Cannot derive Parser

[Proximyst]

With src/pest.rs having:

use pest_derive::*;

#[derive(Parser)]
#[grammar = "grammar.pest"]
pub struct Parser;

on pest_derive v2.1.0 and pest v2.1.0/pest v2.1.2 (same error on both versions), it returns the following errors:

error[E0433]: failed to resolve: could not find `iterators` in `pest`
 --> src/pest.rs:4:10
  |
4 | #[derive(Parser)]
  |          ^^^^^^ could not find `iterators` in `pest`

error[E0433]: failed to resolve: could not find `error` in `pest`
 --> src/pest.rs:4:10
  |
4 | #[derive(Parser)]
  |          ^^^^^^ could not find `error` in `pest`

error[E0433]: failed to resolve: could not find `Atomicity` in `pest`
 --> src/pest.rs:4:10
  |
4 | #[derive(Parser)]
  |          ^^^^^^ could not find `Atomicity` in `pest`

error[E0433]: failed to resolve: could not find `unicode` in `pest`
 --> src/pest.rs:4:10
  |
4 | #[derive(Parser)]
  |          ^^^^^^ could not find `unicode` in `pest`

error[E0404]: expected trait, found struct `pest::Parser`
 --> src/pest.rs:4:10
  |
4 | #[derive(Parser)]
  |          ^^^^^^ not a trait

error[E0412]: cannot find type `ParserState` in module `pest`
 --> src/pest.rs:4:10
  |
4 | #[derive(Parser)]
  |          ^^^^^^ not found in `pest`

error[E0412]: cannot find type `ParseResult` in module `pest`
 --> src/pest.rs:4:10
  |
4 | #[derive(Parser)]
  |          ^^^^^^ not found in `pest`

error[E0425]: cannot find function `state` in module `pest`
 --> src/pest.rs:4:10
  |
4 | #[derive(Parser)]
  |          ^^^^^^ not found in `pest`

This miiight be related to #129

[lwandrebeck]

adding use pest::Parser; should do the trick. Plus I won’t use pub struct Parser; but another name for the struct.
HTH,

[dragostis]

Does the Parser name break this so terribly? If so, it makes sense to have a better error in pest_derive.

[CAD97]

What's happening here is that the derive is trying to find its items in your mod pest. If you use a different module name, it should work. (I've used mod lang { #[derive(pest::Parser)] struct Parser; } many times with no issue.)

@Proximyst what edition are you compiling in? This should not be able to happen in edition=2018. Due to the way proc-macros work, pest requires that the path ::pest refers to the pest crate.

[Proximyst]

Your suggestion works, @CAD97. I'm using 2018 edition; rustc 1.40.0-nightly (87cbf0a54 2019-11-01).

[monoclex]

Any word on this? This should be solvable by prepending :: into whatever macro generates the code, so that it looks like ::pest::stuff.

Here's another workaround, if you're in a pest.rs module:

pub use pest::{error, iterators, state, ParseResult, ParserState};

[berlinshawn063]

I discovered this was for 2 reasons: 1) there was a typo in the .pest file that made the proc crash causing a compiler error; and 2) you need `#[derive(pest_derive::Parser)] to Hy-Vee Consumer Survey it from pest::Parser.