Flux failing on 2025-11-25 rust-verify-std

[nilehmann]

Running flux with 2025-11-25 on the matching rust-verify-std opened PR gives

error[E0999]: unsupported signature
  --> core/src/ops/unsize.rs:36:1
   |
36 | pub trait CoerceUnsized<T: PointeeSized> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: unsupported type `pattern_type!(*const T/#0 is !null)`

error[E0999]: unsupported signature
   --> core/src/ops/unsize.rs:119:1
    |
119 | pub trait DispatchFromDyn<T> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: unsupported type `pattern_type!(T/#0 is !null)`

error[E0999]: unsupported signature
    --> core/src/marker.rs:1014:1
     |
1014 | pub auto trait Unpin {}
     | ^^^^^^^^^^^^^^^^^^^^
     |
     = note: unsupported type `pattern_type!(*const T/#0 is !null)`

error[E0999]: unsupported signature
   --> core/src/marker.rs:914:1
    |
914 | pub unsafe auto trait Freeze {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: unsupported type `pattern_type!(*const T/#0 is !null)`

error[E0999]: unsupported signature
   --> core/src/marker.rs:914:1
    |
914 | pub unsafe auto trait Freeze {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: unsupported type `pattern_type!(*mut T/#0 is !null)`

error: internal compiler error: crates/flux-refineck/src/type_env/place_ty.rs:896:47: Query(Bug { def_id: None, location: "crates/flux-infer/src/infer.rs:878:22", msg: "incompatible types: `†EscapeIterInner<Leaf(4), AlwaysEscaped>` - `EscapeIterInner<Leaf(4), AlwaysEscaped>`" })
   --> core/src/ascii.rs:116:9
    |
116 |         self.0.next()
    |         ^^^^^^

[nilehmann]

#1440 fixes the last error, and #1442 gives a better span for the unsupported pattern_type! errors. Now we get

error[E0999]: unsupported signature
  --> core/src/pat.rs:98:1
   |
98 | / impl<T: PointeeSized, U: PointeeSized> CoerceUnsized<pattern_type!(*const U is !null)> for pattern_type!(*const T is !null) where
99 | |     T: Unsize<U>
   | |________________^
   |
   = note: unsupported type `pattern_type!(*const T/#0 is !null)`

error[E0999]: unsupported signature
   --> core/src/pat.rs:103:1
    |
103 | impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<pattern_type!(U is !null)> for pattern_type!(T is !null) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: unsupported type `pattern_type!(T/#0 is !null)`

error[E0999]: unsupported signature
   --> core/src/pat.rs:105:1
    |
105 | impl<T: PointeeSized> Unpin for pattern_type!(*const T is !null) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: unsupported type `pattern_type!(*const T/#0 is !null)`

error[E0999]: unsupported signature
   --> core/src/pat.rs:107:1
    |
107 | unsafe impl<T: PointeeSized> Freeze for pattern_type!(*const T is !null) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: unsupported type `pattern_type!(*const T/#0 is !null)`

error[E0999]: unsupported signature
   --> core/src/pat.rs:109:1
    |
109 | unsafe impl<T: PointeeSized> Freeze for pattern_type!(*mut T is !null) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: unsupported type `pattern_type!(*mut T/#0 is !null)`

error: internal compiler error: crates/flux-infer/src/infer.rs:755:9: call to `ptr_to_ref` on `DummyEnv`

All unsupported pattern_types! are in impls in core/src/pat.rs. We are including this module in Cargo.toml because some definitions have specs. We could try to ignore those impls or try to implement rudimentary support for pattern types.

We are also getting this new error.

error: internal compiler error: crates/flux-infer/src/infer.rs:755:9: call to `ptr_to_ref` on `DummyEnv`

this may be related to auto-strg

[nilehmann]

#1443 implements a better span for the last error. With that we get

error: internal compiler error: crates/flux-infer/src/infer.rs:755:9: call to `ptr_to_ref` on `DummyEnv`
   --> core/src/bstr/mod.rs:268:33
    |
268 |         ByteStr::from_bytes_mut(&mut [])
    |                                 ^^^^^^^

It turns out that this is not related to auto-strong, but to promoted constants. This is a minimal repro

fn test00() -> &'static mut [i32] {
    &mut []
}

[nilehmann]

#1445 fixes the last error. We are down to only unsupported pattern_type! errors.