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fuchsia / third_party / rust / f2dd585e6433f53c301990b47582d27db9453b84 / . / compiler / rustc_infer / src / infer / error_reporting / mod.rs
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//! Error Reporting Code for the inference engine
//!
//! Because of the way inference, and in particular region inference,
//! works, it often happens that errors are not detected until far after
//! the relevant line of code has been type-checked. Therefore, there is
//! an elaborate system to track why a particular constraint in the
//! inference graph arose so that we can explain to the user what gave
//! rise to a particular error.
//!
//! The system is based around a set of "origin" types. An "origin" is the
//! reason that a constraint or inference variable arose. There are
//! different "origin" enums for different kinds of constraints/variables
//! (e.g., `TypeOrigin`, `RegionVariableOrigin`). An origin always has
//! a span, but also more information so that we can generate a meaningful
//! error message.
//!
//! Having a catalog of all the different reasons an error can arise is
//! also useful for other reasons, like cross-referencing FAQs etc, though
//! we are not really taking advantage of this yet.
//!
//! # Region Inference
//!
//! Region inference is particularly tricky because it always succeeds "in
//! the moment" and simply registers a constraint. Then, at the end, we
//! can compute the full graph and report errors, so we need to be able to
//! store and later report what gave rise to the conflicting constraints.
//!
//! # Subtype Trace
//!
//! Determining whether `T1 <: T2` often involves a number of subtypes and
//! subconstraints along the way. A "TypeTrace" is an extended version
//! of an origin that traces the types and other values that were being
//! compared. It is not necessarily comprehensive (in fact, at the time of
//! this writing it only tracks the root values being compared) but I'd
//! like to extend it to include significant "waypoints". For example, if
//! you are comparing `(T1, T2) <: (T3, T4)`, and the problem is that `T2
//! <: T4` fails, I'd like the trace to include enough information to say
//! "in the 2nd element of the tuple". Similarly, failures when comparing
//! arguments or return types in fn types should be able to cite the
//! specific position, etc.
//!
//! # Reality vs plan
//!
//! Of course, there is still a LOT of code in typeck that has yet to be
//! ported to this system, and which relies on string concatenation at the
//! time of error detection.
use super::lexical_region_resolve::RegionResolutionError;
use super::region_constraints::GenericKind;
use super::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TypeTrace, ValuePairs};
use crate::infer;
use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
use crate::traits::error_reporting::report_object_safety_error;
use crate::traits::{
IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode,
StatementAsExpression,
};
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed, IntoDiagnosticArg};
use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString, MultiSpan};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::lang_items::LangItem;
use rustc_hir::Node;
use rustc_middle::dep_graph::DepContext;
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::relate::{self, RelateResult, TypeRelation};
use rustc_middle::ty::{
self, error::TypeError, Binder, List, Region, Subst, Ty, TyCtxt, TypeFoldable,
TypeSuperVisitable, TypeVisitable,
};
use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span};
use rustc_target::spec::abi;
use std::ops::ControlFlow;
use std::{cmp, fmt, iter};
mod note;
pub(crate) mod need_type_info;
pub use need_type_info::TypeAnnotationNeeded;
pub mod nice_region_error;
pub(super) fn note_and_explain_region<'tcx>(
tcx: TyCtxt<'tcx>,
err: &mut Diagnostic,
prefix: &str,
region: ty::Region<'tcx>,
suffix: &str,
alt_span: Option<Span>,
) {
let (description, span) = match *region {
ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
msg_span_from_free_region(tcx, region, alt_span)
}
ty::RePlaceholder(_) => return,
// FIXME(#13998) RePlaceholder should probably print like
// ReFree rather than dumping Debug output on the user.
//
// We shouldn't really be having unification failures with ReVar
// and ReLateBound though.
ty::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => {
(format!("lifetime {:?}", region), alt_span)
}
};
emit_msg_span(err, prefix, description, span, suffix);
}
fn explain_free_region<'tcx>(
tcx: TyCtxt<'tcx>,
err: &mut Diagnostic,
prefix: &str,
region: ty::Region<'tcx>,
suffix: &str,
) {
let (description, span) = msg_span_from_free_region(tcx, region, None);
label_msg_span(err, prefix, description, span, suffix);
}
fn msg_span_from_free_region<'tcx>(
tcx: TyCtxt<'tcx>,
region: ty::Region<'tcx>,
alt_span: Option<Span>,
) -> (String, Option<Span>) {
match *region {
ty::ReEarlyBound(_) | ty::ReFree(_) => {
let (msg, span) = msg_span_from_early_bound_and_free_regions(tcx, region);
(msg, Some(span))
}
ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
_ => bug!("{:?}", region),
}
}
fn msg_span_from_early_bound_and_free_regions<'tcx>(
tcx: TyCtxt<'tcx>,
region: ty::Region<'tcx>,
) -> (String, Span) {
let scope = region.free_region_binding_scope(tcx).expect_local();
match *region {
ty::ReEarlyBound(ref br) => {
let mut sp = tcx.def_span(scope);
if let Some(param) =
tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
{
sp = param.span;
}
let text = if br.has_name() {
format!("the lifetime `{}` as defined here", br.name)
} else {
format!("the anonymous lifetime as defined here")
};
(text, sp)
}
ty::ReFree(ref fr) => {
if !fr.bound_region.is_named()
&& let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
{
("the anonymous lifetime defined here".to_string(), ty.span)
} else {
match fr.bound_region {
ty::BoundRegionKind::BrNamed(_, name) => {
let mut sp = tcx.def_span(scope);
if let Some(param) =
tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
{
sp = param.span;
}
let text = if name == kw::UnderscoreLifetime {
format!("the anonymous lifetime as defined here")
} else {
format!("the lifetime `{}` as defined here", name)
};
(text, sp)
}
ty::BrAnon(idx) => (
format!("the anonymous lifetime #{} defined here", idx + 1),
tcx.def_span(scope)
),
_ => (
format!("the lifetime `{}` as defined here", region),
tcx.def_span(scope),
),
}
}
}
_ => bug!(),
}
}
fn emit_msg_span(
err: &mut Diagnostic,
prefix: &str,
description: String,
span: Option<Span>,
suffix: &str,
) {
let message = format!("{}{}{}", prefix, description, suffix);
if let Some(span) = span {
err.span_note(span, &message);
} else {
err.note(&message);
}
}
fn label_msg_span(
err: &mut Diagnostic,
prefix: &str,
description: String,
span: Option<Span>,
suffix: &str,
) {
let message = format!("{}{}{}", prefix, description, suffix);
if let Some(span) = span {
err.span_label(span, &message);
} else {
err.note(&message);
}
}
pub fn unexpected_hidden_region_diagnostic<'tcx>(
tcx: TyCtxt<'tcx>,
span: Span,
hidden_ty: Ty<'tcx>,
hidden_region: ty::Region<'tcx>,
opaque_ty: ty::OpaqueTypeKey<'tcx>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
let opaque_ty = tcx.mk_opaque(opaque_ty.def_id.to_def_id(), opaque_ty.substs);
let mut err = struct_span_err!(
tcx.sess,
span,
E0700,
"hidden type for `{opaque_ty}` captures lifetime that does not appear in bounds",
);
// Explain the region we are capturing.
match *hidden_region {
ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
// Assuming regionck succeeded (*), we ought to always be
// capturing *some* region from the fn header, and hence it
// ought to be free. So under normal circumstances, we will go
// down this path which gives a decent human readable
// explanation.
//
// (*) if not, the `tainted_by_errors` field would be set to
// `Some(ErrorGuaranteed)` in any case, so we wouldn't be here at all.
explain_free_region(
tcx,
&mut err,
&format!("hidden type `{}` captures ", hidden_ty),
hidden_region,
"",
);
if let Some(reg_info) = tcx.is_suitable_region(hidden_region) {
let fn_returns = tcx.return_type_impl_or_dyn_traits(reg_info.def_id);
nice_region_error::suggest_new_region_bound(
tcx,
&mut err,
fn_returns,
hidden_region.to_string(),
None,
format!("captures `{}`", hidden_region),
None,
)
}
}
_ => {
// Ugh. This is a painful case: the hidden region is not one
// that we can easily summarize or explain. This can happen
// in a case like
// `src/test/ui/multiple-lifetimes/ordinary-bounds-unsuited.rs`:
//
// ```
// fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> {
// if condition() { a } else { b }
// }
// ```
//
// Here the captured lifetime is the intersection of `'a` and
// `'b`, which we can't quite express.
// We can at least report a really cryptic error for now.
note_and_explain_region(
tcx,
&mut err,
&format!("hidden type `{}` captures ", hidden_ty),
hidden_region,
"",
None,
);
}
}
err
}
impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
pub fn report_region_errors(
&self,
generic_param_scope: LocalDefId,
errors: &[RegionResolutionError<'tcx>],
) {
debug!("report_region_errors(): {} errors to start", errors.len());
// try to pre-process the errors, which will group some of them
// together into a `ProcessedErrors` group:
let errors = self.process_errors(errors);
debug!("report_region_errors: {} errors after preprocessing", errors.len());
for error in errors {
debug!("report_region_errors: error = {:?}", error);
if !self.try_report_nice_region_error(&error) {
match error.clone() {
// These errors could indicate all manner of different
// problems with many different solutions. Rather
// than generate a "one size fits all" error, what we
// attempt to do is go through a number of specific
// scenarios and try to find the best way to present
// the error. If all of these fails, we fall back to a rather
// general bit of code that displays the error information
RegionResolutionError::ConcreteFailure(origin, sub, sup) => {
if sub.is_placeholder() || sup.is_placeholder() {
self.report_placeholder_failure(origin, sub, sup).emit();
} else {
self.report_concrete_failure(origin, sub, sup).emit();
}
}
RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
self.report_generic_bound_failure(
generic_param_scope,
origin.span(),
Some(origin),
param_ty,
sub,
);
}
RegionResolutionError::SubSupConflict(
_,
var_origin,
sub_origin,
sub_r,
sup_origin,
sup_r,
_,
) => {
if sub_r.is_placeholder() {
self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit();
} else if sup_r.is_placeholder() {
self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
} else {
self.report_sub_sup_conflict(
var_origin, sub_origin, sub_r, sup_origin, sup_r,
);
}
}
RegionResolutionError::UpperBoundUniverseConflict(
_,
_,
_,
sup_origin,
sup_r,
) => {
assert!(sup_r.is_placeholder());
// Make a dummy value for the "sub region" --
// this is the initial value of the
// placeholder. In practice, we expect more
// tailored errors that don't really use this
// value.
let sub_r = self.tcx.lifetimes.re_erased;
self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
}
}
}
}
}
// This method goes through all the errors and try to group certain types
// of error together, for the purpose of suggesting explicit lifetime
// parameters to the user. This is done so that we can have a more
// complete view of what lifetimes should be the same.
// If the return value is an empty vector, it means that processing
// failed (so the return value of this method should not be used).
//
// The method also attempts to weed out messages that seem like
// duplicates that will be unhelpful to the end-user. But
// obviously it never weeds out ALL errors.
fn process_errors(
&self,
errors: &[RegionResolutionError<'tcx>],
) -> Vec<RegionResolutionError<'tcx>> {
debug!("process_errors()");
// We want to avoid reporting generic-bound failures if we can
// avoid it: these have a very high rate of being unhelpful in
// practice. This is because they are basically secondary
// checks that test the state of the region graph after the
// rest of inference is done, and the other kinds of errors
// indicate that the region constraint graph is internally
// inconsistent, so these test results are likely to be
// meaningless.
//
// Therefore, we filter them out of the list unless they are
// the only thing in the list.
let is_bound_failure = |e: &RegionResolutionError<'tcx>| match *e {
RegionResolutionError::GenericBoundFailure(..) => true,
RegionResolutionError::ConcreteFailure(..)
| RegionResolutionError::SubSupConflict(..)
| RegionResolutionError::UpperBoundUniverseConflict(..) => false,
};
let mut errors = if errors.iter().all(|e| is_bound_failure(e)) {
errors.to_owned()
} else {
errors.iter().filter(|&e| !is_bound_failure(e)).cloned().collect()
};
// sort the errors by span, for better error message stability.
errors.sort_by_key(|u| match *u {
RegionResolutionError::ConcreteFailure(ref sro, _, _) => sro.span(),
RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(),
RegionResolutionError::SubSupConflict(_, ref rvo, _, _, _, _, _) => rvo.span(),
RegionResolutionError::UpperBoundUniverseConflict(_, ref rvo, _, _, _) => rvo.span(),
});
errors
}
/// Adds a note if the types come from similarly named crates
fn check_and_note_conflicting_crates(&self, err: &mut Diagnostic, terr: TypeError<'tcx>) {
use hir::def_id::CrateNum;
use rustc_hir::definitions::DisambiguatedDefPathData;
use ty::print::Printer;
use ty::subst::GenericArg;
struct AbsolutePathPrinter<'tcx> {
tcx: TyCtxt<'tcx>,
}
struct NonTrivialPath;
impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
type Error = NonTrivialPath;
type Path = Vec<String>;
type Region = !;
type Type = !;
type DynExistential = !;
type Const = !;
fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
self.tcx
}
fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
Err(NonTrivialPath)
}
fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
Err(NonTrivialPath)
}
fn print_dyn_existential(
self,
_predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
) -> Result<Self::DynExistential, Self::Error> {
Err(NonTrivialPath)
}
fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
Err(NonTrivialPath)
}
fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
Ok(vec![self.tcx.crate_name(cnum).to_string()])
}
fn path_qualified(
self,
_self_ty: Ty<'tcx>,
_trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<Self::Path, Self::Error> {
Err(NonTrivialPath)
}
fn path_append_impl(
self,
_print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
_disambiguated_data: &DisambiguatedDefPathData,
_self_ty: Ty<'tcx>,
_trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<Self::Path, Self::Error> {
Err(NonTrivialPath)
}
fn path_append(
self,
print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
disambiguated_data: &DisambiguatedDefPathData,
) -> Result<Self::Path, Self::Error> {
let mut path = print_prefix(self)?;
path.push(disambiguated_data.to_string());
Ok(path)
}
fn path_generic_args(
self,
print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
_args: &[GenericArg<'tcx>],
) -> Result<Self::Path, Self::Error> {
print_prefix(self)
}
}
let report_path_match = |err: &mut Diagnostic, did1: DefId, did2: DefId| {
// Only external crates, if either is from a local
// module we could have false positives
if !(did1.is_local() || did2.is_local()) && did1.krate != did2.krate {
let abs_path =
|def_id| AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]);
// We compare strings because DefPath can be different
// for imported and non-imported crates
let same_path = || -> Result<_, NonTrivialPath> {
Ok(self.tcx.def_path_str(did1) == self.tcx.def_path_str(did2)
|| abs_path(did1)? == abs_path(did2)?)
};
if same_path().unwrap_or(false) {
let crate_name = self.tcx.crate_name(did1.krate);
err.note(&format!(
"perhaps two different versions of crate `{}` are being used?",
crate_name
));
}
}
};
match terr {
TypeError::Sorts(ref exp_found) => {
// if they are both "path types", there's a chance of ambiguity
// due to different versions of the same crate
if let (&ty::Adt(exp_adt, _), &ty::Adt(found_adt, _)) =
(exp_found.expected.kind(), exp_found.found.kind())
{
report_path_match(err, exp_adt.did(), found_adt.did());
}
}
TypeError::Traits(ref exp_found) => {
report_path_match(err, exp_found.expected, exp_found.found);
}
_ => (), // FIXME(#22750) handle traits and stuff
}
}
fn note_error_origin(
&self,
err: &mut Diagnostic,
cause: &ObligationCause<'tcx>,
exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>,
terr: TypeError<'tcx>,
) {
match *cause.code() {
ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => {
let ty = self.resolve_vars_if_possible(root_ty);
if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)))
{
// don't show type `_`
if span.desugaring_kind() == Some(DesugaringKind::ForLoop)
&& let ty::Adt(def, substs) = ty.kind()
&& Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option)
{
err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0)));
} else {
err.span_label(span, format!("this expression has type `{}`", ty));
}
}
if let Some(ty::error::ExpectedFound { found, .. }) = exp_found
&& ty.is_box() && ty.boxed_ty() == found
&& let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
{
err.span_suggestion(
span,
"consider dereferencing the boxed value",
format!("*{}", snippet),
Applicability::MachineApplicable,
);
}
}
ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => {
err.span_label(span, "expected due to this");
}
ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
arm_block_id,
arm_span,
arm_ty,
prior_arm_block_id,
prior_arm_span,
prior_arm_ty,
source,
ref prior_arms,
scrut_hir_id,
opt_suggest_box_span,
scrut_span,
..
}) => match source {
hir::MatchSource::TryDesugar => {
if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found {
let scrut_expr = self.tcx.hir().expect_expr(scrut_hir_id);
let scrut_ty = if let hir::ExprKind::Call(_, args) = &scrut_expr.kind {
let arg_expr = args.first().expect("try desugaring call w/out arg");
self.in_progress_typeck_results.and_then(|typeck_results| {
typeck_results.borrow().expr_ty_opt(arg_expr)
})
} else {
bug!("try desugaring w/out call expr as scrutinee");
};
match scrut_ty {
Some(ty) if expected == ty => {
let source_map = self.tcx.sess.source_map();
err.span_suggestion(
source_map.end_point(cause.span),
"try removing this `?`",
"",
Applicability::MachineApplicable,
);
}
_ => {}
}
}
}
_ => {
// `prior_arm_ty` can be `!`, `expected` will have better info when present.
let t = self.resolve_vars_if_possible(match exp_found {
Some(ty::error::ExpectedFound { expected, .. }) => expected,
_ => prior_arm_ty,
});
let source_map = self.tcx.sess.source_map();
let mut any_multiline_arm = source_map.is_multiline(arm_span);
if prior_arms.len() <= 4 {
for sp in prior_arms {
any_multiline_arm |= source_map.is_multiline(*sp);
err.span_label(*sp, format!("this is found to be of type `{}`", t));
}
} else if let Some(sp) = prior_arms.last() {
any_multiline_arm |= source_map.is_multiline(*sp);
err.span_label(
*sp,
format!("this and all prior arms are found to be of type `{}`", t),
);
}
let outer_error_span = if any_multiline_arm {
// Cover just `match` and the scrutinee expression, not
// the entire match body, to reduce diagram noise.
cause.span.shrink_to_lo().to(scrut_span)
} else {
cause.span
};
let msg = "`match` arms have incompatible types";
err.span_label(outer_error_span, msg);
self.suggest_remove_semi_or_return_binding(
err,
prior_arm_block_id,
prior_arm_ty,
prior_arm_span,
arm_block_id,
arm_ty,
arm_span,
);
if let Some(ret_sp) = opt_suggest_box_span {
// Get return type span and point to it.
self.suggest_boxing_for_return_impl_trait(
err,
ret_sp,
prior_arms.iter().chain(std::iter::once(&arm_span)).map(|s| *s),
);
}
}
},
ObligationCauseCode::IfExpression(box IfExpressionCause {
then_id,
else_id,
then_ty,
else_ty,
outer_span,
opt_suggest_box_span,
}) => {
let then_span = self.find_block_span_from_hir_id(then_id);
let else_span = self.find_block_span_from_hir_id(else_id);
err.span_label(then_span, "expected because of this");
if let Some(sp) = outer_span {
err.span_label(sp, "`if` and `else` have incompatible types");
}
self.suggest_remove_semi_or_return_binding(
err,
Some(then_id),
then_ty,
then_span,
Some(else_id),
else_ty,
else_span,
);
if let Some(ret_sp) = opt_suggest_box_span {
self.suggest_boxing_for_return_impl_trait(
err,
ret_sp,
[then_span, else_span].into_iter(),
);
}
}
ObligationCauseCode::LetElse => {
err.help("try adding a diverging expression, such as `return` or `panic!(..)`");
err.help("...or use `match` instead of `let...else`");
}
_ => {
if let ObligationCauseCode::BindingObligation(_, span)
| ObligationCauseCode::ExprBindingObligation(_, span, ..)
= cause.code().peel_derives()
&& let TypeError::RegionsPlaceholderMismatch = terr
{
err.span_note(*span, "the lifetime requirement is introduced here");
}
}
}
}
fn suggest_remove_semi_or_return_binding(
&self,
err: &mut Diagnostic,
first_id: Option<hir::HirId>,
first_ty: Ty<'tcx>,
first_span: Span,
second_id: Option<hir::HirId>,
second_ty: Ty<'tcx>,
second_span: Span,
) {
let remove_semicolon = [
(first_id, self.resolve_vars_if_possible(second_ty)),
(second_id, self.resolve_vars_if_possible(first_ty)),
]
.into_iter()
.find_map(|(id, ty)| {
let hir::Node::Block(blk) = self.tcx.hir().get(id?) else { return None };
self.could_remove_semicolon(blk, ty)
});
match remove_semicolon {
Some((sp, StatementAsExpression::NeedsBoxing)) => {
err.multipart_suggestion(
"consider removing this semicolon and boxing the expressions",
vec![
(first_span.shrink_to_lo(), "Box::new(".to_string()),
(first_span.shrink_to_hi(), ")".to_string()),
(second_span.shrink_to_lo(), "Box::new(".to_string()),
(second_span.shrink_to_hi(), ")".to_string()),
(sp, String::new()),
],
Applicability::MachineApplicable,
);
}
Some((sp, StatementAsExpression::CorrectType)) => {
err.span_suggestion_short(
sp,
"consider removing this semicolon",
"",
Applicability::MachineApplicable,
);
}
None => {
for (id, ty) in [(first_id, second_ty), (second_id, first_ty)] {
if let Some(id) = id
&& let hir::Node::Block(blk) = self.tcx.hir().get(id)
&& self.consider_returning_binding(blk, ty, err)
{
break;
}
}
}
}
}
fn suggest_boxing_for_return_impl_trait(
&self,
err: &mut Diagnostic,
return_sp: Span,
arm_spans: impl Iterator<Item = Span>,
) {
err.multipart_suggestion(
"you could change the return type to be a boxed trait object",
vec![
(return_sp.with_hi(return_sp.lo() + BytePos(4)), "Box<dyn".to_string()),
(return_sp.shrink_to_hi(), ">".to_string()),
],
Applicability::MaybeIncorrect,
);
let sugg = arm_spans
.flat_map(|sp| {
[(sp.shrink_to_lo(), "Box::new(".to_string()), (sp.shrink_to_hi(), ")".to_string())]
.into_iter()
})
.collect::<Vec<_>>();
err.multipart_suggestion(
"if you change the return type to expect trait objects, box the returned expressions",
sugg,
Applicability::MaybeIncorrect,
);
}
/// Given that `other_ty` is the same as a type argument for `name` in `sub`, populate `value`
/// highlighting `name` and every type argument that isn't at `pos` (which is `other_ty`), and
/// populate `other_value` with `other_ty`.
///
/// ```text
/// Foo<Bar<Qux>>
/// ^^^^--------^ this is highlighted
/// | |
/// | this type argument is exactly the same as the other type, not highlighted
/// this is highlighted
/// Bar<Qux>
/// -------- this type is the same as a type argument in the other type, not highlighted
/// ```
fn highlight_outer(
&self,
value: &mut DiagnosticStyledString,
other_value: &mut DiagnosticStyledString,
name: String,
sub: ty::subst::SubstsRef<'tcx>,
pos: usize,
other_ty: Ty<'tcx>,
) {
// `value` and `other_value` hold two incomplete type representation for display.
// `name` is the path of both types being compared. `sub`
value.push_highlighted(name);
let len = sub.len();
if len > 0 {
value.push_highlighted("<");
}
// Output the lifetimes for the first type
let lifetimes = sub
.regions()
.map(|lifetime| {
let s = lifetime.to_string();
if s.is_empty() { "'_".to_string() } else { s }
})
.collect::<Vec<_>>()
.join(", ");
if !lifetimes.is_empty() {
if sub.regions().count() < len {
value.push_normal(lifetimes + ", ");
} else {
value.push_normal(lifetimes);
}
}
// Highlight all the type arguments that aren't at `pos` and compare the type argument at
// `pos` and `other_ty`.
for (i, type_arg) in sub.types().enumerate() {
if i == pos {
let values = self.cmp(type_arg, other_ty);
value.0.extend((values.0).0);
other_value.0.extend((values.1).0);
} else {
value.push_highlighted(type_arg.to_string());
}
if len > 0 && i != len - 1 {
value.push_normal(", ");
}
}
if len > 0 {
value.push_highlighted(">");
}
}
/// If `other_ty` is the same as a type argument present in `sub`, highlight `path` in `t1_out`,
/// as that is the difference to the other type.
///
/// For the following code:
///
/// ```ignore (illustrative)
/// let x: Foo<Bar<Qux>> = foo::<Bar<Qux>>();
/// ```
///
/// The type error output will behave in the following way:
///
/// ```text
/// Foo<Bar<Qux>>
/// ^^^^--------^ this is highlighted
/// | |
/// | this type argument is exactly the same as the other type, not highlighted
/// this is highlighted
/// Bar<Qux>
/// -------- this type is the same as a type argument in the other type, not highlighted
/// ```
fn cmp_type_arg(
&self,
mut t1_out: &mut DiagnosticStyledString,
mut t2_out: &mut DiagnosticStyledString,
path: String,
sub: &'tcx [ty::GenericArg<'tcx>],
other_path: String,
other_ty: Ty<'tcx>,
) -> Option<()> {
// FIXME/HACK: Go back to `SubstsRef` to use its inherent methods,
// ideally that shouldn't be necessary.
let sub = self.tcx.intern_substs(sub);
for (i, ta) in sub.types().enumerate() {
if ta == other_ty {
self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
return Some(());
}
if let ty::Adt(def, _) = ta.kind() {
let path_ = self.tcx.def_path_str(def.did());
if path_ == other_path {
self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
return Some(());
}
}
}
None
}
/// Adds a `,` to the type representation only if it is appropriate.
fn push_comma(
&self,
value: &mut DiagnosticStyledString,
other_value: &mut DiagnosticStyledString,
len: usize,
pos: usize,
) {
if len > 0 && pos != len - 1 {
value.push_normal(", ");
other_value.push_normal(", ");
}
}
fn normalize_fn_sig_for_diagnostic(&self, sig: ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx> {
if let Some(normalize) = &self.normalize_fn_sig_for_diagnostic {
normalize(self, sig)
} else {
sig
}
}
/// Given two `fn` signatures highlight only sub-parts that are different.
fn cmp_fn_sig(
&self,
sig1: &ty::PolyFnSig<'tcx>,
sig2: &ty::PolyFnSig<'tcx>,
) -> (DiagnosticStyledString, DiagnosticStyledString) {
let sig1 = &self.normalize_fn_sig_for_diagnostic(*sig1);
let sig2 = &self.normalize_fn_sig_for_diagnostic(*sig2);
let get_lifetimes = |sig| {
use rustc_hir::def::Namespace;
let (_, sig, reg) = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS)
.name_all_regions(sig)
.unwrap();
let lts: Vec<String> = reg.into_iter().map(|(_, kind)| kind.to_string()).collect();
(if lts.is_empty() { String::new() } else { format!("for<{}> ", lts.join(", ")) }, sig)
};
let (lt1, sig1) = get_lifetimes(sig1);
let (lt2, sig2) = get_lifetimes(sig2);
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
let mut values = (
DiagnosticStyledString::normal("".to_string()),
DiagnosticStyledString::normal("".to_string()),
);
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
// ^^^^^^
values.0.push(sig1.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
values.1.push(sig2.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
// ^^^^^^^^^^
if sig1.abi != abi::Abi::Rust {
values.0.push(format!("extern {} ", sig1.abi), sig1.abi != sig2.abi);
}
if sig2.abi != abi::Abi::Rust {
values.1.push(format!("extern {} ", sig2.abi), sig1.abi != sig2.abi);
}
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
// ^^^^^^^^
let lifetime_diff = lt1 != lt2;
values.0.push(lt1, lifetime_diff);
values.1.push(lt2, lifetime_diff);
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
// ^^^
values.0.push_normal("fn(");
values.1.push_normal("fn(");
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
// ^^^^^
let len1 = sig1.inputs().len();
let len2 = sig2.inputs().len();
if len1 == len2 {
for (i, (l, r)) in iter::zip(sig1.inputs(), sig2.inputs()).enumerate() {
let (x1, x2) = self.cmp(*l, *r);
(values.0).0.extend(x1.0);
(values.1).0.extend(x2.0);
self.push_comma(&mut values.0, &mut values.1, len1, i);
}
} else {
for (i, l) in sig1.inputs().iter().enumerate() {
values.0.push_highlighted(l.to_string());
if i != len1 - 1 {
values.0.push_highlighted(", ");
}
}
for (i, r) in sig2.inputs().iter().enumerate() {
values.1.push_highlighted(r.to_string());
if i != len2 - 1 {
values.1.push_highlighted(", ");
}
}
}
if sig1.c_variadic {
if len1 > 0 {
values.0.push_normal(", ");
}
values.0.push("...", !sig2.c_variadic);
}
if sig2.c_variadic {
if len2 > 0 {
values.1.push_normal(", ");
}
values.1.push("...", !sig1.c_variadic);
}
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
// ^
values.0.push_normal(")");
values.1.push_normal(")");
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
// ^^^^^^^^
let output1 = sig1.output();
let output2 = sig2.output();
let (x1, x2) = self.cmp(output1, output2);
if !output1.is_unit() {
values.0.push_normal(" -> ");
(values.0).0.extend(x1.0);
}
if !output2.is_unit() {
values.1.push_normal(" -> ");
(values.1).0.extend(x2.0);
}
values
}
/// Compares two given types, eliding parts that are the same between them and highlighting
/// relevant differences, and return two representation of those types for highlighted printing.
pub fn cmp(
&self,
t1: Ty<'tcx>,
t2: Ty<'tcx>,
) -> (DiagnosticStyledString, DiagnosticStyledString) {
debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind());
// helper functions
fn equals<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
match (a.kind(), b.kind()) {
(a, b) if *a == *b => true,
(&ty::Int(_), &ty::Infer(ty::InferTy::IntVar(_)))
| (
&ty::Infer(ty::InferTy::IntVar(_)),
&ty::Int(_) | &ty::Infer(ty::InferTy::IntVar(_)),
)
| (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_)))
| (
&ty::Infer(ty::InferTy::FloatVar(_)),
&ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)),
) => true,
_ => false,
}
}
fn push_ty_ref<'tcx>(
region: ty::Region<'tcx>,
ty: Ty<'tcx>,
mutbl: hir::Mutability,
s: &mut DiagnosticStyledString,
) {
let mut r = region.to_string();
if r == "'_" {
r.clear();
} else {
r.push(' ');
}
s.push_highlighted(format!("&{}{}", r, mutbl.prefix_str()));
s.push_normal(ty.to_string());
}
// process starts here
match (t1.kind(), t2.kind()) {
(&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => {
let did1 = def1.did();
let did2 = def2.did();
let sub_no_defaults_1 =
self.tcx.generics_of(did1).own_substs_no_defaults(self.tcx, sub1);
let sub_no_defaults_2 =
self.tcx.generics_of(did2).own_substs_no_defaults(self.tcx, sub2);
let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
let path1 = self.tcx.def_path_str(did1);
let path2 = self.tcx.def_path_str(did2);
if did1 == did2 {
// Easy case. Replace same types with `_` to shorten the output and highlight
// the differing ones.
// let x: Foo<Bar, Qux> = y::<Foo<Quz, Qux>>();
// Foo<Bar, _>
// Foo<Quz, _>
// --- ^ type argument elided
// |
// highlighted in output
values.0.push_normal(path1);
values.1.push_normal(path2);
// Avoid printing out default generic parameters that are common to both
// types.
let len1 = sub_no_defaults_1.len();
let len2 = sub_no_defaults_2.len();
let common_len = cmp::min(len1, len2);
let remainder1: Vec<_> = sub1.types().skip(common_len).collect();
let remainder2: Vec<_> = sub2.types().skip(common_len).collect();
let common_default_params =
iter::zip(remainder1.iter().rev(), remainder2.iter().rev())
.filter(|(a, b)| a == b)
.count();
let len = sub1.len() - common_default_params;
let consts_offset = len - sub1.consts().count();
// Only draw `<...>` if there are lifetime/type arguments.
if len > 0 {
values.0.push_normal("<");
values.1.push_normal("<");
}
fn lifetime_display(lifetime: Region<'_>) -> String {
let s = lifetime.to_string();
if s.is_empty() { "'_".to_string() } else { s }
}
// At one point we'd like to elide all lifetimes here, they are irrelevant for
// all diagnostics that use this output
//
// Foo<'x, '_, Bar>
// Foo<'y, '_, Qux>
// ^^ ^^ --- type arguments are not elided
// | |
// | elided as they were the same
// not elided, they were different, but irrelevant
//
// For bound lifetimes, keep the names of the lifetimes,
// even if they are the same so that it's clear what's happening
// if we have something like
//
// for<'r, 's> fn(Inv<'r>, Inv<'s>)
// for<'r> fn(Inv<'r>, Inv<'r>)
let lifetimes = sub1.regions().zip(sub2.regions());
for (i, lifetimes) in lifetimes.enumerate() {
let l1 = lifetime_display(lifetimes.0);
let l2 = lifetime_display(lifetimes.1);
if lifetimes.0 != lifetimes.1 {
values.0.push_highlighted(l1);
values.1.push_highlighted(l2);
} else if lifetimes.0.is_late_bound() {
values.0.push_normal(l1);
values.1.push_normal(l2);
} else {
values.0.push_normal("'_");
values.1.push_normal("'_");
}
self.push_comma(&mut values.0, &mut values.1, len, i);
}
// We're comparing two types with the same path, so we compare the type
// arguments for both. If they are the same, do not highlight and elide from the
// output.
// Foo<_, Bar>
// Foo<_, Qux>
// ^ elided type as this type argument was the same in both sides
let type_arguments = sub1.types().zip(sub2.types());
let regions_len = sub1.regions().count();
let num_display_types = consts_offset - regions_len;
for (i, (ta1, ta2)) in type_arguments.take(num_display_types).enumerate() {
let i = i + regions_len;
if ta1 == ta2 {
values.0.push_normal("_");
values.1.push_normal("_");
} else {
let (x1, x2) = self.cmp(ta1, ta2);
(values.0).0.extend(x1.0);
(values.1).0.extend(x2.0);
}
self.push_comma(&mut values.0, &mut values.1, len, i);
}
// Do the same for const arguments, if they are equal, do not highlight and
// elide them from the output.
let const_arguments = sub1.consts().zip(sub2.consts());
for (i, (ca1, ca2)) in const_arguments.enumerate() {
let i = i + consts_offset;
if ca1 == ca2 {
values.0.push_normal("_");
values.1.push_normal("_");
} else {
values.0.push_highlighted(ca1.to_string());
values.1.push_highlighted(ca2.to_string());
}
self.push_comma(&mut values.0, &mut values.1, len, i);
}
// Close the type argument bracket.
// Only draw `<...>` if there are lifetime/type arguments.
if len > 0 {
values.0.push_normal(">");
values.1.push_normal(">");
}
values
} else {
// Check for case:
// let x: Foo<Bar<Qux> = foo::<Bar<Qux>>();
// Foo<Bar<Qux>
// ------- this type argument is exactly the same as the other type
// Bar<Qux>
if self
.cmp_type_arg(
&mut values.0,
&mut values.1,
path1.clone(),
sub_no_defaults_1,
path2.clone(),
t2,
)
.is_some()
{
return values;
}
// Check for case:
// let x: Bar<Qux> = y:<Foo<Bar<Qux>>>();
// Bar<Qux>
// Foo<Bar<Qux>>
// ------- this type argument is exactly the same as the other type
if self
.cmp_type_arg(
&mut values.1,
&mut values.0,
path2,
sub_no_defaults_2,
path1,
t1,
)
.is_some()
{
return values;
}
// We can't find anything in common, highlight relevant part of type path.
// let x: foo::bar::Baz<Qux> = y:<foo::bar::Bar<Zar>>();
// foo::bar::Baz<Qux>
// foo::bar::Bar<Zar>
// -------- this part of the path is different
let t1_str = t1.to_string();
let t2_str = t2.to_string();
let min_len = t1_str.len().min(t2_str.len());
const SEPARATOR: &str = "::";
let separator_len = SEPARATOR.len();
let split_idx: usize =
iter::zip(t1_str.split(SEPARATOR), t2_str.split(SEPARATOR))
.take_while(|(mod1_str, mod2_str)| mod1_str == mod2_str)
.map(|(mod_str, _)| mod_str.len() + separator_len)
.sum();
debug!(
"cmp: separator_len={}, split_idx={}, min_len={}",
separator_len, split_idx, min_len
);
if split_idx >= min_len {
// paths are identical, highlight everything
(
DiagnosticStyledString::highlighted(t1_str),
DiagnosticStyledString::highlighted(t2_str),
)
} else {
let (common, uniq1) = t1_str.split_at(split_idx);
let (_, uniq2) = t2_str.split_at(split_idx);
debug!("cmp: common={}, uniq1={}, uniq2={}", common, uniq1, uniq2);
values.0.push_normal(common);
values.0.push_highlighted(uniq1);
values.1.push_normal(common);
values.1.push_highlighted(uniq2);
values
}
}
}
// When finding T != &T, highlight only the borrow
(&ty::Ref(r1, ref_ty1, mutbl1), _) if equals(ref_ty1, t2) => {
let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
values.1.push_normal(t2.to_string());
values
}
(_, &ty::Ref(r2, ref_ty2, mutbl2)) if equals(t1, ref_ty2) => {
let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
values.0.push_normal(t1.to_string());
push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
values
}
// When encountering &T != &mut T, highlight only the borrow
(&ty::Ref(r1, ref_ty1, mutbl1), &ty::Ref(r2, ref_ty2, mutbl2))
if equals(ref_ty1, ref_ty2) =>
{
let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
values
}
// When encountering tuples of the same size, highlight only the differing types
(&ty::Tuple(substs1), &ty::Tuple(substs2)) if substs1.len() == substs2.len() => {
let mut values =
(DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("("));
let len = substs1.len();
for (i, (left, right)) in substs1.iter().zip(substs2).enumerate() {
let (x1, x2) = self.cmp(left, right);
(values.0).0.extend(x1.0);
(values.1).0.extend(x2.0);
self.push_comma(&mut values.0, &mut values.1, len, i);
}
if len == 1 {
// Keep the output for single element tuples as `(ty,)`.
values.0.push_normal(",");
values.1.push_normal(",");
}
values.0.push_normal(")");
values.1.push_normal(")");
values
}
(ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
let mut values = self.cmp_fn_sig(&sig1, &sig2);
let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did1, substs1));
let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did2, substs2));
let same_path = path1 == path2;
values.0.push(path1, !same_path);
values.1.push(path2, !same_path);
values
}
(ty::FnDef(did1, substs1), ty::FnPtr(sig2)) => {
let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
let mut values = self.cmp_fn_sig(&sig1, sig2);
values.0.push_highlighted(format!(
" {{{}}}",
self.tcx.def_path_str_with_substs(*did1, substs1)
));
values
}
(ty::FnPtr(sig1), ty::FnDef(did2, substs2)) => {
let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
let mut values = self.cmp_fn_sig(sig1, &sig2);
values.1.push_normal(format!(
" {{{}}}",
self.tcx.def_path_str_with_substs(*did2, substs2)
));
values
}
(ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2),
_ => {
if t1 == t2 {
// The two types are the same, elide and don't highlight.
(DiagnosticStyledString::normal("_"), DiagnosticStyledString::normal("_"))
} else {
// We couldn't find anything in common, highlight everything.
(
DiagnosticStyledString::highlighted(t1.to_string()),
DiagnosticStyledString::highlighted(t2.to_string()),
)
}
}
}
}
/// Extend a type error with extra labels pointing at "non-trivial" types, like closures and
/// the return type of `async fn`s.
///
/// `secondary_span` gives the caller the opportunity to expand `diag` with a `span_label`.
///
/// `swap_secondary_and_primary` is used to make projection errors in particular nicer by using
/// the message in `secondary_span` as the primary label, and apply the message that would
/// otherwise be used for the primary label on the `secondary_span` `Span`. This applies on
/// E0271, like `src/test/ui/issues/issue-39970.stderr`.
#[instrument(
level = "debug",
skip(self, diag, secondary_span, swap_secondary_and_primary, prefer_label)
)]
pub fn note_type_err(
&self,
diag: &mut Diagnostic,
cause: &ObligationCause<'tcx>,
secondary_span: Option<(Span, String)>,
mut values: Option<ValuePairs<'tcx>>,
terr: TypeError<'tcx>,
swap_secondary_and_primary: bool,
prefer_label: bool,
) {
let span = cause.span();
// For some types of errors, expected-found does not make
// sense, so just ignore the values we were given.
if let TypeError::CyclicTy(_) = terr {
values = None;
}
struct OpaqueTypesVisitor<'tcx> {
types: FxHashMap<TyCategory, FxHashSet<Span>>,
expected: FxHashMap<TyCategory, FxHashSet<Span>>,
found: FxHashMap<TyCategory, FxHashSet<Span>>,
ignore_span: Span,
tcx: TyCtxt<'tcx>,
}
impl<'tcx> OpaqueTypesVisitor<'tcx> {
fn visit_expected_found(
tcx: TyCtxt<'tcx>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
ignore_span: Span,
) -> Self {
let mut types_visitor = OpaqueTypesVisitor {
types: Default::default(),
expected: Default::default(),
found: Default::default(),
ignore_span,
tcx,
};
// The visitor puts all the relevant encountered types in `self.types`, but in
// here we want to visit two separate types with no relation to each other, so we
// move the results from `types` to `expected` or `found` as appropriate.
expected.visit_with(&mut types_visitor);
std::mem::swap(&mut types_visitor.expected, &mut types_visitor.types);
found.visit_with(&mut types_visitor);
std::mem::swap(&mut types_visitor.found, &mut types_visitor.types);
types_visitor
}
fn report(&self, err: &mut Diagnostic) {
self.add_labels_for_types(err, "expected", &self.expected);
self.add_labels_for_types(err, "found", &self.found);
}
fn add_labels_for_types(
&self,
err: &mut Diagnostic,
target: &str,
types: &FxHashMap<TyCategory, FxHashSet<Span>>,
) {
for (key, values) in types.iter() {
let count = values.len();
let kind = key.descr();
let mut returned_async_output_error = false;
for &sp in values {
if sp.is_desugaring(DesugaringKind::Async) && !returned_async_output_error {
if [sp] != err.span.primary_spans() {
let mut span: MultiSpan = sp.into();
span.push_span_label(
sp,
format!(
"checked the `Output` of this `async fn`, {}{} {}{}",
if count > 1 { "one of the " } else { "" },
target,
kind,
pluralize!(count),
),
);
err.span_note(
span,
"while checking the return type of the `async fn`",
);
} else {
err.span_label(
sp,
format!(
"checked the `Output` of this `async fn`, {}{} {}{}",
if count > 1 { "one of the " } else { "" },
target,
kind,
pluralize!(count),
),
);
err.note("while checking the return type of the `async fn`");
}
returned_async_output_error = true;
} else {
err.span_label(
sp,
format!(
"{}{} {}{}",
if count == 1 { "the " } else { "one of the " },
target,
kind,
pluralize!(count),
),
);
}
}
}
}
}
impl<'tcx> ty::visit::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) {
let span = self.tcx.def_span(def_id);
// Avoid cluttering the output when the "found" and error span overlap:
//
// error[E0308]: mismatched types
// --> $DIR/issue-20862.rs:2:5
// |
// LL | |y| x + y
// | ^^^^^^^^^
// | |
// | the found closure
// | expected `()`, found closure
// |
// = note: expected unit type `()`
// found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
if !self.ignore_span.overlaps(span) {
self.types.entry(kind).or_default().insert(span);
}
}
t.super_visit_with(self)
}
}
debug!("note_type_err(diag={:?})", diag);
enum Mismatch<'a> {
Variable(ty::error::ExpectedFound<Ty<'a>>),
Fixed(&'static str),
}
let (expected_found, exp_found, is_simple_error, values) = match values {
None => (None, Mismatch::Fixed("type"), false, None),
Some(values) => {
let values = self.resolve_vars_if_possible(values);
let (is_simple_error, exp_found) = match values {
ValuePairs::Terms(infer::ExpectedFound { expected, found }) => {
match (expected.unpack(), found.unpack()) {
(ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
let is_simple_err =
expected.is_simple_text() && found.is_simple_text();
OpaqueTypesVisitor::visit_expected_found(
self.tcx, expected, found, span,
)
.report(diag);
(
is_simple_err,
Mismatch::Variable(infer::ExpectedFound { expected, found }),
)
}
(ty::TermKind::Const(_), ty::TermKind::Const(_)) => {
(false, Mismatch::Fixed("constant"))
}
_ => (false, Mismatch::Fixed("type")),
}
}
ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
(false, Mismatch::Fixed("trait"))
}
ValuePairs::Regions(_) => (false, Mismatch::Fixed("lifetime")),
};
let vals = match self.values_str(values) {
Some((expected, found)) => Some((expected, found)),
None => {
// Derived error. Cancel the emitter.
// NOTE(eddyb) this was `.cancel()`, but `diag`
// is borrowed, so we can't fully defuse it.
diag.downgrade_to_delayed_bug();
return;
}
};
(vals, exp_found, is_simple_error, Some(values))
}
};
match terr {
// Ignore msg for object safe coercion
// since E0038 message will be printed
TypeError::ObjectUnsafeCoercion(_) => {}
_ => {
let mut label_or_note = |span: Span, msg: &str| {
if (prefer_label && is_simple_error) || &[span] == diag.span.primary_spans() {
diag.span_label(span, msg);
} else {
diag.span_note(span, msg);
}
};
if let Some((sp, msg)) = secondary_span {
if swap_secondary_and_primary {
let terr = if let Some(infer::ValuePairs::Terms(infer::ExpectedFound {
expected,
..
})) = values
{
format!("expected this to be `{}`", expected)
} else {
terr.to_string()
};
label_or_note(sp, &terr);
label_or_note(span, &msg);
} else {
label_or_note(span, &terr.to_string());
label_or_note(sp, &msg);
}
} else {
label_or_note(span, &terr.to_string());
}
}
};
if let Some((expected, found)) = expected_found {
let (expected_label, found_label, exp_found) = match exp_found {
Mismatch::Variable(ef) => (
ef.expected.prefix_string(self.tcx),
ef.found.prefix_string(self.tcx),
Some(ef),
),
Mismatch::Fixed(s) => (s.into(), s.into(), None),
};
match (&terr, expected == found) {
(TypeError::Sorts(values), extra) => {
let sort_string = |ty: Ty<'tcx>| match (extra, ty.kind()) {
(true, ty::Opaque(def_id, _)) => {
let sm = self.tcx.sess.source_map();
let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
format!(
" (opaque type at <{}:{}:{}>)",
sm.filename_for_diagnostics(&pos.file.name),
pos.line,
pos.col.to_usize() + 1,
)
}
(true, ty::Projection(proj))
if self.tcx.def_kind(proj.item_def_id)
== DefKind::ImplTraitPlaceholder =>
{
let sm = self.tcx.sess.source_map();
let pos = sm.lookup_char_pos(self.tcx.def_span(proj.item_def_id).lo());
format!(
" (trait associated opaque type at <{}:{}:{}>)",
sm.filename_for_diagnostics(&pos.file.name),
pos.line,
pos.col.to_usize() + 1,
)
}
(true, _) => format!(" ({})", ty.sort_string(self.tcx)),
(false, _) => "".to_string(),
};
if !(values.expected.is_simple_text() && values.found.is_simple_text())
|| (exp_found.map_or(false, |ef| {
// This happens when the type error is a subset of the expectation,
// like when you have two references but one is `usize` and the other
// is `f32`. In those cases we still want to show the `note`. If the
// value from `ef` is `Infer(_)`, then we ignore it.
if !ef.expected.is_ty_infer() {
ef.expected != values.expected
} else if !ef.found.is_ty_infer() {
ef.found != values.found
} else {
false
}
}))
{
diag.note_expected_found_extra(
&expected_label,
expected,
&found_label,
found,
&sort_string(values.expected),
&sort_string(values.found),
);
}
}
(TypeError::ObjectUnsafeCoercion(_), _) => {
diag.note_unsuccessful_coercion(found, expected);
}
(_, _) => {
debug!(
"note_type_err: exp_found={:?}, expected={:?} found={:?}",
exp_found, expected, found
);
if !is_simple_error || terr.must_include_note() {
diag.note_expected_found(&expected_label, expected, &found_label, found);
}
}
}
}
let exp_found = match exp_found {
Mismatch::Variable(exp_found) => Some(exp_found),
Mismatch::Fixed(_) => None,
};
let exp_found = match terr {
// `terr` has more accurate type information than `exp_found` in match expressions.
ty::error::TypeError::Sorts(terr)
if exp_found.map_or(false, |ef| terr.found == ef.found) =>
{
Some(terr)
}
_ => exp_found,
};
debug!("exp_found {:?} terr {:?} cause.code {:?}", exp_found, terr, cause.code());
if let Some(exp_found) = exp_found {
let should_suggest_fixes =
if let ObligationCauseCode::Pattern { root_ty, .. } = cause.code() {
// Skip if the root_ty of the pattern is not the same as the expected_ty.
// If these types aren't equal then we've probably peeled off a layer of arrays.
self.same_type_modulo_infer(*root_ty, exp_found.expected)
} else {
true
};
if should_suggest_fixes {
self.suggest_tuple_pattern(cause, &exp_found, diag);
self.suggest_as_ref_where_appropriate(span, &exp_found, diag);
self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
self.suggest_await_on_expect_found(cause, span, &exp_found, diag);
}
}
// In some (most?) cases cause.body_id points to actual body, but in some cases
// it's an actual definition. According to the comments (e.g. in
// librustc_typeck/check/compare_method.rs:compare_predicate_entailment) the latter
// is relied upon by some other code. This might (or might not) need cleanup.
let body_owner_def_id =
self.tcx.hir().opt_local_def_id(cause.body_id).unwrap_or_else(|| {
self.tcx.hir().body_owner_def_id(hir::BodyId { hir_id: cause.body_id })
});
self.check_and_note_conflicting_crates(diag, terr);
self.tcx.note_and_explain_type_err(diag, terr, cause, span, body_owner_def_id.to_def_id());
if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values
&& let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind()
&& let Some(def_id) = def_id.as_local()
&& terr.involves_regions()
{
let span = self.tcx.def_span(def_id);
diag.span_note(span, "this closure does not fulfill the lifetime requirements");
}
// It reads better to have the error origin as the final
// thing.
self.note_error_origin(diag, cause, exp_found, terr);
debug!(?diag);
}
fn suggest_tuple_pattern(
&self,
cause: &ObligationCause<'tcx>,
exp_found: &ty::error::ExpectedFound<Ty<'tcx>>,
diag: &mut Diagnostic,
) {
// Heavily inspired by `FnCtxt::suggest_compatible_variants`, with
// some modifications due to that being in typeck and this being in infer.
if let ObligationCauseCode::Pattern { .. } = cause.code() {
if let ty::Adt(expected_adt, substs) = exp_found.expected.kind() {
let compatible_variants: Vec<_> = expected_adt
.variants()
.iter()
.filter(|variant| {
variant.fields.len() == 1 && variant.ctor_kind == hir::def::CtorKind::Fn
})
.filter_map(|variant| {
let sole_field = &variant.fields[0];
let sole_field_ty = sole_field.ty(self.tcx, substs);
if self.same_type_modulo_infer(sole_field_ty, exp_found.found) {
let variant_path =
with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
// FIXME #56861: DRYer prelude filtering
if let Some(path) = variant_path.strip_prefix("std::prelude::") {
if let Some((_, path)) = path.split_once("::") {
return Some(path.to_string());
}
}
Some(variant_path)
} else {
None
}
})
.collect();
match &compatible_variants[..] {
[] => {}
[variant] => {
diag.multipart_suggestion_verbose(
&format!("try wrapping the pattern in `{}`", variant),
vec![
(cause.span.shrink_to_lo(), format!("{}(", variant)),
(cause.span.shrink_to_hi(), ")".to_string()),
],
Applicability::MaybeIncorrect,
);
}
_ => {
// More than one matching variant.
diag.multipart_suggestions(
&format!(
"try wrapping the pattern in a variant of `{}`",
self.tcx.def_path_str(expected_adt.did())
),
compatible_variants.into_iter().map(|variant| {
vec![
(cause.span.shrink_to_lo(), format!("{}(", variant)),
(cause.span.shrink_to_hi(), ")".to_string()),
]
}),
Applicability::MaybeIncorrect,
);
}
}
}
}
}
pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Binder<'tcx, Ty<'tcx>>> {
if let ty::Opaque(def_id, substs) = ty.kind() {
let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
// Future::Output
let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
let bounds = self.tcx.bound_explicit_item_bounds(*def_id);
for predicate in bounds.transpose_iter().map(|e| e.map_bound(|(p, _)| *p)) {
let predicate = predicate.subst(self.tcx, substs);
let output = predicate
.kind()
.map_bound(|kind| match kind {
ty::PredicateKind::Projection(projection_predicate)
if projection_predicate.projection_ty.item_def_id == item_def_id =>
{
projection_predicate.term.ty()
}
_ => None,
})
.transpose();
if output.is_some() {
// We don't account for multiple `Future::Output = Ty` constraints.
return output;
}
}
}
None
}
/// A possible error is to forget to add `.await` when using futures:
///
/// ```compile_fail,E0308
/// async fn make_u32() -> u32 {
/// 22
/// }
///
/// fn take_u32(x: u32) {}
///
/// async fn foo() {
/// let x = make_u32();
/// take_u32(x);
/// }
/// ```
///
/// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
/// expected type. If this is the case, and we are inside of an async body, it suggests adding
/// `.await` to the tail of the expression.
fn suggest_await_on_expect_found(
&self,
cause: &ObligationCause<'tcx>,
exp_span: Span,
exp_found: &ty::error::ExpectedFound<Ty<'tcx>>,
diag: &mut Diagnostic,
) {
debug!(
"suggest_await_on_expect_found: exp_span={:?}, expected_ty={:?}, found_ty={:?}",
exp_span, exp_found.expected, exp_found.found,
);
if let ObligationCauseCode::CompareImplItemObligation { .. } = cause.code() {
return;
}
match (
self.get_impl_future_output_ty(exp_found.expected).map(Binder::skip_binder),
self.get_impl_future_output_ty(exp_found.found).map(Binder::skip_binder),
) {
(Some(exp), Some(found)) if self.same_type_modulo_infer(exp, found) => match cause
.code()
{
ObligationCauseCode::IfExpression(box IfExpressionCause { then_id, .. }) => {
let then_span = self.find_block_span_from_hir_id(*then_id);
diag.multipart_suggestion(
"consider `await`ing on both `Future`s",
vec![
(then_span.shrink_to_hi(), ".await".to_string()),
(exp_span.shrink_to_hi(), ".await".to_string()),
],
Applicability::MaybeIncorrect,
);
}
ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
prior_arms,
..
}) => {
if let [.., arm_span] = &prior_arms[..] {
diag.multipart_suggestion(
"consider `await`ing on both `Future`s",
vec![
(arm_span.shrink_to_hi(), ".await".to_string()),
(exp_span.shrink_to_hi(), ".await".to_string()),
],
Applicability::MaybeIncorrect,
);
} else {
diag.help("consider `await`ing on both `Future`s");
}
}
_ => {
diag.help("consider `await`ing on both `Future`s");
}
},
(_, Some(ty)) if self.same_type_modulo_infer(exp_found.expected, ty) => {
diag.span_suggestion_verbose(
exp_span.shrink_to_hi(),
"consider `await`ing on the `Future`",
".await",
Applicability::MaybeIncorrect,
);
}
(Some(ty), _) if self.same_type_modulo_infer(ty, exp_found.found) => match cause.code()
{
ObligationCauseCode::Pattern { span: Some(then_span), .. } => {
diag.span_suggestion_verbose(
then_span.shrink_to_hi(),
"consider `await`ing on the `Future`",
".await",
Applicability::MaybeIncorrect,
);
}
ObligationCauseCode::IfExpression(box IfExpressionCause { then_id, .. }) => {
let then_span = self.find_block_span_from_hir_id(*then_id);
diag.span_suggestion_verbose(
then_span.shrink_to_hi(),
"consider `await`ing on the `Future`",
".await",
Applicability::MaybeIncorrect,
);
}
ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
ref prior_arms,
..
}) => {
diag.multipart_suggestion_verbose(
"consider `await`ing on the `Future`",
prior_arms
.iter()
.map(|arm| (arm.shrink_to_hi(), ".await".to_string()))
.collect(),
Applicability::MaybeIncorrect,
);
}
_ => {}
},
_ => {}
}
}
fn suggest_accessing_field_where_appropriate(
&self,
cause: &ObligationCause<'tcx>,
exp_found: &ty::error::ExpectedFound<Ty<'tcx>>,
diag: &mut Diagnostic,
) {
debug!(
"suggest_accessing_field_where_appropriate(cause={:?}, exp_found={:?})",
cause, exp_found
);
if let ty::Adt(expected_def, expected_substs) = exp_found.expected.kind() {
if expected_def.is_enum() {
return;
}
if let Some((name, ty)) = expected_def
.non_enum_variant()
.fields
.iter()
.filter(|field| field.vis.is_accessible_from(field.did, self.tcx))
.map(|field| (field.name, field.ty(self.tcx, expected_substs)))
.find(|(_, ty)| self.same_type_modulo_infer(*ty, exp_found.found))
{
if let ObligationCauseCode::Pattern { span: Some(span), .. } = *cause.code() {
if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
let suggestion = if expected_def.is_struct() {
format!("{}.{}", snippet, name)
} else if expected_def.is_union() {
format!("unsafe {{ {}.{} }}", snippet, name)
} else {
return;
};
diag.span_suggestion(
span,
&format!(
"you might have meant to use field `{}` whose type is `{}`",
name, ty
),
suggestion,
Applicability::MaybeIncorrect,
);
}
}
}
}
}
/// When encountering a case where `.as_ref()` on a `Result` or `Option` would be appropriate,
/// suggests it.
fn suggest_as_ref_where_appropriate(
&self,
span: Span,
exp_found: &ty::error::ExpectedFound<Ty<'tcx>>,
diag: &mut Diagnostic,
) {
if let (ty::Adt(exp_def, exp_substs), ty::Ref(_, found_ty, _)) =
(exp_found.expected.kind(), exp_found.found.kind())
{
if let ty::Adt(found_def, found_substs) = *found_ty.kind() {
if exp_def == &found_def {
let have_as_ref = &[
(
sym::Option,
"you can convert from `&Option<T>` to `Option<&T>` using \
`.as_ref()`",
),
(
sym::Result,
"you can convert from `&Result<T, E>` to \
`Result<&T, &E>` using `.as_ref()`",
),
];
if let Some(msg) = have_as_ref.iter().find_map(|(name, msg)| {
self.tcx.is_diagnostic_item(*name, exp_def.did()).then_some(msg)
}) {
let mut show_suggestion = true;
for (exp_ty, found_ty) in
iter::zip(exp_substs.types(), found_substs.types())
{
match *exp_ty.kind() {
ty::Ref(_, exp_ty, _) => {
match (exp_ty.kind(), found_ty.kind()) {
(_, ty::Param(_))
| (_, ty::Infer(_))
| (ty::Param(_), _)
| (ty::Infer(_), _) => {}
_ if self.same_type_modulo_infer(exp_ty, found_ty) => {}
_ => show_suggestion = false,
};
}
ty::Param(_) | ty::Infer(_) => {}
_ => show_suggestion = false,
}
}
if let (Ok(snippet), true) =
(self.tcx.sess.source_map().span_to_snippet(span), show_suggestion)
{
diag.span_suggestion(
span,
*msg,
// HACK: fix issue# 100605, suggesting convert from &Option<T> to Option<&T>, remove the extra `&`
format!("{}.as_ref()", snippet.trim_start_matches('&')),
Applicability::MachineApplicable,
);
}
}
}
}
}
}
pub fn report_and_explain_type_error(
&self,
trace: TypeTrace<'tcx>,
terr: TypeError<'tcx>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
use crate::traits::ObligationCauseCode::MatchExpressionArm;
debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
let span = trace.cause.span();
let failure_code = trace.cause.as_failure_code(terr);
let mut diag = match failure_code {
FailureCode::Error0038(did) => {
let violations = self.tcx.object_safety_violations(did);
report_object_safety_error(self.tcx, span, did, violations)
}
FailureCode::Error0317(failure_str) => {
struct_span_err!(self.tcx.sess, span, E0317, "{}", failure_str)
}
FailureCode::Error0580(failure_str) => {
struct_span_err!(self.tcx.sess, span, E0580, "{}", failure_str)
}
FailureCode::Error0308(failure_str) => {
let mut err = struct_span_err!(self.tcx.sess, span, E0308, "{}", failure_str);
if let Some((expected, found)) = trace.values.ty() {
match (expected.kind(), found.kind()) {
(ty::Tuple(_), ty::Tuple(_)) => {}
// If a tuple of length one was expected and the found expression has
// parentheses around it, perhaps the user meant to write `(expr,)` to
// build a tuple (issue #86100)
(ty::Tuple(fields), _) => {
self.emit_tuple_wrap_err(&mut err, span, found, fields)
}
// If a character was expected and the found expression is a string literal
// containing a single character, perhaps the user meant to write `'c'` to
// specify a character literal (issue #92479)
(ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
&& let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
&& code.chars().count() == 1
{
err.span_suggestion(
span,
"if you meant to write a `char` literal, use single quotes",
format!("'{}'", code),
Applicability::MachineApplicable,
);
}
}
// If a string was expected and the found expression is a character literal,
// perhaps the user meant to write `"s"` to specify a string literal.
(ty::Ref(_, r, _), ty::Char) if r.is_str() => {
if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
if let Some(code) =
code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
{
err.span_suggestion(
span,
"if you meant to write a `str` literal, use double quotes",
format!("\"{}\"", code),
Applicability::MachineApplicable,
);
}
}
}
_ => {}
}
}
let code = trace.cause.code();
if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
&& let hir::MatchSource::TryDesugar = source
&& let Some((expected_ty, found_ty)) = self.values_str(trace.values)
{
err.note(&format!(
"`?` operator cannot convert from `{}` to `{}`",
found_ty.content(),
expected_ty.content(),
));
}
err
}
FailureCode::Error0644(failure_str) => {
struct_span_err!(self.tcx.sess, span, E0644, "{}", failure_str)
}
};
self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr, false, false);
diag
}
fn emit_tuple_wrap_err(
&self,
err: &mut Diagnostic,
span: Span,
found: Ty<'tcx>,
expected_fields: &List<Ty<'tcx>>,
) {
let [expected_tup_elem] = expected_fields[..] else { return };
if !self.same_type_modulo_infer(expected_tup_elem, found) {
return;
}
let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
else { return };
let msg = "use a trailing comma to create a tuple with one element";
if code.starts_with('(') && code.ends_with(')') {
let before_close = span.hi() - BytePos::from_u32(1);
err.span_suggestion(
span.with_hi(before_close).shrink_to_hi(),
msg,
",",
Applicability::MachineApplicable,
);
} else {
err.multipart_suggestion(
msg,
vec![(span.shrink_to_lo(), "(".into()), (span.shrink_to_hi(), ",)".into())],
Applicability::MachineApplicable,
);
}
}
fn values_str(
&self,
values: ValuePairs<'tcx>,
) -> Option<(DiagnosticStyledString, DiagnosticStyledString)> {
match values {
infer::Regions(exp_found) => self.expected_found_str(exp_found),
infer::Terms(exp_found) => self.expected_found_str_term(exp_found),
infer::TraitRefs(exp_found) => {
let pretty_exp_found = ty::error::ExpectedFound {
expected: exp_found.expected.print_only_trait_path(),
found: exp_found.found.print_only_trait_path(),
};
match self.expected_found_str(pretty_exp_found) {
Some((expected, found)) if expected == found => {
self.expected_found_str(exp_found)
}
ret => ret,
}
}
infer::PolyTraitRefs(exp_found) => {
let pretty_exp_found = ty::error::ExpectedFound {
expected: exp_found.expected.print_only_trait_path(),
found: exp_found.found.print_only_trait_path(),
};
match self.expected_found_str(pretty_exp_found) {
Some((expected, found)) if expected == found => {
self.expected_found_str(exp_found)
}
ret => ret,
}
}
}
}
fn expected_found_str_term(
&self,
exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>,
) -> Option<(DiagnosticStyledString, DiagnosticStyledString)> {
let exp_found = self.resolve_vars_if_possible(exp_found);
if exp_found.references_error() {
return None;
}
Some(match (exp_found.expected.unpack(), exp_found.found.unpack()) {
(ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => self.cmp(expected, found),
_ => (
DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
DiagnosticStyledString::highlighted(exp_found.found.to_string()),
),
})
}
/// Returns a string of the form "expected `{}`, found `{}`".
fn expected_found_str<T: fmt::Display + TypeFoldable<'tcx>>(
&self,
exp_found: ty::error::ExpectedFound<T>,
) -> Option<(DiagnosticStyledString, DiagnosticStyledString)> {
let exp_found = self.resolve_vars_if_possible(exp_found);
if exp_found.references_error() {
return None;
}
Some((
DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
DiagnosticStyledString::highlighted(exp_found.found.to_string()),
))
}
pub fn report_generic_bound_failure(
&self,
generic_param_scope: LocalDefId,
span: Span,
origin: Option<SubregionOrigin<'tcx>>,
bound_kind: GenericKind<'tcx>,
sub: Region<'tcx>,
) {
self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
.emit();
}
pub fn construct_generic_bound_failure(
&self,
generic_param_scope: LocalDefId,
span: Span,
origin: Option<SubregionOrigin<'tcx>>,
bound_kind: GenericKind<'tcx>,
sub: Region<'tcx>,
) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
// Attempt to obtain the span of the parameter so we can
// suggest adding an explicit lifetime bound to it.
let generics = self.tcx.generics_of(generic_param_scope);
// type_param_span is (span, has_bounds)
let type_param_span = match bound_kind {
GenericKind::Param(ref param) => {
// Account for the case where `param` corresponds to `Self`,
// which doesn't have the expected type argument.
if !(generics.has_self && param.index == 0) {
let type_param = generics.type_param(param, self.tcx);
type_param.def_id.as_local().map(|def_id| {
// Get the `hir::Param` to verify whether it already has any bounds.
// We do this to avoid suggesting code that ends up as `T: 'a'b`,
// instead we suggest `T: 'a + 'b` in that case.
let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
let ast_generics = self.tcx.hir().get_generics(hir_id.owner);
let bounds =
ast_generics.and_then(|g| g.bounds_span_for_suggestions(def_id));
// `sp` only covers `T`, change it so that it covers
// `T:` when appropriate
if let Some(span) = bounds {
(span, true)
} else {
let sp = self.tcx.def_span(def_id);
(sp.shrink_to_hi(), false)
}
})
} else {
None
}
}
_ => None,
};
let new_lt = {
let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
let lts_names =
iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p)))
.flat_map(|g| &g.params)
.filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
.map(|p| p.name.as_str())
.collect::<Vec<_>>();
possible
.find(|candidate| !lts_names.contains(&&candidate[..]))
.unwrap_or("'lt".to_string())
};
let add_lt_sugg = generics
.params
.first()
.and_then(|param| param.def_id.as_local())
.map(|def_id| (self.tcx.def_span(def_id).shrink_to_lo(), format!("{}, ", new_lt)));
let labeled_user_string = match bound_kind {
GenericKind::Param(ref p) => format!("the parameter type `{}`", p),
GenericKind::Projection(ref p) => format!("the associated type `{}`", p),
};
if let Some(SubregionOrigin::CompareImplItemObligation {
span,
impl_item_def_id,
trait_item_def_id,
}) = origin
{
return self.report_extra_impl_obligation(
span,
impl_item_def_id,
trait_item_def_id,
&format!("`{}: {}`", bound_kind, sub),
);
}
fn binding_suggestion<'tcx, S: fmt::Display>(
err: &mut Diagnostic,
type_param_span: Option<(Span, bool)>,
bound_kind: GenericKind<'tcx>,
sub: S,
add_lt_sugg: Option<(Span, String)>,
) {
let msg = "consider adding an explicit lifetime bound";
if let Some((sp, has_lifetimes)) = type_param_span {
let suggestion =
if has_lifetimes { format!(" + {}", sub) } else { format!(": {}", sub) };
let mut suggestions = vec![(sp, suggestion)];
if let Some(add_lt_sugg) = add_lt_sugg {
suggestions.push(add_lt_sugg);
}
err.multipart_suggestion_verbose(
format!("{msg}..."),
suggestions,
Applicability::MaybeIncorrect, // Issue #41966
);
} else {
let consider = format!("{} `{}: {}`...", msg, bound_kind, sub);
err.help(&consider);
}
}
let new_binding_suggestion =
|err: &mut Diagnostic, type_param_span: Option<(Span, bool)>| {
let msg = "consider introducing an explicit lifetime bound";
if let Some((sp, has_lifetimes)) = type_param_span {
let suggestion = if has_lifetimes {
format!(" + {}", new_lt)
} else {
format!(": {}", new_lt)
};
let mut sugg =
vec![(sp, suggestion), (span.shrink_to_hi(), format!(" + {}", new_lt))];
if let Some(lt) = add_lt_sugg.clone() {
sugg.push(lt);
sugg.rotate_right(1);
}
// `MaybeIncorrect` due to issue #41966.
err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect);
}
};
#[derive(Debug)]
enum SubOrigin<'hir> {
GAT(&'hir hir::Generics<'hir>),
Impl,
Trait,
Fn,
Unknown,
}
let sub_origin = 'origin: {
match *sub {
ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => {
let node = self.tcx.hir().get_if_local(def_id).unwrap();
match node {
Node::GenericParam(param) => {
for h in self.tcx.hir().parent_iter(param.hir_id) {
break 'origin match h.1 {
Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::TyAlias(..),
generics,
..
})
| Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Type(..),
generics,
..
}) => SubOrigin::GAT(generics),
Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::Fn(..),
..
})
| Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(..),
..
})
| Node::Item(hir::Item {
kind: hir::ItemKind::Fn(..), ..
}) => SubOrigin::Fn,
Node::Item(hir::Item {
kind: hir::ItemKind::Trait(..),
..
}) => SubOrigin::Trait,
Node::Item(hir::Item {
kind: hir::ItemKind::Impl(..), ..
}) => SubOrigin::Impl,
_ => continue,
};
}
}
_ => {}
}
}
_ => {}
}
SubOrigin::Unknown
};
debug!(?sub_origin);
let mut err = match (*sub, sub_origin) {
// In the case of GATs, we have to be careful. If we a type parameter `T` on an impl,
// but a lifetime `'a` on an associated type, then we might need to suggest adding
// `where T: 'a`. Importantly, this is on the GAT span, not on the `T` declaration.
(ty::ReEarlyBound(ty::EarlyBoundRegion { name: _, .. }), SubOrigin::GAT(generics)) => {
// Does the required lifetime have a nice name we can print?
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0309,
"{} may not live long enough",
labeled_user_string
);
let pred = format!("{}: {}", bound_kind, sub);
let suggestion = format!("{} {}", generics.add_where_or_trailing_comma(), pred,);
err.span_suggestion(
generics.tail_span_for_predicate_suggestion(),
"consider adding a where clause",
suggestion,
Applicability::MaybeIncorrect,
);
err
}
(
ty::ReEarlyBound(ty::EarlyBoundRegion { name, .. })
| ty::ReFree(ty::FreeRegion { bound_region: ty::BrNamed(_, name), .. }),
_,
) if name != kw::UnderscoreLifetime => {
// Does the required lifetime have a nice name we can print?
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0309,
"{} may not live long enough",
labeled_user_string
);
// Explicitly use the name instead of `sub`'s `Display` impl. The `Display` impl
// for the bound is not suitable for suggestions when `-Zverbose` is set because it
// uses `Debug` output, so we handle it specially here so that suggestions are
// always correct.
binding_suggestion(&mut err, type_param_span, bound_kind, name, None);
err
}
(ty::ReStatic, _) => {
// Does the required lifetime have a nice name we can print?
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0310,
"{} may not live long enough",
labeled_user_string
);
binding_suggestion(&mut err, type_param_span, bound_kind, "'static", None);
err
}
_ => {
// If not, be less specific.
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0311,
"{} may not live long enough",
labeled_user_string
);
note_and_explain_region(
self.tcx,
&mut err,
&format!("{} must be valid for ", labeled_user_string),
sub,
"...",
None,
);
if let Some(infer::RelateParamBound(_, t, _)) = origin {
let return_impl_trait =
self.tcx.return_type_impl_trait(generic_param_scope).is_some();
let t = self.resolve_vars_if_possible(t);
match t.kind() {
// We've got:
// fn get_later<G, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
// suggest:
// fn get_later<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
ty::Closure(_, _substs) | ty::Opaque(_, _substs) if return_impl_trait => {
new_binding_suggestion(&mut err, type_param_span);
}
_ => {
binding_suggestion(
&mut err,
type_param_span,
bound_kind,
new_lt,
add_lt_sugg,
);
}
}
}
err
}
};
if let Some(origin) = origin {
self.note_region_origin(&mut err, &origin);
}
err
}
fn report_sub_sup_conflict(
&self,
var_origin: RegionVariableOrigin,
sub_origin: SubregionOrigin<'tcx>,
sub_region: Region<'tcx>,
sup_origin: SubregionOrigin<'tcx>,
sup_region: Region<'tcx>,
) {
let mut err = self.report_inference_failure(var_origin);
note_and_explain_region(
self.tcx,
&mut err,
"first, the lifetime cannot outlive ",
sup_region,
"...",
None,
);
debug!("report_sub_sup_conflict: var_origin={:?}", var_origin);
debug!("report_sub_sup_conflict: sub_region={:?}", sub_region);
debug!("report_sub_sup_conflict: sub_origin={:?}", sub_origin);
debug!("report_sub_sup_conflict: sup_region={:?}", sup_region);
debug!("report_sub_sup_conflict: sup_origin={:?}", sup_origin);
if let (&infer::Subtype(ref sup_trace), &infer::Subtype(ref sub_trace)) =
(&sup_origin, &sub_origin)
{
debug!("report_sub_sup_conflict: sup_trace={:?}", sup_trace);
debug!("report_sub_sup_conflict: sub_trace={:?}", sub_trace);
debug!("report_sub_sup_conflict: sup_trace.values={:?}", sup_trace.values);
debug!("report_sub_sup_conflict: sub_trace.values={:?}", sub_trace.values);
if let (Some((sup_expected, sup_found)), Some((sub_expected, sub_found))) =
(self.values_str(sup_trace.values), self.values_str(sub_trace.values))
{
if sub_expected == sup_expected && sub_found == sup_found {
note_and_explain_region(
self.tcx,
&mut err,
"...but the lifetime must also be valid for ",
sub_region,
"...",
None,
);
err.span_note(
sup_trace.cause.span,
&format!("...so that the {}", sup_trace.cause.as_requirement_str()),
);
err.note_expected_found(&"", sup_expected, &"", sup_found);
err.emit();
return;
}
}
}
self.note_region_origin(&mut err, &sup_origin);
note_and_explain_region(
self.tcx,
&mut err,
"but, the lifetime must be valid for ",
sub_region,
"...",
None,
);
self.note_region_origin(&mut err, &sub_origin);
err.emit();
}
/// Determine whether an error associated with the given span and definition
/// should be treated as being caused by the implicit `From` conversion
/// within `?` desugaring.
pub fn is_try_conversion(&self, span: Span, trait_def_id: DefId) -> bool {
span.is_desugaring(DesugaringKind::QuestionMark)
&& self.tcx.is_diagnostic_item(sym::From, trait_def_id)
}
/// Structurally compares two types, modulo any inference variables.
///
/// Returns `true` if two types are equal, or if one type is an inference variable compatible
/// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
/// FloatVar inference type are compatible with themselves or their concrete types (Int and
/// Float types, respectively). When comparing two ADTs, these rules apply recursively.
pub fn same_type_modulo_infer(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
let (a, b) = self.resolve_vars_if_possible((a, b));
SameTypeModuloInfer(self).relate(a, b).is_ok()
}
}
struct SameTypeModuloInfer<'a, 'tcx>(&'a InferCtxt<'a, 'tcx>);
impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.0.tcx
}
fn param_env(&self) -> ty::ParamEnv<'tcx> {
// Unused, only for consts which we treat as always equal
ty::ParamEnv::empty()
}
fn tag(&self) -> &'static str {
"SameTypeModuloInfer"
}
fn a_is_expected(&self) -> bool {
true
}
fn relate_with_variance<T: relate::Relate<'tcx>>(
&mut self,
_variance: ty::Variance,
_info: ty::VarianceDiagInfo<'tcx>,
a: T,
b: T,
) -> relate::RelateResult<'tcx, T> {
self.relate(a, b)
}
fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
match (a.kind(), b.kind()) {
(ty::Int(_) | ty::Uint(_), ty::Infer(ty::InferTy::IntVar(_)))
| (
ty::Infer(ty::InferTy::IntVar(_)),
ty::Int(_) | ty::Uint(_) | ty::Infer(ty::InferTy::IntVar(_)),
)
| (ty::Float(_), ty::Infer(ty::InferTy::FloatVar(_)))
| (
ty::Infer(ty::InferTy::FloatVar(_)),
ty::Float(_) | ty::Infer(ty::InferTy::FloatVar(_)),
)
| (ty::Infer(ty::InferTy::TyVar(_)), _)
| (_, ty::Infer(ty::InferTy::TyVar(_))) => Ok(a),
(ty::Infer(_), _) | (_, ty::Infer(_)) => Err(TypeError::Mismatch),
_ => relate::super_relate_tys(self, a, b),
}
}
fn regions(
&mut self,
a: ty::Region<'tcx>,
b: ty::Region<'tcx>,
) -> RelateResult<'tcx, ty::Region<'tcx>> {
if (a.is_var() && b.is_free_or_static())
|| (b.is_var() && a.is_free_or_static())
|| (a.is_var() && b.is_var())
|| a == b
{
Ok(a)
} else {
Err(TypeError::Mismatch)
}
}
fn binders<T>(
&mut self,
a: ty::Binder<'tcx, T>,
b: ty::Binder<'tcx, T>,
) -> relate::RelateResult<'tcx, ty::Binder<'tcx, T>>
where
T: relate::Relate<'tcx>,
{
Ok(a.rebind(self.relate(a.skip_binder(), b.skip_binder())?))
}
fn consts(
&mut self,
a: ty::Const<'tcx>,
_b: ty::Const<'tcx>,
) -> relate::RelateResult<'tcx, ty::Const<'tcx>> {
// FIXME(compiler-errors): This could at least do some first-order
// relation
Ok(a)
}
}
impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
fn report_inference_failure(
&self,
var_origin: RegionVariableOrigin,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
let br_string = |br: ty::BoundRegionKind| {
let mut s = match br {
ty::BrNamed(_, name) => name.to_string(),
_ => String::new(),
};
if !s.is_empty() {
s.push(' ');
}
s
};
let var_description = match var_origin {
infer::MiscVariable(_) => String::new(),
infer::PatternRegion(_) => " for pattern".to_string(),
infer::AddrOfRegion(_) => " for borrow expression".to_string(),
infer::Autoref(_) => " for autoref".to_string(),
infer::Coercion(_) => " for automatic coercion".to_string(),
infer::LateBoundRegion(_, br, infer::FnCall) => {
format!(" for lifetime parameter {}in function call", br_string(br))
}
infer::LateBoundRegion(_, br, infer::HigherRankedType) => {
format!(" for lifetime parameter {}in generic type", br_string(br))
}
infer::LateBoundRegion(_, br, infer::AssocTypeProjection(def_id)) => format!(
" for lifetime parameter {}in trait containing associated type `{}`",
br_string(br),
self.tcx.associated_item(def_id).name
),
infer::EarlyBoundRegion(_, name) => format!(" for lifetime parameter `{}`", name),
infer::UpvarRegion(ref upvar_id, _) => {
let var_name = self.tcx.hir().name(upvar_id.var_path.hir_id);
format!(" for capture of `{}` by closure", var_name)
}
infer::Nll(..) => bug!("NLL variable found in lexical phase"),
};
struct_span_err!(
self.tcx.sess,
var_origin.span(),
E0495,
"cannot infer an appropriate lifetime{} due to conflicting requirements",
var_description
)
}
}
pub enum FailureCode {
Error0038(DefId),
Error0317(&'static str),
Error0580(&'static str),
Error0308(&'static str),
Error0644(&'static str),
}
pub trait ObligationCauseExt<'tcx> {
fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
fn as_requirement_str(&self) -> &'static str;
}
impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
use self::FailureCode::*;
use crate::traits::ObligationCauseCode::*;
match self.code() {
CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
Error0308("method not compatible with trait")
}
CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
Error0308("type not compatible with trait")
}
CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
Error0308("const not compatible with trait")
}
MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => {
Error0308(match source {
hir::MatchSource::TryDesugar => "`?` operator has incompatible types",
_ => "`match` arms have incompatible types",
})
}
IfExpression { .. } => Error0308("`if` and `else` have incompatible types"),
IfExpressionWithNoElse => Error0317("`if` may be missing an `else` clause"),
LetElse => Error0308("`else` clause of `let...else` does not diverge"),
MainFunctionType => Error0580("`main` function has wrong type"),
StartFunctionType => Error0308("`#[start]` function has wrong type"),
IntrinsicType => Error0308("intrinsic has wrong type"),
MethodReceiver => Error0308("mismatched `self` parameter type"),
// In the case where we have no more specific thing to
// say, also take a look at the error code, maybe we can
// tailor to that.
_ => match terr {
TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
Error0644("closure/generator type that references itself")
}
TypeError::IntrinsicCast => {
Error0308("cannot coerce intrinsics to function pointers")
}
TypeError::ObjectUnsafeCoercion(did) => Error0038(did),
_ => Error0308("mismatched types"),
},
}
}
fn as_requirement_str(&self) -> &'static str {
use crate::traits::ObligationCauseCode::*;
match self.code() {
CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
"method type is compatible with trait"
}
CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
"associated type is compatible with trait"
}
CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
"const is compatible with trait"
}
ExprAssignable => "expression is assignable",
IfExpression { .. } => "`if` and `else` have incompatible types",
IfExpressionWithNoElse => "`if` missing an `else` returns `()`",
MainFunctionType => "`main` function has the correct type",
StartFunctionType => "`#[start]` function has the correct type",
IntrinsicType => "intrinsic has the correct type",
MethodReceiver => "method receiver has the correct type",
_ => "types are compatible",
}
}
}
/// Newtype to allow implementing IntoDiagnosticArg
pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
impl IntoDiagnosticArg for ObligationCauseAsDiagArg<'_> {
fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
use crate::traits::ObligationCauseCode::*;
let kind = match self.0.code() {
CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => "method_compat",
CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => "type_compat",
CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => "const_compat",
ExprAssignable => "expr_assignable",
IfExpression { .. } => "if_else_different",
IfExpressionWithNoElse => "no_else",
MainFunctionType => "fn_main_correct_type",
StartFunctionType => "fn_start_correct_type",
IntrinsicType => "intristic_correct_type",
MethodReceiver => "method_correct_type",
_ => "other",
}
.into();
rustc_errors::DiagnosticArgValue::Str(kind)
}
}
/// This is a bare signal of what kind of type we're dealing with. `ty::TyKind` tracks
/// extra information about each type, but we only care about the category.
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
pub enum TyCategory {
Closure,
Opaque,
Generator(hir::GeneratorKind),
Foreign,
}
impl TyCategory {
fn descr(&self) -> &'static str {
match self {
Self::Closure => "closure",
Self::Opaque => "opaque type",
Self::Generator(gk) => gk.descr(),
Self::Foreign => "foreign type",
}
}
pub fn from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)> {
match *ty.kind() {
ty::Closure(def_id, _) => Some((Self::Closure, def_id)),
ty::Opaque(def_id, _) => Some((Self::Opaque, def_id)),
ty::Generator(def_id, ..) => {
Some((Self::Generator(tcx.generator_kind(def_id).unwrap()), def_id))
}
ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
_ => None,
}
}
}
impl<'tcx> InferCtxt<'_, 'tcx> {
/// Given a [`hir::Block`], get the span of its last expression or
/// statement, peeling off any inner blocks.
pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
let block = block.innermost_block();
if let Some(expr) = &block.expr {
expr.span
} else if let Some(stmt) = block.stmts.last() {
// possibly incorrect trailing `;` in the else arm
stmt.span
} else {
// empty block; point at its entirety
block.span
}
}
/// Given a [`hir::HirId`] for a block, get the span of its last expression
/// or statement, peeling off any inner blocks.
pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span {
match self.tcx.hir().get(hir_id) {
hir::Node::Block(blk) => self.find_block_span(blk),
// The parser was in a weird state if either of these happen, but
// it's better not to panic.
hir::Node::Expr(e) => e.span,
_ => rustc_span::DUMMY_SP,
}
}
/// Be helpful when the user wrote `{... expr; }` and taking the `;` off
/// is enough to fix the error.
pub fn could_remove_semicolon(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
) -> Option<(Span, StatementAsExpression)> {
let blk = blk.innermost_block();
// Do not suggest if we have a tail expr.
if blk.expr.is_some() {
return None;
}
let last_stmt = blk.stmts.last()?;
let hir::StmtKind::Semi(ref last_expr) = last_stmt.kind else {
return None;
};
let last_expr_ty = self.in_progress_typeck_results?.borrow().expr_ty_opt(*last_expr)?;
let needs_box = match (last_expr_ty.kind(), expected_ty.kind()) {
_ if last_expr_ty.references_error() => return None,
_ if self.same_type_modulo_infer(last_expr_ty, expected_ty) => {
StatementAsExpression::CorrectType
}
(ty::Opaque(last_def_id, _), ty::Opaque(exp_def_id, _))
if last_def_id == exp_def_id =>
{
StatementAsExpression::CorrectType
}
(ty::Opaque(last_def_id, last_bounds), ty::Opaque(exp_def_id, exp_bounds)) => {
debug!(
"both opaque, likely future {:?} {:?} {:?} {:?}",
last_def_id, last_bounds, exp_def_id, exp_bounds
);
let last_local_id = last_def_id.as_local()?;
let exp_local_id = exp_def_id.as_local()?;
match (
&self.tcx.hir().expect_item(last_local_id).kind,
&self.tcx.hir().expect_item(exp_local_id).kind,
) {
(
hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: last_bounds, .. }),
hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: exp_bounds, .. }),
) if iter::zip(*last_bounds, *exp_bounds).all(|(left, right)| {
match (left, right) {
(
hir::GenericBound::Trait(tl, ml),
hir::GenericBound::Trait(tr, mr),
) if tl.trait_ref.trait_def_id() == tr.trait_ref.trait_def_id()
&& ml == mr =>
{
true
}
(
hir::GenericBound::LangItemTrait(langl, _, _, argsl),
hir::GenericBound::LangItemTrait(langr, _, _, argsr),
) if langl == langr => {
// FIXME: consider the bounds!
debug!("{:?} {:?}", argsl, argsr);
true
}
_ => false,
}
}) =>
{
StatementAsExpression::NeedsBoxing
}
_ => StatementAsExpression::CorrectType,
}
}
_ => return None,
};
let span = if last_stmt.span.from_expansion() {
let mac_call = rustc_span::source_map::original_sp(last_stmt.span, blk.span);
self.tcx.sess.source_map().mac_call_stmt_semi_span(mac_call)?
} else {
last_stmt.span.with_lo(last_stmt.span.hi() - BytePos(1))
};
Some((span, needs_box))
}
/// Suggest returning a local binding with a compatible type if the block
/// has no return expression.
pub fn consider_returning_binding(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
err: &mut Diagnostic,
) -> bool {
let blk = blk.innermost_block();
// Do not suggest if we have a tail expr.
if blk.expr.is_some() {
return false;
}
let mut shadowed = FxHashSet::default();
let mut candidate_idents = vec![];
let mut find_compatible_candidates = |pat: &hir::Pat<'_>| {
if let hir::PatKind::Binding(_, hir_id, ident, _) = &pat.kind
&& let Some(pat_ty) = self
.in_progress_typeck_results
.and_then(|typeck_results| typeck_results.borrow().node_type_opt(*hir_id))
{
let pat_ty = self.resolve_vars_if_possible(pat_ty);
if self.same_type_modulo_infer(pat_ty, expected_ty)
&& !(pat_ty, expected_ty).references_error()
&& shadowed.insert(ident.name)
{
candidate_idents.push((*ident, pat_ty));
}
}
true
};
let hir = self.tcx.hir();
for stmt in blk.stmts.iter().rev() {
let hir::StmtKind::Local(local) = &stmt.kind else { continue; };
local.pat.walk(&mut find_compatible_candidates);
}
match hir.find(hir.get_parent_node(blk.hir_id)) {
Some(hir::Node::Expr(hir::Expr { hir_id, .. })) => {
match hir.find(hir.get_parent_node(*hir_id)) {
Some(hir::Node::Arm(hir::Arm { pat, .. })) => {
pat.walk(&mut find_compatible_candidates);
}
Some(
hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body), .. })
| hir::Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::Fn(_, body),
..
})
| hir::Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(body)),
..
})
| hir::Node::Expr(hir::Expr {
kind: hir::ExprKind::Closure(hir::Closure { body, .. }),
..
}),
) => {
for param in hir.body(*body).params {
param.pat.walk(&mut find_compatible_candidates);
}
}
Some(hir::Node::Expr(hir::Expr {
kind:
hir::ExprKind::If(
hir::Expr { kind: hir::ExprKind::Let(let_), .. },
then_block,
_,
),
..
})) if then_block.hir_id == *hir_id => {
let_.pat.walk(&mut find_compatible_candidates);
}
_ => {}
}
}
_ => {}
}
match &candidate_idents[..] {
[(ident, _ty)] => {
let sm = self.tcx.sess.source_map();
if let Some(stmt) = blk.stmts.last() {
let stmt_span = sm.stmt_span(stmt.span, blk.span);
let sugg = if sm.is_multiline(blk.span)
&& let Some(spacing) = sm.indentation_before(stmt_span)
{
format!("\n{spacing}{ident}")
} else {
format!(" {ident}")
};
err.span_suggestion_verbose(
stmt_span.shrink_to_hi(),
format!("consider returning the local binding `{ident}`"),
sugg,
Applicability::MaybeIncorrect,
);
} else {
let sugg = if sm.is_multiline(blk.span)
&& let Some(spacing) = sm.indentation_before(blk.span.shrink_to_lo())
{
format!("\n{spacing} {ident}\n{spacing}")
} else {
format!(" {ident} ")
};
let left_span = sm.span_through_char(blk.span, '{').shrink_to_hi();
err.span_suggestion_verbose(
sm.span_extend_while(left_span, |c| c.is_whitespace()).unwrap_or(left_span),
format!("consider returning the local binding `{ident}`"),
sugg,
Applicability::MaybeIncorrect,
);
}
true
}
values if (1..3).contains(&values.len()) => {
let spans = values.iter().map(|(ident, _)| ident.span).collect::<Vec<_>>();
err.span_note(spans, "consider returning one of these bindings");
true
}
_ => false,
}
}
}