manual_midpoint: support signed integer types as well

`midpoint()` for integer types has been stabilized in Rust 1.87.

Author: samueltardieu

clippy_lints/src/operators/manual_midpoint.rs

@@ -6,7 +6,7 @@ use rustc_ast::BinOpKind;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::LateContext;
-use rustc_middle::ty;
+use rustc_middle::ty::{self, Ty};
 
 use super::MANUAL_MIDPOINT;
 
@@ -18,8 +18,7 @@ pub(super) fn check<'tcx>(
     right: &'tcx Expr<'_>,
     msrv: &Msrv,
 ) {
-    if msrv.meets(msrvs::UINT_FLOAT_MIDPOINT)
-        && !left.span.from_expansion()
+    if !left.span.from_expansion()
         && !right.span.from_expansion()
         && op == BinOpKind::Div
         && (is_integer_literal(right, 2) || is_float_literal(right, 2.0))
@@ -30,8 +29,7 @@ pub(super) fn check<'tcx>(
         && left_ty == right_ty
         // Do not lint on `(_+1)/2` and `(1+_)/2`, it is likely a `div_ceil()` operation
         && !is_integer_literal(ll_expr, 1) && !is_integer_literal(lr_expr, 1)
-        // FIXME: Also lint on signed integers when rust-lang/rust#134340 is merged
-        && matches!(left_ty.kind(), ty::Uint(_) | ty::Float(_))
+        && is_midpoint_implemented(left_ty, msrv)
     {
         let mut app = Applicability::MachineApplicable;
         let left_sugg = Sugg::hir_with_context(cx, ll_expr, expr.span.ctxt(), "..", &mut app);
@@ -56,3 +54,11 @@ fn add_operands<'e, 'tcx>(expr: &'e Expr<'tcx>) -> Option<(&'e Expr<'tcx>, &'e E
         _ => None,
     }
 }
+
+fn is_midpoint_implemented(ty: Ty<'_>, msrv: &Msrv) -> bool {
+    match ty.kind() {
+        ty::Uint(_) | ty::Float(_) => msrv.meets(msrvs::UINT_FLOAT_MIDPOINT),
+        ty::Int(_) => msrv.meets(msrvs::INT_MIDPOINT),
+        _ => false,
+    }
+}

clippy_utils/src/msrvs.rs

@@ -19,6 +19,7 @@ macro_rules! msrv_aliases {
 
 // names may refer to stabilized feature flags or library items
 msrv_aliases! {
+    1,87,0 { INT_MIDPOINT }
     1,85,0 { UINT_FLOAT_MIDPOINT }
     1,84,0 { CONST_OPTION_AS_SLICE }
     1,83,0 { CONST_EXTERN_FN, CONST_FLOAT_BITS_CONV, CONST_FLOAT_CLASSIFY, CONST_MUT_REFS, CONST_UNWRAP }

tests/ui/manual_midpoint.rs

@@ -61,3 +61,14 @@ fn main() {
     let _ = (f + 1.0) / 2.0; //~ ERROR: manual implementation of `midpoint`
     let _ = (1.0 + f) / 2.0; //~ ERROR: manual implementation of `midpoint`
 }
+
+#[clippy::msrv = "1.86"]
+fn older_signed_midpoint(i: i32) {
+    // Do not lint
+    let _ = (i + 10) / 2;
+}
+
+#[clippy::msrv = "1.87"]
+fn signed_midpoint(i: i32) {
+    let _ = (i + 10) / 2; //~ ERROR: manual implementation of `midpoint`
+}