Auto merge of #7396 - ranweiler:zero-offset, r=Manishearth

Fix invocation of `zst_offset` lint

The `zst_offset` lint was broken by a refactoring regression in 21083875d211c29fcfa4a21fcd66d4601d2b618b. In the invocation of the `zst_offset` check [here](https://github.com/rust-lang/rust-clippy/commit/21083875d211c29fcfa4a21fcd66d4601d2b618b#diff-7f73f6fe28c04b654223c09c42fe02937d2351fc58a91d21ab812aaf6f9b185dR1927), we shadow the already-destructured receiver `recv`, and accidentally pass the first argument of the method as if it were the receiver.

This was not caught because the UI test expectation was never correct (a bad cast obscured the actual test result).

This PR:
- Fixes the existing test expectation
- Tests both `const` and `mut` raw pointers
- Passes the actual receiver to the lint's implementation

Fixes #7395.

changelog: Fix [`zst_offset`] invocation and test

3 files changed, 63 insertions, 14 deletions

diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index c6bef7bc5d5..21585543b0a 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -2036,7 +2036,7 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
 fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Option<&RustcVersion>) {
     if let Some((name, [recv, args @ ..], span)) = method_call!(expr) {
         match (name, args) {
-            ("add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub", [recv, _]) => {
+            ("add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub", [_arg]) => {
                 zst_offset::check(cx, expr, recv);
             },
             ("and_then", [arg]) => {
diff --git a/tests/ui/zero_offset.rs b/tests/ui/zero_offset.rs
index 2de904376ad..6c190a4c86c 100644
--- a/tests/ui/zero_offset.rs
+++ b/tests/ui/zero_offset.rs
@@ -1,12 +1,18 @@
 fn main() {
     unsafe {
-        let x = &() as *const ();
-        x.offset(0);
-        x.wrapping_add(0);
-        x.sub(0);
-        x.wrapping_sub(0);
+        let m = &mut () as *mut ();
+        m.offset(0);
+        m.wrapping_add(0);
+        m.sub(0);
+        m.wrapping_sub(0);
 
-        let y = &1 as *const u8;
-        y.offset(0);
+        let c = &() as *const ();
+        c.offset(0);
+        c.wrapping_add(0);
+        c.sub(0);
+        c.wrapping_sub(0);
+
+        let sized = &1 as *const i32;
+        sized.offset(0);
     }
 }
diff --git a/tests/ui/zero_offset.stderr b/tests/ui/zero_offset.stderr
index cfcd7de2b3d..b12c8e9a73c 100644
--- a/tests/ui/zero_offset.stderr
+++ b/tests/ui/zero_offset.stderr
@@ -1,9 +1,52 @@
-error[E0606]: casting `&i32` as `*const u8` is invalid
-  --> $DIR/zero_offset.rs:9:17
+error: offset calculation on zero-sized value
+  --> $DIR/zero_offset.rs:4:9
    |
-LL |         let y = &1 as *const u8;
-   |                 ^^^^^^^^^^^^^^^
+LL |         m.offset(0);
+   |         ^^^^^^^^^^^
+   |
+   = note: `#[deny(clippy::zst_offset)]` on by default
+
+error: offset calculation on zero-sized value
+  --> $DIR/zero_offset.rs:5:9
+   |
+LL |         m.wrapping_add(0);
+   |         ^^^^^^^^^^^^^^^^^
+
+error: offset calculation on zero-sized value
+  --> $DIR/zero_offset.rs:6:9
+   |
+LL |         m.sub(0);
+   |         ^^^^^^^^
+
+error: offset calculation on zero-sized value
+  --> $DIR/zero_offset.rs:7:9
+   |
+LL |         m.wrapping_sub(0);
+   |         ^^^^^^^^^^^^^^^^^
+
+error: offset calculation on zero-sized value
+  --> $DIR/zero_offset.rs:10:9
+   |
+LL |         c.offset(0);
+   |         ^^^^^^^^^^^
+
+error: offset calculation on zero-sized value
+  --> $DIR/zero_offset.rs:11:9
+   |
+LL |         c.wrapping_add(0);
+   |         ^^^^^^^^^^^^^^^^^
+
+error: offset calculation on zero-sized value
+  --> $DIR/zero_offset.rs:12:9
+   |
+LL |         c.sub(0);
+   |         ^^^^^^^^
+
+error: offset calculation on zero-sized value
+  --> $DIR/zero_offset.rs:13:9
+   |
+LL |         c.wrapping_sub(0);
+   |         ^^^^^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error: aborting due to 8 previous errors
 
-For more information about this error, try `rustc --explain E0606`.