Test RUSTC_OVERRIDE_VERSION_STRING

Author: oli-obk

src/tools/compiletest/src/header.rs

@@ -330,6 +330,7 @@ impl TestProps {
     pub fn from_file(testfile: &Path, revision: Option<&str>, config: &Config) -> Self {
         let mut props = TestProps::new();
         props.load_from(testfile, revision, config);
+        props.exec_env.push(("RUSTC".to_string(), config.rustc_path.display().to_string()));
 
         match (props.pass_mode, props.fail_mode) {
             (None, None) if config.mode == Mode::Ui => props.fail_mode = Some(FailMode::Check),

tests/ui/feature-gates/version_check.rs

@@ -0,0 +1,18 @@
+//@ run-pass
+//@ ignore-wasm
+//@ ignore-emscripten
+//@ ignore-sgx
+// FIXME: this should be more like //@ needs-subprocesses
+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_OVERRIDE_VERSION_STRING", signalled_version)
+        .arg("--version")
+        .output()
+        .unwrap()
+        .stdout;
+    let version = std::str::from_utf8(&version).unwrap().strip_prefix("rustc ").unwrap().trim_end();
+    assert_ne!(version, signalled_version);
+}