[ASTImporter] Fix redecl failures of FunctionTemplateSpec

Authored by martong on Mar 19 2019, 7:04 AM.


[ASTImporter] Fix redecl failures of FunctionTemplateSpec

Redecl chains of function template specializations are not handled well
currently. We want to handle them similarly to functions, i.e. try to
keep the structure of the original AST as much as possible. The aim is
to not squash a prototype with a definition, rather we create both and
put them in a redecl chain.

Reviewers: a_sidorin, shafik, a.sidorin

Subscribers: rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58668

llvm-svn: 356455