We might get into bad situations where we try to embed the signature of
an inner lambda into an outer lambda which cannot work: the inner lambda
wants to embed the name of the outer lambda!
Instead, omit the return type for lambdas.
This fixes PR26105.
N.B. While we are here, make lambdas nested within functions use an
artificial scope so that they can get demangled.
llvm-svn: 258003
The Itanium ABI will give out the same mangling number for two different
lambdas if their call operators have different types. The MS ABI cannot
do the same because it does not mangle the return type into it's
lambdas.
This fixes PR20719.
llvm-svn: 216259