`clippy::type_repetition_in_bounds` clippy warning inside `#[query_group]`

[Wodann]

When using the #[salsa::invoke(...)] attribute inside a #[query_group], clippy complains about type repetition inside the function's bounds.

This is the code in question:

#[salsa::query_group(IrDatabaseStorage)]
pub trait IrDatabase: hir::HirDatabase {
    /// Get the LLVM context that should be used for all generation steps.
    #[salsa::input]
    fn context(&self) -> Arc<Context>;

    /// Gets the optimization level for generation.
    #[salsa::input]
    fn optimization_lvl(&self) -> OptimizationLevel;

    /// Returns the target for code generation.
    #[salsa::input]
    fn target(&self) -> Target;

    /// Given a type, return the corresponding IR type.
    #[salsa::invoke(crate::ir::ty::ir_query)]
    fn type_ir(&self, ty: hir::Ty) -> AnyTypeEnum;

    /// Given a `hir::FileId` generate code for the module.
    #[salsa::invoke(crate::ir::module::ir_query)]
    fn module_ir(&self, file: hir::FileId) -> Arc<ModuleIR>;

    /// Given a type, return the runtime `TypeInfo` that can be used to reflect the type.
    #[salsa::invoke(crate::code_gen::symbols::type_info_query)]
    fn type_info(&self, ty: hir::Ty) -> TypeInfo;
}

and these are the consequent warnings in clippy:

warning: this type has already been used as a bound predicate
  --> crates\mun_codegen\src\db.rs:26:8
   |
26 |     fn type_ir(&self, ty: hir::Ty) -> AnyTypeEnum;
   |        ^^^^^^^
   |
   = note: `#[warn(clippy::type_repetition_in_bounds)]` on by default
   = help: consider combining the bounds: `type_ir: IrDatabase + salsa::plumbing::HasQueryGroup<IrDatabaseStorage>`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

warning: this type has already been used as a bound predicate
  --> crates\mun_codegen\src\db.rs:26:8
   |
26 |     fn type_ir(&self, ty: hir::Ty) -> AnyTypeEnum;
   |        ^^^^^^^
   |
   = help: consider combining the bounds: `type_ir: salsa::plumbing::HasQueryGroup<IrDatabaseStorage> + salsa::Database`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

warning: this type has already been used as a bound predicate
  --> crates\mun_codegen\src\db.rs:30:8
   |
30 |     fn module_ir(&self, file: hir::FileId) -> Arc<ModuleIR>;
   |        ^^^^^^^^^
   |
   = help: consider combining the bounds: `module_ir: IrDatabase + salsa::plumbing::HasQueryGroup<IrDatabaseStorage>`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

warning: this type has already been used as a bound predicate
  --> crates\mun_codegen\src\db.rs:30:8
   |
30 |     fn module_ir(&self, file: hir::FileId) -> Arc<ModuleIR>;
   |        ^^^^^^^^^
   |
   = help: consider combining the bounds: `module_ir: salsa::plumbing::HasQueryGroup<IrDatabaseStorage> + salsa::Database`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

warning: this type has already been used as a bound predicate
  --> crates\mun_codegen\src\db.rs:34:8
   |
34 |     fn type_info(&self, ty: hir::Ty) -> TypeInfo;
   |        ^^^^^^^^^
   |
   = help: consider combining the bounds: `type_info: IrDatabase + salsa::plumbing::HasQueryGroup<IrDatabaseStorage>`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

warning: this type has already been used as a bound predicate
  --> crates\mun_codegen\src\db.rs:34:8
   |
34 |     fn type_info(&self, ty: hir::Ty) -> TypeInfo;
   |        ^^^^^^^^^
   |
   = help: consider combining the bounds: `type_info: salsa::plumbing::HasQueryGroup<IrDatabaseStorage> + salsa::Database`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

Used version:

salsa="0.12"

[jonas-schievink]

This is a bug in Clippy. It needs to check if the code originates from a macro expansion.

[rail-rain]

Aparrently, it's already reported, fixed and will be shipped with 1.47.

[matklad]

Thanks for those links @rail-rain! I think we should then close this!