Lint more cases of ptr::eq()

Also, do not strip conversions of a function pointer to a `*const`, as
no implicit conversion will take place.

Author: samueltardieu

clippy_lints/src/operators/ptr_eq.rs

@@ -4,6 +4,7 @@ use clippy_utils::std_or_core;
 use rustc_errors::Applicability;
 use rustc_hir::{BinOpKind, Expr, ExprKind};
 use rustc_lint::LateContext;
+use rustc_middle::ty::{self, Ty};
 
 use super::PTR_EQ;
 
@@ -15,14 +16,21 @@ pub(super) fn check<'tcx>(
     right: &'tcx Expr<'_>,
 ) {
     if BinOpKind::Eq == op {
+        // Remove one level of usize conversion if any
         let (left, right) = match (expr_as_cast_to_usize(cx, left), expr_as_cast_to_usize(cx, right)) {
             (Some(lhs), Some(rhs)) => (lhs, rhs),
             _ => (left, right),
         };
 
-        if let Some(left_var) = expr_as_cast_to_raw_pointer(cx, left)
-            && let Some(right_var) = expr_as_cast_to_raw_pointer(cx, right)
-            && let Some(left_snip) = left_var.span.get_source_text(cx)
+        // This lint concerns raw pointers
+        let (left_ty, right_ty) = (cx.typeck_results().expr_ty(left), cx.typeck_results().expr_ty(right));
+        if !left_ty.is_raw_ptr() || !right_ty.is_raw_ptr() {
+            return;
+        }
+
+        let (left_var, right_var) = (peel_raw_casts(cx, left, left_ty), peel_raw_casts(cx, right, right_ty));
+
+        if let Some(left_snip) = left_var.span.get_source_text(cx)
             && let Some(right_snip) = right_var.span.get_source_text(cx)
         {
             let Some(top_crate) = std_or_core(cx) else { return };
@@ -50,13 +58,16 @@ fn expr_as_cast_to_usize<'tcx>(cx: &LateContext<'tcx>, cast_expr: &'tcx Expr<'_>
     None
 }
 
-// If the given expression is a cast to a `*const` pointer, return the lhs of the cast
-// E.g., `foo as *const _` returns `foo`.
-fn expr_as_cast_to_raw_pointer<'tcx>(cx: &LateContext<'tcx>, cast_expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
-    if cx.typeck_results().expr_ty(cast_expr).is_raw_ptr() {
-        if let ExprKind::Cast(expr, _) = cast_expr.kind {
-            return Some(expr);
-        }
+// Peel raw casts if the remaining expression can be coerced to it
+fn peel_raw_casts<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, expr_ty: Ty<'tcx>) -> &'tcx Expr<'tcx> {
+    if let ExprKind::Cast(inner, _) = expr.kind
+        && let ty::RawPtr(target_ty, _) = expr_ty.kind()
+        && let inner_ty = cx.typeck_results().expr_ty(inner)
+        && let ty::RawPtr(inner_target_ty, _) | ty::Ref(_, inner_target_ty, _) = inner_ty.kind()
+        && target_ty == inner_target_ty
+    {
+        peel_raw_casts(cx, inner, inner_ty)
+    } else {
+        expr
     }
-    None
 }

tests/ui/ptr_eq.fixed

@@ -20,8 +20,10 @@ fn main() {
     //~^ ptr_eq
     let _ = std::ptr::eq(a, b);
     //~^ ptr_eq
-    let _ = a.as_ptr() == b as *const _;
-    let _ = a.as_ptr() == b.as_ptr();
+    let _ = std::ptr::eq(a.as_ptr(), b as *const _);
+    //~^ ptr_eq
+    let _ = std::ptr::eq(a.as_ptr(), b.as_ptr());
+    //~^ ptr_eq
 
     // Do not lint
 
@@ -31,9 +33,19 @@ fn main() {
     let a = &mut [1, 2, 3];
     let b = &mut [1, 2, 3];
 
-    let _ = a.as_mut_ptr() == b as *mut [i32] as *mut _;
-    let _ = a.as_mut_ptr() == b.as_mut_ptr();
+    let _ = std::ptr::eq(a.as_mut_ptr(), b as *mut [i32] as *mut _);
+    //~^ ptr_eq
+    let _ = std::ptr::eq(a.as_mut_ptr(), b.as_mut_ptr());
+    //~^ ptr_eq
 
     let _ = a == b;
     let _ = core::ptr::eq(a, b);
+
+    let (x, y) = (&0u32, &mut 1u32);
+    let _ = std::ptr::eq(x, y);
+    //~^ ptr_eq
+
+    #[allow(clippy::eq_op)]
+    let _issue14337 = std::ptr::eq(main as *const (), main as *const ());
+    //~^ ptr_eq
 }

tests/ui/ptr_eq.rs

@@ -21,7 +21,9 @@ fn main() {
     let _ = a as *const _ == b as *const _;
     //~^ ptr_eq
     let _ = a.as_ptr() == b as *const _;
+    //~^ ptr_eq
     let _ = a.as_ptr() == b.as_ptr();
+    //~^ ptr_eq
 
     // Do not lint
 
@@ -32,8 +34,18 @@ fn main() {
     let b = &mut [1, 2, 3];
 
     let _ = a.as_mut_ptr() == b as *mut [i32] as *mut _;
+    //~^ ptr_eq
     let _ = a.as_mut_ptr() == b.as_mut_ptr();
+    //~^ ptr_eq
 
     let _ = a == b;
     let _ = core::ptr::eq(a, b);
+
+    let (x, y) = (&0u32, &mut 1u32);
+    let _ = x as *const u32 == y as *mut u32 as *const u32;
+    //~^ ptr_eq
+
+    #[allow(clippy::eq_op)]
+    let _issue14337 = main as *const () == main as *const ();
+    //~^ ptr_eq
 }

tests/ui/ptr_eq.stderr

@@ -13,5 +13,41 @@ error: use `std::ptr::eq` when comparing raw pointers
 LL |     let _ = a as *const _ == b as *const _;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a, b)`
 
-error: aborting due to 2 previous errors
+error: use `std::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq.rs:23:13
+   |
+LL |     let _ = a.as_ptr() == b as *const _;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a.as_ptr(), b as *const _)`
+
+error: use `std::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq.rs:25:13
+   |
+LL |     let _ = a.as_ptr() == b.as_ptr();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a.as_ptr(), b.as_ptr())`
+
+error: use `std::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq.rs:36:13
+   |
+LL |     let _ = a.as_mut_ptr() == b as *mut [i32] as *mut _;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a.as_mut_ptr(), b as *mut [i32] as *mut _)`
+
+error: use `std::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq.rs:38:13
+   |
+LL |     let _ = a.as_mut_ptr() == b.as_mut_ptr();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a.as_mut_ptr(), b.as_mut_ptr())`
+
+error: use `std::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq.rs:45:13
+   |
+LL |     let _ = x as *const u32 == y as *mut u32 as *const u32;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(x, y)`
+
+error: use `std::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq.rs:49:23
+   |
+LL |     let _issue14337 = main as *const () == main as *const ();
+   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(main as *const (), main as *const ())`
+
+error: aborting due to 8 previous errors
 

tests/ui/ptr_eq_no_std.fixed

@@ -32,8 +32,10 @@ fn main() {
     //~^ ptr_eq
     let _ = core::ptr::eq(a, b);
     //~^ ptr_eq
-    let _ = a.as_ptr() == b as *const _;
-    let _ = a.as_ptr() == b.as_ptr();
+    let _ = core::ptr::eq(a.as_ptr(), b as *const _);
+    //~^ ptr_eq
+    let _ = core::ptr::eq(a.as_ptr(), b.as_ptr());
+    //~^ ptr_eq
 
     // Do not lint
 
@@ -43,8 +45,10 @@ fn main() {
     let a = &mut [1, 2, 3];
     let b = &mut [1, 2, 3];
 
-    let _ = a.as_mut_ptr() == b as *mut [i32] as *mut _;
-    let _ = a.as_mut_ptr() == b.as_mut_ptr();
+    let _ = core::ptr::eq(a.as_mut_ptr(), b as *mut [i32] as *mut _);
+    //~^ ptr_eq
+    let _ = core::ptr::eq(a.as_mut_ptr(), b.as_mut_ptr());
+    //~^ ptr_eq
 
     let _ = a == b;
     let _ = core::ptr::eq(a, b);

tests/ui/ptr_eq_no_std.rs

@@ -33,7 +33,9 @@ fn main() {
     let _ = a as *const _ == b as *const _;
     //~^ ptr_eq
     let _ = a.as_ptr() == b as *const _;
+    //~^ ptr_eq
     let _ = a.as_ptr() == b.as_ptr();
+    //~^ ptr_eq
 
     // Do not lint
 
@@ -44,7 +46,9 @@ fn main() {
     let b = &mut [1, 2, 3];
 
     let _ = a.as_mut_ptr() == b as *mut [i32] as *mut _;
+    //~^ ptr_eq
     let _ = a.as_mut_ptr() == b.as_mut_ptr();
+    //~^ ptr_eq
 
     let _ = a == b;
     let _ = core::ptr::eq(a, b);

tests/ui/ptr_eq_no_std.stderr

@@ -13,5 +13,29 @@ error: use `core::ptr::eq` when comparing raw pointers
 LL |     let _ = a as *const _ == b as *const _;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `core::ptr::eq(a, b)`
 
-error: aborting due to 2 previous errors
+error: use `core::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq_no_std.rs:35:13
+   |
+LL |     let _ = a.as_ptr() == b as *const _;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `core::ptr::eq(a.as_ptr(), b as *const _)`
+
+error: use `core::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq_no_std.rs:37:13
+   |
+LL |     let _ = a.as_ptr() == b.as_ptr();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `core::ptr::eq(a.as_ptr(), b.as_ptr())`
+
+error: use `core::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq_no_std.rs:48:13
+   |
+LL |     let _ = a.as_mut_ptr() == b as *mut [i32] as *mut _;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `core::ptr::eq(a.as_mut_ptr(), b as *mut [i32] as *mut _)`
+
+error: use `core::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq_no_std.rs:50:13
+   |
+LL |     let _ = a.as_mut_ptr() == b.as_mut_ptr();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `core::ptr::eq(a.as_mut_ptr(), b.as_mut_ptr())`
+
+error: aborting due to 6 previous errors