[clang][ASTImporter] Not using consumeError at failed import of in-class initializer.

[balazske]

Summary

The error can be returned from the function, the problem written in comment before
does not exist. The same is done already in ASTImporter at various import failures.

After a declaration is created in an ASTNodeImporter import function
with GetImportedOrCreateDecl, that function registers it with
MapImported. At many places import errors can happen after this
and the error is returned. The same can be done in the place where
the in-class initializer is imported.

[balazske]

I wanted to remove this one instance of consumeError because the change in D122525, to ensure that consumeError is called really only from ImportDeclContext (and other places where it is not relevant).

[martong]

Thanks! Good catch!

(For inexperienced readers, let me explain why I accepted the patch: If there is an error then the imported Decl is marked as erroneous, i.e an Error object is associated with the imported Decl, thus users of the ASTImporter can react according to the set error.)

clang/lib/AST/ASTImporter.cpp

if (FieldDecl *FoundField = dyn_cast<FieldDecl>(FoundDecl)) {
         // "To" context.  However, the "From" context might instantiated that,
         // thus we have to merge that.
         if (Expr *FromInitializer = D->getInClassInitializer()) {
           // We don't have yet the initializer set.
           if (FoundField->hasInClassInitializer() &&
               !FoundField->getInClassInitializer()) {
             if (ExpectedExpr ToInitializerOrErr = import(FromInitializer))
               FoundField->setInClassInitializer(*ToInitializerOrErr);
-            else {
-              // We can't return error here,
-              // since we already mapped D as imported.
-              // FIXME: warning message?
-              consumeError(ToInitializerOrErr.takeError());
-              return FoundField;
-            }
+            else
+              return ToInitializerOrErr.takeError();
           }
         }
         return FoundField;
       }
 
       // FIXME: Why is this case not handled with calling HandleNameConflict?
       Importer.ToDiag(Loc, diag::warn_odr_field_type_inconsistent)
         << Name << D->getType() << FoundField->getType();