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Emit error in collecting_trait_impl_trait_tys on mismatched signatures #104214

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Nov 12, 2022
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Emit error in collecting_trait_impl_trait_tys on mismatched signatures #104214

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247 changes: 142 additions & 105 deletions compiler/rustc_hir_analysis/src/check/compare_method.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,14 +9,15 @@ use rustc_hir::intravisit;
use rustc_hir::{GenericParamKind, ImplItemKind, TraitItemKind};
use rustc_infer::infer::outlives::env::OutlivesEnvironment;
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_infer::infer::{self, TyCtxtInferExt};
use rustc_infer::infer::{self, InferCtxt, TyCtxtInferExt};
use rustc_infer::traits::util;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::util::ExplicitSelf;
use rustc_middle::ty::InternalSubsts;
use rustc_middle::ty::{
self, AssocItem, DefIdTree, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitable,
self, AssocItem, DefIdTree, TraitRef, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable,
TypeVisitable,
};
use rustc_middle::ty::{FnSig, InternalSubsts};
use rustc_middle::ty::{GenericParamDefKind, ToPredicate, TyCtxt};
use rustc_span::Span;
use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
Expand Down Expand Up @@ -303,102 +304,19 @@ fn compare_predicate_entailment<'tcx>(
}

if let Err(terr) = result {
debug!("sub_types failed: impl ty {:?}, trait ty {:?}", impl_fty, trait_fty);
debug!(?terr, "sub_types failed: impl ty {:?}, trait ty {:?}", impl_fty, trait_fty);

let (impl_err_span, trait_err_span) =
extract_spans_for_error_reporting(&infcx, terr, &cause, impl_m, trait_m);

cause.span = impl_err_span;

let mut diag = struct_span_err!(
tcx.sess,
cause.span(),
E0053,
"method `{}` has an incompatible type for trait",
trait_m.name
);
match &terr {
TypeError::ArgumentMutability(0) | TypeError::ArgumentSorts(_, 0)
if trait_m.fn_has_self_parameter =>
{
let ty = trait_sig.inputs()[0];
let sugg = match ExplicitSelf::determine(ty, |_| ty == impl_trait_ref.self_ty()) {
ExplicitSelf::ByValue => "self".to_owned(),
ExplicitSelf::ByReference(_, hir::Mutability::Not) => "&self".to_owned(),
ExplicitSelf::ByReference(_, hir::Mutability::Mut) => "&mut self".to_owned(),
_ => format!("self: {ty}"),
};

// When the `impl` receiver is an arbitrary self type, like `self: Box<Self>`, the
// span points only at the type `Box<Self`>, but we want to cover the whole
// argument pattern and type.
let span = match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind {
ImplItemKind::Fn(ref sig, body) => tcx
.hir()
.body_param_names(body)
.zip(sig.decl.inputs.iter())
.map(|(param, ty)| param.span.to(ty.span))
.next()
.unwrap_or(impl_err_span),
_ => bug!("{:?} is not a method", impl_m),
};

diag.span_suggestion(
span,
"change the self-receiver type to match the trait",
sugg,
Applicability::MachineApplicable,
);
}
TypeError::ArgumentMutability(i) | TypeError::ArgumentSorts(_, i) => {
if trait_sig.inputs().len() == *i {
// Suggestion to change output type. We do not suggest in `async` functions
// to avoid complex logic or incorrect output.
match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind {
ImplItemKind::Fn(ref sig, _)
if sig.header.asyncness == hir::IsAsync::NotAsync =>
{
let msg = "change the output type to match the trait";
let ap = Applicability::MachineApplicable;
match sig.decl.output {
hir::FnRetTy::DefaultReturn(sp) => {
let sugg = format!("-> {} ", trait_sig.output());
diag.span_suggestion_verbose(sp, msg, sugg, ap);
}
hir::FnRetTy::Return(hir_ty) => {
let sugg = trait_sig.output();
diag.span_suggestion(hir_ty.span, msg, sugg, ap);
}
};
}
_ => {}
};
} else if let Some(trait_ty) = trait_sig.inputs().get(*i) {
diag.span_suggestion(
impl_err_span,
"change the parameter type to match the trait",
trait_ty,
Applicability::MachineApplicable,
);
}
}
_ => {}
}

infcx.err_ctxt().note_type_err(
&mut diag,
&cause,
trait_err_span.map(|sp| (sp, "type in trait".to_owned())),
Some(infer::ValuePairs::Terms(ExpectedFound {
expected: trait_fty.into(),
found: impl_fty.into(),
})),
let emitted = report_trait_method_mismatch(
tcx,
&mut cause,
&infcx,
terr,
false,
false,
(trait_m, trait_fty),
(impl_m, impl_fty),
&trait_sig,
&impl_trait_ref,
);

return Err(diag.emit());
return Err(emitted);
}

// Check that all obligations are satisfied by the implementation's
Expand All @@ -424,6 +342,7 @@ fn compare_predicate_entailment<'tcx>(
Ok(())
}

#[instrument(skip(tcx), level = "debug", ret)]
pub fn collect_trait_impl_trait_tys<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: DefId,
Expand All @@ -437,7 +356,7 @@ pub fn collect_trait_impl_trait_tys<'tcx>(

let impl_m_hir_id = tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local());
let return_span = tcx.hir().fn_decl_by_hir_id(impl_m_hir_id).unwrap().output.span();
let cause = ObligationCause::new(
let mut cause = ObligationCause::new(
return_span,
impl_m_hir_id,
ObligationCauseCode::CompareImplItemObligation {
Expand Down Expand Up @@ -514,23 +433,35 @@ pub fn collect_trait_impl_trait_tys<'tcx>(
}
}

debug!(?trait_sig, ?impl_sig, "equating function signatures");

let trait_fty = tcx.mk_fn_ptr(ty::Binder::dummy(trait_sig));
let impl_fty = tcx.mk_fn_ptr(ty::Binder::dummy(impl_sig));

// Unify the whole function signature. We need to do this to fully infer
// the lifetimes of the return type, but do this after unifying just the
// return types, since we want to avoid duplicating errors from
// `compare_predicate_entailment`.
match infcx
.at(&cause, param_env)
.eq(tcx.mk_fn_ptr(ty::Binder::dummy(trait_sig)), tcx.mk_fn_ptr(ty::Binder::dummy(impl_sig)))
{
match infcx.at(&cause, param_env).eq(trait_fty, impl_fty) {
Ok(infer::InferOk { value: (), obligations }) => {
ocx.register_obligations(obligations);
}
Err(terr) => {
let guar = tcx.sess.delay_span_bug(
return_span,
format!("could not unify `{trait_sig}` and `{impl_sig}`: {terr:?}"),
// This function gets called during `compare_predicate_entailment` when normalizing a
// signature that contains RPITIT. When the method signatures don't match, we have to
// emit an error now because `compare_predicate_entailment` will not report the error
// when normalization fails.
let emitted = report_trait_method_mismatch(
tcx,
&mut cause,
infcx,
terr,
(trait_m, trait_fty),
(impl_m, impl_fty),
&trait_sig,
&impl_trait_ref,
);
return Err(guar);
return Err(emitted);
}
}

Expand Down Expand Up @@ -690,6 +621,112 @@ impl<'tcx> TypeFolder<'tcx> for ImplTraitInTraitCollector<'_, 'tcx> {
}
}

fn report_trait_method_mismatch<'tcx>(
tcx: TyCtxt<'tcx>,
cause: &mut ObligationCause<'tcx>,
infcx: &InferCtxt<'tcx>,
terr: TypeError<'tcx>,
(trait_m, trait_fty): (&AssocItem, Ty<'tcx>),
(impl_m, impl_fty): (&AssocItem, Ty<'tcx>),
trait_sig: &FnSig<'tcx>,
impl_trait_ref: &TraitRef<'tcx>,
) -> ErrorGuaranteed {
let (impl_err_span, trait_err_span) =
extract_spans_for_error_reporting(&infcx, terr, &cause, impl_m, trait_m);

cause.span = impl_err_span;

let mut diag = struct_span_err!(
tcx.sess,
cause.span(),
E0053,
"method `{}` has an incompatible type for trait",
trait_m.name
);
match &terr {
TypeError::ArgumentMutability(0) | TypeError::ArgumentSorts(_, 0)
if trait_m.fn_has_self_parameter =>
{
let ty = trait_sig.inputs()[0];
let sugg = match ExplicitSelf::determine(ty, |_| ty == impl_trait_ref.self_ty()) {
ExplicitSelf::ByValue => "self".to_owned(),
ExplicitSelf::ByReference(_, hir::Mutability::Not) => "&self".to_owned(),
ExplicitSelf::ByReference(_, hir::Mutability::Mut) => "&mut self".to_owned(),
_ => format!("self: {ty}"),
};

// When the `impl` receiver is an arbitrary self type, like `self: Box<Self>`, the
// span points only at the type `Box<Self`>, but we want to cover the whole
// argument pattern and type.
let span = match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind {
ImplItemKind::Fn(ref sig, body) => tcx
.hir()
.body_param_names(body)
.zip(sig.decl.inputs.iter())
.map(|(param, ty)| param.span.to(ty.span))
.next()
.unwrap_or(impl_err_span),
_ => bug!("{:?} is not a method", impl_m),
};

diag.span_suggestion(
span,
"change the self-receiver type to match the trait",
sugg,
Applicability::MachineApplicable,
);
}
TypeError::ArgumentMutability(i) | TypeError::ArgumentSorts(_, i) => {
if trait_sig.inputs().len() == *i {
// Suggestion to change output type. We do not suggest in `async` functions
// to avoid complex logic or incorrect output.
match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind {
ImplItemKind::Fn(ref sig, _)
if sig.header.asyncness == hir::IsAsync::NotAsync =>
{
let msg = "change the output type to match the trait";
let ap = Applicability::MachineApplicable;
match sig.decl.output {
hir::FnRetTy::DefaultReturn(sp) => {
let sugg = format!("-> {} ", trait_sig.output());
diag.span_suggestion_verbose(sp, msg, sugg, ap);
}
hir::FnRetTy::Return(hir_ty) => {
let sugg = trait_sig.output();
diag.span_suggestion(hir_ty.span, msg, sugg, ap);
}
};
}
_ => {}
};
} else if let Some(trait_ty) = trait_sig.inputs().get(*i) {
diag.span_suggestion(
impl_err_span,
"change the parameter type to match the trait",
trait_ty,
Applicability::MachineApplicable,
);
}
}
_ => {}
}

infcx.err_ctxt().note_type_err(
&mut diag,
&cause,
trait_err_span.map(|sp| (sp, "type in trait".to_owned())),
Some(infer::ValuePairs::Terms(ExpectedFound {
expected: trait_fty.into(),
found: impl_fty.into(),
})),
terr,
false,
false,
);

return diag.emit();
}

fn check_region_bounds_on_impl_item<'tcx>(
tcx: TyCtxt<'tcx>,
impl_m: &ty::AssocItem,
Expand Down
51 changes: 51 additions & 0 deletions src/test/ui/impl-trait/in-trait/method-signature-matches.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,51 @@
// edition: 2021

#![feature(return_position_impl_trait_in_trait, async_fn_in_trait)]
#![allow(incomplete_features)]

trait Uwu {
fn owo(x: ()) -> impl Sized;
}

impl Uwu for () {
fn owo(_: u8) {}
//~^ ERROR method `owo` has an incompatible type for trait
}

trait AsyncUwu {
async fn owo(x: ()) {}
}

impl AsyncUwu for () {
async fn owo(_: u8) {}
//~^ ERROR method `owo` has an incompatible type for trait
}

trait TooMuch {
fn calm_down_please() -> impl Sized;
}

impl TooMuch for () {
fn calm_down_please(_: (), _: (), _: ()) {}
//~^ ERROR method `calm_down_please` has 3 parameters but the declaration in trait `TooMuch::calm_down_please` has 0
}

trait TooLittle {
fn come_on_a_little_more_effort(_: (), _: (), _: ()) -> impl Sized;
}

impl TooLittle for () {
fn come_on_a_little_more_effort() {}
//~^ ERROR method `come_on_a_little_more_effort` has 0 parameters but the declaration in trait `TooLittle::come_on_a_little_more_effort` has 3
}

trait Lifetimes {
fn early<'early, T>(x: &'early T) -> impl Sized;
}

impl Lifetimes for () {
fn early<'late, T>(_: &'late ()) {}
//~^ ERROR method `early` has an incompatible type for trait
}

fn main() {}
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