Various improvements to the incompatible_msrv lint

clippy_lints/src/incompatible_msrv.rs

@@ -1,8 +1,8 @@
 use clippy_config::Conf;
-use clippy_utils::diagnostics::span_lint;
+use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::is_in_test;
 use clippy_utils::msrvs::Msrv;
-use rustc_attr_data_structures::{RustcVersion, StabilityLevel, StableSince};
+use rustc_attr_data_structures::{RustcVersion, Stability, StableSince};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::{Expr, ExprKind, HirId, QPath};
 use rustc_lint::{LateContext, LateLintPass};
@@ -33,15 +33,54 @@ declare_clippy_lint! {
     ///
     /// To fix this problem, either increase your MSRV or use another item
     /// available in your current MSRV.
+    ///
+    /// You can also locally change the MSRV that should be checked by Clippy,
+    /// for example if a feature in your crate (e.g., `modern_compiler`) should
+    /// allow you to use an item:
+    ///
+    /// ```no_run
+    /// //! This crate has a MSRV of 1.3.0, but we also have an optional feature
+    /// //! `sleep_well` which requires at least Rust 1.4.0.
+    ///
+    /// // When the `sleep_well` feature is set, do not warn for functions available
+    /// // in Rust 1.4.0 and below.
+    /// #![cfg_attr(feature = "sleep_well", clippy::msrv = "1.4.0")]
+    ///
+    /// use std::time::Duration;
+    ///
+    /// #[cfg(feature = "sleep_well")]
+    /// fn sleep_for_some_time() {
+    ///     std::thread::sleep(Duration::new(1, 0)); // Will not trigger the lint
+    /// }
+    /// ```
+    ///
+    /// You can also increase the MSRV in tests, by using:
+    ///
+    /// ```no_run
+    /// // Use a much higher MSRV for tests while keeping the main one low
+    /// #![cfg_attr(test, clippy::msrv = "1.85.0")]
+    ///
+    /// #[test]
+    /// fn my_test() {
+    ///     // The tests can use items introduced in Rust 1.85.0 and lower
+    ///     // without triggering the `incompatible_msrv` lint.
+    /// }
+    /// ```
     #[clippy::version = "1.78.0"]
     pub INCOMPATIBLE_MSRV,
     suspicious,
     "ensures that all items used in the crate are available for the current MSRV"
 }
 
+#[derive(Clone, Copy)]
+enum Availability {
+    FeatureEnabled,
+    Since(RustcVersion),
+}
+
 pub struct IncompatibleMsrv {
     msrv: Msrv,
-    is_above_msrv: FxHashMap<DefId, RustcVersion>,
+    availability_cache: FxHashMap<DefId, Availability>,
     check_in_tests: bool,
 }
 
@@ -51,35 +90,32 @@ impl IncompatibleMsrv {
     pub fn new(conf: &'static Conf) -> Self {
         Self {
             msrv: conf.msrv,
-            is_above_msrv: FxHashMap::default(),
+            availability_cache: FxHashMap::default(),
             check_in_tests: conf.check_incompatible_msrv_in_tests,
         }
     }
 
-    fn get_def_id_version(&mut self, tcx: TyCtxt<'_>, def_id: DefId) -> RustcVersion {
-        if let Some(version) = self.is_above_msrv.get(&def_id) {
-            return *version;
+    /// Returns the availability of `def_id`, whether it is enabled through a feature or
+    /// available since a given version (the default being Rust 1.0.0).
+    fn get_def_id_availability(&mut self, tcx: TyCtxt<'_>, def_id: DefId) -> Availability {
+        if let Some(availability) = self.availability_cache.get(&def_id) {
+            return *availability;
         }
-        let version = if let Some(version) = tcx
-            .lookup_stability(def_id)
-            .and_then(|stability| match stability.level {
-                StabilityLevel::Stable {
-                    since: StableSince::Version(version),
-                    ..
-                } => Some(version),
-                _ => None,
-            }) {
-            version
+        let stability = tcx.lookup_stability(def_id);
+        let version = if stability.is_some_and(|stability| tcx.features().enabled(stability.feature)) {
+            Availability::FeatureEnabled
+        } else if let Some(StableSince::Version(version)) = stability.as_ref().and_then(Stability::stable_since) {
+            Availability::Since(version)
         } else if let Some(parent_def_id) = tcx.opt_parent(def_id) {
-            self.get_def_id_version(tcx, parent_def_id)
+            self.get_def_id_availability(tcx, parent_def_id)
         } else {
-            RustcVersion {
+            Availability::Since(RustcVersion {
                 major: 1,
                 minor: 0,
                 patch: 0,
-            }
+            })
         };
-        self.is_above_msrv.insert(def_id, version);
+        self.availability_cache.insert(def_id, version);
         version
     }
 
@@ -110,40 +146,57 @@ impl IncompatibleMsrv {
 
         if (self.check_in_tests || !is_in_test(cx.tcx, node))
             && let Some(current) = self.msrv.current(cx)
-            && let version = self.get_def_id_version(cx.tcx, def_id)
+            && let Availability::Since(version) = self.get_def_id_availability(cx.tcx, def_id)
             && version > current
         {
-            span_lint(
+            span_lint_and_then(
                 cx,
                 INCOMPATIBLE_MSRV,
                 span,
                 format!(
                     "current MSRV (Minimum Supported Rust Version) is `{current}` but this item is stable since `{version}`"
                 ),
+                |diag| {
+                    if is_under_cfg_attribute(cx, node) {
+                        diag.note_once("you may want to conditionally increase the MSRV considered by Clippy using the `clippy::msrv` attribute");
+                    }
+                },
             );
         }
     }
 }
 
 impl<'tcx> LateLintPass<'tcx> for IncompatibleMsrv {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+        // TODO: check for const stability when in const context
         match expr.kind {
             ExprKind::MethodCall(_, _, _, span) => {
                 if let Some(method_did) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
                     self.emit_lint_if_under_msrv(cx, method_did, expr.hir_id, span);
                 }
             },
-            ExprKind::Call(call, _) => {
-                // Desugaring into function calls by the compiler will use `QPath::LangItem` variants. Those should
-                // not be linted as they will not be generated in older compilers if the function is not available,
-                // and the compiler is allowed to call unstable functions.
-                if let ExprKind::Path(qpath @ (QPath::Resolved(..) | QPath::TypeRelative(..))) = call.kind
-                    && let Some(path_def_id) = cx.qpath_res(&qpath, call.hir_id).opt_def_id()
-                {
-                    self.emit_lint_if_under_msrv(cx, path_def_id, expr.hir_id, call.span);
+            // Desugaring into function calls by the compiler will use `QPath::LangItem` variants. Those should
+            // not be linted as they will not be generated in older compilers if the function is not available,
+            // and the compiler is allowed to call unstable functions.
+            ExprKind::Path(qpath @ (QPath::Resolved(..) | QPath::TypeRelative(..))) => {
+                if let Some(path_def_id) = cx.qpath_res(&qpath, expr.hir_id).opt_def_id() {
+                    self.emit_lint_if_under_msrv(cx, path_def_id, expr.hir_id, expr.span);
                 }
             },
             _ => {},
         }
     }
 }
+
+/// Heuristic checking if the node `hir_id` is under a `#[cfg()]` or `#[cfg_attr()]`
+/// attribute.
+fn is_under_cfg_attribute(cx: &LateContext<'_>, hir_id: HirId) -> bool {
+    cx.tcx.hir_parent_id_iter(hir_id).any(|id| {
+        cx.tcx.hir_attrs(id).iter().any(|attr| {
+            matches!(
+                attr.ident().map(|ident| ident.name),
+                Some(sym::cfg_trace | sym::cfg_attr_trace)
+            )
+        })
+    })
+}

tests/ui-toml/check_incompatible_msrv_in_tests/check_incompatible_msrv_in_tests.enabled.stderr

@@ -18,6 +18,8 @@ error: current MSRV (Minimum Supported Rust Version) is `1.3.0` but this item is
    |
 LL |         sleep(Duration::new(1, 0));
    |         ^^^^^
+   |
+   = note: you may want to conditionally increase the MSRV considered by Clippy using the `clippy::msrv` attribute
 
 error: aborting due to 3 previous errors
 

tests/ui/checked_conversions.fixed

@@ -95,7 +95,7 @@ pub const fn issue_8898(i: u32) -> bool {
 #[clippy::msrv = "1.33"]
 fn msrv_1_33() {
     let value: i64 = 33;
-    let _ = value <= (u32::MAX as i64) && value >= 0;
+    let _ = value <= (u32::max_value() as i64) && value >= 0;
 }
 
 #[clippy::msrv = "1.34"]

tests/ui/checked_conversions.rs

@@ -95,13 +95,13 @@ pub const fn issue_8898(i: u32) -> bool {
 #[clippy::msrv = "1.33"]
 fn msrv_1_33() {
     let value: i64 = 33;
-    let _ = value <= (u32::MAX as i64) && value >= 0;
+    let _ = value <= (u32::max_value() as i64) && value >= 0;
 }
 
 #[clippy::msrv = "1.34"]
 fn msrv_1_34() {
     let value: i64 = 34;
-    let _ = value <= (u32::MAX as i64) && value >= 0;
+    let _ = value <= (u32::max_value() as i64) && value >= 0;
     //~^ checked_conversions
 }
 

tests/ui/checked_conversions.stderr

@@ -100,8 +100,8 @@ LL |     let _ = value <= u16::MAX as u32 && value as i32 == 5;
 error: checked cast can be simplified
   --> tests/ui/checked_conversions.rs:104:13
    |
-LL |     let _ = value <= (u32::MAX as i64) && value >= 0;
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `u32::try_from(value).is_ok()`
+LL |     let _ = value <= (u32::max_value() as i64) && value >= 0;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `u32::try_from(value).is_ok()`
 
 error: aborting due to 17 previous errors
 

tests/ui/incompatible_msrv.rs

@@ -1,6 +1,7 @@
 #![warn(clippy::incompatible_msrv)]
 #![feature(custom_inner_attributes)]
-#![feature(panic_internals)]
+#![allow(stable_features)]
+#![feature(strict_provenance)] // For use in test
 #![clippy::msrv = "1.3.0"]
 
 use std::collections::HashMap;
@@ -13,6 +14,8 @@ fn foo() {
     let mut map: HashMap<&str, u32> = HashMap::new();
     assert_eq!(map.entry("poneyland").key(), &"poneyland");
     //~^ incompatible_msrv
+    //~| NOTE: `-D clippy::incompatible-msrv` implied by `-D warnings`
+    //~| HELP: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
 
     if let Entry::Vacant(v) = map.entry("poneyland") {
         v.into_key();
@@ -43,21 +46,22 @@ fn core_special_treatment(p: bool) {
 
     // But still lint code calling `core` functions directly
     if p {
-        core::panicking::panic("foo");
-        //~^ ERROR: is `1.3.0` but this item is stable since `1.6.0`
+        let _ = core::iter::once_with(|| 0);
+        //~^ incompatible_msrv
     }
 
     // Lint code calling `core` from non-`core` macros
     macro_rules! my_panic {
         ($msg:expr) => {
-            core::panicking::panic($msg)
-        }; //~^ ERROR: is `1.3.0` but this item is stable since `1.6.0`
+            let _ = core::iter::once_with(|| $msg);
+            //~^ incompatible_msrv
+        };
     }
     my_panic!("foo");
 
     // Lint even when the macro comes from `core` and calls `core` functions
-    assert!(core::panicking::panic("out of luck"));
-    //~^ ERROR: is `1.3.0` but this item is stable since `1.6.0`
+    assert!(core::iter::once_with(|| 0).next().is_some());
+    //~^ incompatible_msrv
 }
 
 #[clippy::msrv = "1.26.0"]
@@ -70,7 +74,40 @@ fn lang_items() {
 #[clippy::msrv = "1.80.0"]
 fn issue14212() {
     let _ = std::iter::repeat_n((), 5);
-    //~^ ERROR: is `1.80.0` but this item is stable since `1.82.0`
+    //~^ incompatible_msrv
+}
+
+fn local_msrv_change_suggestion() {
+    let _ = std::iter::repeat_n((), 5);
+    //~^ incompatible_msrv
+
+    #[cfg(any(test, not(test)))]
+    {
+        let _ = std::iter::repeat_n((), 5);
+        //~^ incompatible_msrv
+        //~| NOTE: you may want to conditionally increase the MSRV
+
+        // Emit the additional note only once
+        let _ = std::iter::repeat_n((), 5);
+        //~^ incompatible_msrv
+    }
+}
+
+#[clippy::msrv = "1.78.0"]
+fn feature_enable_14425(ptr: *const u8) -> usize {
+    // Do not warn, because it is enabled through a feature even though
+    // it is stabilized only since Rust 1.84.0.
+    let r = ptr.addr();
+
+    // Warn about this which has been introduced in the same Rust version
+    // but is not allowed through a feature.
+    r.isqrt()
+    //~^ incompatible_msrv
+}
+
+fn non_fn_items() {
+    let _ = std::io::ErrorKind::CrossesDevices;
+    //~^ incompatible_msrv
 }
 
 fn main() {}