Add test for well known names defined by rustc

Author: Urgau

src/test/ui/check-cfg/well-known-names.rs

@@ -0,0 +1,27 @@
+// This test checks that we lint on non well known names and that we don't lint on well known names
+//
+// check-pass
+// compile-flags: --check-cfg=names() -Z unstable-options
+
+#[cfg(target_oz = "linux")]
+//~^ WARNING unexpected `cfg` condition name
+fn target_os_misspell() {}
+
+#[cfg(target_os = "linux")]
+fn target_os() {}
+
+#[cfg(features = "foo")]
+//~^ WARNING unexpected `cfg` condition name
+fn feature_misspell() {}
+
+#[cfg(feature = "foo")]
+fn feature() {}
+
+#[cfg(uniw)]
+//~^ WARNING unexpected `cfg` condition name
+fn unix_misspell() {}
+
+#[cfg(unix)]
+fn unix() {}
+
+fn main() {}

src/test/ui/check-cfg/well-known-names.stderr

@@ -0,0 +1,22 @@
+warning: unexpected `cfg` condition name
+  --> $DIR/well-known-names.rs:6:7
+   |
+LL | #[cfg(target_oz = "linux")]
+   |       ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: unexpected `cfg` condition name
+  --> $DIR/well-known-names.rs:13:7
+   |
+LL | #[cfg(features = "foo")]
+   |       ^^^^^^^^^^^^^^^^
+
+warning: unexpected `cfg` condition name
+  --> $DIR/well-known-names.rs:20:7
+   |
+LL | #[cfg(uniw)]
+   |       ^^^^
+
+warning: 3 warnings emitted
+