Ensure that peeling does not recurse into macros (rust-lang#14527)

We do not want to remove casts done inside macros. Also, when printing
the suggestion, take it from the same context as the origin expression
(the root context).

Problems found while working on rust-lang#14526, but should be merged even if
rust-lang#14526 is not.

changelog: none

Author: Alexendoo

src/tools/clippy/clippy_lints/src/ptr.rs

@@ -799,8 +799,9 @@ fn check_ptr_eq<'tcx>(
 
     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 mut app = Applicability::MachineApplicable;
+    let left_snip = Sugg::hir_with_context(cx, left_var, expr.span.ctxt(), "_", &mut app);
+    let right_snip = Sugg::hir_with_context(cx, right_var, expr.span.ctxt(), "_", &mut app);
     {
         let Some(top_crate) = std_or_core(cx) else { return };
         let invert = if op == BinOpKind::Eq { "" } else { "!" };
@@ -811,15 +812,16 @@ fn check_ptr_eq<'tcx>(
             format!("use `{top_crate}::ptr::eq` when comparing raw pointers"),
             "try",
             format!("{invert}{top_crate}::ptr::eq({left_snip}, {right_snip})"),
-            Applicability::MachineApplicable,
+            app,
         );
     }
 }
 
 // If the given expression is a cast to a usize, return the lhs of the cast
 // E.g., `foo as *const _ as usize` returns `foo as *const _`.
 fn expr_as_cast_to_usize<'tcx>(cx: &LateContext<'tcx>, cast_expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
-    if cx.typeck_results().expr_ty(cast_expr) == cx.tcx.types.usize
+    if !cast_expr.span.from_expansion()
+        && cx.typeck_results().expr_ty(cast_expr) == cx.tcx.types.usize
         && let ExprKind::Cast(expr, _) = cast_expr.kind
     {
         Some(expr)
@@ -830,7 +832,8 @@ fn expr_as_cast_to_usize<'tcx>(cx: &LateContext<'tcx>, cast_expr: &'tcx 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
+    if !expr.span.from_expansion()
+        && 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()

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

@@ -4,6 +4,9 @@ macro_rules! mac {
     ($a:expr, $b:expr) => {
         $a as *const _ as usize == $b as *const _ as usize
     };
+    (cast $a:expr) => {
+        $a as *const [i32; 3]
+    };
 }
 
 macro_rules! another_mac {
@@ -51,4 +54,8 @@ fn main() {
     #[allow(clippy::eq_op)]
     let _issue14337 = std::ptr::eq(main as *const (), main as *const ());
     //~^ ptr_eq
+
+    // Do not peel the content of macros
+    let _ = std::ptr::eq(mac!(cast a), mac!(cast b));
+    //~^ ptr_eq
 }

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

@@ -4,6 +4,9 @@ macro_rules! mac {
     ($a:expr, $b:expr) => {
         $a as *const _ as usize == $b as *const _ as usize
     };
+    (cast $a:expr) => {
+        $a as *const [i32; 3]
+    };
 }
 
 macro_rules! another_mac {
@@ -51,4 +54,8 @@ fn main() {
     #[allow(clippy::eq_op)]
     let _issue14337 = main as *const () == main as *const ();
     //~^ ptr_eq
+
+    // Do not peel the content of macros
+    let _ = mac!(cast a) as *const _ == mac!(cast b) as *const _;
+    //~^ ptr_eq
 }

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

@@ -1,5 +1,5 @@
 error: use `std::ptr::eq` when comparing raw pointers
-  --> tests/ui/ptr_eq.rs:19:13
+  --> tests/ui/ptr_eq.rs:22:13
    |
 LL |     let _ = a as *const _ as usize == b as *const _ as usize;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a, b)`
@@ -8,52 +8,58 @@ LL |     let _ = a as *const _ as usize == b as *const _ as usize;
    = help: to override `-D warnings` add `#[allow(clippy::ptr_eq)]`
 
 error: use `std::ptr::eq` when comparing raw pointers
-  --> tests/ui/ptr_eq.rs:21:13
+  --> tests/ui/ptr_eq.rs:24:13
    |
 LL |     let _ = a as *const _ == b as *const _;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a, b)`
 
 error: use `std::ptr::eq` when comparing raw pointers
-  --> tests/ui/ptr_eq.rs:23:13
+  --> tests/ui/ptr_eq.rs:26:13
    |
 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
+  --> tests/ui/ptr_eq.rs:28:13
    |
 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
+  --> tests/ui/ptr_eq.rs:39:13
    |
 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
+  --> tests/ui/ptr_eq.rs:41:13
    |
 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
+  --> tests/ui/ptr_eq.rs:48:13
    |
 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:48:13
+  --> tests/ui/ptr_eq.rs:51:13
    |
 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:52:23
+  --> tests/ui/ptr_eq.rs:55:23
    |
 LL |     let _issue14337 = main as *const () == main as *const ();
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(main as *const (), main as *const ())`
 
-error: aborting due to 9 previous errors
+error: use `std::ptr::eq` when comparing raw pointers
+  --> tests/ui/ptr_eq.rs:59:13
+   |
+LL |     let _ = mac!(cast a) as *const _ == mac!(cast b) as *const _;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(mac!(cast a), mac!(cast b))`
+
+error: aborting due to 10 previous errors