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Auto merge of #109753 - compiler-errors:replenish-region-constraints, r=aliemjay

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Clone region var origins instead of taking them in borrowck

Fixes an issue with the new solver where reporting a borrow-checker error ICEs because it calls `InferCtxt::evaluate_obligation`.

This also removes a handful of unnecessary `tcx.infer_ctxt().build()` calls that are only there to mitigate this same exact issue, but with the old solver.

Fixes compiler-errors/next-solver-hir-issues#12.

----

This implements `@aliemjay's` solution where we just don't *take* the region constraints, but clone them. This potentially makes it easier to write a bug about taking region constraints twice or never at all, but again, not many folks are touching this code.
This commit is contained in:
bors 2023-04-22 15:15:51 +00:00
commit 4396ceca05
6 changed files with 43 additions and 33 deletions
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20
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
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@ -10,7 +10,6 @@ use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::intravisit::{walk_block, walk_expr, Visitor};
use rustc_hir::{AsyncGeneratorKind, GeneratorKind, LangItem};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_infer::traits::ObligationCause;
use rustc_middle::hir::nested_filter::OnlyBodies;
use rustc_middle::mir::tcx::PlaceTy;
@ -643,11 +642,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let Some(default_trait) = tcx.get_diagnostic_item(sym::Default) else {
return false;
};
// Regions are already solved, so we must use a fresh InferCtxt,
// but the type has region variables, so erase those.
tcx.infer_ctxt()
.build()
.type_implements_trait(default_trait, [tcx.erase_regions(ty)], param_env)
self.infcx
.type_implements_trait(default_trait, [ty], param_env)
.must_apply_modulo_regions()
};
@ -740,13 +736,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
fn suggest_cloning(&self, err: &mut Diagnostic, ty: Ty<'tcx>, span: Span) {
let tcx = self.infcx.tcx;
// Try to find predicates on *generic params* that would allow copying `ty`
let infcx = tcx.infer_ctxt().build();
if let Some(clone_trait_def) = tcx.lang_items().clone_trait()
&& infcx
&& self.infcx
.type_implements_trait(
clone_trait_def,
[tcx.erase_regions(ty)],
[ty],
self.param_env,
)
.must_apply_modulo_regions()
@ -770,12 +764,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
.and_then(|def_id| tcx.hir().get_generics(def_id))
else { return; };
// Try to find predicates on *generic params* that would allow copying `ty`
let infcx = tcx.infer_ctxt().build();
let ocx = ObligationCtxt::new(&infcx);
let ocx = ObligationCtxt::new(&self.infcx);
let copy_did = tcx.require_lang_item(LangItem::Copy, Some(span));
let cause = ObligationCause::misc(span, self.mir_def_id());
ocx.register_bound(cause, self.param_env, infcx.tcx.erase_regions(ty), copy_did);
ocx.register_bound(cause, self.param_env, ty, copy_did);
let errors = ocx.select_all_or_error();
// Only emit suggestion if all required predicates are on generic
@ -2219,7 +2212,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let tcx = self.infcx.tcx;
let return_ty = self.regioncx.universal_regions().unnormalized_output_ty;
let return_ty = tcx.erase_regions(return_ty);
// to avoid panics
if let Some(iter_trait) = tcx.get_diagnostic_item(sym::Iterator)