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android / toolchain / rustc / 87880447cc5437c45a3562596a9766d9797e7318 / . / 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::errors::{self, ObligationCauseFailureCode, TypeErrorAdditionalDiags};
use crate::infer;
use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
use crate::infer::ExpectedFound;
use crate::traits::{
IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode,
PredicateObligation,
};
use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed, IntoDiagnosticArg};
use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::intravisit::Visitor;
use rustc_hir::lang_items::LangItem;
use rustc_hir::Node;
use rustc_middle::dep_graph::DepContext;
use rustc_middle::ty::print::with_forced_trimmed_paths;
use rustc_middle::ty::relate::{self, RelateResult, TypeRelation};
use rustc_middle::ty::{
self, error::TypeError, List, Region, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
TypeVisitable, TypeVisitableExt,
};
use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span};
use rustc_target::spec::abi;
use std::borrow::Cow;
use std::ops::{ControlFlow, Deref};
use std::path::PathBuf;
use std::{cmp, fmt, iter};
mod note;
mod note_and_explain;
mod suggest;
pub(crate) mod need_type_info;
pub use need_type_info::TypeAnnotationNeeded;
pub mod nice_region_error;
/// Makes a valid string literal from a string by escaping special characters (" and \),
/// unless they are already escaped.
fn escape_literal(s: &str) -> String {
let mut escaped = String::with_capacity(s.len());
let mut chrs = s.chars().peekable();
while let Some(first) = chrs.next() {
match (first, chrs.peek()) {
('\\', Some(&delim @ '"') | Some(&delim @ '\'')) => {
escaped.push('\\');
escaped.push(delim);
chrs.next();
}
('"' | '\'', _) => {
escaped.push('\\');
escaped.push(first)
}
(c, _) => escaped.push(c),
};
}
escaped
}
/// A helper for building type related errors. The `typeck_results`
/// field is only populated during an in-progress typeck.
/// Get an instance by calling `InferCtxt::err_ctxt` or `FnCtxt::err_ctxt`.
///
/// You must only create this if you intend to actually emit an error.
/// This provides a lot of utility methods which should not be used
/// during the happy path.
pub struct TypeErrCtxt<'a, 'tcx> {
pub infcx: &'a InferCtxt<'tcx>,
pub typeck_results: Option<std::cell::Ref<'a, ty::TypeckResults<'tcx>>>,
pub fallback_has_occurred: bool,
pub normalize_fn_sig: Box<dyn Fn(ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx> + 'a>,
pub autoderef_steps:
Box<dyn Fn(Ty<'tcx>) -> Vec<(Ty<'tcx>, Vec<PredicateObligation<'tcx>>)> + 'a>,
}
impl Drop for TypeErrCtxt<'_, '_> {
fn drop(&mut self) {
if let Some(_) = self.infcx.tcx.sess.has_errors_or_delayed_span_bugs() {
// ok, emitted an error.
} else {
self.infcx
.tcx
.sess
.delay_good_path_bug("used a `TypeErrCtxt` without raising an error or lint");
}
}
}
impl TypeErrCtxt<'_, '_> {
/// This is just to avoid a potential footgun of accidentally
/// dropping `typeck_results` by calling `InferCtxt::err_ctxt`
#[deprecated(note = "you already have a `TypeErrCtxt`")]
#[allow(unused)]
pub fn err_ctxt(&self) -> ! {
bug!("called `err_ctxt` on `TypeErrCtxt`. Try removing the call");
}
}
impl<'tcx> Deref for TypeErrCtxt<'_, 'tcx> {
type Target = InferCtxt<'tcx>;
fn deref(&self) -> &InferCtxt<'tcx> {
&self.infcx
}
}
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::RePlaceholder(_) | ty::ReStatic => {
msg_span_from_named_region(tcx, region, alt_span)
}
ty::ReError(_) => return,
// 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_named_region(tcx, region, None);
label_msg_span(err, prefix, description, span, suffix);
}
fn msg_span_from_named_region<'tcx>(
tcx: TyCtxt<'tcx>,
region: ty::Region<'tcx>,
alt_span: Option<Span>,
) -> (String, Option<Span>) {
match *region {
ty::ReEarlyBound(ref br) => {
let scope = region.free_region_binding_scope(tcx).expect_local();
let span = if let Some(param) =
tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
{
param.span
} else {
tcx.def_span(scope)
};
let text = if br.has_name() {
format!("the lifetime `{}` as defined here", br.name)
} else {
"the anonymous lifetime as defined here".to_string()
};
(text, Some(span))
}
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(), Some(ty.span))
} else {
let scope = region.free_region_binding_scope(tcx).expect_local();
match fr.bound_region {
ty::BoundRegionKind::BrNamed(_, name) => {
let span = if let Some(param) =
tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
{
param.span
} else {
tcx.def_span(scope)
};
let text = if name == kw::UnderscoreLifetime {
"the anonymous lifetime as defined here".to_string()
} else {
format!("the lifetime `{name}` as defined here")
};
(text, Some(span))
}
ty::BrAnon(span) => (
"the anonymous lifetime as defined here".to_string(),
Some(match span {
Some(span) => span,
None => tcx.def_span(scope)
})
),
_ => (
format!("the lifetime `{region}` as defined here"),
Some(tcx.def_span(scope)),
),
}
}
}
ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
ty::RePlaceholder(ty::PlaceholderRegion {
bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrNamed(def_id, name), .. },
..
}) => (format!("the lifetime `{name}` as defined here"), Some(tcx.def_span(def_id))),
ty::RePlaceholder(ty::PlaceholderRegion {
bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(Some(span)), .. },
..
}) => ("the anonymous lifetime defined here".to_owned(), Some(span)),
ty::RePlaceholder(ty::PlaceholderRegion {
bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(None), .. },
..
}) => ("an anonymous lifetime".to_owned(), None),
_ => bug!("{:?}", region),
}
}
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);
}
}
#[instrument(level = "trace", skip(tcx))]
pub fn unexpected_hidden_region_diagnostic<'tcx>(
tcx: TyCtxt<'tcx>,
span: Span,
hidden_ty: Ty<'tcx>,
hidden_region: ty::Region<'tcx>,
opaque_ty_key: ty::OpaqueTypeKey<'tcx>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
let mut err = tcx.sess.create_err(errors::OpaqueCapturesLifetime {
span,
opaque_ty: Ty::new_opaque(tcx, opaque_ty_key.def_id.to_def_id(), opaque_ty_key.args),
opaque_ty_span: tcx.def_span(opaque_ty_key.def_id),
});
// 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 `{hidden_ty}` captures "),
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,
Some(reg_info.def_id),
)
}
}
ty::RePlaceholder(_) => {
explain_free_region(
tcx,
&mut err,
&format!("hidden type `{}` captures ", hidden_ty),
hidden_region,
"",
);
}
ty::ReError(_) => {
err.delay_as_bug();
}
_ => {
// 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
// `tests/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 `{hidden_ty}` captures "),
hidden_region,
"",
None,
);
}
}
err
}
impl<'tcx> InferCtxt<'tcx> {
pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
let (def_id, args) = match *ty.kind() {
ty::Alias(_, ty::AliasTy { def_id, args, .. })
if matches!(self.tcx.def_kind(def_id), DefKind::OpaqueTy) =>
{
(def_id, args)
}
ty::Alias(_, ty::AliasTy { def_id, args, .. })
if self.tcx.is_impl_trait_in_trait(def_id) =>
{
(def_id, args)
}
_ => return None,
};
let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
self.tcx.explicit_item_bounds(def_id).iter_instantiated_copied(self.tcx, args).find_map(
|(predicate, _)| {
predicate
.kind()
.map_bound(|kind| match kind {
ty::ClauseKind::Projection(projection_predicate)
if projection_predicate.projection_ty.def_id == item_def_id =>
{
projection_predicate.term.ty()
}
_ => None,
})
.no_bound_vars()
.flatten()
},
)
}
}
impl<'tcx> TypeErrCtxt<'_, 'tcx> {
pub fn report_region_errors(
&self,
generic_param_scope: LocalDefId,
errors: &[RegionResolutionError<'tcx>],
) -> ErrorGuaranteed {
if let Some(guaranteed) = self.infcx.tainted_by_errors() {
return guaranteed;
}
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();
}
}
}
}
self.tcx
.sess
.delay_span_bug(self.tcx.def_span(generic_param_scope), "expected region errors")
}
// 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::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::PolyExistentialPredicate<'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 report definitions from different crates. If both definitions
// are from a local module we could have false positives, e.g.
// let _ = [{struct Foo; Foo}, {struct Foo; Foo}];
if 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);
let msg = if did1.is_local() || did2.is_local() {
format!(
"the crate `{crate_name}` is compiled multiple times, possibly with different configurations"
)
} else {
format!(
"perhaps two different versions of crate `{crate_name}` are being used?"
)
};
err.note(msg);
}
}
};
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, args) = 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 `{}`", args.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::BlockTailExpression(
_,
hir::MatchSource::TryDesugar(scrut_hir_id),
) => {
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.typeck_results.as_ref().and_then(|typeck_results| {
typeck_results.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,
);
}
_ => {}
}
}
},
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,
opt_suggest_box_span,
scrut_span,
..
}) => match source {
hir::MatchSource::TryDesugar(scrut_hir_id) => {
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.typeck_results.as_ref().and_then(|typeck_results| {
typeck_results.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 = if any_multiline_arm || !source_map.is_multiline(cause.span) {
// 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, msg);
if let Some(subdiag) = self.suggest_remove_semi_or_return_binding(
prior_arm_block_id,
prior_arm_ty,
prior_arm_span,
arm_block_id,
arm_ty,
arm_span,
) {
err.subdiagnostic(subdiag);
}
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");
}
if let Some(subdiag) = self.suggest_remove_semi_or_return_binding(
Some(then_id),
then_ty,
then_span,
Some(else_id),
else_ty,
else_span,
) {
err.subdiagnostic(subdiag);
}
// don't suggest wrapping either blocks in `if .. {} else {}`
let is_empty_arm = |id| {
let hir::Node::Block(blk) = self.tcx.hir().get(id)
else {
return false;
};
if blk.expr.is_some() || !blk.stmts.is_empty() {
return false;
}
let Some((_, hir::Node::Expr(expr))) = self.tcx.hir().parent_iter(id).nth(1)
else {
return false;
};
matches!(expr.kind, hir::ExprKind::If(..))
};
if let Some(ret_sp) = opt_suggest_box_span
&& !is_empty_arm(then_id)
&& !is_empty_arm(else_id)
{
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");
}
}
}
}
/// 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::GenericArgsRef<'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 `GenericArgsRef` to use its inherent methods,
// ideally that shouldn't be necessary.
let sub = self.tcx.mk_args(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(", ");
}
}
/// 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)(*sig1);
let sig2 = &(self.normalize_fn_sig)(*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_values().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_args_no_defaults(self.tcx, sub1);
let sub_no_defaults_2 =
self.tcx.generics_of(did2).own_args_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 && !self.tcx.sess.verbose() {
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 && !self.tcx.sess.verbose() {
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!(?separator_len, ?split_idx, ?min_len, "cmp");
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!(?common, ?uniq1, ?uniq2, "cmp");
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(args1), &ty::Tuple(args2)) if args1.len() == args2.len() => {
let mut values =
(DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("("));
let len = args1.len();
for (i, (left, right)) in args1.iter().zip(args2).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, args1), ty::FnDef(did2, args2)) => {
let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
let mut values = self.cmp_fn_sig(&sig1, &sig2);
let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_args(*did1, args1));
let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_args(*did2, args2));
let same_path = path1 == path2;
values.0.push(path1, !same_path);
values.1.push(path2, !same_path);
values
}
(ty::FnDef(did1, args1), ty::FnPtr(sig2)) => {
let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
let mut values = self.cmp_fn_sig(&sig1, sig2);
values.0.push_highlighted(format!(
" {{{}}}",
self.tcx.def_path_str_with_args(*did1, args1)
));
values
}
(ty::FnPtr(sig1), ty::FnDef(did2, args2)) => {
let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
let mut values = self.cmp_fn_sig(sig1, &sig2);
values
.1
.push_normal(format!(" {{{}}}", self.tcx.def_path_str_with_args(*did2, args2)));
values
}
(ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2),
_ => {
if t1 == t2 && !self.tcx.sess.verbose() {
// 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 `tests/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, Cow<'static, str>)>,
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: FxIndexMap<TyCategory, FxIndexSet<Span>>,
expected: FxIndexMap<TyCategory, FxIndexSet<Span>>,
found: FxIndexMap<TyCategory, FxIndexSet<Span>>,
ignore_span: Span,
tcx: TyCtxt<'tcx>,
}
impl<'tcx> OpaqueTypesVisitor<'tcx> {
fn visit_expected_found(
tcx: TyCtxt<'tcx>,
expected: impl TypeVisitable<TyCtxt<'tcx>>,
found: impl TypeVisitable<TyCtxt<'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: &FxIndexMap<TyCategory, FxIndexSet<Span>>,
) {
for (key, values) in types.iter() {
let count = values.len();
let kind = key.descr();
for &sp in values {
err.span_label(
sp,
format!(
"{}{} {}{}",
if count == 1 { "the " } else { "one of the " },
target,
kind,
pluralize!(count),
),
);
}
}
}
}
impl<'tcx> ty::visit::TypeVisitor<TyCtxt<'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:_]`
//
// Also ignore opaque `Future`s that come from async fns.
if !self.ignore_span.overlaps(span)
&& !span.is_desugaring(DesugaringKind::Async)
{
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::Sigs(infer::ExpectedFound { expected, found }) => {
OpaqueTypesVisitor::visit_expected_found(self.tcx, expected, found, span)
.report(diag);
(false, Mismatch::Fixed("signature"))
}
ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
(false, Mismatch::Fixed("trait"))
}
ValuePairs::Aliases(infer::ExpectedFound { expected, .. }) => {
(false, Mismatch::Fixed(self.tcx.def_descr(expected.def_id)))
}
ValuePairs::Regions(_) => (false, Mismatch::Fixed("lifetime")),
ValuePairs::ExistentialTraitRef(_) => {
(false, Mismatch::Fixed("existential trait ref"))
}
ValuePairs::ExistentialProjection(_) => {
(false, Mismatch::Fixed("existential projection"))
}
};
let Some(vals) = self.values_str(values) else {
// 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;
};
(Some(vals), exp_found, is_simple_error, Some(values))
}
};
let mut label_or_note = |span: Span, msg: Cow<'static, 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
{
Cow::from(format!("expected this to be `{expected}`"))
} else {
terr.to_string(self.tcx)
};
label_or_note(sp, terr);
label_or_note(span, msg);
} else {
label_or_note(span, terr.to_string(self.tcx));
label_or_note(sp, msg);
}
} else {
if let Some(values) = values
&& let Some((e, f)) = values.ty()
&& let TypeError::ArgumentSorts(..) | TypeError::Sorts(_) = terr
{
let e = self.tcx.erase_regions(e);
let f = self.tcx.erase_regions(f);
let expected = with_forced_trimmed_paths!(e.sort_string(self.tcx));
let found = with_forced_trimmed_paths!(f.sort_string(self.tcx));
if expected == found {
label_or_note(span, terr.to_string(self.tcx));
} else {
label_or_note(span, Cow::from(format!("expected {expected}, found {found}")));
}
} else {
label_or_note(span, terr.to_string(self.tcx));
}
}
if let Some((expected, found, exp_p, found_p)) = 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),
};
enum Similar<'tcx> {
Adts { expected: ty::AdtDef<'tcx>, found: ty::AdtDef<'tcx> },
PrimitiveFound { expected: ty::AdtDef<'tcx>, found: Ty<'tcx> },
PrimitiveExpected { expected: Ty<'tcx>, found: ty::AdtDef<'tcx> },
}
let similarity = |ExpectedFound { expected, found }: ExpectedFound<Ty<'tcx>>| {
if let ty::Adt(expected, _) = expected.kind() && let Some(primitive) = found.primitive_symbol() {
let path = self.tcx.def_path(expected.did()).data;
let name = path.last().unwrap().data.get_opt_name();
if name == Some(primitive) {
return Some(Similar::PrimitiveFound { expected: *expected, found });
}
} else if let Some(primitive) = expected.primitive_symbol() && let ty::Adt(found, _) = found.kind() {
let path = self.tcx.def_path(found.did()).data;
let name = path.last().unwrap().data.get_opt_name();
if name == Some(primitive) {
return Some(Similar::PrimitiveExpected { expected, found: *found });
}
} else if let ty::Adt(expected, _) = expected.kind() && let ty::Adt(found, _) = found.kind() {
if !expected.did().is_local() && expected.did().krate == found.did().krate {
// Most likely types from different versions of the same crate
// are in play, in which case this message isn't so helpful.
// A "perhaps two different versions..." error is already emitted for that.
return None;
}
let f_path = self.tcx.def_path(found.did()).data;
let e_path = self.tcx.def_path(expected.did()).data;
if let (Some(e_last), Some(f_last)) = (e_path.last(), f_path.last()) && e_last == f_last {
return Some(Similar::Adts{expected: *expected, found: *found});
}
}
None
};
match terr {
// If two types mismatch but have similar names, mention that specifically.
TypeError::Sorts(values) if let Some(s) = similarity(values) => {
let diagnose_primitive =
|prim: Ty<'tcx>,
shadow: Ty<'tcx>,
defid: DefId,
diagnostic: &mut Diagnostic| {
let name = shadow.sort_string(self.tcx);
diagnostic.note(format!(
"{prim} and {name} have similar names, but are actually distinct types"
));
diagnostic
.note(format!("{prim} is a primitive defined by the language"));
let def_span = self.tcx.def_span(defid);
let msg = if defid.is_local() {
format!("{name} is defined in the current crate")
} else {
let crate_name = self.tcx.crate_name(defid.krate);
format!("{name} is defined in crate `{crate_name}`")
};
diagnostic.span_note(def_span, msg);
};
let diagnose_adts =
|expected_adt : ty::AdtDef<'tcx>,
found_adt: ty::AdtDef<'tcx>,
diagnostic: &mut Diagnostic| {
let found_name = values.found.sort_string(self.tcx);
let expected_name = values.expected.sort_string(self.tcx);
let found_defid = found_adt.did();
let expected_defid = expected_adt.did();
diagnostic.note(format!("{found_name} and {expected_name} have similar names, but are actually distinct types"));
for (defid, name) in
[(found_defid, found_name), (expected_defid, expected_name)]
{
let def_span = self.tcx.def_span(defid);
let msg = if found_defid.is_local() && expected_defid.is_local() {
let module = self
.tcx
.parent_module_from_def_id(defid.expect_local())
.to_def_id();
let module_name = self.tcx.def_path(module).to_string_no_crate_verbose();
format!("{name} is defined in module `crate{module_name}` of the current crate")
} else if defid.is_local() {
format!("{name} is defined in the current crate")
} else {
let crate_name = self.tcx.crate_name(defid.krate);
format!("{name} is defined in crate `{crate_name}`")
};
diagnostic.span_note(def_span, msg);
}
};
match s {
Similar::Adts{expected, found} => {
diagnose_adts(expected, found, diag)
}
Similar::PrimitiveFound{expected, found: prim} => {
diagnose_primitive(prim, values.expected, expected.did(), diag)
}
Similar::PrimitiveExpected{expected: prim, found} => {
diagnose_primitive(prim, values.found, found.did(), diag)
}
}
}
TypeError::Sorts(values) => {
let extra = expected == found;
let sort_string = |ty: Ty<'tcx>, path: Option<PathBuf>| {
let mut s = match (extra, ty.kind()) {
(true, ty::Alias(ty::Opaque, ty::AliasTy { 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::Alias(ty::Projection, proj))
if self.tcx.is_impl_trait_in_trait(proj.def_id) =>
{
let sm = self.tcx.sess.source_map();
let pos = sm.lookup_char_pos(self.tcx.def_span(proj.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 let Some(path) = path {
s.push_str(&format!(
"\nthe full type name has been written to '{}'",
path.display(),
));
}
s
};
if !(values.expected.is_simple_text() && values.found.is_simple_text())
|| (exp_found.is_some_and(|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_or_numeric_infer() {
ef.expected != values.expected
} else if !ef.found.is_ty_or_numeric_infer() {
ef.found != values.found
} else {
false
}
}))
{
if let Some(ExpectedFound { found: found_ty, .. }) = exp_found {
// `Future` is a special opaque type that the compiler
// will try to hide in some case such as `async fn`, so
// to make an error more use friendly we will
// avoid to suggest a mismatch type with a
// type that the user usually are not using
// directly such as `impl Future<Output = u8>`.
if !self.tcx.ty_is_opaque_future(found_ty) {
diag.note_expected_found_extra(
&expected_label,
expected,
&found_label,
found,
&sort_string(values.expected, exp_p),
&sort_string(values.found, found_p),
);
}
}
}
}
_ => {
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.is_some_and(|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
};
// FIXME(#73154): For now, we do leak check when coercing function
// pointers in typeck, instead of only during borrowck. This can lead
// to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
if should_suggest_fixes
&& !matches!(terr, TypeError::RegionsInsufficientlyPolymorphic(..))
{
self.suggest_tuple_pattern(cause, &exp_found, diag);
self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
self.suggest_await_on_expect_found(cause, span, &exp_found, diag);
self.suggest_function_pointers(cause, span, &exp_found, diag);
}
}
self.check_and_note_conflicting_crates(diag, terr);
self.note_and_explain_type_err(diag, terr, cause, span, cause.body_id.to_def_id());
if let Some(exp_found) = exp_found
&& let exp_found = TypeError::Sorts(exp_found)
&& exp_found != terr
{
self.note_and_explain_type_err(
diag,
exp_found,
cause,
span,
cause.body_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");
self.suggest_for_all_lifetime_closure(span, self.tcx.hir().get_by_def_id(def_id), &exp_found, diag);
}
// It reads better to have the error origin as the final
// thing.
self.note_error_origin(diag, cause, exp_found, terr);
debug!(?diag);
}
pub fn type_error_additional_suggestions(
&self,
trace: &TypeTrace<'tcx>,
terr: TypeError<'tcx>,
) -> Vec<TypeErrorAdditionalDiags> {
use crate::traits::ObligationCauseCode::{BlockTailExpression, MatchExpressionArm};
let mut suggestions = Vec::new();
let span = trace.cause.span();
let values = self.resolve_vars_if_possible(trace.values);
if let Some((expected, found)) = 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), _) => {
suggestions.extend(self.suggest_wrap_to_build_a_tuple( span, found, fields))
}
// If a byte was expected and the found expression is a char literal
// containing a single ASCII character, perhaps the user meant to write `b'c'` to
// specify a byte literal
(ty::Uint(ty::UintTy::U8), ty::Char) => {
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('\''))
// forbid all Unicode escapes
&& !code.starts_with("\\u")
// forbids literal Unicode characters beyond ASCII
&& code.chars().next().is_some_and(|c| c.is_ascii())
{
suggestions.push(TypeErrorAdditionalDiags::MeantByteLiteral {
span,
code: escape_literal(code),
})
}
}
// 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
{
suggestions.push(TypeErrorAdditionalDiags::MeantCharLiteral {
span,
code: escape_literal(code),
})
}
}
// 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('\''))
{
suggestions.push(TypeErrorAdditionalDiags::MeantStrLiteral {
span,
code: escape_literal(code),
})
}
}
}
// For code `if Some(..) = expr `, the type mismatch may be expected `bool` but found `()`,
// we try to suggest to add the missing `let` for `if let Some(..) = expr`
(ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
suggestions.extend(self.suggest_let_for_letchains(&trace.cause, span));
}
(ty::Array(_, _), ty::Array(_, _)) => {
suggestions.extend(self.suggest_specify_actual_length(terr, trace, span))
}
_ => {}
}
}
let code = trace.cause.code();
if let &(MatchExpressionArm(box MatchExpressionArmCause { source, .. })
| BlockTailExpression(.., source)
) = code
&& let hir::MatchSource::TryDesugar(_) = source
&& let Some((expected_ty, found_ty, _, _)) = self.values_str(trace.values)
{
suggestions.push(TypeErrorAdditionalDiags::TryCannotConvert {
found: found_ty.content(),
expected: expected_ty.content(),
});
}
suggestions
}
fn suggest_specify_actual_length(
&self,
terr: TypeError<'_>,
trace: &TypeTrace<'_>,
span: Span,
) -> Option<TypeErrorAdditionalDiags> {
let hir = self.tcx.hir();
let TypeError::FixedArraySize(sz) = terr else {
return None;
};
let tykind = match hir.find_by_def_id(trace.cause.body_id) {
Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })) => {
let body = hir.body(*body_id);
struct LetVisitor<'v> {
span: Span,
result: Option<&'v hir::Ty<'v>>,
}
impl<'v> Visitor<'v> for LetVisitor<'v> {
fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) {
if self.result.is_some() {
return;
}
// Find a local statement where the initializer has
// the same span as the error and the type is specified.
if let hir::Stmt {
kind: hir::StmtKind::Local(hir::Local {
init: Some(hir::Expr {
span: init_span,
..
}),
ty: Some(array_ty),
..
}),
..
} = s
&& init_span == &self.span {
self.result = Some(*array_ty);
}
}
}
let mut visitor = LetVisitor { span, result: None };
visitor.visit_body(body);
visitor.result.map(|r| &r.peel_refs().kind)
}
Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _, _), .. })) => {
Some(&ty.peel_refs().kind)
}
_ => None,
};
if let Some(tykind) = tykind
&& let hir::TyKind::Array(_, length) = tykind
&& let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
&& let Some(span) = self.tcx.hir().opt_span(*hir_id)
{
Some(TypeErrorAdditionalDiags::ConsiderSpecifyingLength { span, length: sz.found })
} else {
None
}
}
pub fn report_and_explain_type_error(
&self,
trace: TypeTrace<'tcx>,
terr: TypeError<'tcx>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
let span = trace.cause.span();
let failure_code = trace.cause.as_failure_code_diag(
terr,
span,
self.type_error_additional_suggestions(&trace, terr),
);
let mut diag = self.tcx.sess.create_err(failure_code);
self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr, false, false);
diag
}
fn suggest_wrap_to_build_a_tuple(
&self,
span: Span,
found: Ty<'tcx>,
expected_fields: &List<Ty<'tcx>>,
) -> Option<TypeErrorAdditionalDiags> {
let [expected_tup_elem] = expected_fields[..] else { return None };
if !self.same_type_modulo_infer(expected_tup_elem, found) {
return None;
}
let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) else { return None };
let sugg = if code.starts_with('(') && code.ends_with(')') {
let before_close = span.hi() - BytePos::from_u32(1);
TypeErrorAdditionalDiags::TupleOnlyComma {
span: span.with_hi(before_close).shrink_to_hi(),
}
} else {
TypeErrorAdditionalDiags::TupleAlsoParentheses {
span_low: span.shrink_to_lo(),
span_high: span.shrink_to_hi(),
}
};
Some(sugg)
}
fn values_str(
&self,
values: ValuePairs<'tcx>,
) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
{
match values {
infer::Regions(exp_found) => self.expected_found_str(exp_found),
infer::Terms(exp_found) => self.expected_found_str_term(exp_found),
infer::Aliases(exp_found) => self.expected_found_str(exp_found),
infer::ExistentialTraitRef(exp_found) => self.expected_found_str(exp_found),
infer::ExistentialProjection(exp_found) => self.expected_found_str(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,
}
}
infer::Sigs(exp_found) => {
let exp_found = self.resolve_vars_if_possible(exp_found);
if exp_found.references_error() {
return None;
}
let (exp, fnd) = self.cmp_fn_sig(
&ty::Binder::dummy(exp_found.expected),
&ty::Binder::dummy(exp_found.found),
);
Some((exp, fnd, None, None))
}
}
}
fn expected_found_str_term(
&self,
exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>,
) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
{
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)) => {
let (mut exp, mut fnd) = self.cmp(expected, found);
// Use the terminal width as the basis to determine when to compress the printed
// out type, but give ourselves some leeway to avoid ending up creating a file for
// a type that is somewhat shorter than the path we'd write to.
let len = self.tcx.sess().diagnostic_width() + 40;
let exp_s = exp.content();
let fnd_s = fnd.content();
let mut exp_p = None;
let mut fnd_p = None;
if exp_s.len() > len {
let (exp_s, exp_path) = self.tcx.short_ty_string(expected);
exp = DiagnosticStyledString::highlighted(exp_s);
exp_p = exp_path;
}
if fnd_s.len() > len {
let (fnd_s, fnd_path) = self.tcx.short_ty_string(found);
fnd = DiagnosticStyledString::highlighted(fnd_s);
fnd_p = fnd_path;
}
(exp, fnd, exp_p, fnd_p)
}
_ => (
DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
DiagnosticStyledString::highlighted(exp_found.found.to_string()),
None,
None,
),
})
}
/// Returns a string of the form "expected `{}`, found `{}`".
fn expected_found_str<T: fmt::Display + TypeFoldable<TyCtxt<'tcx>>>(
&self,
exp_found: ty::error::ExpectedFound<T>,
) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
{
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()),
None,
None,
))
}
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<'tcx, 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 mut is_synthetic = false;
let mut ast_generics = None;
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);
is_synthetic = type_param.kind.is_synthetic();
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);
ast_generics = self.tcx.hir().get_generics(hir_id.owner.def_id);
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 mut add_lt_suggs: Vec<Option<_>> = vec![];
if is_synthetic {
if let Some(ast_generics) = ast_generics {
let named_lifetime_param_exist = ast_generics.params.iter().any(|p| {
matches!(
p.kind,
hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit }
)
});
if named_lifetime_param_exist && let [param, ..] = ast_generics.params
{
add_lt_suggs.push(Some((
self.tcx.def_span(param.def_id).shrink_to_lo(),
format!("{new_lt}, "),
)));
} else {
add_lt_suggs
.push(Some((ast_generics.span.shrink_to_hi(), format!("<{new_lt}>"))));
}
}
} else {
if let [param, ..] = &generics.params[..] && let Some(def_id) = param.def_id.as_local()
{
add_lt_suggs
.push(Some((self.tcx.def_span(def_id).shrink_to_lo(), format!("{new_lt}, "))));
}
}
if let Some(ast_generics) = ast_generics {
for p in ast_generics.params {
if p.is_elided_lifetime() {
if self
.tcx
.sess
.source_map()
.span_to_prev_source(p.span.shrink_to_hi())
.ok()
.is_some_and(|s| *s.as_bytes().last().unwrap() == b'&')
{
add_lt_suggs
.push(Some(
(
p.span.shrink_to_hi(),
if let Ok(snip) = self.tcx.sess.source_map().span_to_next_source(p.span)
&& snip.starts_with(' ')
{
new_lt.to_string()
} else {
format!("{new_lt} ")
}
)
));
} else {
add_lt_suggs.push(Some((p.span.shrink_to_hi(), format!("<{new_lt}>"))));
}
}
}
}
let labeled_user_string = match bound_kind {
GenericKind::Param(ref p) => format!("the parameter type `{p}`"),
GenericKind::Alias(ref p) => match p.kind(self.tcx) {
ty::AliasKind::Projection | ty::AliasKind::Inherent => {
format!("the associated type `{p}`")
}
ty::AliasKind::Weak => format!("the type alias `{p}`"),
ty::AliasKind::Opaque => format!("the opaque 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_suggs: Vec<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)];
for add_lt_sugg in add_lt_suggs.into_iter().flatten() {
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}"))];
for lt in add_lt_suggs.clone().into_iter().flatten() {
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::Type(..),
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, vec![]);
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", vec![]);
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!("{labeled_user_string} must be valid for "),
sub,
"...",
None,
);
if let Some(infer::RelateParamBound(_, t, _)) = origin {
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(..) | ty::Alias(ty::Opaque, ..) => {
new_binding_suggestion(&mut err, type_param_span);
}
_ => {
binding_suggestion(
&mut err,
type_param_span,
bound_kind,
new_lt,
add_lt_suggs,
);
}
}
}
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) = sup_origin
&& let infer::Subtype(ref sub_trace) = sub_origin
&& let Some((sup_expected, sup_found, _, _)) = self.values_str(sup_trace.values)
&& let Some((sub_expected, sub_found, _, _)) = self.values_str(sub_trace.values)
&& 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);
if sub_region.is_error() | sup_region.is_error() {
err.delay_as_bug();
} else {
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);
if sub_region.is_error() | sup_region.is_error() {
err.delay_as_bug();
} else {
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<T: relate::Relate<'tcx>>(&self, a: T, b: T) -> bool {
let (a, b) = self.resolve_vars_if_possible((a, b));
SameTypeModuloInfer(self).relate(a, b).is_ok()
}
}
struct SameTypeModuloInfer<'a, 'tcx>(&'a InferCtxt<'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::structurally_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<'tcx> InferCtxt<'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 `{var_name}` by closure")
}
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 {
Error0317,
Error0580,
Error0308,
Error0644,
}
pub trait ObligationCauseExt<'tcx> {
fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
fn as_failure_code_diag(
&self,
terr: TypeError<'tcx>,
span: Span,
subdiags: Vec<TypeErrorAdditionalDiags>,
) -> ObligationCauseFailureCode;
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() {
IfExpressionWithNoElse => Error0317,
MainFunctionType => Error0580,
CompareImplItemObligation { .. }
| MatchExpressionArm(_)
| IfExpression { .. }
| LetElse
| StartFunctionType
| IntrinsicType
| MethodReceiver => Error0308,
// 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,
TypeError::IntrinsicCast => Error0308,
_ => Error0308,
},
}
}
fn as_failure_code_diag(
&self,
terr: TypeError<'tcx>,
span: Span,
subdiags: Vec<TypeErrorAdditionalDiags>,
) -> ObligationCauseFailureCode {
use crate::traits::ObligationCauseCode::*;
match self.code() {
CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
ObligationCauseFailureCode::MethodCompat { span, subdiags }
}
CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
ObligationCauseFailureCode::TypeCompat { span, subdiags }
}
CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
ObligationCauseFailureCode::ConstCompat { span, subdiags }
}
BlockTailExpression(.., hir::MatchSource::TryDesugar(_)) => {
ObligationCauseFailureCode::TryCompat { span, subdiags }
}
MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => match source {
hir::MatchSource::TryDesugar(_) => {
ObligationCauseFailureCode::TryCompat { span, subdiags }
}
_ => ObligationCauseFailureCode::MatchCompat { span, subdiags },
},
IfExpression { .. } => ObligationCauseFailureCode::IfElseDifferent { span, subdiags },
IfExpressionWithNoElse => ObligationCauseFailureCode::NoElse { span },
LetElse => ObligationCauseFailureCode::NoDiverge { span, subdiags },
MainFunctionType => ObligationCauseFailureCode::FnMainCorrectType { span },
StartFunctionType => ObligationCauseFailureCode::FnStartCorrectType { span, subdiags },
IntrinsicType => ObligationCauseFailureCode::IntrinsicCorrectType { span, subdiags },
MethodReceiver => ObligationCauseFailureCode::MethodCorrectType { span, subdiags },
// 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() => {
ObligationCauseFailureCode::ClosureSelfref { span }
}
TypeError::IntrinsicCast => {
ObligationCauseFailureCode::CantCoerce { span, subdiags }
}
_ => ObligationCauseFailureCode::Generic { span, subdiags },
},
}
}
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 => "intrinsic_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,
OpaqueFuture,
Generator(hir::GeneratorKind),
Foreign,
}
impl TyCategory {
fn descr(&self) -> &'static str {
match self {
Self::Closure => "closure",
Self::Opaque => "opaque type",
Self::OpaqueFuture => "future",
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::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => {
let kind =
if tcx.ty_is_opaque_future(ty) { Self::OpaqueFuture } else { Self::Opaque };
Some((kind, 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,
}
}
}