check is violation ty included by const val

Author: bvanjoi

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

@@ -3,7 +3,7 @@ use rustc_hir::def_id::DefId;
 use rustc_index::Idx;
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::Obligation;
-use rustc_middle::mir;
+use rustc_middle::mir::{self, ConstValue};
 use rustc_middle::thir::{FieldPat, Pat, PatKind};
 use rustc_middle::ty::{self, Ty, TyCtxt, ValTree};
 use rustc_session::lint;
@@ -198,7 +198,7 @@ impl<'tcx> ConstToPat<'tcx> {
                     // We errored. Signal that in the pattern, so that follow up errors can be silenced.
                     let kind = PatKind::Error(e);
                     return Box::new(Pat { span: self.span, ty: cv.ty(), kind });
-                } else if let ty::Adt(..) = cv.ty().kind() && matches!(cv, mir::Const::Val(..)) {
+                } else if let ty::Adt(..) = cv.ty().kind() && let mir::Const::Val(const_val, const_ty) = cv && self.is_ty_included_by_const_val(const_val, const_ty, non_sm_ty) {
                     // This branch is only entered when the current `cv` is `mir::Const::Val`.
                     // This is because `mir::Const::ty` has already been handled by `Self::recur`
                     // and the invalid types may be ignored.
@@ -266,6 +266,34 @@ impl<'tcx> ConstToPat<'tcx> {
         inlined_const_as_pat
     }
 
+    // Check if `child` is included within the const value.
+    fn is_ty_included_by_const_val(
+        &self,
+        const_val: ConstValue<'tcx>,
+        parent: Ty<'tcx>,
+        child: Ty<'tcx>,
+    ) -> bool {
+        if parent == self.tcx().normalize_erasing_regions(self.param_env, child) {
+            return true;
+        }
+        match parent.kind() {
+            ty::Adt(..) | ty::Tuple(_) | ty::Array(..) => {
+                let destructured = self
+                    .tcx()
+                    .try_destructure_mir_constant_for_user_output(
+                        const_val,
+                        self.tcx().normalize_erasing_regions(self.param_env, parent),
+                    )
+                    .unwrap();
+                destructured
+                    .fields
+                    .iter()
+                    .any(|field| self.is_ty_included_by_const_val(field.0, field.1, child))
+            }
+            _ => false,
+        }
+    }
+
     #[instrument(level = "trace", skip(self), ret)]
     fn type_has_partial_eq_impl(&self, ty: Ty<'tcx>) -> bool {
         // double-check there even *is* a semantic `PartialEq` to dispatch to.

tests/ui/pattern/issue-117626.rs

@@ -0,0 +1,21 @@
+// check-pass
+
+#[derive(PartialEq)]
+struct NonMatchable;
+
+impl Eq for NonMatchable {}
+
+#[derive(PartialEq, Eq)]
+enum Foo {
+    A(NonMatchable),
+    B(*const u8),
+}
+
+const CONST: Foo = Foo::B(std::ptr::null());
+
+fn main() {
+    match CONST {
+        CONST => 0,
+        _ => 1,
+    };
+}