Build fails in Rust 1.48.0 nightly

[ekexium]

Build succeeds for rust 1.46.0 stable, but failed for Rust 1.48.0 nightly.
I'm using proptest 0.10.1 and proptest-derive 0.2.0.

Example:

use proptest::{arbitrary::any_with, collection::size_range};
use proptest_derive::Arbitrary;
#[derive(Arbitrary)]
pub struct Key(
    #[proptest(strategy = "any_with::<Vec<u8>>((size_range(1024), ()))")]
    pub Vec<u8>,
);

Build error:

❯ cargo build
   Compiling play v0.1.0 (/Users/ekexium/code/play)
error: [proptest_derive, E0026] during #[derive(Arbitrary)]:
The attribute modifier `strategy` inside `#[proptest(..)]` must have the format `#[proptest(strategy = "<expr>")]` where `<expr>` is a valid Rust expression. Please see: https://PATH/TO/foo#E0026 for more information.
 --> src/lib.rs:3:17
  |
3 | #[derive(Debug, Arbitrary)]
  |                 ^^^^^^^^^
  |
  = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)

warning: unused imports: `arbitrary::any_with`, `collection::size_range`
 --> src/lib.rs:1:16
  |
1 | use proptest::{arbitrary::any_with, collection::size_range};
  |                ^^^^^^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

error: aborting due to previous error; 1 warning emitted

error: could not compile `play`.

To learn more, run the command again with --verbose.

Don't know if it's a bug. Do you have any idea?

[Centril]

Can you please paste the build error?

[ekexium]

Can you please paste the build error?

Sorry I put the wrong content in build errors. It's Updated.

[Centril]

Odd. This error arises when proptest_derive gets a malformed expression, according to syn.

• Throws the error: https://github.com/AltSysrq/proptest/blob/a82973133a5d5ea5571a4bce075b6a9aa6c9f8c6/proptest-derive/src/attr.rs#L442
• Parses the expression: https://github.com/AltSysrq/proptest/blob/a82973133a5d5ea5571a4bce075b6a9aa6c9f8c6/proptest-derive/src/attr.rs#L437
• You'll end up here, which routes to syn's .parse(): https://github.com/AltSysrq/proptest/blob/a82973133a5d5ea5571a4bce075b6a9aa6c9f8c6/proptest-derive/src/attr.rs#L569

The token stream any_with::<Vec<u8>>((size_range(1024), ())) is however definitely a well-formed Rust expression syntactically, unless there are issues in rustc's pretty printing or so. Could you test whether rustc handles this right? The syn dependency shouldn't have been changed since we aren't using 1.0+ yet and 0.15.*. shouldn't have been changed.

[Centril]

Maybe caused by rust-lang/rust#76399.

[ekexium]

Latest nightly doesn't have this problem