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Infer params inside trait args during projection #577

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merged 1 commit into from
Dec 18, 2023
Merged

Infer params inside trait args during projection #577

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37 changes: 22 additions & 15 deletions crates/flux-middle/src/rty/projections.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ use rustc_trait_selection::traits::SelectionContext;

use super::{
fold::{FallibleTypeFolder, TypeSuperFoldable},
AliasKind, AliasTy, BaseTy, BoundRegion, Clause, ClauseKind, Expr, GenericArg,
AliasKind, AliasTy, BaseTy, BoundRegion, Clause, ClauseKind, Expr, GenericArg, GenericArgs,
ProjectionPredicate, Region, Ty, TyKind,
};
use crate::{
Expand Down Expand Up @@ -72,17 +72,17 @@ impl<'sess, 'tcx, 'cx> Normalizer<'sess, 'tcx, 'cx> {
// to infer a substitution
// IntoIter<{v. i32[v] | v > 0}, Global> against IntoIter<T, A>
// => {T -> {v. i32[v] | v > 0}, A -> Global}
let rustc_self_ty = self
let impl_trait_ref = self
.tcx()
.impl_trait_ref(impl_def_id)
.unwrap()
.skip_binder()
.self_ty();
.skip_binder();

let generics = self.tcx().generics_of(impl_def_id);

let args =
TVarSubst::mk_subst(self.tcx(), generics, &rustc_self_ty, obligation.self_ty());
let mut subst = TVarSubst::new(generics);
subst.infer_from_args(impl_trait_ref.args, &obligation.args);
let args = subst.finish(self.tcx(), generics);

// 2. Get the associated type in the impl block and apply the substitution to it
let assoc_type_id = self
Expand Down Expand Up @@ -331,16 +331,16 @@ struct TVarSubst {
}

impl TVarSubst {
fn mk_subst<'tcx>(
fn new(generics: &rustc_middle::ty::Generics) -> Self {
Self { args: vec![None; generics.count()] }
}

fn finish<'tcx>(
self,
tcx: TyCtxt<'tcx>,
generics: &'tcx rustc_middle::ty::Generics,
src: &rustc_middle::ty::Ty,
dst: &Ty,
) -> Vec<GenericArg> {
let mut subst = TVarSubst { args: vec![None; generics.count()] };
subst.infer_from_ty(src, dst);
subst
.args
self.args
.into_iter()
.enumerate()
.map(|(idx, arg)| {
Expand Down Expand Up @@ -368,7 +368,14 @@ impl TVarSubst {
}
}

fn infer_from_arg(&mut self, src: &rustc_middle::ty::GenericArg, dst: &GenericArg) {
fn infer_from_args(&mut self, src: rustc_middle::ty::GenericArgsRef, dst: &GenericArgs) {
debug_assert_eq!(src.len(), dst.len());
for (src, dst) in iter::zip(src, dst) {
self.infer_from_arg(src, dst);
}
}

fn infer_from_arg(&mut self, src: rustc_middle::ty::GenericArg, dst: &GenericArg) {
match dst {
GenericArg::Ty(dst) => {
self.infer_from_ty(&src.as_type().unwrap(), dst);
Expand All @@ -390,7 +397,7 @@ impl TVarSubst {
{
debug_assert_eq!(src_subst.len(), dst_subst.len());
for (src_arg, dst_arg) in iter::zip(*src_subst, dst_subst) {
self.infer_from_arg(&src_arg, dst_arg);
self.infer_from_arg(src_arg, dst_arg);
}
} else {
bug!("unexpected type {dst:?}");
Expand Down
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