LLVM updated its repo “deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty main” to point to the nightly build of the development branch clang-9.
The previous tip-of-trunk snapshot now resides in “deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-8 main” and will soon be released as clang-8.
However, Travis does not whitelist “deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-8 main” yet, so we can’t run C++ repo’s compling with clang-8 without sudo support.
The llvm dev cycle is about 6 months and I previously submitted an issue for the clang-7 to clang-8 transition here: https://github.com/travis-ci/travis-ci/issues/10069