rename rustc_attr to rustc_attr_parsing and create rustc_attr_data_structures

compiler/rustc_attr_data_structures/src/version.rs

@@ -0,0 +1,21 @@
+use std::fmt::{self, Display};
+
+use rustc_macros::{Decodable, Encodable, HashStable_Generic, current_rustc_version};
+
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(HashStable_Generic)]
+pub struct RustcVersion {
+    pub major: u16,
+    pub minor: u16,
+    pub patch: u16,
+}
+
+impl RustcVersion {
+    pub const CURRENT: Self = current_rustc_version!();
+}
+
+impl Display for RustcVersion {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(formatter, "{}.{}.{}", self.major, self.minor, self.patch)
+    }
+}