This is a retry of https://reviews.llvm.org/D114583, which was backed
out for regressions. This fixes
Clang Format is detecting a nested scope followed by another open brace
as a braced initializer list due to incorrectly thinking it's matching a
braced initializer at the end of a constructor initializer list which is
followed by the body open brace.
Unfortunately, UnwrappedLineParser isn't doing a very detailed parse, so
it's not super straightforward to distinguish these cases given the
current structure of calculateBraceTypes. My current hypothesis is that
these can be disambiguated by looking at the token preceding the
l_brace, as initializer list parameters will be preceded by an
identifier, but a scope block generally will not (barring the MACRO
To this end, I am adding tracking of the previous token to the LBraceStack
to help scope this particular case.