BTreeMap: complete the compile-time test_variance test case Some of the items added to the new `test_sync` belonged in the old `test_variance` as well. And fixed inconsistent paths to nearby modules. r? @Mark-Simulacrum
BTreeMap: complete the compile-time test_variance test case Some of the items added to the new `test_sync` belonged in the old `test_variance` as well. And fixed inconsistent paths to nearby modules. r? @Mark-Simulacrum