Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Fix inference issues with unconstrained base expr in type_changing_struct_update #97705

Merged
merged 3 commits into from
Jun 12, 2022
Merged

Fix inference issues with unconstrained base expr in type_changing_struct_update #97705

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
6c00e54
Guide inference along during type_changing_struct_update
compiler-errors Jun 3, 2022
d9ddaf0
Use if-let instead of match with guard
compiler-errors Jun 11, 2022
5052911
Stop using string equality to check if ADT is a union
compiler-errors Jun 11, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
152 changes: 85 additions & 67 deletions compiler/rustc_typeck/src/check/expr.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -41,8 +41,7 @@ use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKi
use rustc_infer::infer::InferOk;
use rustc_middle::middle::stability;
use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
use rustc_middle::ty::error::ExpectedFound;
use rustc_middle::ty::error::TypeError::{FieldMisMatch, Sorts};
use rustc_middle::ty::error::TypeError::FieldMisMatch;
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TypeFoldable};
use rustc_session::parse::feature_err;
Expand All @@ -65,7 +64,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
&self,
expr: &'tcx hir::Expr<'tcx>,
expected: Ty<'tcx>,
extend_err: impl Fn(&mut Diagnostic),
extend_err: impl FnMut(&mut Diagnostic),
) -> Ty<'tcx> {
self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
}
Expand All @@ -74,7 +73,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
&self,
expr: &'tcx hir::Expr<'tcx>,
expected: Expectation<'tcx>,
extend_err: impl Fn(&mut Diagnostic),
mut extend_err: impl FnMut(&mut Diagnostic),
) -> Ty<'tcx> {
let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
let mut ty = self.check_expr_with_expectation(expr, expected);
Expand Down Expand Up @@ -1480,10 +1479,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// re-link the regions that EIfEO can erase.
self.demand_eqtype(span, adt_ty_hint, adt_ty);

let (substs, adt_kind, kind_name) = match adt_ty.kind() {
ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
_ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
let ty::Adt(adt, substs) = adt_ty.kind() else {
span_bug!(span, "non-ADT passed to check_expr_struct_fields");
};
let adt_kind = adt.adt_kind();

let mut remaining_fields = variant
.fields
Expand Down Expand Up @@ -1521,7 +1520,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
});
} else {
self.report_unknown_field(
adt_ty, variant, field, ast_fields, kind_name, expr_span,
adt_ty,
variant,
field,
ast_fields,
adt.variant_descr(),
expr_span,
);
}

Expand All @@ -1534,7 +1538,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}

// Make sure the programmer specified correct number of fields.
if kind_name == "union" {
if adt_kind == AdtKind::Union {
if ast_fields.len() != 1 {
struct_span_err!(
tcx.sess,
Expand All @@ -1557,67 +1561,81 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// FIXME: We are currently creating two branches here in order to maintain
// consistency. But they should be merged as much as possible.
let fru_tys = if self.tcx.features().type_changing_struct_update {
let base_ty = self.check_expr(base_expr);
match adt_ty.kind() {
ty::Adt(adt, substs) if adt.is_struct() => {
match base_ty.kind() {
ty::Adt(base_adt, base_subs) if adt == base_adt => {
variant
.fields
.iter()
.map(|f| {
let fru_ty = self.normalize_associated_types_in(
expr_span,
self.field_ty(base_expr.span, f, base_subs),
);
let ident = self
.tcx
.adjust_ident(f.ident(self.tcx), variant.def_id);
if let Some(_) = remaining_fields.remove(&ident) {
let target_ty =
self.field_ty(base_expr.span, f, substs);
let cause = self.misc(base_expr.span);
match self
.at(&cause, self.param_env)
.sup(target_ty, fru_ty)
{
Ok(InferOk { obligations, value: () }) => {
self.register_predicates(obligations)
}
// FIXME: Need better diagnostics for `FieldMisMatch` error
Err(_) => {
self.report_mismatched_types(
&cause,
target_ty,
fru_ty,
FieldMisMatch(variant.name, ident.name),
)
.emit();
}
}
if let ty::Adt(adt, substs) = adt_ty.kind() && adt.is_struct() {
// Make an ADT with fresh inference substitutions. This
// will allow us to guide inference along so that, e.g.
// ```
// let x = MyStruct<'a, B, const C: usize> {
// f: 1,
// ..Default::default()
// };
// ```
// will have the default base expression constrained to
// `MyStruct<'_, _, _>`, as opposed to just `_`... This
// will allow us to then do a subtyping relation on all
// of the `remaining_fields` below, per the RFC.
let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
let base_ty = self.check_expr_has_type_or_error(
base_expr,
fresh_base_ty,
|_| {
error_happened = true;
},
);
let base_ty = self.shallow_resolve(base_ty);
if let ty::Adt(base_adt, base_substs) = base_ty.kind() && adt == base_adt {
variant
.fields
.iter()
.map(|f| {
let fru_ty = self.normalize_associated_types_in(
expr_span,
self.field_ty(base_expr.span, f, base_substs),
);
let ident = self
.tcx
.adjust_ident(f.ident(self.tcx), variant.def_id);
if let Some(_) = remaining_fields.remove(&ident) {
let target_ty =
self.field_ty(base_expr.span, f, substs);
let cause = self.misc(base_expr.span);
match self
.at(&cause, self.param_env)
.sup(target_ty, fru_ty)
{
Ok(InferOk { obligations, value: () }) => {
self.register_predicates(obligations)
}
fru_ty
})
.collect()
}
_ => {
self.report_mismatched_types(
&self.misc(base_expr.span),
adt_ty,
base_ty,
Sorts(ExpectedFound::new(true, adt_ty, base_ty)),
)
.emit();
return;
}
// FIXME: Need better diagnostics for `FieldMisMatch` error
Err(_) => {
self.report_mismatched_types(
&cause,
target_ty,
fru_ty,
FieldMisMatch(variant.name, ident.name),
)
.emit();
}
}
}
self.resolve_vars_if_possible(fru_ty)
})
.collect()
} else {
if !error_happened && !base_ty.references_error() {
span_bug!(base_expr.span, "expected an error to have been reported in `check_expr_has_type_or_error`");
}
}
_ => {
self.tcx
.sess
.emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
return;
}
} else {
// Check the base_expr, regardless of a bad expected adt_ty, so we can get
// type errors on that expression, too.
self.check_expr(base_expr);
self.tcx
.sess
.emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
return;
}
} else {
self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
Expand Down Expand Up @@ -1653,7 +1671,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
};
self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
} else if kind_name != "union" && !remaining_fields.is_empty() {
} else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
let inaccessible_remaining_fields = remaining_fields.iter().any(|(_, (_, field))| {
!field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
});
Expand Down
31 changes: 31 additions & 0 deletions src/test/ui/rfcs/rfc-2528-type-changing-struct-update/issue-96878.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
// check-pass

#![feature(type_changing_struct_update)]
#![allow(incomplete_features)]

use std::borrow::Cow;
use std::marker::PhantomData;

#[derive(Default)]
struct NonGeneric {
field1: usize,
}

#[derive(Default)]
struct Generic<T, U> {
field1: T,
field2: U,
}

#[derive(Default)]
struct MoreGeneric<'a, const N: usize> {
// If only `for<const N: usize> [u32; N]: Default`...
field1: PhantomData<[u32; N]>,
field2: Cow<'a, str>,
}

fn main() {
let default1 = NonGeneric { ..Default::default() };
let default2: Generic<i32, f32> = Generic { ..Default::default() };
let default3: MoreGeneric<'static, 12> = MoreGeneric { ..Default::default() };
}