Parse rustc version at compile time

compiler/rustc_attr/src/builtin.rs

@@ -10,10 +10,9 @@ use rustc_session::config::ExpectedValues;
 use rustc_session::lint::builtin::UNEXPECTED_CFGS;
 use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_session::parse::{feature_err, ParseSess};
-use rustc_session::Session;
+use rustc_session::{RustcVersion, Session};
 use rustc_span::hygiene::Transparency;
 use rustc_span::{symbol::sym, symbol::Symbol, Span};
-use std::fmt::{self, Display};
 use std::num::NonZeroU32;
 
 use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
@@ -24,8 +23,6 @@ use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
 /// For more, see [this pull request](https://github.com/rust-lang/rust/pull/100591).
 pub const VERSION_PLACEHOLDER: &str = "CURRENT_RUSTC_VERSION";
 
-pub const CURRENT_RUSTC_VERSION: &str = env!("CFG_RELEASE");
-
 pub fn is_builtin_attr(attr: &Attribute) -> bool {
     attr.is_doc_comment() || attr.ident().is_some_and(|ident| is_builtin_attr_name(ident.name))
 }
@@ -153,7 +150,7 @@ pub enum StabilityLevel {
 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 #[derive(HashStable_Generic)]
 pub enum Since {
-    Version(Version),
+    Version(RustcVersion),
     /// Stabilized in the upcoming version, whatever number that is.
     Current,
     /// Failed to parse a stabilization version.
@@ -382,7 +379,7 @@ fn parse_stability(sess: &Session, attr: &Attribute) -> Option<(Symbol, Stabilit
     let since = if let Some(since) = since {
         if since.as_str() == VERSION_PLACEHOLDER {
             Since::Current
-        } else if let Some(version) = parse_version(since.as_str(), false) {
+        } else if let Some(version) = parse_version(since) {
             Since::Version(version)
         } else {
             sess.emit_err(session_diagnostics::InvalidSince { span: attr.span });
@@ -567,31 +564,20 @@ fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &F
     }
 }
 
-#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[derive(HashStable_Generic)]
-pub struct Version {
-    pub major: u16,
-    pub minor: u16,
-    pub patch: u16,
-}
-
-fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
-    let mut components = s.split('-');
+/// Parse a rustc version number written inside string literal in an attribute,
+/// like appears in `since = "1.0.0"`. Suffixes like "-dev" and "-nightly" are
+/// not accepted in this position, unlike when parsing CFG_RELEASE.
+fn parse_version(s: Symbol) -> Option<RustcVersion> {
+    let mut components = s.as_str().split('-');
     let d = components.next()?;
-    if !allow_appendix && components.next().is_some() {
+    if components.next().is_some() {
         return None;
     }
     let mut digits = d.splitn(3, '.');
     let major = digits.next()?.parse().ok()?;
     let minor = digits.next()?.parse().ok()?;
     let patch = digits.next().unwrap_or("0").parse().ok()?;
-    Some(Version { major, minor, patch })
-}
-
-impl Display for Version {
-    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(formatter, "{}.{}.{}", self.major, self.minor, self.patch)
-    }
+    Some(RustcVersion { major, minor, patch })
 }
 
 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
@@ -623,17 +609,16 @@ pub fn eval_condition(
                     return false;
                 }
             };
-            let Some(min_version) = parse_version(min_version.as_str(), false) else {
+            let Some(min_version) = parse_version(*min_version) else {
                 sess.emit_warning(session_diagnostics::UnknownVersionLiteral { span: *span });
                 return false;
             };
-            let rustc_version = parse_version(CURRENT_RUSTC_VERSION, true).unwrap();
 
             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
             if sess.assume_incomplete_release {
-                rustc_version > min_version
+                RustcVersion::CURRENT > min_version
             } else {
-                rustc_version >= min_version
+                RustcVersion::CURRENT >= min_version
             }
         }
         ast::MetaItemKind::List(mis) => {

compiler/rustc_attr/src/lib.rs

@@ -27,6 +27,6 @@ pub use StabilityLevel::*;
 
 pub use rustc_ast::attr::*;
 
-pub(crate) use rustc_ast::HashStableContext;
+pub(crate) use rustc_session::HashStableContext;
 
 fluent_messages! { "../messages.ftl" }