let-else: add deref-coercion tests · rust-lang/rust@fec8a50 (original) (raw)
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// check-pass
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//
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//
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// We attempt to let Bar::Present(_): &mut Bar = foo else { ... } where foo is meant to
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// Deref/DerefMut to Bar. You can do this with an irrefutable binding, so it should work with
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// let-else too.
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#![feature(let_else)]
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use std::ops::{Deref, DerefMut};
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struct Foo(Bar);
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enum Bar {
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Present(u32),
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Absent,
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}
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impl Deref for Foo {
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type Target = Bar;
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fn deref(&self) -> &Bar {
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&self.0
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}
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}
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impl DerefMut for Foo {
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fn deref_mut(&mut self) -> &mut Bar {
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&mut self.0
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}
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}
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impl Bar {
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fn bar(&self) -> Option {
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let Bar::Present(z): &Bar = self else {
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return None;
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};
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return Some(*z);
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}
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}
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impl Foo {
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fn set_bar_annotated(&mut self, value: u32) {
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let Bar::Present(z): &mut Bar = self else { // OK
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return;
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};
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*z = value;
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}
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}
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fn main() {
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let mut foo = Foo(Bar::Present(1));
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foo.set_bar_annotated(42);
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assert_eq!(foo.bar(), Some(42));
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irrefutable::inner();
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}
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// The original, to show it works for irrefutable let decls
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mod irrefutable {
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use std::ops::{Deref, DerefMut};
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struct Foo(Bar);
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struct Bar(u32);
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impl Deref for Foo {
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type Target = Bar;
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fn deref(&self) -> &Bar {
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&self.0
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}
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}
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impl DerefMut for Foo {
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fn deref_mut(&mut self) -> &mut Bar {
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&mut self.0
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}
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}
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fn foo(x: &mut Foo) {
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let Bar(z): &mut Bar = x; // OK
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*z = 42;
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assert_eq!((x.0).0, 42);
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}
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pub fn inner() {
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foo(&mut Foo(Bar(1)));
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}
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}
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