AST validation doesn't correctly deal with impls nested within associated functions (original) (raw)

The following programs get wrongfully rejected since my PR #119505 (nightly-2024-01-04):

pub struct S;

trait Trait { fn provided() { impl S { pub fn perform() {} //~ ERROR visibility qualifiers are not permitted here } } }

pub struct S; struct Expr;

trait Trait { fn required(_: Expr<{ impl S { pub fn perform() {} //~ ERROR visibility qualifiers are not permitted here } 0 }>); }

The following program was incorrectly rejected even before my PR #119505 (nightly-2024-01-04):

#![feature(const_trait_impl, effects)]

pub struct S;

#[const_trait] trait Trait { fn required(); }

impl const Trait for () { fn required() { impl S { pub fn perform() {} //~ ERROR visibility qualifiers are not permitted here } } }

The following programs lead to an ICE even before my PR (e.g., in nightly-2023-12-31):

#![feature(const_trait_impl, effects)]

pub struct S; #[const_trait] trait Trait { fn provided() { impl S { fn perform<T: const Trait>() {} // should've gotten rejected during AST validation //^ ICE no host param id for call in const yet no errors reported } } }

#![feature(const_trait_impl, effects)]

pub struct S; struct Expr;

#[const_trait] trait Trait { fn required(_: Expr<{ impl S { fn perform<T: const Trait>() {} // should've gotten rejected during AST validation //^ ICE no host param id for call in const yet no errors reported } 0 }>); }

#![feature(const_trait_impl, effects)]

struct S; #[const_trait] trait Trait {}

const fn f<T: Trait<{ struct I<U: const Trait<0>>(U); // should've gotten rejected during AST validation //^ ICE no host param id for call in const yet no errors reported 0 }>>() {}

There are many more issues and probably many more ways to reproduce this, e.g. we don't visit attributes on associated functions under certain circumstances (I couldn't find a reproducer yet in which you can observe the bug).