# execute tests in the standard library in stage0
./x.py test --stage 0 src/libstd
+ # execute tests in the core and standard library in stage0,
+ # without running doc tests (thus avoid depending on building the compiler)
+ ./x.py test --stage 0 --no-doc src/libcore src/libstd
+
# execute all doc tests
./x.py test src/doc
```
// Since libcore defines many fundamental lang items, all tests live in a
// separate crate, libcoretest, to avoid bizarre issues.
+//
+// Here we explicitly #[cfg]-out this whole crate when testing. If we don't do
+// this, both the generated test artifact and the linked libtest (which
+// transitively includes libcore) will both define the same set of lang items,
+// and this will cause the E0152 "duplicate lang item found" error. See
+// discussion in #50466 for details.
+//
+// This cfg won't affect doc tests.
#![cfg(not(test))]
#![stable(feature = "core", since = "1.6.0")]