Auto merge of rust-lang#13168 - Alexendoo:std-instead-of-core-msrv, r=Manishearth

Make `std_instead_of_core` somewhat MSRV aware

For rust-lang#13158, this catches some things e.g. `core::net` and the recently stable `core::error` but not things moved individually like `UnwindSafe`, as far as I can see the version for those isn't easily available

Beta nominating since ideally we'd get this change in the same version as `core::error` becomes stable

cc `@kpreid`

changelog: none

Author: bors

src/tools/clippy/clippy_lints/src/lib.rs

@@ -1034,7 +1034,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
             allow_comparison_to_zero,
         ))
     });
-    store.register_late_pass(|_| Box::<std_instead_of_core::StdReexports>::default());
+    store.register_late_pass(move |_| Box::new(std_instead_of_core::StdReexports::new(conf)));
     store.register_late_pass(move |_| Box::new(instant_subtraction::InstantSubtraction::new(msrv())));
     store.register_late_pass(|_| Box::new(partialeq_to_none::PartialeqToNone));
     store.register_late_pass(move |_| Box::new(manual_clamp::ManualClamp::new(msrv())));

src/tools/clippy/clippy_lints/src/std_instead_of_core.rs

@@ -1,11 +1,15 @@
+use clippy_config::msrvs::Msrv;
+use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::is_from_proc_macro;
+use rustc_attr::{StabilityLevel, StableSince};
 use rustc_errors::Applicability;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{HirId, Path, PathSegment};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
+use rustc_semver::RustcVersion;
 use rustc_session::impl_lint_pass;
 use rustc_span::symbol::kw;
 use rustc_span::{sym, Span};
@@ -66,6 +70,10 @@ declare_clippy_lint! {
     /// imported from core to ensure disabling `alloc` does not cause the crate to fail to compile. This lint
     /// is also useful for crates migrating to become `no_std` compatible.
     ///
+    /// ### Known problems
+    /// The lint is only partially aware of the required MSRV for items that were originally in `std` but moved
+    /// to `core`.
+    ///
     /// ### Example
     /// ```no_run
     /// # extern crate alloc;
@@ -81,20 +89,30 @@ declare_clippy_lint! {
     "type is imported from alloc when available in core"
 }
 
-#[derive(Default)]
 pub struct StdReexports {
     // Paths which can be either a module or a macro (e.g. `std::env`) will cause this check to happen
     // twice. First for the mod, second for the macro. This is used to avoid the lint reporting for the macro
     // when the path could be also be used to access the module.
     prev_span: Span,
+    msrv: Msrv,
+}
+
+impl StdReexports {
+    pub fn new(conf: &'static Conf) -> Self {
+        Self {
+            prev_span: Span::default(),
+            msrv: conf.msrv.clone(),
+        }
+    }
 }
+
 impl_lint_pass!(StdReexports => [STD_INSTEAD_OF_CORE, STD_INSTEAD_OF_ALLOC, ALLOC_INSTEAD_OF_CORE]);
 
 impl<'tcx> LateLintPass<'tcx> for StdReexports {
     fn check_path(&mut self, cx: &LateContext<'tcx>, path: &Path<'tcx>, _: HirId) {
         if let Res::Def(_, def_id) = path.res
             && let Some(first_segment) = get_first_segment(path)
-            && is_stable(cx, def_id)
+            && is_stable(cx, def_id, &self.msrv)
             && !in_external_macro(cx.sess(), path.span)
             && !is_from_proc_macro(cx, &first_segment.ident)
         {
@@ -131,6 +149,8 @@ impl<'tcx> LateLintPass<'tcx> for StdReexports {
             }
         }
     }
+
+    extract_msrv_attr!(LateContext);
 }
 
 /// Returns the first named segment of a [`Path`].
@@ -146,16 +166,29 @@ fn get_first_segment<'tcx>(path: &Path<'tcx>) -> Option<&'tcx PathSegment<'tcx>>
     }
 }
 
-/// Checks if all ancestors of `def_id` are stable, to avoid linting
-/// [unstable moves](https://github.com/rust-lang/rust/pull/95956)
-fn is_stable(cx: &LateContext<'_>, mut def_id: DefId) -> bool {
+/// Checks if all ancestors of `def_id` meet `msrv` to avoid linting [unstable moves](https://github.com/rust-lang/rust/pull/95956)
+/// or now stable moves that were once unstable.
+///
+/// Does not catch individually moved items
+fn is_stable(cx: &LateContext<'_>, mut def_id: DefId, msrv: &Msrv) -> bool {
     loop {
-        if cx
-            .tcx
-            .lookup_stability(def_id)
-            .map_or(false, |stability| stability.is_unstable())
+        if let Some(stability) = cx.tcx.lookup_stability(def_id)
+            && let StabilityLevel::Stable {
+                since,
+                allowed_through_unstable_modules: false,
+            } = stability.level
         {
-            return false;
+            let stable = match since {
+                StableSince::Version(v) => {
+                    msrv.meets(RustcVersion::new(v.major.into(), v.minor.into(), v.patch.into()))
+                },
+                StableSince::Current => msrv.current().is_none(),
+                StableSince::Err => false,
+            };
+
+            if !stable {
+                return false;
+            }
         }
 
         match cx.tcx.opt_parent(def_id) {

src/tools/clippy/tests/ui/std_instead_of_core.fixed

@@ -75,8 +75,17 @@ mod std_in_proc_macro_derive {
     struct B {}
 }
 
-fn main() {
-    std_instead_of_core();
-    std_instead_of_alloc();
-    alloc_instead_of_core();
+// Some intrinsics are usable on stable but live in an unstable module, but should still suggest
+// replacing std -> core
+fn intrinsic(a: *mut u8, b: *mut u8) {
+    unsafe {
+        core::intrinsics::copy(a, b, 1);
+        //~^ std_instead_of_core
+    }
 }
+
+#[clippy::msrv = "1.76"]
+fn msrv_1_76(_: std::net::IpAddr) {}
+
+#[clippy::msrv = "1.77"]
+fn msrv_1_77(_: core::net::IpAddr) {}

src/tools/clippy/tests/ui/std_instead_of_core.rs

@@ -75,8 +75,17 @@ mod std_in_proc_macro_derive {
     struct B {}
 }
 
-fn main() {
-    std_instead_of_core();
-    std_instead_of_alloc();
-    alloc_instead_of_core();
+// Some intrinsics are usable on stable but live in an unstable module, but should still suggest
+// replacing std -> core
+fn intrinsic(a: *mut u8, b: *mut u8) {
+    unsafe {
+        std::intrinsics::copy(a, b, 1);
+        //~^ std_instead_of_core
+    }
 }
+
+#[clippy::msrv = "1.76"]
+fn msrv_1_76(_: std::net::IpAddr) {}
+
+#[clippy::msrv = "1.77"]
+fn msrv_1_77(_: std::net::IpAddr) {}

src/tools/clippy/tests/ui/std_instead_of_core.stderr

@@ -85,5 +85,17 @@ LL |     use alloc::slice::from_ref;
    = note: `-D clippy::alloc-instead-of-core` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::alloc_instead_of_core)]`
 
-error: aborting due to 13 previous errors
+error: used import from `std` instead of `core`
+  --> tests/ui/std_instead_of_core.rs:82:9
+   |
+LL |         std::intrinsics::copy(a, b, 1);
+   |         ^^^ help: consider importing the item from `core`: `core`
+
+error: used import from `std` instead of `core`
+  --> tests/ui/std_instead_of_core.rs:91:17
+   |
+LL | fn msrv_1_77(_: std::net::IpAddr) {}
+   |                 ^^^ help: consider importing the item from `core`: `core`
+
+error: aborting due to 15 previous errors