Auto merge of #12617 - y21:issue-12616, r=Alexendoo

avoid an ICE in `ptr_as_ptr` when getting the def_id of a local

Fixes #12616

`Res::def_id` can panic, so avoid calling it in favor of `opt_def_id`, so we can gracefully handle resolutions that don't have a `DefId` (e.g. local variables) and get a false negative in the worst case, rather than an ICE

changelog: Fix ICE in [`ptr_as_ptr`] when the cast expression is a function call to a local variable

Author: bors

Diff for: clippy_lints/src/casts/ptr_as_ptr.rs

@@ -62,8 +62,8 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, msrv: &Msrv) {
         // we omit following `cast`:
         let omit_cast = if let ExprKind::Call(func, []) = cast_expr.kind
             && let ExprKind::Path(ref qpath @ QPath::Resolved(None, path)) = func.kind
+            && let Some(method_defid) = path.res.opt_def_id()
         {
-            let method_defid = path.res.def_id();
             if cx.tcx.is_diagnostic_item(sym::ptr_null, method_defid) {
                 OmitFollowedCastReason::Null(qpath)
             } else if cx.tcx.is_diagnostic_item(sym::ptr_null_mut, method_defid) {

Diff for: tests/ui/crashes/ice-12616.fixed

@@ -0,0 +1,7 @@
+#![warn(clippy::ptr_as_ptr)]
+#![allow(clippy::unnecessary_operation, clippy::unnecessary_cast)]
+
+fn main() {
+    let s = std::ptr::null::<()>;
+    s().cast::<()>();
+}

Diff for: tests/ui/crashes/ice-12616.rs

@@ -0,0 +1,7 @@
+#![warn(clippy::ptr_as_ptr)]
+#![allow(clippy::unnecessary_operation, clippy::unnecessary_cast)]
+
+fn main() {
+    let s = std::ptr::null::<()>;
+    s() as *const ();
+}

Diff for: tests/ui/crashes/ice-12616.stderr

@@ -0,0 +1,19 @@
+error: `as` casting between raw pointers without changing its mutability
+  --> tests/ui/crashes/ice-12616.rs:6:5
+   |
+LL |     s() as *const ();
+   |     ^^^^^^^^^^^^^^^^ help: try `pointer::cast`, a safer alternative: `s().cast::<()>()`
+   |
+   = note: `-D clippy::ptr-as-ptr` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::ptr_as_ptr)]`
+
+error: `as` casting between raw pointers without changing its mutability
+  --> tests/ui/crashes/ice-12616.rs:6:5
+   |
+LL |     s() as *const ();
+   |     ^^^^^^^^^^^^^^^^ help: try `pointer::cast`, a safer alternative: `s().cast::<()>()`
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 2 previous errors
+