73 lines
1.6 KiB
Rust
73 lines
1.6 KiB
Rust
#![feature(never_patterns)]
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#![allow(incomplete_features)]
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enum Void {}
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fn main() {}
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// The classic use for empty types.
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fn safe_unwrap_result<T>(res: Result<T, Void>) {
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let Ok(_x) = res; //~ ERROR refutable pattern in local binding
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let (Ok(_x) | Err(!)) = &res;
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let (Ok(_x) | Err(&!)) = res.as_ref();
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}
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// Check we only accept `!` where we want to.
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fn never_pattern_location(void: Void) {
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// FIXME(never_patterns): Don't accept on a non-empty type.
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match Some(0) {
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None => {}
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Some(!),
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}
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// FIXME(never_patterns): Don't accept on an arbitrary type, even if there are no more branches.
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match () {
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() => {}
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!,
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}
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// FIXME(never_patterns): Don't accept even on an empty branch.
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match None::<Void> {
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None => {}
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!,
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}
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// FIXME(never_patterns): Let alone if the emptiness is behind a reference.
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match None::<&Void> {
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None => {}
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!,
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}
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// Participate in match ergonomics.
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match &void {
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!
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}
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match &&void {
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!
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}
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match &&void {
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&!
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}
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match &None::<Void> {
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None => {}
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Some(!)
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}
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match None::<&Void> {
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None => {}
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Some(!),
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}
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// Accept on a composite empty type.
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match None::<&(u32, Void)> {
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None => {}
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Some(&!),
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}
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// Accept on an simple empty type.
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match None::<Void> {
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None => {}
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Some(!),
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}
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match None::<&Void> {
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None => {}
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Some(&!),
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}
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match None::<&(u32, Void)> {
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None => {}
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Some(&(_, !)),
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}
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}
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