Merge pull request #19391 from DougGregor/assoc-conformance-default-witnesses

[ABI] Associated conformance defaults

lib/AST/ASTContext.cpp

@@ -285,6 +285,11 @@ FOR_KNOWN_FOUNDATION_TYPES(CACHE_FOUNDATION_DECL)
   llvm::DenseMap<std::pair<const ProtocolDecl *, AssociatedTypeDecl *>, Type>
     DefaultTypeWitnesses;
 
+  /// Default associated conformance witnesses for protocols.
+  llvm::DenseMap<std::tuple<const ProtocolDecl *, CanType, ProtocolDecl *>,
+                 ProtocolConformanceRef>
+    DefaultAssociatedConformanceWitnesses;
+
   /// \brief Structure that captures data that is segregated into different
   /// arenas.
   struct Arena {
@@ -1709,6 +1714,32 @@ void ProtocolDecl::setDefaultTypeWitness(AssociatedTypeDecl *assocType,
   (void)pair;
 }
 
+Optional<ProtocolConformanceRef>
+ProtocolDecl::getDefaultAssociatedConformanceWitness(
+                                             CanType association,
+                                             ProtocolDecl *requirement) const {
+  auto &ctx = getASTContext();
+  auto found =
+    ctx.getImpl().DefaultAssociatedConformanceWitnesses.find(
+      std::make_tuple(this, association, requirement));
+  if (found == ctx.getImpl().DefaultAssociatedConformanceWitnesses.end())
+    return None;
+
+  return found->second;
+}
+
+void ProtocolDecl::setDefaultAssociatedConformanceWitness(
+                                          CanType association,
+                                          ProtocolDecl *requirement,
+                                          ProtocolConformanceRef conformance) {
+  auto &ctx = getASTContext();
+  auto pair = ctx.getImpl().DefaultAssociatedConformanceWitnesses.insert(
+                std::make_pair(std::make_tuple(this, association, requirement),
+                               conformance));
+  assert(pair.second && "Already have a default associated conformance");
+  (void)pair;
+}
+
 bool ASTContext::canImportModule(std::pair<Identifier, SourceLoc> ModulePath) {
   // If this module has already been successfully imported, it is importable.
   if (getLoadedModule(ModulePath) != nullptr)