Tracking Issue for Rustc Public: Expose Type and Const Parameter Constraints

This is a tracking issue for Rustc public API.

Feature gate: #![feature(rustc_public_generic_clauses)]

Problem

Currently, the APIs in Rustc public missing some information required for building full fidelity tools on top of it.

(1) Trait bounds:

trait Step {}
  fn advance<T: Step>(value: T) -> T {
      value
  }

Rustc Public exposes that advance has a type parameter named T, but not the constraint T: Step.

(2) Const types:

fn f<const N: usize>()

Rustc Public reveals that N is a const generic but not its type.

Public API

The FnDef type could be extended by two new functions:

impl FnDef {
      pub fn generics_of(&self) -> Generics;

      pub fn clauses_of(&self) -> GenericClauses;
      pub fn explicit_clauses_of(&self) -> GenericClauses;
  }

Alternatively, the trait bound info could be included in Generics

For the const c: usize problem, GenericParamDefKind would be extended for the Const variant to also carry a type.

Steps / History

• ACP: rust-lang/libs-team#...
• Implementation: #...
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

This seems to be a simple API extension, so no open questions.

• None yet.