1 files changed, 47 insertions, 0 deletions
diff --git a/compiler/rustc_hir/src/version.rs b/compiler/rustc_hir/src/version.rs
new file mode 100644
index 00000000000..ab5ab026b4c
--- /dev/null
+++ b/compiler/rustc_hir/src/version.rs
@@ -0,0 +1,47 @@
+use std::fmt::{self, Display};
+use std::sync::OnceLock;
+
+use rustc_macros::{
+    Decodable, Encodable, HashStable_Generic, PrintAttribute, current_rustc_version,
+};
+
+use crate::attrs::PrintAttribute;
+
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(HashStable_Generic, PrintAttribute)]
+pub struct RustcVersion {
+    pub major: u16,
+    pub minor: u16,
+    pub patch: u16,
+}
+
+impl RustcVersion {
+    pub const CURRENT: Self = current_rustc_version!();
+    pub fn current_overridable() -> Self {
+        *CURRENT_OVERRIDABLE.get_or_init(|| {
+            if let Ok(override_var) = std::env::var("RUSTC_OVERRIDE_VERSION_STRING")
+                && let Some(override_) = Self::parse_str(&override_var)
+            {
+                override_
+            } else {
+                Self::CURRENT
+            }
+        })
+    }
+    fn parse_str(value: &str) -> Option<Self> {
+        // Ignore any suffixes such as "-dev" or "-nightly".
+        let mut components = value.split('-').next().unwrap().splitn(3, '.');
+        let major = components.next()?.parse().ok()?;
+        let minor = components.next()?.parse().ok()?;
+        let patch = components.next().unwrap_or("0").parse().ok()?;
+        Some(RustcVersion { major, minor, patch })
+    }
+}
+
+static CURRENT_OVERRIDABLE: OnceLock<RustcVersion> = OnceLock::new();
+
+impl Display for RustcVersion {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(formatter, "{}.{}.{}", self.major, self.minor, self.patch)
+    }
+}