Unrolled build for #157707

Rollup merge of #157707 - clubby789:lint-rust-version, r=JonathanBrouwer

Introduce `-Z lint-rust-version`

Implements rust-lang/compiler-team#950 by adding the unstable flag and updating the lint machinery to accept an MSRV.

Copies most of the approach from #149870

Tracking issue: #157574

Author: rust-timer

Cargo.lock

@@ -4298,6 +4298,7 @@ dependencies = [
 name = "rustc_lint_defs"
 version = "0.0.0"
 dependencies = [
+ "rustc_ast",
  "rustc_data_structures",
  "rustc_error_messages",
  "rustc_hir_id",

compiler/rustc_ast/src/attr/version.rs

@@ -24,14 +24,24 @@ impl RustcVersion {
             }
         })
     }
+
+    /// Parse a [`RustcVersion`] with an optional patch version, ignoring suffixes such as `-dev` or `-nightly`.
     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 })
     }
+
+    /// Parse a [`RustcVersion`] which is exactly `<major>.<minor>.<patch>`, with no suffix.
+    pub fn parse_str_strict(value: &str) -> Option<Self> {
+        let mut components = value.splitn(3, '.');
+        let major = components.next()?.parse().ok()?;
+        let minor = components.next()?.parse().ok()?;
+        let patch = components.next()?.parse().ok()?;
+        Some(RustcVersion { major, minor, patch })
+    }
 }
 
 static CURRENT_OVERRIDABLE: OnceLock<RustcVersion> = OnceLock::new();

compiler/rustc_errors/src/diagnostic.rs

@@ -7,6 +7,7 @@ use std::panic;
 use std::path::PathBuf;
 use std::thread::panicking;
 
+use rustc_ast::attr::version::RustcVersion;
 use rustc_data_structures::sync::{DynSend, DynSync};
 use rustc_error_messages::{DiagArgMap, DiagArgName, DiagArgValue, IntoDiagArg};
 use rustc_lint_defs::{Applicability, LintExpectationId};
@@ -175,6 +176,8 @@ pub struct IsLint {
     pub(crate) name: String,
     /// Indicates whether this lint should show up in cargo's future breakage report.
     has_future_breakage: bool,
+    /// Indicates the minimum rust version this lint applies to
+    rust_version: Option<RustcVersion>,
 }
 
 #[derive(Debug, PartialEq, Eq)]
@@ -308,6 +311,11 @@ impl DiagInner {
         matches!(self.is_lint, Some(IsLint { has_future_breakage: true, .. }))
     }
 
+    /// Indicates the minimum rust version this lint applies to.
+    pub(crate) fn rust_version(&self) -> Option<RustcVersion> {
+        self.is_lint.as_ref().and_then(|is| is.rust_version)
+    }
+
     pub(crate) fn is_force_warn(&self) -> bool {
         match self.level {
             Level::ForceWarning => {
@@ -1152,8 +1160,13 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
         self
     } }
 
-    pub fn is_lint(&mut self, name: String, has_future_breakage: bool) -> &mut Self {
-        self.is_lint = Some(IsLint { name, has_future_breakage });
+    pub fn is_lint(
+        &mut self,
+        name: String,
+        has_future_breakage: bool,
+        rust_version: Option<RustcVersion>,
+    ) -> &mut Self {
+        self.is_lint = Some(IsLint { name, has_future_breakage, rust_version });
         self
     }
 

compiler/rustc_errors/src/lib.rs

@@ -46,6 +46,7 @@ pub use diagnostic_impls::{
 };
 pub use emitter::ColorConfig;
 use emitter::{DynEmitter, Emitter};
+use rustc_ast::attr::version::RustcVersion;
 use rustc_data_structures::AtomicRef;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hash::StableHasher;
@@ -365,6 +366,9 @@ struct DiagCtxtInner {
     /// The file where the ICE information is stored. This allows delayed_span_bug backtraces to be
     /// stored along side the main panic backtrace.
     ice_file: Option<PathBuf>,
+
+    /// Controlled by `-Z lint-rust-version`; this allows avoiding emitting lints which would raise MSRV.
+    msrv: Option<RustcVersion>,
 }
 
 /// A key denoting where from a diagnostic was stashed.
@@ -479,6 +483,11 @@ impl DiagCtxt {
         self
     }
 
+    pub fn with_msrv(mut self, msrv: RustcVersion) -> Self {
+        self.inner.get_mut().msrv = Some(msrv);
+        self
+    }
+
     pub fn new(emitter: Box<DynEmitter>) -> Self {
         Self { inner: Lock::new(DiagCtxtInner::new(emitter)) }
     }
@@ -526,6 +535,7 @@ impl DiagCtxt {
             future_breakage_diagnostics,
             fulfilled_expectations,
             ice_file: _,
+            msrv: _,
         } = inner.deref_mut();
 
         // For the `Vec`s and `HashMap`s, we overwrite with an empty container to free the
@@ -1193,6 +1203,7 @@ impl DiagCtxtInner {
             future_breakage_diagnostics: Vec::new(),
             fulfilled_expectations: Default::default(),
             ice_file: None,
+            msrv: None,
         }
     }
 
@@ -1307,6 +1318,12 @@ impl DiagCtxtInner {
             }
         }
 
+        if let (Some(msrv), Some(diag_msrv)) = (self.msrv, diagnostic.rust_version())
+            && diag_msrv > msrv
+        {
+            return None;
+        }
+
         TRACK_DIAGNOSTIC(diagnostic, &mut |mut diagnostic| {
             if let Some(code) = diagnostic.code {
                 self.emitted_diagnostic_codes.insert(code);

compiler/rustc_lint_defs/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
+rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_error_messages = { path = "../rustc_error_messages" }
 rustc_hir_id = { path = "../rustc_hir_id" }

compiler/rustc_lint_defs/src/lib.rs

@@ -1,6 +1,7 @@
 use std::borrow::Cow;
 use std::fmt::Display;
 
+use rustc_ast::attr::version::RustcVersion;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_data_structures::stable_hash::{StableCompare, StableHash, StableHashCtxt, StableHasher};
 use rustc_error_messages::{DiagArgValue, IntoDiagArg};
@@ -305,6 +306,9 @@ pub struct Lint {
 
     /// `true` if this lint is unaffected by `-D warnings`
     pub ignore_deny_warnings: bool,
+
+    /// Used to avoid lints which would affect MSRV
+    pub rust_version: Option<RustcVersion>,
 }
 
 /// Extra information for a future incompatibility lint.
@@ -521,7 +525,40 @@ impl Lint {
             crate_level_only: false,
             eval_always: false,
             ignore_deny_warnings: false,
+            rust_version: None,
+        }
+    }
+
+    // FIXME(const-hack): This is used so that `declare_lint` can declare an MSRV statically.
+    // `RustcVersion::parse_str_strict` should ideally be used instead.
+    pub const fn parse_rust_version(version: &str) -> RustcVersion {
+        const fn parse_part(input: &mut &[u8]) -> u16 {
+            let mut val = 0;
+            let mut idx = 0;
+            while idx < input.len() {
+                let v = input[idx];
+                match v {
+                    b'0'..=b'9' => {
+                        val = val * 10 + (v - b'0') as u16;
+                    }
+                    b'.' => {
+                        idx += 1;
+                        break;
+                    }
+                    _ => panic!("invalid character in version"),
+                }
+                idx += 1;
+            }
+            *input = input.split_at(idx).1;
+            val
         }
+
+        let mut bytes = version.as_bytes();
+        let major = parse_part(&mut bytes);
+        let minor = parse_part(&mut bytes);
+        let patch = parse_part(&mut bytes);
+        assert!(bytes.is_empty());
+        RustcVersion { major, minor, patch }
     }
 
     /// Gets the lint's name, with ASCII letters converted to lowercase.
@@ -671,6 +708,7 @@ macro_rules! declare_lint {
         $($field:ident : $val:expr),* $(,)*
      }; )?
      $(@edition $lint_edition:ident => $edition_level:ident;)?
+     $(@msrv = $msrv:literal;)?
      $($v:ident),*) => (
         $(#[$attr])*
         $vis static $NAME: &$crate::Lint = &$crate::Lint {
@@ -687,6 +725,7 @@ macro_rules! declare_lint {
             }),)?
             $(edition_lint_opts: Some(($crate::Edition::$lint_edition, $crate::$edition_level)),)?
             $(eval_always: $eval_always,)?
+            $(rust_version: Some($crate::Lint::parse_rust_version($msrv)),)?
             ..$crate::Lint::default_fields_for_macro()
         };
     );

compiler/rustc_middle/src/lint.rs

@@ -514,7 +514,7 @@ pub fn emit_lint_base<'a, D: Diagnostic<'a, ()> + 'a>(
             err.disable_suggestions();
         }
 
-        err.is_lint(lint.name_lower(), has_future_breakage);
+        err.is_lint(lint.name_lower(), has_future_breakage, lint.rust_version);
         // Lint diagnostics that are covered by the expect level will not be emitted outside
         // the compiler. It is therefore not necessary to add any information for the user.
         // This will therefore directly call the decorate function which will in turn emit

compiler/rustc_session/src/config.rs

@@ -3059,6 +3059,7 @@ pub(crate) mod dep_tracking {
     use std::path::PathBuf;
 
     use rustc_abi::Align;
+    use rustc_ast::attr::version::RustcVersion;
     use rustc_data_structures::fx::FxIndexMap;
     use rustc_data_structures::stable_hash::StableHasher;
     use rustc_errors::LanguageIdentifier;
@@ -3184,7 +3185,8 @@ pub(crate) mod dep_tracking {
         InliningThreshold,
         FunctionReturn,
         Align,
-        CodegenRetagOptions
+        CodegenRetagOptions,
+        RustcVersion,
     );
 
     impl<T1, T2> DepTrackingHash for (T1, T2)

compiler/rustc_session/src/errors.rs

@@ -82,7 +82,11 @@ pub fn feature_warn_issue(
     // Decorate this as a future-incompatibility lint as in rustc_middle::lint::lint_level
     let lint = UNSTABLE_SYNTAX_PRE_EXPANSION;
     let future_incompatible = lint.future_incompatible.as_ref().unwrap();
-    err.is_lint(lint.name_lower(), /* has_future_breakage */ false);
+    err.is_lint(
+        lint.name_lower(),
+        /* has_future_breakage */ false,
+        /* rust_version */ None,
+    );
     err.warn(lint.desc);
     err.note(format!("for more information, see {}", future_incompatible.reason.reference()));
 

compiler/rustc_session/src/options.rs

@@ -4,6 +4,7 @@ use std::path::PathBuf;
 use std::str;
 
 use rustc_abi::Align;
+use rustc_ast::attr::version::RustcVersion;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::profiling::TimePassesFormat;
 use rustc_data_structures::stable_hash::StableHasher;
@@ -846,6 +847,7 @@ mod desc {
         super::mitigation_coverage::DeniedPartialMitigationKind::KINDS;
     pub(crate) const parse_deny_partial_mitigations: &str =
         super::mitigation_coverage::DeniedPartialMitigationKind::KINDS;
+    pub(crate) const parse_rust_version: &str = "a rust version (`xx.yy.zz`)";
 }
 
 pub mod parse {
@@ -2054,6 +2056,18 @@ pub mod parse {
         };
         true
     }
+
+    pub(crate) fn parse_rust_version(slot: &mut Option<RustcVersion>, v: Option<&str>) -> bool {
+        let Some(v) = v else {
+            return false;
+        };
+        if let Some(version) = RustcVersion::parse_str_strict(v) {
+            *slot = Some(version);
+            true
+        } else {
+            false
+        }
+    }
 }
 
 options! {
@@ -2454,6 +2468,8 @@ options! {
         "lint LLVM IR (default: no)"),
     lint_mir: bool = (false, parse_bool, [UNTRACKED],
         "lint MIR before and after each transformation"),
+    lint_rust_version: Option<RustcVersion> = (None, parse_rust_version, [TRACKED],
+        "control the minimum rust version for lints"),
     llvm_module_flag: Vec<(String, u32, String)> = (Vec::new(), parse_llvm_module_flag, [TRACKED],
         "a list of module flags to pass to LLVM (space separated)"),
     llvm_plugins: Vec<String> = (Vec::new(), parse_list, [TRACKED],