Rollup merge of #94315 - lcnr:auto-trait-lint-update, r=oli-obk

update auto trait lint for `PhantomData`

cc #93367 (comment)

Author: Manishearth

compiler/rustc_typeck/src/coherence/orphan.rs

@@ -439,6 +439,7 @@ fn fast_reject_auto_impl<'tcx>(tcx: TyCtxt<'tcx>, trait_def_id: DefId, self_ty:
             }
 
             match t.kind() {
+                ty::Adt(def, substs) if def.is_phantom_data() => substs.super_visit_with(self),
                 ty::Adt(def, substs) => {
                     // @lcnr: This is the only place where cycles can happen. We avoid this
                     // by only visiting each `DefId` once.

src/test/ui/auto-traits/suspicious-impls-lint.rs

@@ -1,5 +1,7 @@
 #![deny(suspicious_auto_trait_impls)]
 
+use std::marker::PhantomData;
+
 struct MayImplementSendOk<T>(T);
 unsafe impl<T: Send> Send for MayImplementSendOk<T> {} // ok
 
@@ -31,4 +33,12 @@ unsafe impl<T: Send> Send for TwoParamsSame<T, T> {}
 //~^ ERROR
 //~| WARNING this will change its meaning
 
+pub struct WithPhantomDataNonSend<T, U>(PhantomData<*const T>, U);
+unsafe impl<T> Send for WithPhantomDataNonSend<T, i8> {} // ok
+
+pub struct WithPhantomDataSend<T, U>(PhantomData<T>, U);
+unsafe impl<T> Send for WithPhantomDataSend<*const T, i8> {}
+//~^ ERROR
+//~| WARNING this will change its meaning
+
 fn main() {}

src/test/ui/auto-traits/suspicious-impls-lint.stderr

@@ -1,5 +1,5 @@
 error: cross-crate traits with a default impl, like `Send`, should not be specialized
-  --> $DIR/suspicious-impls-lint.rs:7:1
+  --> $DIR/suspicious-impls-lint.rs:9:1
    |
 LL | unsafe impl<T: Send> Send for MayImplementSendErr<&T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -12,41 +12,56 @@ LL | #![deny(suspicious_auto_trait_impls)]
    = warning: this will change its meaning in a future release!
    = note: for more information, see issue #93367 <https://github.com/rust-lang/rust/issues/93367>
 note: try using the same sequence of generic parameters as the struct definition
-  --> $DIR/suspicious-impls-lint.rs:6:1
+  --> $DIR/suspicious-impls-lint.rs:8:1
    |
 LL | struct MayImplementSendErr<T>(T);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: `&T` is not a generic parameter
 
 error: cross-crate traits with a default impl, like `Send`, should not be specialized
-  --> $DIR/suspicious-impls-lint.rs:19:1
+  --> $DIR/suspicious-impls-lint.rs:21:1
    |
 LL | unsafe impl Send for ContainsVec<i32> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = warning: this will change its meaning in a future release!
    = note: for more information, see issue #93367 <https://github.com/rust-lang/rust/issues/93367>
 note: try using the same sequence of generic parameters as the struct definition
-  --> $DIR/suspicious-impls-lint.rs:18:1
+  --> $DIR/suspicious-impls-lint.rs:20:1
    |
 LL | struct ContainsVec<T>(Vec<T>);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: `i32` is not a generic parameter
 
 error: cross-crate traits with a default impl, like `Send`, should not be specialized
-  --> $DIR/suspicious-impls-lint.rs:30:1
+  --> $DIR/suspicious-impls-lint.rs:32:1
    |
 LL | unsafe impl<T: Send> Send for TwoParamsSame<T, T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = warning: this will change its meaning in a future release!
    = note: for more information, see issue #93367 <https://github.com/rust-lang/rust/issues/93367>
 note: try using the same sequence of generic parameters as the struct definition
-  --> $DIR/suspicious-impls-lint.rs:29:1
+  --> $DIR/suspicious-impls-lint.rs:31:1
    |
 LL | struct TwoParamsSame<T, U>(T, U);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: `T` is mentioned multiple times
 
-error: aborting due to 3 previous errors
+error: cross-crate traits with a default impl, like `Send`, should not be specialized
+  --> $DIR/suspicious-impls-lint.rs:40:1
+   |
+LL | unsafe impl<T> Send for WithPhantomDataSend<*const T, i8> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = warning: this will change its meaning in a future release!
+   = note: for more information, see issue #93367 <https://github.com/rust-lang/rust/issues/93367>
+note: try using the same sequence of generic parameters as the struct definition
+  --> $DIR/suspicious-impls-lint.rs:39:1
+   |
+LL | pub struct WithPhantomDataSend<T, U>(PhantomData<T>, U);
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: `*const T` is not a generic parameter
+
+error: aborting due to 4 previous errors