Avoid replacing the definition of CURRENT_RUSTC_VERSION

compiler/rustc_attr_data_structures/src/stability.rs

@@ -9,7 +9,12 @@ use crate::RustcVersion;
 /// `since` field of the `#[stable]` attribute.
 ///
 /// For more, see [this pull request](https://github.com/rust-lang/rust/pull/100591).
-pub const VERSION_PLACEHOLDER: &str = "CURRENT_RUSTC_VERSION";
+pub const VERSION_PLACEHOLDER: &str = concat!("CURRENT_RUSTC_VERSIO", "N");
+// Note that the `concat!` macro above prevents `src/tools/replace-version-placeholder` from
+// replacing the constant with the current version. Hardcoding the tool to skip this file doesn't
+// work as the file can (and at some point will) be moved around.
+//
+// Turning the `concat!` macro into a string literal will make Pietro cry. That'd be sad :(
 
 /// Represents the following attributes:
 ///

src/tools/replace-version-placeholder/src/main.rs

@@ -11,12 +11,7 @@ fn main() {
     let version_str = version_str.trim();
     walk::walk_many(
         &[&root_path.join("compiler"), &root_path.join("library")],
-        |path, _is_dir| {
-            walk::filter_dirs(path)
-                // We exempt these as they require the placeholder
-                // for their operation
-                || path.ends_with("compiler/rustc_attr/src/builtin.rs")
-        },
+        |path, _is_dir| walk::filter_dirs(path),
         &mut |entry, contents| {
             if !contents.contains(VERSION_PLACEHOLDER) {
                 return;