afcb938116
This stabilises RFC 2086 (https://github.com/rust-lang/rust/issues/44495). Co-Authored-By: Sebastian Malton <sebastian@malton.name>
43 lines
1.3 KiB
Rust
43 lines
1.3 KiB
Rust
// run-pass
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#![feature(type_alias_enum_variants)]
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#![allow(irrefutable_let_patterns)]
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#[allow(dead_code)]
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enum Enum<T> { TSVariant(T), SVariant { v: T } }
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type Alias<T> = Enum<T>;
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type AliasFixed = Enum<()>;
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macro_rules! is_variant {
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(TSVariant, $expr:expr) => (is_variant!(@check TSVariant, (_), $expr));
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(SVariant, $expr:expr) => (is_variant!(@check SVariant, { v: _ }, $expr));
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(@check $variant:ident, $matcher:tt, $expr:expr) => (
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assert!(if let Enum::$variant::<()> $matcher = $expr { true } else { false },
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"expr does not have correct type");
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);
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}
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fn main() {
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// Tuple struct variant
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is_variant!(TSVariant, Enum::TSVariant(()));
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is_variant!(TSVariant, Enum::TSVariant::<()>(()));
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is_variant!(TSVariant, Enum::<()>::TSVariant(()));
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is_variant!(TSVariant, Alias::TSVariant(()));
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is_variant!(TSVariant, Alias::<()>::TSVariant(()));
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is_variant!(TSVariant, AliasFixed::TSVariant(()));
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// Struct variant
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is_variant!(SVariant, Enum::SVariant { v: () });
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is_variant!(SVariant, Enum::SVariant::<()> { v: () });
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is_variant!(SVariant, Enum::<()>::SVariant { v: () });
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is_variant!(SVariant, Alias::SVariant { v: () });
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is_variant!(SVariant, Alias::<()>::SVariant { v: () });
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is_variant!(SVariant, AliasFixed::SVariant { v: () });
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}
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