133 lines
2.9 KiB
Rust
133 lines
2.9 KiB
Rust
// run-pass
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// Tests that you can use an early-bound lifetime parameter as
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// on of the generic parameters in a trait.
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trait Trait<'a> {
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fn long(&'a self) -> isize;
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fn short<'b>(&'b self) -> isize;
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}
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fn poly_invoke<'c, T: Trait<'c>>(x: &'c T) -> (isize, isize) {
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let l = x.long();
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let s = x.short();
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(l,s)
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}
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fn object_invoke1<'d>(x: &'d dyn Trait<'d>) -> (isize, isize) {
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let l = x.long();
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let s = x.short();
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(l,s)
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}
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struct Struct1<'e> {
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f: &'e (dyn Trait<'e>+'e)
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}
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fn field_invoke1<'f, 'g>(x: &'g Struct1<'f>) -> (isize,isize) {
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let l = x.f.long();
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let s = x.f.short();
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(l,s)
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}
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struct Struct2<'h, 'i:'h> {
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f: &'h (dyn Trait<'i>+'h)
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}
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fn object_invoke2<'j, 'k>(x: &'k dyn Trait<'j>) -> isize {
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x.short()
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}
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fn field_invoke2<'l, 'm, 'n>(x: &'n Struct2<'l,'m>) -> isize {
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x.f.short()
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}
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trait MakerTrait {
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fn mk() -> Self;
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}
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fn make_val<T:MakerTrait>() -> T {
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MakerTrait::mk()
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}
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trait RefMakerTrait<'q> {
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fn mk(_: Self) -> &'q Self;
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}
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fn make_ref<'r, T:RefMakerTrait<'r>>(t:T) -> &'r T {
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RefMakerTrait::mk(t)
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}
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impl<'s> Trait<'s> for (isize,isize) {
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fn long(&'s self) -> isize {
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let &(x,_) = self;
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x
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}
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fn short<'b>(&'b self) -> isize {
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let &(_,y) = self;
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y
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}
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}
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impl<'t> MakerTrait for Box<dyn Trait<'t>+'static> {
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fn mk() -> Box<dyn Trait<'t>+'static> {
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let tup: Box<(isize, isize)> = Box::new((4,5));
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tup as Box<dyn Trait>
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}
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}
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enum List<'l> {
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Cons(isize, &'l List<'l>),
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Null
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}
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impl<'l> List<'l> {
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fn car<'m>(&'m self) -> isize {
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match self {
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&List::Cons(car, _) => car,
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&List::Null => panic!(),
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}
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}
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fn cdr<'n>(&'n self) -> &'l List<'l> {
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match self {
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&List::Cons(_, cdr) => cdr,
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&List::Null => panic!(),
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}
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}
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}
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impl<'t> RefMakerTrait<'t> for List<'t> {
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fn mk(l:List<'t>) -> &'t List<'t> {
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l.cdr()
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}
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}
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pub fn main() {
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let t = (2,3);
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let o = &t as &dyn Trait;
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let s1 = Struct1 { f: o };
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let s2 = Struct2 { f: o };
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assert_eq!(poly_invoke(&t), (2,3));
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assert_eq!(object_invoke1(&t), (2,3));
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assert_eq!(field_invoke1(&s1), (2,3));
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assert_eq!(object_invoke2(&t), 3);
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assert_eq!(field_invoke2(&s2), 3);
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let m : Box<dyn Trait> = make_val();
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// assert_eq!(object_invoke1(&*m), (4,5));
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// ~~~~~~~~~~~~~~~~~~~
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// this call yields a compilation error; see ui/span/dropck-object-cycle.rs
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// for details.
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assert_eq!(object_invoke2(&*m), 5);
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// The RefMakerTrait above is pretty strange (i.e., it is strange
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// to consume a value of type T and return a &T). Easiest thing
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// that came to my mind: consume a cell of a linked list and
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// return a reference to the list it points to.
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let l0 = List::Null;
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let l1 = List::Cons(1, &l0);
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let l2 = List::Cons(2, &l1);
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let rl1 = &l1;
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let r = make_ref(l2);
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assert_eq!(rl1.car(), r.car());
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}
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