Rollup merge of #134776 - estebank:vanilla-ice, r=lcnr

Avoid ICE: Account for `for<'a>` types when checking for non-structural type in constant as pattern

When we encounter a constant in a pattern, we check if it is non-structural. If so, we check if the type implements `PartialEq`, but for types with escaping bound vars the check would be incorrect as is, so we break early. This is ok because these types would be filtered anyways.

Slight tweak to output to remove unnecessary context as a drive-by.

Fix #134764.

3 files changed, 104 insertions, 51 deletions

diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
index 2b3c98db966..3853b95f78b 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
@@ -1,3 +1,5 @@
+use core::ops::ControlFlow;
+
 use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_apfloat::Float;
 use rustc_data_structures::fx::FxHashSet;
@@ -8,7 +10,9 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::Obligation;
 use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::thir::{FieldPat, Pat, PatKind};
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt, TypeVisitor, ValTree};
+use rustc_middle::ty::{
+    self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitableExt, TypeVisitor, ValTree,
+};
 use rustc_middle::{mir, span_bug};
 use rustc_span::def_id::DefId;
 use rustc_span::{Span, sym};
@@ -185,7 +189,7 @@ impl<'tcx> ConstToPat<'tcx> {
 
         if !inlined_const_as_pat.references_error() {
             // Always check for `PartialEq` if we had no other errors yet.
-            if !type_has_partial_eq_impl(self.tcx, typing_env, ty).0 {
+            if !type_has_partial_eq_impl(self.tcx, typing_env, ty).has_impl {
                 let mut err = self.tcx.dcx().create_err(TypeNotPartialEq { span: self.span, ty });
                 extend_type_not_partial_eq(self.tcx, typing_env, ty, &mut err);
                 return self.mk_err(err, ty);
@@ -219,12 +223,13 @@ impl<'tcx> ConstToPat<'tcx> {
                 // Extremely important check for all ADTs! Make sure they opted-in to be used in
                 // patterns.
                 debug!("adt_def {:?} has !type_marked_structural for cv.ty: {:?}", adt_def, ty);
-                let (_impls_partial_eq, derived, structural, impl_def_id) =
-                    type_has_partial_eq_impl(self.tcx, self.typing_env, ty);
+                let PartialEqImplStatus {
+                    is_derived, structural_partial_eq, non_blanket_impl, ..
+                } = type_has_partial_eq_impl(self.tcx, self.typing_env, ty);
                 let (manual_partialeq_impl_span, manual_partialeq_impl_note) =
-                    match (structural, impl_def_id) {
+                    match (structural_partial_eq, non_blanket_impl) {
                         (true, _) => (None, false),
-                        (_, Some(def_id)) if def_id.is_local() && !derived => {
+                        (_, Some(def_id)) if def_id.is_local() && !is_derived => {
                             (Some(tcx.def_span(def_id)), false)
                         }
                         _ => (None, true),
@@ -379,41 +384,50 @@ fn extend_type_not_partial_eq<'tcx>(
         adts_without_partialeq: FxHashSet<Span>,
         /// The user has written `impl PartialEq for Ty` which means it's non-structual,
         /// but we don't have a span to point at, so we'll just add them as a `note`.
-        manual: Vec<Ty<'tcx>>,
+        manual: FxHashSet<Ty<'tcx>>,
         /// The type has no `PartialEq` implementation, neither manual or derived, but
         /// we don't have a span to point at, so we'll just add them as a `note`.
-        without: Vec<Ty<'tcx>>,
+        without: FxHashSet<Ty<'tcx>>,
     }
 
     impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for UsedParamsNeedInstantiationVisitor<'tcx> {
+        type Result = ControlFlow<()>;
         fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
-            if let ty::Adt(def, _args) = ty.kind() {
-                let ty_def_id = def.did();
-                let ty_def_span = self.tcx.def_span(ty_def_id);
-                let (impls_partial_eq, derived, structural, impl_def_id) =
-                    type_has_partial_eq_impl(self.tcx, self.typing_env, ty);
-                match (impls_partial_eq, derived, structural, impl_def_id) {
-                    (_, _, true, _) => {}
-                    (true, false, _, Some(def_id)) if def_id.is_local() => {
-                        self.adts_with_manual_partialeq.insert(self.tcx.def_span(def_id));
-                    }
-                    (true, false, _, _) if ty_def_id.is_local() => {
-                        self.adts_with_manual_partialeq.insert(ty_def_span);
-                    }
-                    (false, _, _, _) if ty_def_id.is_local() => {
-                        self.adts_without_partialeq.insert(ty_def_span);
-                    }
-                    (true, false, _, _) => {
-                        self.manual.push(ty);
-                    }
-                    (false, _, _, _) => {
-                        self.without.push(ty);
-                    }
-                    _ => {}
-                };
+            match ty.kind() {
+                ty::Dynamic(..) => return ControlFlow::Break(()),
+                ty::FnPtr(..) => return ControlFlow::Continue(()),
+                ty::Adt(def, _args) => {
+                    let ty_def_id = def.did();
+                    let ty_def_span = self.tcx.def_span(ty_def_id);
+                    let PartialEqImplStatus {
+                        has_impl,
+                        is_derived,
+                        structural_partial_eq,
+                        non_blanket_impl,
+                    } = type_has_partial_eq_impl(self.tcx, self.typing_env, ty);
+                    match (has_impl, is_derived, structural_partial_eq, non_blanket_impl) {
+                        (_, _, true, _) => {}
+                        (true, false, _, Some(def_id)) if def_id.is_local() => {
+                            self.adts_with_manual_partialeq.insert(self.tcx.def_span(def_id));
+                        }
+                        (true, false, _, _) if ty_def_id.is_local() => {
+                            self.adts_with_manual_partialeq.insert(ty_def_span);
+                        }
+                        (false, _, _, _) if ty_def_id.is_local() => {
+                            self.adts_without_partialeq.insert(ty_def_span);
+                        }
+                        (true, false, _, _) => {
+                            self.manual.insert(ty);
+                        }
+                        (false, _, _, _) => {
+                            self.without.insert(ty);
+                        }
+                        _ => {}
+                    };
+                    ty.super_visit_with(self)
+                }
+                _ => ty.super_visit_with(self),
             }
-            use rustc_middle::ty::TypeSuperVisitable;
-            ty.super_visit_with(self)
         }
     }
     let mut v = UsedParamsNeedInstantiationVisitor {
@@ -421,10 +435,12 @@ fn extend_type_not_partial_eq<'tcx>(
         typing_env,
         adts_with_manual_partialeq: FxHashSet::default(),
         adts_without_partialeq: FxHashSet::default(),
-        manual: vec![],
-        without: vec![],
+        manual: FxHashSet::default(),
+        without: FxHashSet::default(),
     };
-    v.visit_ty(ty);
+    if v.visit_ty(ty).is_break() {
+        return;
+    }
     #[allow(rustc::potential_query_instability)] // Span labels will be sorted by the rendering
     for span in v.adts_with_manual_partialeq {
         err.span_note(span, "the `PartialEq` trait must be derived, manual `impl`s are not sufficient; see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details");
@@ -436,29 +452,38 @@ fn extend_type_not_partial_eq<'tcx>(
             "must be annotated with `#[derive(PartialEq)]` to be usable in patterns",
         );
     }
-    for ty in v.manual {
+    #[allow(rustc::potential_query_instability)]
+    let mut manual: Vec<_> = v.manual.into_iter().map(|t| t.to_string()).collect();
+    manual.sort();
+    for ty in manual {
         err.note(format!(
             "`{ty}` must be annotated with `#[derive(PartialEq)]` to be usable in patterns, manual `impl`s are not sufficient; see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details"
         ));
     }
-    for ty in v.without {
+    #[allow(rustc::potential_query_instability)]
+    let mut without: Vec<_> = v.without.into_iter().map(|t| t.to_string()).collect();
+    without.sort();
+    for ty in without {
         err.note(format!(
             "`{ty}` must be annotated with `#[derive(PartialEq)]` to be usable in patterns"
         ));
     }
 }
 
+#[derive(Debug)]
+struct PartialEqImplStatus {
+    has_impl: bool,
+    is_derived: bool,
+    structural_partial_eq: bool,
+    non_blanket_impl: Option<DefId>,
+}
+
 #[instrument(level = "trace", skip(tcx), ret)]
 fn type_has_partial_eq_impl<'tcx>(
     tcx: TyCtxt<'tcx>,
     typing_env: ty::TypingEnv<'tcx>,
     ty: Ty<'tcx>,
-) -> (
-    /* has impl */ bool,
-    /* is derived */ bool,
-    /* structural partial eq */ bool,
-    /* non-blanket impl */ Option<DefId>,
-) {
+) -> PartialEqImplStatus {
     let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(typing_env);
     // double-check there even *is* a semantic `PartialEq` to dispatch to.
     //
@@ -495,10 +520,10 @@ fn type_has_partial_eq_impl<'tcx>(
     // that patterns can only do things that the code could also do without patterns, but it is
     // needed for backwards compatibility. The actual pattern matching compares primitive values,
     // `PartialEq::eq` never gets invoked, so there's no risk of us running non-const code.
-    (
-        infcx.predicate_must_hold_modulo_regions(&partial_eq_obligation),
-        automatically_derived,
-        structural_peq,
-        impl_def_id,
-    )
+    PartialEqImplStatus {
+        has_impl: infcx.predicate_must_hold_modulo_regions(&partial_eq_obligation),
+        is_derived: automatically_derived,
+        structural_partial_eq: structural_peq,
+        non_blanket_impl: impl_def_id,
+    }
 }
diff --git a/tests/ui/consts/const_in_pattern/non_structural_with_escaping_bounds.rs b/tests/ui/consts/const_in_pattern/non_structural_with_escaping_bounds.rs
new file mode 100644
index 00000000000..e5d095fd617
--- /dev/null
+++ b/tests/ui/consts/const_in_pattern/non_structural_with_escaping_bounds.rs
@@ -0,0 +1,15 @@
+#![feature(structural_match)]
+impl<T: ?Sized> std::marker::StructuralPartialEq for O<T> { }
+
+enum O<T: ?Sized> {
+    Some(*const T),
+    None,
+}
+
+const C: O<dyn for<'a> Fn(Box<dyn Fn(&'a u8)>)> = O::None;
+
+fn main() {
+    match O::None {
+        C => (), //~ ERROR constant of non-structural type
+    }
+}
diff --git a/tests/ui/consts/const_in_pattern/non_structural_with_escaping_bounds.stderr b/tests/ui/consts/const_in_pattern/non_structural_with_escaping_bounds.stderr
new file mode 100644
index 00000000000..371be9982f7
--- /dev/null
+++ b/tests/ui/consts/const_in_pattern/non_structural_with_escaping_bounds.stderr
@@ -0,0 +1,13 @@
+error: constant of non-structural type `O<dyn for<'a> Fn(Box<dyn Fn(&'a u8)>)>` in a pattern
+  --> $DIR/non_structural_with_escaping_bounds.rs:13:9
+   |
+LL | const C: O<dyn for<'a> Fn(Box<dyn Fn(&'a u8)>)> = O::None;
+   | ----------------------------------------------- constant defined here
+...
+LL |         C => (),
+   |         ^ constant of non-structural type
+   |
+   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
+
+error: aborting due to 1 previous error
+