$ tree
.
├── bar
│   ├── bar.cpp
│   └── BUILD
├── BUILD
├── foo.cpp
└── WORKSPACE

cc_binary(
    name = "foo",
    srcs = [ "foo.cpp" ],
    deps = [ "//bar" ],
)

cc_library(
    name = "bar",
    srcs = ["bar.cpp"],
)

Target '//bar:bar' is not visible from target '//:foo'. Check the visibility declaration of the former target if you think the dependency is legitimate.

cc_library(
    name = "bar",
    srcs = ["bar.cpp"],
    visibility = ["//__pkg__"],
)