+  llvm::Optional<std::pair<ContextKind, StringRef>>
+  translateContext(clang::DeclContext *context);
+
   /// Add an entry to the lookup table.
   ///
   /// \param name The Swift name of the entry.