ptr_as_ptr: move to if (#15480)

changelog: none

Author: samueltardieu

clippy_lints/src/casts/mod.rs

@@ -875,6 +875,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
             cast_slice_from_raw_parts::check(cx, expr, cast_from_expr, cast_to, self.msrv);
             cast_ptr_alignment::check(cx, expr, cast_from, cast_to);
             ptr_cast_constness::check(cx, expr, cast_from_expr, cast_from, cast_to, self.msrv);
+            ptr_as_ptr::check(cx, expr, cast_from_expr, cast_from, cast_to_hir, cast_to, self.msrv);
             as_ptr_cast_mut::check(cx, expr, cast_from_expr, cast_to);
             fn_to_numeric_cast_any::check(cx, expr, cast_from_expr, cast_from, cast_to);
             confusing_method_to_numeric_cast::check(cx, expr, cast_from_expr, cast_from, cast_to);
@@ -916,7 +917,6 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
             cast_slice_from_raw_parts::check_implicit_cast(cx, expr);
         }
         cast_ptr_alignment::check_cast_method(cx, expr);
-        ptr_as_ptr::check(cx, expr, self.msrv);
         cast_slice_different_sizes::check(cx, expr, self.msrv);
         ptr_cast_constness::check_null_ptr_cast_method(cx, expr);
     }

clippy_lints/src/casts/ptr_as_ptr.rs

@@ -4,9 +4,9 @@ use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::sugg::Sugg;
 use rustc_errors::Applicability;
-use rustc_hir::{Expr, ExprKind, Mutability, QPath, TyKind};
+use rustc_hir::{self as hir, Expr, ExprKind, QPath, TyKind};
 use rustc_lint::LateContext;
-use rustc_middle::ty;
+use rustc_middle::ty::{self, Ty};
 use rustc_span::{Span, sym};
 
 use super::PTR_AS_PTR;
@@ -26,21 +26,26 @@ impl OmitFollowedCastReason<'_> {
     }
 }
 
-pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>, msrv: Msrv) {
-    if let ExprKind::Cast(cast_expr, cast_to_hir_ty) = expr.kind
-        && let (cast_from, cast_to) = (cx.typeck_results().expr_ty(cast_expr), cx.typeck_results().expr_ty(expr))
-        && let ty::RawPtr(_, from_mutbl) = cast_from.kind()
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &Expr<'tcx>,
+    cast_from_expr: &Expr<'_>,
+    cast_from: Ty<'_>,
+    cast_to_hir: &hir::Ty<'_>,
+    cast_to: Ty<'tcx>,
+    msrv: Msrv,
+) {
+    if let ty::RawPtr(_, from_mutbl) = cast_from.kind()
         && let ty::RawPtr(to_pointee_ty, to_mutbl) = cast_to.kind()
-        && matches!((from_mutbl, to_mutbl),
-            (Mutability::Not, Mutability::Not) | (Mutability::Mut, Mutability::Mut))
+        && from_mutbl == to_mutbl
         // The `U` in `pointer::cast` have to be `Sized`
         // as explained here: https://github.com/rust-lang/rust/issues/60602.
         && to_pointee_ty.is_sized(cx.tcx, cx.typing_env())
         && msrv.meets(cx, msrvs::POINTER_CAST)
         && !is_from_proc_macro(cx, expr)
     {
         let mut app = Applicability::MachineApplicable;
-        let turbofish = match &cast_to_hir_ty.kind {
+        let turbofish = match &cast_to_hir.kind {
             TyKind::Infer(()) => String::new(),
             TyKind::Ptr(mut_ty) => {
                 if matches!(mut_ty.ty.kind, TyKind::Infer(())) {
@@ -58,7 +63,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>, msrv: Msrv)
         // following `cast` does not compile because it fails to infer what type is expected
         // as type argument to `std::ptr::ptr_null` or `std::ptr::ptr_null_mut`, so
         // we omit following `cast`:
-        let omit_cast = if let ExprKind::Call(func, []) = cast_expr.kind
+        let omit_cast = if let ExprKind::Call(func, []) = cast_from_expr.kind
             && let ExprKind::Path(ref qpath @ QPath::Resolved(None, path)) = func.kind
             && let Some(method_defid) = path.res.opt_def_id()
         {
@@ -76,7 +81,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>, msrv: Msrv)
             let method = snippet_with_applicability(cx, qpath_span_without_turbofish(method), "..", &mut app);
             ("try call directly", format!("{method}{turbofish}()"))
         } else {
-            let cast_expr_sugg = Sugg::hir_with_context(cx, cast_expr, expr.span.ctxt(), "_", &mut app);
+            let cast_expr_sugg = Sugg::hir_with_context(cx, cast_from_expr, expr.span.ctxt(), "_", &mut app);
 
             (
                 "try `pointer::cast`, a safer alternative",