Parse rustc version at compile time

compiler/rustc_macros/src/lib.rs

@@ -15,6 +15,7 @@ use synstructure::decl_derive;
 
 use proc_macro::TokenStream;
 
+mod current_version;
 mod diagnostics;
 mod hash_stable;
 mod lift;
@@ -25,6 +26,11 @@ mod symbols;
 mod type_foldable;
 mod type_visitable;
 
+#[proc_macro]
+pub fn current_rustc_version(input: TokenStream) -> TokenStream {
+    current_version::current_version(input)
+}
+
 #[proc_macro]
 pub fn rustc_queries(input: TokenStream) -> TokenStream {
     query::rustc_queries(input)