[c++17] Fix assertion on synthesizing deduction guides after a fatal error.
After a fatal error Sema::InstantiatingTemplate doesn't allow further
instantiation and doesn't push a CodeSynthesisContext. When we tried to
synthesize implicit deduction guides from constructors we hit the
assertion
> Assertion failed: (!CodeSynthesisContexts.empty() && "Cannot perform an instantiation without some context on the " "instantiation stack"), function SubstType, file clang/lib/Sema/SemaTemplateInstantiate.cpp, line 1580.
Fix by avoiding deduction guide synthesis if InstantiatingTemplate is invalid.
rdar://problem/39051732
Reviewers: rsmith
Reviewed By: rsmith
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D46446
llvm-svn: 332307
2 files changed