incompatible_msrv: lint function calls with any argument count

The lint for function calls was previously restricted, without
documentation, to functions taking exactly one argument.

However, it is necessary to special case some macro expansions
from the standard library, namely `core`. Macros such as `panic!()`
or `assert_eq!()` exist since Rust 1.0.0, but modern compilers use
function introduced in later Rust versions in their expansion. While
it is desirable to lint code inside macros, using MSRV-incompatible
functions coming from `core` in macro expansions has been special-cased
to not trigger this lint to prevent false positives.

Author: samueltardieu

clippy_lints/src/incompatible_msrv.rs

@@ -9,7 +9,7 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::impl_lint_pass;
 use rustc_span::def_id::DefId;
-use rustc_span::{ExpnKind, Span};
+use rustc_span::{ExpnKind, Span, sym};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -95,6 +95,19 @@ impl IncompatibleMsrv {
             // Intentionally not using `.from_expansion()`, since we do still care about macro expansions
             return;
         }
+        // Functions coming from `core` while expanding a macro such as `assert*!()` get to cheat too: the
+        // macros may have existed prior to the checked MSRV, but their expansion with a recent compiler
+        // might use recent functions or methods. Compiling with an older compiler would not use those.
+        if span.from_expansion()
+            && cx.tcx.crate_name(def_id.krate) == sym::core
+            && span
+                .ctxt()
+                .outer_expn_data()
+                .macro_def_id
+                .is_some_and(|def_id| cx.tcx.crate_name(def_id.krate) == sym::core)
+        {
+            return;
+        }
         self.emit_lint_for(cx, span, version);
     }
 
@@ -125,7 +138,7 @@ impl<'tcx> LateLintPass<'tcx> for IncompatibleMsrv {
                     self.emit_lint_if_under_msrv(cx, method_did, expr.hir_id, span);
                 }
             },
-            ExprKind::Call(call, [_]) => {
+            ExprKind::Call(call, _) => {
                 if let ExprKind::Path(qpath) = call.kind
                     && let Some(path_def_id) = cx.qpath_res(&qpath, call.hir_id).opt_def_id()
                 {

tests/ui/incompatible_msrv.rs

@@ -1,5 +1,6 @@
 #![warn(clippy::incompatible_msrv)]
 #![feature(custom_inner_attributes)]
+#![feature(panic_internals)]
 #![clippy::msrv = "1.3.0"]
 
 use std::collections::HashMap;
@@ -33,4 +34,20 @@ async fn issue12273(v: impl Future<Output = ()>) {
     v.await;
 }
 
+fn core_special_treatment() {
+    panic!("foo"); // Do not lint
+    core::panicking::panic("foo");
+    //~^ ERROR: is `1.3.0` but this item is stable since `1.6.0`
+}
+
+#[clippy::msrv = "1.26.0"]
+fn lang_items() {
+    let _ = 1..=3;
+}
+
+#[clippy::msrv = "1.80.0"]
+fn issue14212() {
+    let _ = std::iter::repeat_n((), 5);
+}
+
 fn main() {}

tests/ui/incompatible_msrv.stderr

@@ -1,5 +1,5 @@
 error: current MSRV (Minimum Supported Rust Version) is `1.3.0` but this item is stable since `1.10.0`
-  --> tests/ui/incompatible_msrv.rs:13:39
+  --> tests/ui/incompatible_msrv.rs:14:39
    |
 LL |     assert_eq!(map.entry("poneyland").key(), &"poneyland");
    |                                       ^^^^^
@@ -8,16 +8,28 @@ LL |     assert_eq!(map.entry("poneyland").key(), &"poneyland");
    = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
 
 error: current MSRV (Minimum Supported Rust Version) is `1.3.0` but this item is stable since `1.12.0`
-  --> tests/ui/incompatible_msrv.rs:16:11
+  --> tests/ui/incompatible_msrv.rs:17:11
    |
 LL |         v.into_key();
    |           ^^^^^^^^^^
 
 error: current MSRV (Minimum Supported Rust Version) is `1.3.0` but this item is stable since `1.4.0`
-  --> tests/ui/incompatible_msrv.rs:20:5
+  --> tests/ui/incompatible_msrv.rs:21:5
    |
 LL |     sleep(Duration::new(1, 0));
    |     ^^^^^
 
-error: aborting due to 3 previous errors
+error: current MSRV (Minimum Supported Rust Version) is `1.3.0` but this item is stable since `1.6.0`
+  --> tests/ui/incompatible_msrv.rs:39:5
+   |
+LL |     core::panicking::panic("foo");
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error: current MSRV (Minimum Supported Rust Version) is `1.80.0` but this item is stable since `1.82.0`
+  --> tests/ui/incompatible_msrv.rs:50:13
+   |
+LL |     let _ = std::iter::repeat_n((), 5);
+   |             ^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors