Fix IsStructuralMatch specialization for EnumDecl to prevent re-importing an EnumDecl while trying to complete it

[shafik]

Summary

We may try and re-import an EnumDecl while trying to complete it in IsStructuralMatch(...) specialization for EnumDecl. This change mirrors a similar fix for the specialization for RecordDecl.

[shafik]

LLDB regression test that goes with this fix: https://reviews.llvm.org/D59847

[JDevlieghere]

lib/AST/ASTImporter.cpp

1951 ↗

(On Diff #192354)

if (Decl *ToOrigin = Importer.GetOriginalDecl(ToEnum)) 
  if (auto *ToOriginEnum = dyn_cast<EnumDecl>(ToOrigin))
    ToEnum = ToOriginEnum;

[martong]

LGTM!

[shafik]

Fixes based on comments.

[shafik]

lib/AST/ASTImporter.cpp

1951 ↗

(On Diff #192354)

I normally just match the local style but this is indeed much better style.

[a_sidorin]

Post-LGTM with some stylish nits.

cfe/trunk/lib/AST/ASTImporter.cpp

1950

completin_g_; also, comments are required to be ended with dot.

cfe/trunk/lib/AST/ASTImporter.cpp

bool ASTNodeImporter::IsStructuralMatch(VarDecl *FromVar, VarDecl *ToVar,
   StructuralEquivalenceContext Ctx(
       Importer.getFromContext(), Importer.getToContext(),
       Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer),
       false, Complain);
   return Ctx.IsEquivalent(FromVar, ToVar);
 }
 
 bool ASTNodeImporter::IsStructuralMatch(EnumDecl *FromEnum, EnumDecl *ToEnum) {
+  // Eliminate a potential failure point where we attempt to re-import
+  // something we're trying to import while completin ToEnum
+  if (Decl *ToOrigin = Importer.GetOriginalDecl(ToEnum))
+    if (auto *ToOriginEnum = dyn_cast<EnumDecl>(ToOrigin))
+        ToEnum = ToOriginEnum;
+
   StructuralEquivalenceContext Ctx(
       Importer.getFromContext(), Importer.getToContext(),
       Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer));
   return Ctx.IsEquivalent(FromEnum, ToEnum);
 }
 
 bool ASTNodeImporter::IsStructuralMatch(FunctionTemplateDecl *From,
                                         FunctionTemplateDecl *To) {