146     // imported from the temporary ASTContext to a persistent ASTContext.  in ImportImpl()
147     // Then the ExternalASTMerger tries to import from the persistent  in ImportImpl()
150     // the other (persistent) ASTImporter to this (temporary) ASTImporter.  in ImportImpl()
153     //  Target AST <--- 3. Indirect import --- Persistent AST  in ImportImpl()
154     //       ^            of persistent decl        ^  in ImportImpl()
156     // 1. Current import           2. Tracking back to persistent decl  in ImportImpl()
157     // 4. Map persistent decl                       |  in ImportImpl()
164     Decl *Persistent = SourceMerger->FindOriginalDecl(FromD);  in ImportImpl()  local
165     // FromD isn't from a persistent AST, so just do a normal import.  in ImportImpl()
166     if (!Persistent)  in ImportImpl()
168     // Now ask the current ExternalASTMerger to try import the persistent  in ImportImpl()
170     ASTContext &PersistentCtx = Persistent->getASTContext();  in ImportImpl()
175     auto DeclOrErr = OtherImporter.Import(Persistent);  in ImportImpl()
176     // Errors when importing the persistent decl are treated as if we  in ImportImpl()