Add functional #[cfg(version)] test

Author: est31

tests/ui/feature-gates/cfg-version-expand.rs

@@ -0,0 +1,30 @@
+//@ run-pass
+//@ rustc-env:RUSTC_OVERRIDE_VERSION_STRING=1.50.3
+
+#![feature(cfg_version)]
+
+#[cfg(version("1.49.0"))]
+const ON_1_49_0: bool = true;
+#[cfg(version("1.50"))]
+const ON_1_50_0: bool = true;
+#[cfg(not(version("1.51")))]
+const ON_1_51_0: bool = false;
+
+// This one uses the wrong syntax, so doesn't eval to true
+#[warn(unexpected_cfgs)]
+#[cfg(not(version = "1.48.0"))] //~ WARN unexpected `cfg` condition name: `version`
+const ON_1_48_0: bool = false;
+
+fn main() {
+    assert!(!ON_1_48_0);
+    assert!(ON_1_49_0);
+    assert!(ON_1_50_0);
+    assert!(!ON_1_51_0);
+    assert!(cfg!(version("1.1")));
+    assert!(cfg!(version("1.49")));
+    assert!(cfg!(version("1.50.0")));
+    assert!(cfg!(version("1.50.3")));
+    assert!(!cfg!(version("1.50.4")));
+    assert!(!cfg!(version("1.51")));
+    assert!(!cfg!(version("1.100")));
+}

tests/ui/feature-gates/cfg-version-expand.stderr

@@ -0,0 +1,13 @@
+warning: unexpected `cfg` condition name: `version`
+  --> $DIR/cfg-version-expand.rs:15:11
+   |
+LL | #[cfg(not(version = "1.48.0"))]
+   |           ^^^^^^^^^^^^^^^^^^
+   |
+   = help: expected names are: `FALSE` and `test` and 31 more
+   = help: to expect this configuration use `--check-cfg=cfg(version, values("1.48.0"))`
+   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
+   = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: 1 warning emitted
+