Only consider impliciy unboxed closure impl if the obligation is
actually for `Fn`, `FnMut`, or `FnOnce`. Fixes #18019
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@ -608,6 +608,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
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* unified during the confirmation step.
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*/
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let tcx = self.tcx();
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let kind = if Some(obligation.trait_ref.def_id) == tcx.lang_items.fn_trait() {
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ty::FnUnboxedClosureKind
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} else if Some(obligation.trait_ref.def_id) == tcx.lang_items.fn_mut_trait() {
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ty::FnMutUnboxedClosureKind
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} else if Some(obligation.trait_ref.def_id) == tcx.lang_items.fn_once_trait() {
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ty::FnOnceUnboxedClosureKind
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} else {
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return Ok(()); // not a fn trait, ignore
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};
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let self_ty = self.infcx.shallow_resolve(obligation.self_ty());
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let closure_def_id = match ty::get(self_ty).sty {
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ty::ty_unboxed_closure(id, _) => id,
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@ -622,37 +633,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
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self_ty.repr(self.tcx()),
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obligation.repr(self.tcx()));
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let tcx = self.tcx();
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let fn_traits = [
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(ty::FnUnboxedClosureKind, tcx.lang_items.fn_trait()),
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(ty::FnMutUnboxedClosureKind, tcx.lang_items.fn_mut_trait()),
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(ty::FnOnceUnboxedClosureKind, tcx.lang_items.fn_once_trait()),
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];
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for tuple in fn_traits.iter() {
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let kind = match tuple {
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&(kind, Some(ref fn_trait))
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if *fn_trait == obligation.trait_ref.def_id =>
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{
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kind
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}
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_ => continue,
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};
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// Check to see whether the argument and return types match.
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let closure_kind = match self.typer.unboxed_closures().borrow().find(&closure_def_id) {
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Some(closure) => closure.kind,
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None => {
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self.tcx().sess.span_bug(
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obligation.cause.span,
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format!("No entry for unboxed closure: {}",
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closure_def_id.repr(self.tcx())).as_slice());
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}
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};
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if closure_kind != kind {
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continue;
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let closure_kind = match self.typer.unboxed_closures().borrow().find(&closure_def_id) {
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Some(closure) => closure.kind,
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None => {
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self.tcx().sess.span_bug(
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obligation.cause.span,
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format!("No entry for unboxed closure: {}",
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closure_def_id.repr(self.tcx())).as_slice());
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}
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};
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if closure_kind == kind {
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candidates.vec.push(UnboxedClosureCandidate(closure_def_id));
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}
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@ -0,0 +1,32 @@
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Test that we correctly infer that `E` must be `()` here. This is
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// known because there is just one impl that could apply where
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// `Self=()`.
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pub trait FromError<E> {
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fn from_error(err: E) -> Self;
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}
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impl<E> FromError<E> for E {
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fn from_error(err: E) -> E {
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err
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}
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}
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fn test() -> Result<(), ()> {
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Err(FromError::from_error(()))
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}
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fn main() {
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let result = (|| Err(FromError::from_error(())))();
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let foo: () = result.unwrap_or(());
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}
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