Test RUSTC_FORCE_RUSTC_VERSION

Author: oli-obk

tests/ui/feature-gates/version_check.rs

@@ -0,0 +1,23 @@
+//@ run-pass
+use std::process::Command;
+
+fn main() {
+    let signalled_version = "Ceci n'est pas une rustc";
+    let version = Command::new(std::env::var_os("RUSTC").unwrap())
+        .env("RUSTC_FORCE_RUSTC_VERSION", signalled_version)
+        .arg("--version")
+        .output()
+        .unwrap()
+        .stdout;
+    let version = String::from_utf8(version).unwrap();
+    assert_ne!(version, signalled_version);
+    let version = Command::new(std::env::var_os("RUSTC").unwrap())
+        .env("RUSTC_FORCE_RUSTC_VERSION", signalled_version)
+        .arg("--version")
+        .arg("--verbose")
+        .output()
+        .unwrap()
+        .stdout;
+    let version = String::from_utf8(version).unwrap();
+    assert_ne!(version, signalled_version);
+}