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Document some builtin impls in the next solver #122238

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merged 2 commits into from
Mar 14, 2024
Merged

Document some builtin impls in the next solver #122238

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4b76fac
Document some builtin impls in the next solver
fee1-dead Mar 9, 2024
69d781a
move impl documentation to their actual locations
fee1-dead Mar 14, 2024
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10 changes: 10 additions & 0 deletions compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -120,6 +120,8 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<'tcx>(
ty: Ty<'tcx>,
) -> Result<Vec<ty::Binder<'tcx, Ty<'tcx>>>, NoSolution> {
match *ty.kind() {
// impl Sized for u*, i*, bool, f*, FnDef, FnPtr, *(const/mut) T, char, &mut? T, [T; N], dyn* Trait, !
// impl Sized for Coroutine, CoroutineWitness, Closure, CoroutineClosure
ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
| ty::Uint(_)
| ty::Int(_)
Expand Down Expand Up @@ -152,8 +154,10 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<'tcx>(
bug!("unexpected type `{ty}`")
}

// impl Sized for (T1, T2, .., Tn) where T1: Sized, T2: Sized, .. Tn: Sized
ty::Tuple(tys) => Ok(tys.iter().map(ty::Binder::dummy).collect()),

// impl Sized for Adt where T: Sized forall T in field types
ty::Adt(def, args) => {
let sized_crit = def.sized_constraint(ecx.tcx());
Ok(sized_crit.iter_instantiated(ecx.tcx(), args).map(ty::Binder::dummy).collect())
Expand All @@ -167,6 +171,7 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
ty: Ty<'tcx>,
) -> Result<Vec<ty::Binder<'tcx, Ty<'tcx>>>, NoSolution> {
match *ty.kind() {
// impl Copy/Clone for FnDef, FnPtr
ty::FnDef(..) | ty::FnPtr(_) | ty::Error(_) => Ok(vec![]),

// Implementations are provided in core
Expand Down Expand Up @@ -196,12 +201,16 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
bug!("unexpected type `{ty}`")
}

// impl Copy/Clone for (T1, T2, .., Tn) where T1: Copy/Clone, T2: Copy/Clone, .. Tn: Copy/Clone
ty::Tuple(tys) => Ok(tys.iter().map(ty::Binder::dummy).collect()),

// impl Copy/Clone for Closure where Self::TupledUpvars: Copy/Clone
ty::Closure(_, args) => Ok(vec![ty::Binder::dummy(args.as_closure().tupled_upvars_ty())]),

ty::CoroutineClosure(..) => Err(NoSolution),

// only when `coroutine_clone` is enabled and the coroutine is movable
// impl Copy/Clone for Coroutine where T: Copy/Clone forall T in (upvars, witnesses)
ty::Coroutine(def_id, args) => match ecx.tcx().coroutine_movability(def_id) {
Movability::Static => Err(NoSolution),
Movability::Movable => {
Expand All @@ -217,6 +226,7 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
}
},

// impl Copy/Clone for CoroutineWitness where T: Copy/Clone forall T in coroutine_hidden_types
ty::CoroutineWitness(def_id, args) => Ok(ecx
.tcx()
.coroutine_hidden_types(def_id)
Expand Down
8 changes: 8 additions & 0 deletions compiler/rustc_trait_selection/src/solve/trait_goals.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -251,13 +251,15 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
) -> QueryResult<'tcx> {
let self_ty = goal.predicate.self_ty();
match goal.predicate.polarity {
// impl FnPtr for FnPtr {}
ty::ImplPolarity::Positive => {
if self_ty.is_fn_ptr() {
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
} else {
Err(NoSolution)
}
}
// impl !FnPtr for T where T != FnPtr && T is rigid {}
ty::ImplPolarity::Negative => {
// If a type is rigid and not a fn ptr, then we know for certain
// that it does *not* implement `FnPtr`.
Expand Down Expand Up @@ -375,6 +377,12 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
}
}

/// ```rust, ignore (not valid rust syntax)
/// impl Tuple for () {}
/// impl Tuple for (T1,) {}
/// impl Tuple for (T1, T2) {}
/// impl Tuple for (T1, .., Tn) {}
/// ```
fn consider_builtin_tuple_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
Expand Down
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