Coercion sites are not consistent between struct tuples and structs

[nox]

pub struct Struct<K: 'static> {
    pub field: K,
}

static STRUCT: Struct<&'static [u8]> = Struct {
    field: &[1]
};

pub struct Tuple<K: 'static>(K);

static TUPLE: Tuple<&'static [u8]> = Tuple(&[1]);

STRUCT fails to type check, while TUPLE succeeds.

<anon>:7:40: 9:2 error: mismatched types:
 expected `Struct<&'static [u8]>`,
    found `Struct<&[_; 1]>`
(expected slice,
    found array of 1 elements) [E0308]
<anon>:7 static STRUCT: Struct<&'static [u8]> = Struct {
<anon>:8     field: &[1]
<anon>:9 };
<anon>:7:40: 9:2 help: see the detailed explanation for E0308

[SimonSapin]

This coercion is important when using b"…" byte string literals.

[eddyb]

The tuple struct case is actually the function call "expected type" propagation, which would have to be adapted to struct literals as well.

[nox]

Yes.

[SimonSapin]

Coercion already happens in non-generic struct literals:

struct Foo { s: &'static [u8] }
static FOO: Foo = Foo { s: b"foo" };

[eddyb]

@SimonSapin Yes, but the field types are taken from the struct and not combined with the overall expected type for the struct literal.

[abonander]

I just discovered this bug/unexpected behavior today (#34240). I would like to see some movement on it because it's surprising that these two don't work the same way.

Here's a workaround I found; it's ugly as hell but I'm using it in a generated file that no human would want to look through anyway: https://is.gd/boA5ut

I tried type ascription but it seems to not cue coercion, it just moves the type error: https://is.gd/yut0EK

It seems that forcing a concrete type on the struct literal works as well (I didn't expect this syntax to work, honestly): https://is.gd/ZipLo1 Unfortunately this won't work for me because I'm using phf_codegen too and I can't add this extra syntax myself.

[nox]

Any news on this?

[KalitaAlexey]

Is anyone working on it?