1
Fork 0

Point at method chains on E0271 errors

This commit is contained in:
Esteban Küber 2022-12-12 17:39:08 -08:00
parent 984eab57f7
commit 294944dfec
3 changed files with 138 additions and 89 deletions

View file

@ -352,6 +352,14 @@ pub trait TypeErrCtxtExt<'tcx> {
param_env: ty::ParamEnv<'tcx>,
err: &mut Diagnostic,
);
fn probe_assoc_types_at_expr(
&self,
type_diffs: &[TypeError<'tcx>],
span: Span,
prev_ty: Ty<'tcx>,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
) -> Vec<Option<(Span, (DefId, Ty<'tcx>))>>;
}
fn predicate_constraint(generics: &hir::Generics<'_>, pred: ty::Predicate<'_>) -> (Span, String) {
@ -3152,23 +3160,37 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
if let ObligationCauseCode::ExprBindingObligation(def_id, _, _, idx) = parent_code.deref()
&& let predicates = self.tcx.predicates_of(def_id).instantiate_identity(self.tcx)
&& let Some(pred) = predicates.predicates.get(*idx)
&& let Ok(trait_pred) = pred.kind().try_map_bound(|pred| match pred {
{
if let Ok(trait_pred) = pred.kind().try_map_bound(|pred| match pred {
ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred)) => Ok(trait_pred),
_ => Err(()),
})
{
let mut c = CollectAllMismatches {
infcx: self.infcx,
param_env,
errors: vec![],
};
if let Ok(trait_predicate) = predicate.kind().try_map_bound(|pred| match pred {
ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred)) => Ok(trait_pred),
_ => Err(()),
}) {
&& let Ok(trait_predicate) = predicate.kind().try_map_bound(|pred| match pred {
ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred)) => Ok(trait_pred),
_ => Err(()),
})
{
let mut c = CollectAllMismatches {
infcx: self.infcx,
param_env,
errors: vec![],
};
if let Ok(_) = c.relate(trait_pred, trait_predicate) {
type_diffs = c.errors;
}
} else if let ty::PredicateKind::Clause(
ty::Clause::Projection(proj)
) = pred.kind().skip_binder()
&& let ty::PredicateKind::Clause(
ty::Clause::Projection(projection)
) = predicate.kind().skip_binder()
{
type_diffs = vec![
Sorts(ty::error::ExpectedFound {
expected: self.tcx.mk_ty(ty::Alias(ty::Projection, proj.projection_ty)),
found: projection.term.ty().unwrap(),
}),
];
}
}
if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = expr.kind
@ -3221,10 +3243,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
let tcx = self.tcx;
let mut print_root_expr = true;
let mut assocs = vec![];
// We still want to point at the different methods even if there hasn't
// been a change of assoc type.
let mut call_spans = vec![];
let mut expr = expr;
let mut prev_ty = self.resolve_vars_if_possible(
typeck_results.expr_ty_adjusted_opt(expr).unwrap_or(tcx.ty_error()),
@ -3234,63 +3254,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
// vec![1, 2, 3].iter().map(mapper).sum<i32>()
// ^^^^^^ ^^^^^^^^^^^
expr = rcvr_expr;
let mut assocs_in_this_method = Vec::with_capacity(type_diffs.len());
call_spans.push(span);
let ocx = ObligationCtxt::new_in_snapshot(self.infcx);
for diff in &type_diffs {
let Sorts(expected_found) = diff else { continue; };
let ty::Alias(ty::Projection, proj) = expected_found.expected.kind() else { continue; };
let origin =
TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span };
let trait_def_id = proj.trait_def_id(self.tcx);
// Make `Self` be equivalent to the type of the call chain
// expression we're looking at now, so that we can tell what
// for example `Iterator::Item` is at this point in the chain.
let substs = InternalSubsts::for_item(self.tcx, trait_def_id, |param, _| {
match param.kind {
ty::GenericParamDefKind::Type { .. } => {
if param.index == 0 {
return prev_ty.into();
}
}
ty::GenericParamDefKind::Lifetime
| ty::GenericParamDefKind::Const { .. } => {}
}
self.var_for_def(span, param)
});
// This will hold the resolved type of the associated type, if the
// current expression implements the trait that associated type is
// in. For example, this would be what `Iterator::Item` is here.
let ty_var = self.infcx.next_ty_var(origin);
// This corresponds to `<ExprTy as Iterator>::Item = _`.
let projection = ty::Binder::dummy(ty::PredicateKind::Clause(
ty::Clause::Projection(ty::ProjectionPredicate {
projection_ty: tcx.mk_alias_ty(proj.def_id, substs),
term: ty_var.into(),
}),
));
// Add `<ExprTy as Iterator>::Item = _` obligation.
ocx.register_obligation(Obligation::misc(
self.tcx,
span,
expr.hir_id,
param_env,
projection,
));
if ocx.select_where_possible().is_empty() {
// `ty_var` now holds the type that `Item` is for `ExprTy`.
let ty_var = self.resolve_vars_if_possible(ty_var);
assocs_in_this_method.push(Some((span, (proj.def_id, ty_var))));
} else {
// `<ExprTy as Iterator>` didn't select, so likely we've
// reached the end of the iterator chain, like the originating
// `Vec<_>`.
// Keep the space consistent for later zipping.
assocs_in_this_method.push(None);
}
}
let assocs_in_this_method =
self.probe_assoc_types_at_expr(&type_diffs, span, prev_ty, expr.hir_id, param_env);
assocs.push(assocs_in_this_method);
prev_ty = self.resolve_vars_if_possible(
typeck_results.expr_ty_adjusted_opt(expr).unwrap_or(tcx.ty_error()),
@ -3300,17 +3265,32 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
&& let hir::Path { res: hir::def::Res::Local(hir_id), .. } = path
&& let Some(hir::Node::Pat(binding)) = self.tcx.hir().find(*hir_id)
&& let parent_hir_id = self.tcx.hir().get_parent_node(binding.hir_id)
&& let Some(hir::Node::Local(local)) = self.tcx.hir().find(parent_hir_id)
&& let Some(binding_expr) = local.init
&& let Some(parent) = self.tcx.hir().find(parent_hir_id)
{
// We've reached the root of the method call chain and it is a
// binding. Get the binding creation and try to continue the chain.
expr = binding_expr;
// We've reached the root of the method call chain...
if let hir::Node::Local(local) = parent
&& let Some(binding_expr) = local.init
{
// ...and it is a binding. Get the binding creation and continue the chain.
expr = binding_expr;
}
if let hir::Node::Param(param) = parent {
// ...and it is a an fn argument.
let prev_ty = self.resolve_vars_if_possible(
typeck_results.node_type_opt(param.hir_id).unwrap_or(tcx.ty_error()),
);
let assocs_in_this_method = self.probe_assoc_types_at_expr(&type_diffs, param.ty_span, prev_ty, param.hir_id, param_env);
if assocs_in_this_method.iter().any(|a| a.is_some()) {
assocs.push(assocs_in_this_method);
print_root_expr = false;
}
break;
}
}
}
// We want the type before deref coercions, otherwise we talk about `&[_]`
// instead of `Vec<_>`.
if let Some(ty) = typeck_results.expr_ty_opt(expr) {
if let Some(ty) = typeck_results.expr_ty_opt(expr) && print_root_expr {
let ty = with_forced_trimmed_paths!(self.ty_to_string(ty));
// Point at the root expression
// vec![1, 2, 3].iter().map(mapper).sum<i32>()
@ -3324,7 +3304,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
let Some(prev_assoc_in_method) = assocs.peek() else {
for entry in assocs_in_method {
let Some((span, (assoc, ty))) = entry else { continue; };
if type_diffs.iter().any(|diff| {
if primary_spans.is_empty() || type_diffs.iter().any(|diff| {
let Sorts(expected_found) = diff else { return false; };
self.can_eq(param_env, expected_found.found, ty).is_ok()
}) {
@ -3380,13 +3360,6 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
}
}
}
for span in call_spans {
if span_labels.iter().find(|(s, _)| *s == span).is_none() {
// Ensure we are showing the entire chain, even if the assoc types
// haven't changed.
span_labels.push((span, String::new()));
}
}
if !primary_spans.is_empty() {
let mut multi_span: MultiSpan = primary_spans.into();
for (span, label) in span_labels {
@ -3394,13 +3367,70 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
}
err.span_note(
multi_span,
format!(
"the method call chain might not have had the expected \
associated types",
),
format!("the method call chain might not have had the expected associated types"),
);
}
}
fn probe_assoc_types_at_expr(
&self,
type_diffs: &[TypeError<'tcx>],
span: Span,
prev_ty: Ty<'tcx>,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
) -> Vec<Option<(Span, (DefId, Ty<'tcx>))>> {
let ocx = ObligationCtxt::new_in_snapshot(self.infcx);
let mut assocs_in_this_method = Vec::with_capacity(type_diffs.len());
for diff in type_diffs {
let Sorts(expected_found) = diff else { continue; };
let ty::Alias(ty::Projection, proj) = expected_found.expected.kind() else { continue; };
let origin = TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span };
let trait_def_id = proj.trait_def_id(self.tcx);
// Make `Self` be equivalent to the type of the call chain
// expression we're looking at now, so that we can tell what
// for example `Iterator::Item` is at this point in the chain.
let substs = InternalSubsts::for_item(self.tcx, trait_def_id, |param, _| {
match param.kind {
ty::GenericParamDefKind::Type { .. } => {
if param.index == 0 {
return prev_ty.into();
}
}
ty::GenericParamDefKind::Lifetime | ty::GenericParamDefKind::Const { .. } => {}
}
self.var_for_def(span, param)
});
// This will hold the resolved type of the associated type, if the
// current expression implements the trait that associated type is
// in. For example, this would be what `Iterator::Item` is here.
let ty_var = self.infcx.next_ty_var(origin);
// This corresponds to `<ExprTy as Iterator>::Item = _`.
let projection = ty::Binder::dummy(ty::PredicateKind::Clause(ty::Clause::Projection(
ty::ProjectionPredicate {
projection_ty: self.tcx.mk_alias_ty(proj.def_id, substs),
term: ty_var.into(),
},
)));
// Add `<ExprTy as Iterator>::Item = _` obligation.
ocx.register_obligation(Obligation::misc(
self.tcx, span, body_id, param_env, projection,
));
if ocx.select_where_possible().is_empty() {
// `ty_var` now holds the type that `Item` is for `ExprTy`.
let ty_var = self.resolve_vars_if_possible(ty_var);
assocs_in_this_method.push(Some((span, (proj.def_id, ty_var))));
} else {
// `<ExprTy as Iterator>` didn't select, so likely we've
// reached the end of the iterator chain, like the originating
// `Vec<_>`.
// Keep the space consistent for later zipping.
assocs_in_this_method.push(None);
}
}
assocs_in_this_method
}
}
/// Add a hint to add a missing borrow or remove an unnecessary one.