toplevel_ref_arg triggers on macro-generated code

[jplatte]

Not sure whether this is intended behaviour, but currently pretty much all SQLx query_as! invocations trigger this lint, e.g.

sqlx::query_as!(SomeType, "SELECT * FROM table WHERE id = $1", id)
    .fetch_one(pool)
    .await

ref on an entire let pattern is discouraged, take a reference with & instead

Meta

• cargo clippy -V: clippy 0.0.212 (6c8927b 2020-07-26)
• rustc -Vv:

  rustc 1.47.0-nightly (6c8927b0c 2020-07-26)
  binary: rustc
  commit-hash: 6c8927b0cf80ceee19386026cf9d7fd4fd9d486f
  commit-date: 2020-07-26
  host: x86_64-unknown-linux-gnu
  release: 1.47.0-nightly
  LLVM version: 10.0
  

[abonander]

This can be trivially fixed in SQLx, but in general it would be nice to know how we could avoid triggering lint warnings in generated code which the user has no control over.

[abonander]

It's also worth mentioning that this warning was produced with sqlx 0.4.0-beta.1

[Ryan1729]

it would be nice to know how we could avoid triggering lint warnings in generated code which the user has no control over.

Depending on what form the macro output takes, you could add an #[allow(clippy::foo)] annotation to it.

For instance, if the output is an expression, you can wrap the output in a block and add an inner attribute at the top.

Playground example

[ebroto]

To fix this issue, we can use the utils::in_macro function to check if we have to bail out. This lint is found in the misc.rs module.

For the tests, we should create two macros, and use them:

• one that generates a function using ref in parameter position. Example:
• another that generates a let binding using ref.

For example:

macro_rules! gen_binding {
    () => {
        let ref _y = 42;
    }
}

macro_rules! gen_function {
    () => {
        fn fun_example(ref _x: usize) {}
    }
}

(playground)