Make lambda introduce a context in DU chain
Summary:
Lambda in clang completion were not introducing a context. This
had the effect of making all local variable in a global lambda
highlighted as a global
BUG: 387994
Reviewers: KDevelop, mwolff
Reviewed By: KDevelop, mwolff
Subscribers: kfunk, mwolff, kdevelop-devel
Differential Revision: https://phabricator.kde.org/D11303
(cherry picked from commit 335786a16731b093bf6b027c8c51ef653425b73a)