67 lines
1.5 KiB
Rust
67 lines
1.5 KiB
Rust
// Test that we correctly infer variance for region parameters in
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// various self-contained types.
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#![feature(rustc_attrs)]
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// Regions that just appear in normal spots are contravariant:
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#[rustc_variance]
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struct Test2<'a, 'b, 'c> { //~ ERROR ['a: +, 'b: +, 'c: +]
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x: &'a isize,
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y: &'b [isize],
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c: &'c str
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}
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// Those same annotations in function arguments become covariant:
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#[rustc_variance]
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struct Test3<'a, 'b, 'c> { //~ ERROR ['a: -, 'b: -, 'c: -]
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x: extern "Rust" fn(&'a isize),
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y: extern "Rust" fn(&'b [isize]),
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c: extern "Rust" fn(&'c str),
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}
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// Mutability induces invariance:
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#[rustc_variance]
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struct Test4<'a, 'b:'a> { //~ ERROR ['a: +, 'b: o]
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x: &'a mut &'b isize,
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}
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// Mutability induces invariance, even when in a
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// contravariant context:
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#[rustc_variance]
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struct Test5<'a, 'b:'a> { //~ ERROR ['a: -, 'b: o]
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x: extern "Rust" fn(&'a mut &'b isize),
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}
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// Invariance is a trap from which NO ONE CAN ESCAPE.
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// In other words, even though the `&'b isize` occurs in
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// an argument list (which is contravariant), that
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// argument list occurs in an invariant context.
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#[rustc_variance]
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struct Test6<'a, 'b:'a> { //~ ERROR ['a: +, 'b: o]
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x: &'a mut extern "Rust" fn(&'b isize),
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}
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// No uses at all is bivariant:
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#[rustc_variance]
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struct Test7<'a> { //~ ERROR ['a: *]
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//~^ ERROR: `'a` is never used
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x: isize
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}
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// Try enums too.
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#[rustc_variance]
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enum Test8<'a, 'b, 'c:'b> { //~ ERROR ['a: -, 'b: +, 'c: o]
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Test8A(extern "Rust" fn(&'a isize)),
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Test8B(&'b [isize]),
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Test8C(&'b mut &'c str),
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}
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fn main() {}
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