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Rollup merge of #96854 - jackh726:subst-cleanup, r=compiler-errors
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Some subst cleanup

Two separate things here. Both changes are useful for some refactoring I'm doing to add an "EarlyBinder" newtype. (Part of chalkification).

1) Remove `subst_spanned` and just use `subst`. It wasn't used much anyways. In practice, I think we can probably get most of the info just from the actual error message. If not, outputting logs should do the trick. (The specific line probably wouldn't help much anyways).

2) Call `.subst()` before `replace_bound_vars_with_fresh_vars` and `erase_late_bound_regions` in three places that do the opposite. I think there might have been some time in the past that the order here matter for something, but this shouldn't be the case anymore. Conceptually, it makes more sense to the of the *early bound* vars on `fn`s as "outside" the late bound vars.
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@matthiaskrgr
matthiaskrgr authored May 9, 2022
2 parents 84a8f8d + 657499d commit 0e00ed5
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Showing 6 changed files with 26 additions and 73 deletions.
48 changes: 10 additions & 38 deletions compiler/rustc_middle/src/ty/subst.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ use rustc_data_structures::intern::{Interned, WithStableHash};
use rustc_hir::def_id::DefId;
use rustc_macros::HashStable;
use rustc_serialize::{self, Decodable, Encodable};
use rustc_span::{Span, DUMMY_SP};
use rustc_span::DUMMY_SP;
use smallvec::SmallVec;

use core::intrinsics;
Expand Down Expand Up @@ -498,34 +498,14 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
}
}

///////////////////////////////////////////////////////////////////////////
// Public trait `Subst`
//
// Just call `foo.subst(tcx, substs)` to perform a substitution across
// `foo`. Or use `foo.subst_spanned(tcx, substs, Some(span))` when
// there is more information available (for better errors).

// Just call `foo.subst(tcx, substs)` to perform a substitution across `foo`.
pub trait Subst<'tcx>: Sized {
fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> Self {
self.subst_spanned(tcx, substs, None)
}

fn subst_spanned(
self,
tcx: TyCtxt<'tcx>,
substs: &[GenericArg<'tcx>],
span: Option<Span>,
) -> Self;
fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> Self;
}

impl<'tcx, T: TypeFoldable<'tcx>> Subst<'tcx> for T {
fn subst_spanned(
self,
tcx: TyCtxt<'tcx>,
substs: &[GenericArg<'tcx>],
span: Option<Span>,
) -> T {
let mut folder = SubstFolder { tcx, substs, span, binders_passed: 0 };
fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> T {
let mut folder = SubstFolder { tcx, substs, binders_passed: 0 };
self.fold_with(&mut folder)
}
}
Expand All @@ -537,9 +517,6 @@ struct SubstFolder<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
substs: &'a [GenericArg<'tcx>],

/// The location for which the substitution is performed, if available.
span: Option<Span>,

/// Number of region binders we have passed through while doing the substitution
binders_passed: u32,
}
Expand Down Expand Up @@ -571,13 +548,12 @@ impl<'a, 'tcx> TypeFolder<'tcx> for SubstFolder<'a, 'tcx> {
match rk {
Some(GenericArgKind::Lifetime(lt)) => self.shift_region_through_binders(lt),
_ => {
let span = self.span.unwrap_or(DUMMY_SP);
let msg = format!(
"Region parameter out of range \
when substituting in region {} (index={})",
data.name, data.index
);
span_bug!(span, "{}", msg);
span_bug!(DUMMY_SP, "{}", msg);
}
}
}
Expand Down Expand Up @@ -617,9 +593,8 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
let ty = match opt_ty {
Some(GenericArgKind::Type(ty)) => ty,
Some(kind) => {
let span = self.span.unwrap_or(DUMMY_SP);
span_bug!(
span,
DUMMY_SP,
"expected type for `{:?}` ({:?}/{}) but found {:?} \
when substituting, substs={:?}",
p,
Expand All @@ -630,9 +605,8 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
);
}
None => {
let span = self.span.unwrap_or(DUMMY_SP);
span_bug!(
span,
DUMMY_SP,
"type parameter `{:?}` ({:?}/{}) out of range \
when substituting, substs={:?}",
p,
Expand All @@ -652,9 +626,8 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
let ct = match opt_ct {
Some(GenericArgKind::Const(ct)) => ct,
Some(kind) => {
let span = self.span.unwrap_or(DUMMY_SP);
span_bug!(
span,
DUMMY_SP,
"expected const for `{:?}` ({:?}/{}) but found {:?} \
when substituting substs={:?}",
p,
Expand All @@ -665,9 +638,8 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
);
}
None => {
let span = self.span.unwrap_or(DUMMY_SP);
span_bug!(
span,
DUMMY_SP,
"const parameter `{:?}` ({:?}/{}) out of range \
when substituting substs={:?}",
p,
Expand Down
10 changes: 2 additions & 8 deletions compiler/rustc_typeck/src/astconv/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -523,11 +523,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
self.astconv
.normalize_ty(
self.span,
tcx.at(self.span).type_of(param.def_id).subst_spanned(
tcx,
substs,
Some(self.span),
),
tcx.at(self.span).type_of(param.def_id).subst(tcx, substs),
)
.into()
}
Expand All @@ -547,9 +543,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
GenericParamDefKind::Const { has_default } => {
let ty = tcx.at(self.span).type_of(param.def_id);
if !infer_args && has_default {
tcx.const_param_default(param.def_id)
.subst_spanned(tcx, substs.unwrap(), Some(self.span))
.into()
tcx.const_param_default(param.def_id).subst(tcx, substs.unwrap()).into()
} else {
if infer_args {
self.astconv.ct_infer(ty, Some(param), self.span).into()
Expand Down
9 changes: 2 additions & 7 deletions compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1403,10 +1403,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// is missing.
let default = tcx.type_of(param.def_id);
self.fcx
.normalize_ty(
self.span,
default.subst_spanned(tcx, substs.unwrap(), Some(self.span)),
)
.normalize_ty(self.span, default.subst(tcx, substs.unwrap()))
.into()
} else {
// If no type arguments were provided, we have to infer them.
Expand All @@ -1418,9 +1415,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
GenericParamDefKind::Const { has_default } => {
if !infer_args && has_default {
tcx.const_param_default(param.def_id)
.subst_spanned(tcx, substs.unwrap(), Some(self.span))
.into()
tcx.const_param_default(param.def_id).subst(tcx, substs.unwrap()).into()
} else {
self.fcx.var_for_def(self.span, param)
}
Expand Down
16 changes: 5 additions & 11 deletions compiler/rustc_typeck/src/check/method/confirm.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -462,19 +462,13 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {

let sig = self.tcx.fn_sig(def_id);

// Instantiate late-bound regions and substitute the trait
// parameters into the method type to get the actual method type.
//
// N.B., instantiate late-bound regions first so that
// `instantiate_type_scheme` can normalize associated types that
// may reference those regions.
let method_sig = self.replace_bound_vars_with_fresh_vars(sig);
debug!("late-bound lifetimes from method instantiated, method_sig={:?}", method_sig);
let sig = sig.subst(self.tcx, all_substs);
debug!("type scheme substituted, sig={:?}", sig);

let method_sig = method_sig.subst(self.tcx, all_substs);
debug!("type scheme substituted, method_sig={:?}", method_sig);
let sig = self.replace_bound_vars_with_fresh_vars(sig);
debug!("late-bound lifetimes from method instantiated, sig={:?}", sig);

(method_sig, method_predicates)
(sig, method_predicates)
}

fn add_obligations(
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_typeck/src/check/method/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -461,8 +461,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// `instantiate_type_scheme` can normalize associated types that
// may reference those regions.
let fn_sig = tcx.fn_sig(def_id);
let fn_sig = self.replace_bound_vars_with_fresh_vars(span, infer::FnCall, fn_sig).0;
let fn_sig = fn_sig.subst(self.tcx, substs);
let fn_sig = self.replace_bound_vars_with_fresh_vars(span, infer::FnCall, fn_sig).0;

let InferOk { value, obligations: o } = if is_op {
self.normalize_op_associated_types_in_as_infer_ok(span, fn_sig, opt_input_expr)
Expand Down
14 changes: 6 additions & 8 deletions compiler/rustc_typeck/src/check/method/probe.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1784,12 +1784,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
let generics = self.tcx.generics_of(method);
assert_eq!(substs.len(), generics.parent_count as usize);

// Erase any late-bound regions from the method and substitute
// in the values from the substitution.
let xform_fn_sig = self.erase_late_bound_regions(fn_sig);

if generics.params.is_empty() {
xform_fn_sig.subst(self.tcx, substs)
let xform_fn_sig = if generics.params.is_empty() {
fn_sig.subst(self.tcx, substs)
} else {
let substs = InternalSubsts::for_item(self.tcx, method, |param, _| {
let i = param.index as usize;
Expand All @@ -1807,8 +1803,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
}
}
});
xform_fn_sig.subst(self.tcx, substs)
}
fn_sig.subst(self.tcx, substs)
};

self.erase_late_bound_regions(xform_fn_sig)
}

/// Gets the type of an impl and generate substitutions with placeholders.
Expand Down

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