bjoernager/rust
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added a suggestion to create a const item if the fn in the array repeat expression is a const fn

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This commit is contained in:
Henry Boisdequin 2021-01-29 11:54:19 +05:30
parent 368275062f
commit c2e849c022
7 changed files with 87 additions and 4 deletions
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13
compiler/rustc_mir/src/borrow_check/type_check/mod.rs
View file

@ -43,6 +43,9 @@ use rustc_trait_selection::traits::{self, ObligationCause, PredicateObligations}
use crate::dataflow::impls::MaybeInitializedPlaces;
use crate::dataflow::move_paths::MoveData;
use crate::dataflow::ResultsCursor;
use crate::transform::{
check_consts::ConstCx, promote_consts::is_const_fn_in_array_repeat_expression,
};
use crate::borrow_check::{
borrow_set::BorrowSet,
@ -1988,18 +1991,24 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
Operand::Copy(..) | Operand::Constant(..) => {
// These are always okay: direct use of a const, or a value that can evidently be copied.
}
Operand::Move(_) => {
Operand::Move(place) => {
// Make sure that repeated elements implement `Copy`.
let span = body.source_info(location).span;
let ty = operand.ty(body, tcx);
if !self.infcx.type_is_copy_modulo_regions(self.param_env, ty, span) {
let ccx = ConstCx::new_with_param_env(tcx, body, self.param_env);
let is_const_fn =
is_const_fn_in_array_repeat_expression(&ccx, &place, &body);
debug!("check_rvalue: is_const_fn={:?}", is_const_fn);
let def_id = body.source.def_id().expect_local();
self.infcx.report_selection_error(
&traits::Obligation::new(
ObligationCause::new(
span,
self.tcx().hir().local_def_id_to_hir_id(def_id),
traits::ObligationCauseCode::RepeatVec,
traits::ObligationCauseCode::RepeatVec(is_const_fn),
),
self.param_env,
ty::Binder::bind(ty::TraitRef::new(

35
compiler/rustc_mir/src/transform/promote_consts.rs
View file

@ -1231,3 +1231,38 @@ pub fn promote_candidates<'tcx>(
promotions
}
/// This function returns `true` if the function being called in the array
/// repeat expression is a `const` function.
crate fn is_const_fn_in_array_repeat_expression<'tcx>(
ccx: &ConstCx<'_, 'tcx>,
place: &Place<'tcx>,
body: &Body<'tcx>,
) -> bool {
match place.as_local() {
// rule out cases such as: `let my_var = some_fn(); [my_var; N]`
Some(local) if body.local_decls[local].is_user_variable() => return false,
None => return false,
_ => {}
}
for block in body.basic_blocks() {
if let Some(Terminator { kind: TerminatorKind::Call { func, destination, .. }, .. }) =
&block.terminator
{
if let Operand::Constant(box Constant { literal: ty::Const { ty, .. }, .. }) = func {
if let ty::FnDef(def_id, _) = *ty.kind() {
if let Some((destination_place, _)) = destination {
if destination_place == place {
if is_const_fn(ccx.tcx, def_id) {
return true;
}
}
}
}
}
}
}
false
}