40 lines
715 B
Rust
40 lines
715 B
Rust
// Tests that a non-const default impl can be specialized by a const trait impl,
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// but that the default impl cannot be used in a const context.
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// run-pass
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#![feature(const_trait_impl)]
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#![feature(min_specialization)]
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#[const_trait]
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trait Value {
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fn value() -> u32;
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}
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const fn get_value<T: ~const Value>() -> u32 {
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T::value()
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}
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impl<T> Value for T {
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default fn value() -> u32 {
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println!("You can't do that (constly)");
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0
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}
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}
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struct FortyTwo;
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impl const Value for FortyTwo {
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fn value() -> u32 {
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42
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}
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}
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fn main() {
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let zero = get_value::<()>();
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assert_eq!(zero, 0);
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const FORTY_TWO: u32 = get_value::<FortyTwo>();
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assert_eq!(FORTY_TWO, 42);
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}
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