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Implement lint for obligations broken by never type fallback change #125289

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Merged
merged 7 commits into from
Jun 13, 2024
Merged

Implement lint for obligations broken by never type fallback change #125289

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83f8f9f
Implement lint for obligations broken by never type fallback change
WaffleLapkin May 19, 2024
b88d03b
Add a fast exit to `lint_obligations_broken_by_never_type_fallback_ch…
WaffleLapkin May 20, 2024
0f41d26
Apply review nits
WaffleLapkin May 20, 2024
268b556
Bless a test
WaffleLapkin May 20, 2024
a22f8aa
Fixup clippy tests
WaffleLapkin May 23, 2024
8400cd0
Fixup links in lint docs
WaffleLapkin May 22, 2024
ea98e42
rebase blessing
WaffleLapkin Jun 13, 2024
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@WaffleLapkin
WaffleLapkin committed Jun 13, 2024
commit 0f41d26f419dc7cdaa01941604faf188123d3ea0
19 changes: 8 additions & 11 deletions compiler/rustc_hir_typeck/src/fallback.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,17 +8,13 @@ use rustc_data_structures::{
use rustc_hir as hir;
use rustc_hir::intravisit::Visitor;
use rustc_hir::HirId;
use rustc_infer::{
infer::{DefineOpaqueTypes, InferOk},
traits::ObligationCause,
};
use rustc_infer::infer::{DefineOpaqueTypes, InferOk};
use rustc_middle::bug;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable};
use rustc_session::lint;
use rustc_span::DUMMY_SP;
use rustc_span::{def_id::LocalDefId, Span};
use rustc_trait_selection::traits::ObligationCtxt;
use rustc_type_ir::TyVid;
use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt};

#[derive(Copy, Clone)]
pub enum DivergingFallbackBehavior {
Expand Down Expand Up @@ -479,7 +475,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
fn lint_obligations_broken_by_never_type_fallback_change(
&self,
behavior: DivergingFallbackBehavior,
diverging_vids: &[TyVid],
diverging_vids: &[ty::TyVid],
) {
let DivergingFallbackBehavior::FallbackToUnit = behavior else { return };

Expand All @@ -489,7 +485,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
}

// Returns errors which happen if fallback is set to `fallback`
let try_out = |fallback| {
let remaining_errors_if_fallback_to = |fallback| {
self.probe(|_| {
let obligations = self.fulfillment_cx.borrow().pending_obligations();
let ocx = ObligationCtxt::new(&self.infcx);
Expand All @@ -498,7 +494,8 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
for &diverging_vid in diverging_vids {
let diverging_ty = Ty::new_var(self.tcx, diverging_vid);

_ = ocx.eq(&ObligationCause::dummy(), self.param_env, diverging_ty, fallback);
ocx.eq(&ObligationCause::dummy(), self.param_env, diverging_ty, fallback)
.expect("expected diverging var to be unconstrained");
}

ocx.select_where_possible()
Expand All @@ -507,9 +504,9 @@ impl<'tcx> FnCtxt<'_, 'tcx> {

// If we have no errors with `fallback = ()`, but *do* have errors with `fallback = !`,
// then this code will be broken by the never type fallback change.qba
let unit_errors = try_out(self.tcx.types.unit);
let unit_errors = remaining_errors_if_fallback_to(self.tcx.types.unit);
if unit_errors.is_empty()
&& let never_errors = try_out(self.tcx.types.never)
&& let never_errors = remaining_errors_if_fallback_to(self.tcx.types.never)
&& !never_errors.is_empty()
{
self.tcx.emit_node_span_lint(
Expand Down