These are the packages that would be merged, in order:

[ebuild   R    ] dev-lang/rust-bin-1.31.0:stable::gentoo  USE="(-clippy) -doc -libressl -rustfmt" ABI_X86="(64) -32 (-x32)" CPU_FLAGS_X86="sse2" 0 KiB
[ebuild   R    ] virtual/cargo-1.31.0::gentoo  0 KiB
[ebuild     U  ] virtual/rust-1.31.0::gentoo [1.29.2::gentoo] 0 KiB