32 lines
522 B
Rust
32 lines
522 B
Rust
// check-pass
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trait Variable<'a> {
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type Type;
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}
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impl Variable<'_> for () {
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type Type = ();
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}
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fn check<F, T>(_: F)
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where
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F: Fn(T), // <- if removed, all fn_* then require type annotations
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F: for<'a> Fn(<T as Variable<'a>>::Type),
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T: for<'a> Variable<'a>,
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{
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}
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fn test(arg: impl Fn(())) {
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fn fn_1(_: ()) {}
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let fn_2 = |_: ()| ();
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let fn_3 = |a| fn_1(a);
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let fn_4 = arg;
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check(fn_1); // Error
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check(fn_2); // Ok
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check(fn_3); // Ok
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check(fn_4); // Error
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}
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fn main() {}
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