Rollup merge of rust-lang#42730 - VBChunguk:boxed-wild-pattern, r=eddyb

Use T as the subpattern type of Box<T>

The subpattern type of boxes being nil does not make sense because of box patterns. They should have their inner type as the subpattern type.

Fixes rust-lang#42679, which describes ICE caused by the bug.

src/librustc_const_eval/_match.rs

@@ -774,21 +774,26 @@ fn constructor_sub_pattern_tys<'a, 'tcx: 'a>(cx: &MatchCheckCtxt<'a, 'tcx>,
  },
  ty::TyRef(_, ref ty_and_mut) => vec![ty_and_mut.ty],
  ty::TyAdt(adt, substs) => {
- adt.variants[ctor.variant_index_for_adt(adt)].fields.iter().map(|field| {
- let is_visible = adt.is_enum()
- || field.vis.is_accessible_from(cx.module, cx.tcx);
- if is_visible {
- field.ty(cx.tcx, substs)
- } else {
- // Treat all non-visible fields as nil. They
- // can't appear in any other pattern from
- // this match (because they are private),
- // so their type does not matter - but
- // we don't want to know they are
- // uninhabited.
- cx.tcx.mk_nil()
- }
- }).collect()
+ if adt.is_box() {
+ // Use T as the sub pattern type of Box<T>.
+ vec![substs[0].as_type().unwrap()]
+ } else {
+ adt.variants[ctor.variant_index_for_adt(adt)].fields.iter().map(|field| {
+ let is_visible = adt.is_enum()
+ || field.vis.is_accessible_from(cx.module, cx.tcx);
+ if is_visible {
+ field.ty(cx.tcx, substs)
+ } else {
+ // Treat all non-visible fields as nil. They
+ // can't appear in any other pattern from
+ // this match (because they are private),
+ // so their type does not matter - but
+ // we don't want to know they are
+ // uninhabited.
+ cx.tcx.mk_nil()
+ }
+ }).collect()
+ }
  }
  _ => vec![],
  }

src/test/run-pass/issue-42679.rs

@@ -0,0 +1,31 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(box_syntax)]
+#![feature(box_patterns)]
+
+#[derive(Debug, PartialEq)]
+enum Test {
+ Foo(usize),
+ Bar(isize),
+}
+
+fn main() {
+ let a = box Test::Foo(10);
+ let b = box Test::Bar(-20);
+ match (a, b) {
+ (_, box Test::Foo(_)) => unreachable!(),
+ (box Test::Foo(x), b) => {
+ assert_eq!(x, 10);
+ assert_eq!(b, box Test::Bar(-20));
+ },
+ _ => unreachable!(),
+ }
+}