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fix type of const params in assoc fns. #70276

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fix type of const params in assoc fns. #70276

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a624df6
fix type of const params in associated types.
lcnr Mar 21, 2020
2445375
fix type of const params in assoc fn.
lcnr Mar 22, 2020
5cad151
Merge branch 'master' into issue70273
lcnr Mar 22, 2020
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12 changes: 6 additions & 6 deletions src/librustc_typeck/collect/type_of.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -256,10 +256,10 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
// figure out which generic parameter it corresponds to and return
// the relevant type.
let generics = match path.res {
Res::Def(DefKind::Ctor(..), def_id)
| Res::Def(DefKind::AssocTy, def_id) => {
tcx.generics_of(tcx.parent(def_id).unwrap())
}
Res::Def(
DefKind::Ctor(..) | DefKind::AssocTy | DefKind::AssocFn,
def_id,
) => tcx.generics_of(tcx.parent(def_id).unwrap()),
Res::Def(_, def_id) => tcx.generics_of(def_id),
res => {
tcx.sess.delay_span_bug(
Expand Down Expand Up @@ -291,8 +291,8 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
tcx.sess.delay_span_bug(
DUMMY_SP,
&format!(
"missing generic parameter for `AnonConst`, parent {:?}",
parent_node
"missing generic parameter for `AnonConst`, parent: {:?}, path.res: {:?}",
parent_node, path.res
),
);
tcx.types.err
Expand Down
1 change: 1 addition & 0 deletions src/librustc_typeck/lib.rs
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Expand Up @@ -62,6 +62,7 @@ This API is completely unstable and subject to change.
#![feature(crate_visibility_modifier)]
#![feature(in_band_lifetimes)]
#![feature(nll)]
#![feature(or_patterns)]
#![feature(try_blocks)]
#![feature(never_type)]
#![feature(slice_partition_dedup)]
Expand Down
17 changes: 17 additions & 0 deletions src/test/ui/const-generics/issues/issue70273-assoc-fn.rs
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@@ -0,0 +1,17 @@
// check-pass

#![feature(const_generics)]
//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash

trait T<const A: usize> {
fn f();
}
struct S;

impl T<0usize> for S {
fn f() {}
}

fn main() {
let _err = <S as T<0usize>>::f();
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<S as T<123>>::f::<456>() should also work, if you added a const param to f as well.

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will add a test

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I mean you'll need to implement it, it won't work with the current approach.

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@lcnr lcnr Mar 22, 2020 •
edited
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for whatever reason adding a const param to f actually prevents the ice. not quite sure why, but this is new behavior so lets add a test for it

The following works on the current nightly.

#![feature(const_generics)]
//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash

trait T<const A: usize> {
    fn l<const N: usize>() -> usize;
    fn r<const N: usize>() -> usize;
}

struct S;

impl<const N: usize> T<N> for S {
    fn l<const M: usize>() -> usize { N }
    fn r<const M: usize>() -> usize { M }
}

fn main() {
   assert_eq!(<S as T<123>>::l::<456>(), 123);
   assert_eq!(<S as T<123>>::r::<456>(), 456);
}

playground

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Oh, oops, it's because both the trait and the method have the exact same number of parameters and the same types. Make one of them a bool instead of usize, then you should see how it thinks the method segment has the trait's parameter (which is wrong).

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jup. Quite surprisingly, using usize and u16 works 🤔
but using bool and usize does not work on nightly rn

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Yes, because the integer literals will work with any integer type.

}
8 changes: 8 additions & 0 deletions src/test/ui/const-generics/issues/issue70273-assoc-fn.stderr
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@@ -0,0 +1,8 @@
warning: the feature `const_generics` is incomplete and may cause the compiler to crash
--> $DIR/issue70273-assoc-fn.rs:3:12
|
LL | #![feature(const_generics)]
| ^^^^^^^^^^^^^^
|
= note: `#[warn(incomplete_features)]` on by default