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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:18:32 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:18:32 +0000
commit4547b622d8d29df964fa2914213088b148c498fc (patch)
tree9fc6b25f3c3add6b745be9a2400a6e96140046e9 /compiler/rustc_traits/src/codegen.rs
parentReleasing progress-linux version 1.66.0+dfsg1-1~progress7.99u1. (diff)
downloadrustc-4547b622d8d29df964fa2914213088b148c498fc.tar.xz
rustc-4547b622d8d29df964fa2914213088b148c498fc.zip
Merging upstream version 1.67.1+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'compiler/rustc_traits/src/codegen.rs')
-rw-r--r--compiler/rustc_traits/src/codegen.rs88
1 files changed, 88 insertions, 0 deletions
diff --git a/compiler/rustc_traits/src/codegen.rs b/compiler/rustc_traits/src/codegen.rs
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+// This file contains various trait resolution methods used by codegen.
+// They all assume regions can be erased and monomorphic types. It
+// seems likely that they should eventually be merged into more
+// general routines.
+
+use rustc_infer::infer::{DefiningAnchor, TyCtxtInferExt};
+use rustc_infer::traits::FulfillmentErrorCode;
+use rustc_middle::traits::CodegenObligationError;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
+use rustc_trait_selection::traits::{
+ ImplSource, Obligation, ObligationCause, SelectionContext, TraitEngine, TraitEngineExt,
+ Unimplemented,
+};
+
+/// Attempts to resolve an obligation to an `ImplSource`. The result is
+/// a shallow `ImplSource` resolution, meaning that we do not
+/// (necessarily) resolve all nested obligations on the impl. Note
+/// that type check should guarantee to us that all nested
+/// obligations *could be* resolved if we wanted to.
+///
+/// This also expects that `trait_ref` is fully normalized.
+pub fn codegen_select_candidate<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ (param_env, trait_ref): (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>),
+) -> Result<&'tcx ImplSource<'tcx, ()>, CodegenObligationError> {
+ // We expect the input to be fully normalized.
+ debug_assert_eq!(trait_ref, tcx.normalize_erasing_regions(param_env, trait_ref));
+
+ // Do the initial selection for the obligation. This yields the
+ // shallow result we are looking for -- that is, what specific impl.
+ let infcx = tcx
+ .infer_ctxt()
+ .ignoring_regions()
+ .with_opaque_type_inference(DefiningAnchor::Bubble)
+ .build();
+ //~^ HACK `Bubble` is required for
+ // this test to pass: type-alias-impl-trait/assoc-projection-ice.rs
+ let mut selcx = SelectionContext::new(&infcx);
+
+ let obligation_cause = ObligationCause::dummy();
+ let obligation = Obligation::new(tcx, obligation_cause, param_env, trait_ref);
+
+ let selection = match selcx.select(&obligation) {
+ Ok(Some(selection)) => selection,
+ Ok(None) => return Err(CodegenObligationError::Ambiguity),
+ Err(Unimplemented) => return Err(CodegenObligationError::Unimplemented),
+ Err(e) => {
+ bug!("Encountered error `{:?}` selecting `{:?}` during codegen", e, trait_ref)
+ }
+ };
+
+ debug!(?selection);
+
+ // Currently, we use a fulfillment context to completely resolve
+ // all nested obligations. This is because they can inform the
+ // inference of the impl's type parameters.
+ let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(tcx);
+ let impl_source = selection.map(|predicate| {
+ fulfill_cx.register_predicate_obligation(&infcx, predicate);
+ });
+
+ // In principle, we only need to do this so long as `impl_source`
+ // contains unbound type parameters. It could be a slight
+ // optimization to stop iterating early.
+ let errors = fulfill_cx.select_all_or_error(&infcx);
+ if !errors.is_empty() {
+ // `rustc_monomorphize::collector` assumes there are no type errors.
+ // Cycle errors are the only post-monomorphization errors possible; emit them now so
+ // `rustc_ty_utils::resolve_associated_item` doesn't return `None` post-monomorphization.
+ for err in errors {
+ if let FulfillmentErrorCode::CodeCycle(cycle) = err.code {
+ infcx.err_ctxt().report_overflow_obligation_cycle(&cycle);
+ }
+ }
+ return Err(CodegenObligationError::FulfillmentError);
+ }
+
+ let impl_source = infcx.resolve_vars_if_possible(impl_source);
+ let impl_source = infcx.tcx.erase_regions(impl_source);
+
+ // Opaque types may have gotten their hidden types constrained, but we can ignore them safely
+ // as they will get constrained elsewhere, too.
+ // (ouz-a) This is required for `type-alias-impl-trait/assoc-projection-ice.rs` to pass
+ let _ = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
+
+ Ok(&*tcx.arena.alloc(impl_source))
+}