[PATCH] D62375: [ASTImporter] Mark erroneous nodes in from ctx

[Gabor Marton via Phabricator via cfe-commits]

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During import of a specific Decl D, it may happen that some AST nodes
had already been created before we recognize an error. In this case we
signal back the error to the caller, but the "to" context remains
polluted with those nodes which had been created. Ideally, those nodes
should not had been created, but that time we did not know about the
error, the error happened later.  Since the AST is immutable (most of
the cases we can't remove existing nodes) we choose to mark these nodes
as erroneous.
Here are the steps of the algorithm:

1. We keep track of the nodes which we visit during the import of D: See

ImportPathTy.

2. If a Decl is already imported and it is already on the import path

(we have a cycle) then we copy/store the relevant part of the import
path. We store these cycles for each Decl.

3. When we recognize an error during the import of D then we set up this

error to all Decls in the stored cycles for D and we clear the stored
cycles.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D62375

Files:
  clang/include/clang/AST/ASTImporter.h
  clang/lib/AST/ASTImporter.cpp
  clang/unittests/AST/ASTImporterTest.cpp

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