rustc_trait_selection/error_reporting/infer/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 std::borrow::Cow;
use std::ops::ControlFlow;
use std::path::PathBuf;
use std::{cmp, fmt, iter};
use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
use rustc_errors::{Applicability, Diag, DiagStyledString, IntoDiagArg, StringPart, pluralize};
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
use rustc_hir::intravisit::Visitor;
use rustc_hir::lang_items::LangItem;
use rustc_hir::{self as hir};
use rustc_macros::extension;
use rustc_middle::bug;
use rustc_middle::dep_graph::DepContext;
use rustc_middle::ty::error::{ExpectedFound, TypeError, TypeErrorToStringExt};
use rustc_middle::ty::print::{PrintError, PrintTraitRefExt as _, with_forced_trimmed_paths};
use rustc_middle::ty::{
self, List, Region, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable, TypeVisitable,
TypeVisitableExt,
};
use rustc_span::{BytePos, DesugaringKind, Pos, Span, sym};
use rustc_target::spec::abi;
use tracing::{debug, instrument};
use crate::error_reporting::TypeErrCtxt;
use crate::errors::{ObligationCauseFailureCode, TypeErrorAdditionalDiags};
use crate::infer;
use crate::infer::relate::{self, RelateResult, TypeRelation};
use crate::infer::{InferCtxt, TypeTrace, ValuePairs};
use crate::traits::{
IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode,
};
mod note_and_explain;
mod suggest;
pub mod need_type_info;
pub mod nice_region_error;
pub mod region;
pub mod sub_relations;
/// 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
}
impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
// [Note-Type-error-reporting]
// An invariant is that anytime the expected or actual type is Error (the special
// error type, meaning that an error occurred when typechecking this expression),
// this is a derived error. The error cascaded from another error (that was already
// reported), so it's not useful to display it to the user.
// The following methods implement this logic.
// They check if either the actual or expected type is Error, and don't print the error
// in this case. The typechecker should only ever report type errors involving mismatched
// types using one of these methods, and should not call span_err directly for such
// errors.
pub fn type_error_struct_with_diag<M>(
&self,
sp: Span,
mk_diag: M,
actual_ty: Ty<'tcx>,
) -> Diag<'a>
where
M: FnOnce(String) -> Diag<'a>,
{
let actual_ty = self.resolve_vars_if_possible(actual_ty);
debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
let mut err = mk_diag(self.ty_to_string(actual_ty));
// Don't report an error if actual type is `Error`.
if actual_ty.references_error() {
err.downgrade_to_delayed_bug();
}
err
}
pub fn report_mismatched_types(
&self,
cause: &ObligationCause<'tcx>,
expected: Ty<'tcx>,
actual: Ty<'tcx>,
err: TypeError<'tcx>,
) -> Diag<'a> {
self.report_and_explain_type_error(TypeTrace::types(cause, true, expected, actual), err)
}
pub fn report_mismatched_consts(
&self,
cause: &ObligationCause<'tcx>,
expected: ty::Const<'tcx>,
actual: ty::Const<'tcx>,
err: TypeError<'tcx>,
) -> Diag<'a> {
self.report_and_explain_type_error(TypeTrace::consts(cause, true, expected, actual), err)
}
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_super_predicates(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_term.def_id == item_def_id =>
{
projection_predicate.term.as_type()
}
_ => None,
})
.no_bound_vars()
.flatten()
})
}
/// Adds a note if the types come from similarly named crates
fn check_and_note_conflicting_crates(&self, err: &mut Diag<'_>, terr: TypeError<'tcx>) {
use hir::def_id::CrateNum;
use rustc_hir::definitions::DisambiguatedDefPathData;
use ty::GenericArg;
use ty::print::Printer;
struct AbsolutePathPrinter<'tcx> {
tcx: TyCtxt<'tcx>,
segments: Vec<String>,
}
impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
self.tcx
}
fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
Err(fmt::Error)
}
fn print_type(&mut self, _ty: Ty<'tcx>) -> Result<(), PrintError> {
Err(fmt::Error)
}
fn print_dyn_existential(
&mut self,
_predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
) -> Result<(), PrintError> {
Err(fmt::Error)
}
fn print_const(&mut self, _ct: ty::Const<'tcx>) -> Result<(), PrintError> {
Err(fmt::Error)
}
fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError> {
self.segments = vec![self.tcx.crate_name(cnum).to_string()];
Ok(())
}
fn path_qualified(
&mut self,
_self_ty: Ty<'tcx>,
_trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<(), PrintError> {
Err(fmt::Error)
}
fn path_append_impl(
&mut self,
_print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
_disambiguated_data: &DisambiguatedDefPathData,
_self_ty: Ty<'tcx>,
_trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<(), PrintError> {
Err(fmt::Error)
}
fn path_append(
&mut self,
print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
disambiguated_data: &DisambiguatedDefPathData,
) -> Result<(), PrintError> {
print_prefix(self)?;
self.segments.push(disambiguated_data.to_string());
Ok(())
}
fn path_generic_args(
&mut self,
print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
_args: &[GenericArg<'tcx>],
) -> Result<(), PrintError> {
print_prefix(self)
}
}
let report_path_match = |err: &mut Diag<'_>, 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| {
let mut printer = AbsolutePathPrinter { tcx: self.tcx, segments: vec![] };
printer.print_def_path(def_id, &[]).map(|_| printer.segments)
};
// We compare strings because DefPath can be different
// for imported and non-imported crates
let same_path = || -> Result<_, PrintError> {
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 Diag<'_>,
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.boxed_ty() == Some(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_non_diverging_arms,
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_non_diverging_arms.len() <= 4 {
for sp in prior_non_diverging_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_non_diverging_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);
}
}
},
ObligationCauseCode::IfExpression(box IfExpressionCause {
then_id,
else_id,
then_ty,
else_ty,
outer_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);
}
}
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::WhereClause(_, span)
| ObligationCauseCode::WhereClauseInExpr(_, span, ..) =
cause.code().peel_derives()
&& !span.is_dummy()
&& 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 DiagStyledString,
other_value: &mut DiagStyledString,
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,
t1_out: &mut DiagStyledString,
t2_out: &mut DiagStyledString,
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(t1_out, 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(t1_out, 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 DiagStyledString,
other_value: &mut DiagStyledString,
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>,
) -> (DiagStyledString, DiagStyledString) {
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_items().map(|(_, kind)| kind.to_string()).into_sorted_stable_ord();
(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 =
(DiagStyledString::normal("".to_string()), DiagStyledString::normal("".to_string()));
// unsafe extern "C" for<'a> fn(&'a T) -> &'a T
// ^^^^^^
values.0.push(sig1.safety.prefix_str(), sig1.safety != sig2.safety);
values.1.push(sig2.safety.prefix_str(), sig1.safety != sig2.safety);
// 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);
let output_diff = x1 != x2;
if !output1.is_unit() || output_diff {
values.0.push_normal(" -> ");
(values.0).0.extend(x1.0);
}
if !output2.is_unit() || output_diff {
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>) -> (DiagStyledString, DiagStyledString) {
debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind());
// helper functions
let recurse = |t1, t2, values: &mut (DiagStyledString, DiagStyledString)| {
let (x1, x2) = self.cmp(t1, t2);
(values.0).0.extend(x1.0);
(values.1).0.extend(x2.0);
};
fn fmt_region<'tcx>(region: ty::Region<'tcx>) -> String {
let mut r = region.to_string();
if r == "'_" {
r.clear();
} else {
r.push(' ');
}
format!("&{r}")
}
fn push_ref<'tcx>(
region: ty::Region<'tcx>,
mutbl: hir::Mutability,
s: &mut DiagStyledString,
) {
s.push_highlighted(fmt_region(region));
s.push_highlighted(mutbl.prefix_str());
}
fn maybe_highlight<T: Eq + ToString>(
t1: T,
t2: T,
(buf1, buf2): &mut (DiagStyledString, DiagStyledString),
tcx: TyCtxt<'_>,
) {
let highlight = t1 != t2;
let (t1, t2) = if highlight || tcx.sess.opts.verbose {
(t1.to_string(), t2.to_string())
} else {
// The two types are the same, elide and don't highlight.
("_".into(), "_".into())
};
buf1.push(t1, highlight);
buf2.push(t2, highlight);
}
fn cmp_ty_refs<'tcx>(
r1: ty::Region<'tcx>,
mut1: hir::Mutability,
r2: ty::Region<'tcx>,
mut2: hir::Mutability,
ss: &mut (DiagStyledString, DiagStyledString),
) {
let (r1, r2) = (fmt_region(r1), fmt_region(r2));
if r1 != r2 {
ss.0.push_highlighted(r1);
ss.1.push_highlighted(r2);
} else {
ss.0.push_normal(r1);
ss.1.push_normal(r2);
}
if mut1 != mut2 {
ss.0.push_highlighted(mut1.prefix_str());
ss.1.push_highlighted(mut2.prefix_str());
} else {
ss.0.push_normal(mut1.prefix_str());
ss.1.push_normal(mut2.prefix_str());
}
}
// 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 generics1 = self.tcx.generics_of(did1);
let generics2 = self.tcx.generics_of(did2);
let non_default_after_default = generics1
.check_concrete_type_after_default(self.tcx, sub1)
|| generics2.check_concrete_type_after_default(self.tcx, sub2);
let sub_no_defaults_1 = if non_default_after_default {
generics1.own_args(sub1)
} else {
generics1.own_args_no_defaults(self.tcx, sub1)
};
let sub_no_defaults_2 = if non_default_after_default {
generics2.own_args(sub2)
} else {
generics2.own_args_no_defaults(self.tcx, sub2)
};
let mut values = (DiagStyledString::new(), DiagStyledString::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_bound() || self.tcx.sess.opts.verbose {
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.opts.verbose {
values.0.push_normal("_");
values.1.push_normal("_");
} else {
recurse(ta1, ta2, &mut values);
}
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;
maybe_highlight(ca1, ca2, &mut values, self.tcx);
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
(
DiagStyledString::highlighted(t1_str),
DiagStyledString::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`, compare the references, then recurse into pointee type
(&ty::Ref(r1, ref_ty1, mutbl1), &ty::Ref(r2, ref_ty2, mutbl2)) => {
let mut values = (DiagStyledString::new(), DiagStyledString::new());
cmp_ty_refs(r1, mutbl1, r2, mutbl2, &mut values);
recurse(ref_ty1, ref_ty2, &mut values);
values
}
// When finding T != &T, highlight the borrow
(&ty::Ref(r1, ref_ty1, mutbl1), _) => {
let mut values = (DiagStyledString::new(), DiagStyledString::new());
push_ref(r1, mutbl1, &mut values.0);
recurse(ref_ty1, t2, &mut values);
values
}
(_, &ty::Ref(r2, ref_ty2, mutbl2)) => {
let mut values = (DiagStyledString::new(), DiagStyledString::new());
push_ref(r2, mutbl2, &mut values.1);
recurse(t1, ref_ty2, &mut values);
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 = (DiagStyledString::normal("("), DiagStyledString::normal("("));
let len = args1.len();
for (i, (left, right)) in args1.iter().zip(args2).enumerate() {
recurse(left, right, &mut values);
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(sig_tys2, hdr2)) => {
let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
let mut values = self.cmp_fn_sig(&sig1, &sig_tys2.with(*hdr2));
values.0.push_highlighted(format!(
" {{{}}}",
self.tcx.def_path_str_with_args(*did1, args1)
));
values
}
(ty::FnPtr(sig_tys1, hdr1), ty::FnDef(did2, args2)) => {
let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
let mut values = self.cmp_fn_sig(&sig_tys1.with(*hdr1), &sig2);
values
.1
.push_normal(format!(" {{{}}}", self.tcx.def_path_str_with_args(*did2, args2)));
values
}
(ty::FnPtr(sig_tys1, hdr1), ty::FnPtr(sig_tys2, hdr2)) => {
self.cmp_fn_sig(&sig_tys1.with(*hdr1), &sig_tys2.with(*hdr2))
}
_ => {
let mut strs = (DiagStyledString::new(), DiagStyledString::new());
maybe_highlight(t1, t2, &mut strs, self.tcx);
strs
}
}
}
/// 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 Diag<'_>,
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 Diag<'_>) {
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 Diag<'_>,
target: &str,
types: &FxIndexMap<TyCategory, FxIndexSet<Span>>,
) {
for (kind, values) in types.iter() {
let count = values.len();
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>) {
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(ExpectedFound { expected, found }) => {
match (expected.unpack(), found.unpack()) {
(ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
let is_simple_err = expected.is_simple_text(self.tcx)
&& found.is_simple_text(self.tcx);
OpaqueTypesVisitor::visit_expected_found(
self.tcx, expected, found, span,
)
.report(diag);
(
is_simple_err,
Mismatch::Variable(ExpectedFound { expected, found }),
)
}
(ty::TermKind::Const(_), ty::TermKind::Const(_)) => {
(false, Mismatch::Fixed("constant"))
}
_ => (false, Mismatch::Fixed("type")),
}
}
ValuePairs::PolySigs(ExpectedFound { expected, found }) => {
OpaqueTypesVisitor::visit_expected_found(self.tcx, expected, found, span)
.report(diag);
(false, Mismatch::Fixed("signature"))
}
ValuePairs::TraitRefs(_) => (false, Mismatch::Fixed("trait")),
ValuePairs::Aliases(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(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, path)) = 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, diag: &mut Diag<'_>| {
let name = shadow.sort_string(self.tcx);
diag.note(format!(
"{prim} and {name} have similar names, but are actually distinct types"
));
diag.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}`")
};
diag.span_note(def_span, msg);
};
let diagnose_adts =
|expected_adt: ty::AdtDef<'tcx>,
found_adt: ty::AdtDef<'tcx>,
diag: &mut Diag<'_>| {
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();
diag.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}`")
};
diag.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>| 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 !(values.expected.is_simple_text(self.tcx)
&& values.found.is_simple_text(self.tcx))
|| (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),
&sort_string(values.found),
);
if let Some(path) = path {
diag.note(format!(
"the full type name has been written to '{}'",
path.display(),
));
diag.note("consider using `--verbose` to print the full type name to the console");
}
}
}
}
}
_ => {
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);
if let Some(ty::Closure(_, args)) =
exp_found.map(|expected_type_found| expected_type_found.found.kind())
{
diag.highlighted_note(vec![
StringPart::normal("closure has signature: `"),
StringPart::highlighted(
self.tcx
.signature_unclosure(
args.as_closure().sig(),
rustc_hir::Safety::Safe,
)
.to_string(),
),
StringPart::normal("`"),
]);
}
}
}
}
}
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.suggest_turning_stmt_into_expr(cause, &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::TraitRefs(exp_found)) = values
&& let ty::Closure(def_id, _) = exp_found.expected.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_node_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> {
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)
&& code.starts_with("'")
&& code.ends_with("'")
{
suggestions.push(TypeErrorAdditionalDiags::MeantStrLiteral {
start: span.with_hi(span.lo() + BytePos(1)),
end: span.with_lo(span.hi() - BytePos(1)),
});
}
}
// 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 &(ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
source,
..
})
| ObligationCauseCode::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 self.tcx.hir_node_by_def_id(trace.cause.body_id) {
hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. }) => {
let body = hir.body(*body_id);
struct LetVisitor {
span: Span,
}
impl<'v> Visitor<'v> for LetVisitor {
type Result = ControlFlow<&'v hir::TyKind<'v>>;
fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) -> Self::Result {
// 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::Let(hir::LetStmt {
init: Some(hir::Expr { span: init_span, .. }),
ty: Some(array_ty),
..
}),
..
} = s
&& init_span == &self.span
{
ControlFlow::Break(&array_ty.peel_refs().kind)
} else {
ControlFlow::Continue(())
}
}
}
LetVisitor { span }.visit_body(body).break_value()
}
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(ct) = length
{
let span = ct.span();
Some(TypeErrorAdditionalDiags::ConsiderSpecifyingLength { span, length: sz.found })
} else {
None
}
}
pub fn report_and_explain_type_error(
&self,
trace: TypeTrace<'tcx>,
terr: TypeError<'tcx>,
) -> Diag<'a> {
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.dcx().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<(DiagStyledString, DiagStyledString, Option<PathBuf>)> {
match values {
ValuePairs::Regions(exp_found) => self.expected_found_str(exp_found),
ValuePairs::Terms(exp_found) => self.expected_found_str_term(exp_found),
ValuePairs::Aliases(exp_found) => self.expected_found_str(exp_found),
ValuePairs::ExistentialTraitRef(exp_found) => self.expected_found_str(exp_found),
ValuePairs::ExistentialProjection(exp_found) => self.expected_found_str(exp_found),
ValuePairs::TraitRefs(exp_found) => {
let pretty_exp_found = ty::error::ExpectedFound {
expected: exp_found.expected.print_trait_sugared(),
found: exp_found.found.print_trait_sugared(),
};
match self.expected_found_str(pretty_exp_found) {
Some((expected, found, _)) if expected == found => {
self.expected_found_str(exp_found)
}
ret => ret,
}
}
ValuePairs::PolySigs(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(&exp_found.expected, &exp_found.found);
Some((exp, fnd, None))
}
}
}
fn expected_found_str_term(
&self,
exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>,
) -> Option<(DiagStyledString, DiagStyledString, 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 path = None;
if exp_s.len() > len {
let exp_s = self.tcx.short_ty_string(expected, &mut path);
exp = DiagStyledString::highlighted(exp_s);
}
if fnd_s.len() > len {
let fnd_s = self.tcx.short_ty_string(found, &mut path);
fnd = DiagStyledString::highlighted(fnd_s);
}
(exp, fnd, path)
}
_ => (
DiagStyledString::highlighted(exp_found.expected.to_string()),
DiagStyledString::highlighted(exp_found.found.to_string()),
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<(DiagStyledString, DiagStyledString, Option<PathBuf>)> {
let exp_found = self.resolve_vars_if_possible(exp_found);
if exp_found.references_error() {
return None;
}
Some((
DiagStyledString::highlighted(exp_found.expected.to_string()),
DiagStyledString::highlighted(exp_found.found.to_string()),
None,
))
}
/// 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<TyCtxt<'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<TyCtxt<'tcx>> for SameTypeModuloInfer<'_, 'tcx> {
fn cx(&self) -> TyCtxt<'tcx> {
self.0.tcx
}
fn relate_with_variance<T: relate::Relate<TyCtxt<'tcx>>>(
&mut self,
_variance: ty::Variance,
_info: ty::VarianceDiagInfo<TyCtxt<'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())
|| (b.is_var() && a.is_free())
|| (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<TyCtxt<'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)
}
}
pub enum FailureCode {
Error0317,
Error0580,
Error0308,
Error0644,
}
#[extension(pub trait ObligationCauseExt<'tcx>)]
impl<'tcx> ObligationCause<'tcx> {
fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
match self.code() {
ObligationCauseCode::IfExpressionWithNoElse => FailureCode::Error0317,
ObligationCauseCode::MainFunctionType => FailureCode::Error0580,
ObligationCauseCode::CompareImplItem { .. }
| ObligationCauseCode::MatchExpressionArm(_)
| ObligationCauseCode::IfExpression { .. }
| ObligationCauseCode::LetElse
| ObligationCauseCode::StartFunctionType
| ObligationCauseCode::LangFunctionType(_)
| ObligationCauseCode::IntrinsicType
| ObligationCauseCode::MethodReceiver => FailureCode::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_coroutine() || ty.is_coroutine_closure() =>
{
FailureCode::Error0644
}
TypeError::IntrinsicCast => FailureCode::Error0308,
_ => FailureCode::Error0308,
},
}
}
fn as_failure_code_diag(
&self,
terr: TypeError<'tcx>,
span: Span,
subdiags: Vec<TypeErrorAdditionalDiags>,
) -> ObligationCauseFailureCode {
match self.code() {
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => {
ObligationCauseFailureCode::MethodCompat { span, subdiags }
}
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
ObligationCauseFailureCode::TypeCompat { span, subdiags }
}
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
ObligationCauseFailureCode::ConstCompat { span, subdiags }
}
ObligationCauseCode::BlockTailExpression(.., hir::MatchSource::TryDesugar(_)) => {
ObligationCauseFailureCode::TryCompat { span, subdiags }
}
ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
source, ..
}) => match source {
hir::MatchSource::TryDesugar(_) => {
ObligationCauseFailureCode::TryCompat { span, subdiags }
}
_ => ObligationCauseFailureCode::MatchCompat { span, subdiags },
},
ObligationCauseCode::IfExpression { .. } => {
ObligationCauseFailureCode::IfElseDifferent { span, subdiags }
}
ObligationCauseCode::IfExpressionWithNoElse => {
ObligationCauseFailureCode::NoElse { span }
}
ObligationCauseCode::LetElse => {
ObligationCauseFailureCode::NoDiverge { span, subdiags }
}
ObligationCauseCode::MainFunctionType => {
ObligationCauseFailureCode::FnMainCorrectType { span }
}
ObligationCauseCode::StartFunctionType => {
ObligationCauseFailureCode::FnStartCorrectType { span, subdiags }
}
&ObligationCauseCode::LangFunctionType(lang_item_name) => {
ObligationCauseFailureCode::FnLangCorrectType { span, subdiags, lang_item_name }
}
ObligationCauseCode::IntrinsicType => {
ObligationCauseFailureCode::IntrinsicCorrectType { span, subdiags }
}
ObligationCauseCode::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_coroutine() || ty.is_coroutine_closure() =>
{
ObligationCauseFailureCode::ClosureSelfref { span }
}
TypeError::IntrinsicCast => {
ObligationCauseFailureCode::CantCoerce { span, subdiags }
}
_ => ObligationCauseFailureCode::Generic { span, subdiags },
},
}
}
fn as_requirement_str(&self) -> &'static str {
match self.code() {
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => {
"method type is compatible with trait"
}
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
"associated type is compatible with trait"
}
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
"const is compatible with trait"
}
ObligationCauseCode::MainFunctionType => "`main` function has the correct type",
ObligationCauseCode::StartFunctionType => "`#[start]` function has the correct type",
ObligationCauseCode::LangFunctionType(_) => "lang item function has the correct type",
ObligationCauseCode::IntrinsicType => "intrinsic has the correct type",
ObligationCauseCode::MethodReceiver => "method receiver has the correct type",
_ => "types are compatible",
}
}
}
/// Newtype to allow implementing IntoDiagArg
pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
impl IntoDiagArg for ObligationCauseAsDiagArg<'_> {
fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
let kind = match self.0.code() {
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => "method_compat",
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => "type_compat",
ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
"const_compat"
}
ObligationCauseCode::MainFunctionType => "fn_main_correct_type",
ObligationCauseCode::StartFunctionType => "fn_start_correct_type",
ObligationCauseCode::LangFunctionType(_) => "fn_lang_correct_type",
ObligationCauseCode::IntrinsicType => "intrinsic_correct_type",
ObligationCauseCode::MethodReceiver => "method_correct_type",
_ => "other",
}
.into();
rustc_errors::DiagArgValue::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,
Coroutine(hir::CoroutineKind),
Foreign,
}
impl fmt::Display for TyCategory {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::Closure => "closure".fmt(f),
Self::Opaque => "opaque type".fmt(f),
Self::OpaqueFuture => "future".fmt(f),
Self::Coroutine(gk) => gk.fmt(f),
Self::Foreign => "foreign type".fmt(f),
}
}
}
impl TyCategory {
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::Coroutine(def_id, ..) => {
Some((Self::Coroutine(tcx.coroutine_kind(def_id).unwrap()), def_id))
}
ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
_ => None,
}
}
}