8fe936099a
fix a ui test use `into` fix clippy ui test fix a run-make-fulldeps test implement `IntoQueryParam<DefId>` for `OwnerId` use `OwnerId` for more queries change the type of `ParentOwnerIterator::Item` to `(OwnerId, OwnerNode)`
992 lines
41 KiB
Rust
992 lines
41 KiB
Rust
use crate::traits::{ObligationCause, ObligationCauseCode};
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use crate::ty::diagnostics::suggest_constraining_type_param;
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use crate::ty::print::{FmtPrinter, Printer};
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use crate::ty::{self, BoundRegionKind, Region, Ty, TyCtxt};
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use hir::def::DefKind;
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use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect};
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use rustc_errors::{pluralize, Diagnostic, MultiSpan};
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use rustc_hir as hir;
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use rustc_hir::def_id::DefId;
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use rustc_span::symbol::{sym, Symbol};
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use rustc_span::{BytePos, Span};
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use rustc_target::spec::abi;
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use std::borrow::Cow;
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use std::fmt;
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#[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable, Lift)]
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pub struct ExpectedFound<T> {
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pub expected: T,
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pub found: T,
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}
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impl<T> ExpectedFound<T> {
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pub fn new(a_is_expected: bool, a: T, b: T) -> Self {
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if a_is_expected {
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ExpectedFound { expected: a, found: b }
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} else {
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ExpectedFound { expected: b, found: a }
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}
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}
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}
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// Data structures used in type unification
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#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift)]
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#[rustc_pass_by_value]
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pub enum TypeError<'tcx> {
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Mismatch,
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ConstnessMismatch(ExpectedFound<ty::BoundConstness>),
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PolarityMismatch(ExpectedFound<ty::ImplPolarity>),
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UnsafetyMismatch(ExpectedFound<hir::Unsafety>),
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AbiMismatch(ExpectedFound<abi::Abi>),
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Mutability,
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ArgumentMutability(usize),
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TupleSize(ExpectedFound<usize>),
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FixedArraySize(ExpectedFound<u64>),
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ArgCount,
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FieldMisMatch(Symbol, Symbol),
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RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>),
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RegionsInsufficientlyPolymorphic(BoundRegionKind, Region<'tcx>),
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RegionsOverlyPolymorphic(BoundRegionKind, Region<'tcx>),
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RegionsPlaceholderMismatch,
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Sorts(ExpectedFound<Ty<'tcx>>),
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ArgumentSorts(ExpectedFound<Ty<'tcx>>, usize),
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IntMismatch(ExpectedFound<ty::IntVarValue>),
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FloatMismatch(ExpectedFound<ty::FloatTy>),
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Traits(ExpectedFound<DefId>),
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VariadicMismatch(ExpectedFound<bool>),
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/// Instantiating a type variable with the given type would have
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/// created a cycle (because it appears somewhere within that
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/// type).
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CyclicTy(Ty<'tcx>),
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CyclicConst(ty::Const<'tcx>),
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ProjectionMismatched(ExpectedFound<DefId>),
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ExistentialMismatch(
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ExpectedFound<&'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>>,
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),
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ObjectUnsafeCoercion(DefId),
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ConstMismatch(ExpectedFound<ty::Const<'tcx>>),
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IntrinsicCast,
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/// Safe `#[target_feature]` functions are not assignable to safe function pointers.
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TargetFeatureCast(DefId),
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}
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impl TypeError<'_> {
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pub fn involves_regions(self) -> bool {
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match self {
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TypeError::RegionsDoesNotOutlive(_, _)
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| TypeError::RegionsInsufficientlyPolymorphic(_, _)
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| TypeError::RegionsOverlyPolymorphic(_, _)
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| TypeError::RegionsPlaceholderMismatch => true,
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_ => false,
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}
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}
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}
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/// Explains the source of a type err in a short, human readable way. This is meant to be placed
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/// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()`
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/// afterwards to present additional details, particularly when it comes to lifetime-related
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/// errors.
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impl<'tcx> fmt::Display for TypeError<'tcx> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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use self::TypeError::*;
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fn report_maybe_different(
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f: &mut fmt::Formatter<'_>,
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expected: &str,
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found: &str,
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) -> fmt::Result {
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// A naive approach to making sure that we're not reporting silly errors such as:
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// (expected closure, found closure).
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if expected == found {
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write!(f, "expected {}, found a different {}", expected, found)
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} else {
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write!(f, "expected {}, found {}", expected, found)
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}
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}
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let br_string = |br: ty::BoundRegionKind| match br {
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ty::BrNamed(_, name) => format!(" {}", name),
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_ => String::new(),
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};
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match *self {
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CyclicTy(_) => write!(f, "cyclic type of infinite size"),
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CyclicConst(_) => write!(f, "encountered a self-referencing constant"),
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Mismatch => write!(f, "types differ"),
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ConstnessMismatch(values) => {
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write!(f, "expected {} bound, found {} bound", values.expected, values.found)
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}
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PolarityMismatch(values) => {
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write!(f, "expected {} polarity, found {} polarity", values.expected, values.found)
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}
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UnsafetyMismatch(values) => {
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write!(f, "expected {} fn, found {} fn", values.expected, values.found)
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}
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AbiMismatch(values) => {
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write!(f, "expected {} fn, found {} fn", values.expected, values.found)
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}
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ArgumentMutability(_) | Mutability => write!(f, "types differ in mutability"),
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TupleSize(values) => write!(
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f,
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"expected a tuple with {} element{}, found one with {} element{}",
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values.expected,
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pluralize!(values.expected),
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values.found,
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pluralize!(values.found)
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),
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FixedArraySize(values) => write!(
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f,
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"expected an array with a fixed size of {} element{}, found one with {} element{}",
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values.expected,
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pluralize!(values.expected),
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values.found,
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pluralize!(values.found)
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),
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ArgCount => write!(f, "incorrect number of function parameters"),
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FieldMisMatch(adt, field) => write!(f, "field type mismatch: {}.{}", adt, field),
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RegionsDoesNotOutlive(..) => write!(f, "lifetime mismatch"),
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// Actually naming the region here is a bit confusing because context is lacking
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RegionsInsufficientlyPolymorphic(..) => {
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write!(f, "one type is more general than the other")
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}
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RegionsOverlyPolymorphic(br, _) => write!(
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f,
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"expected concrete lifetime, found bound lifetime parameter{}",
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br_string(br)
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),
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RegionsPlaceholderMismatch => write!(f, "one type is more general than the other"),
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ArgumentSorts(values, _) | Sorts(values) => ty::tls::with(|tcx| {
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report_maybe_different(
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f,
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&values.expected.sort_string(tcx),
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&values.found.sort_string(tcx),
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)
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}),
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Traits(values) => ty::tls::with(|tcx| {
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report_maybe_different(
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f,
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&format!("trait `{}`", tcx.def_path_str(values.expected)),
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&format!("trait `{}`", tcx.def_path_str(values.found)),
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)
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}),
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IntMismatch(ref values) => {
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let expected = match values.expected {
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ty::IntVarValue::IntType(ty) => ty.name_str(),
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ty::IntVarValue::UintType(ty) => ty.name_str(),
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};
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let found = match values.found {
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ty::IntVarValue::IntType(ty) => ty.name_str(),
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ty::IntVarValue::UintType(ty) => ty.name_str(),
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};
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write!(f, "expected `{}`, found `{}`", expected, found)
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}
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FloatMismatch(ref values) => {
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write!(
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f,
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"expected `{}`, found `{}`",
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values.expected.name_str(),
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values.found.name_str()
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)
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}
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VariadicMismatch(ref values) => write!(
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f,
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"expected {} fn, found {} function",
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if values.expected { "variadic" } else { "non-variadic" },
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if values.found { "variadic" } else { "non-variadic" }
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),
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ProjectionMismatched(ref values) => ty::tls::with(|tcx| {
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write!(
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f,
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"expected {}, found {}",
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tcx.def_path_str(values.expected),
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tcx.def_path_str(values.found)
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)
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}),
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ExistentialMismatch(ref values) => report_maybe_different(
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f,
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&format!("trait `{}`", values.expected),
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&format!("trait `{}`", values.found),
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),
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ConstMismatch(ref values) => {
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write!(f, "expected `{}`, found `{}`", values.expected, values.found)
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}
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IntrinsicCast => write!(f, "cannot coerce intrinsics to function pointers"),
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TargetFeatureCast(_) => write!(
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f,
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"cannot coerce functions with `#[target_feature]` to safe function pointers"
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),
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ObjectUnsafeCoercion(_) => write!(f, "coercion to object-unsafe trait object"),
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}
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}
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}
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impl<'tcx> TypeError<'tcx> {
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pub fn must_include_note(self) -> bool {
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use self::TypeError::*;
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match self {
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CyclicTy(_) | CyclicConst(_) | UnsafetyMismatch(_) | ConstnessMismatch(_)
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| PolarityMismatch(_) | Mismatch | AbiMismatch(_) | FixedArraySize(_)
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| ArgumentSorts(..) | Sorts(_) | IntMismatch(_) | FloatMismatch(_)
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| VariadicMismatch(_) | TargetFeatureCast(_) => false,
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Mutability
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| ArgumentMutability(_)
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| TupleSize(_)
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| ArgCount
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| FieldMisMatch(..)
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| RegionsDoesNotOutlive(..)
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| RegionsInsufficientlyPolymorphic(..)
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| RegionsOverlyPolymorphic(..)
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| RegionsPlaceholderMismatch
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| Traits(_)
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| ProjectionMismatched(_)
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| ExistentialMismatch(_)
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| ConstMismatch(_)
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| IntrinsicCast
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| ObjectUnsafeCoercion(_) => true,
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}
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}
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}
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impl<'tcx> Ty<'tcx> {
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pub fn sort_string(self, tcx: TyCtxt<'_>) -> Cow<'static, str> {
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match *self.kind() {
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ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => {
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format!("`{}`", self).into()
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}
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ty::Tuple(ref tys) if tys.is_empty() => format!("`{}`", self).into(),
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ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.def_path_str(def.did())).into(),
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ty::Foreign(def_id) => format!("extern type `{}`", tcx.def_path_str(def_id)).into(),
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ty::Array(t, n) => {
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if t.is_simple_ty() {
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return format!("array `{}`", self).into();
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}
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let n = tcx.lift(n).unwrap();
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if let ty::ConstKind::Value(v) = n.kind() {
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if let Some(n) = v.try_to_machine_usize(tcx) {
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return format!("array of {} element{}", n, pluralize!(n)).into();
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}
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}
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"array".into()
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}
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ty::Slice(ty) if ty.is_simple_ty() => format!("slice `{}`", self).into(),
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ty::Slice(_) => "slice".into(),
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ty::RawPtr(tymut) => {
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let tymut_string = match tymut.mutbl {
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hir::Mutability::Mut => tymut.to_string(),
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hir::Mutability::Not => format!("const {}", tymut.ty),
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};
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if tymut_string != "_" && (tymut.ty.is_simple_text() || tymut_string.len() < "const raw pointer".len()) {
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format!("`*{}`", tymut_string).into()
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} else {
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// Unknown type name, it's long or has type arguments
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"raw pointer".into()
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}
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},
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ty::Ref(_, ty, mutbl) => {
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let tymut = ty::TypeAndMut { ty, mutbl };
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let tymut_string = tymut.to_string();
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if tymut_string != "_"
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&& (ty.is_simple_text() || tymut_string.len() < "mutable reference".len())
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{
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format!("`&{}`", tymut_string).into()
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} else {
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// Unknown type name, it's long or has type arguments
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match mutbl {
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hir::Mutability::Mut => "mutable reference",
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_ => "reference",
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}
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.into()
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}
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}
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ty::FnDef(..) => "fn item".into(),
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ty::FnPtr(_) => "fn pointer".into(),
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ty::Dynamic(ref inner, ..) if let Some(principal) = inner.principal() => {
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format!("trait object `dyn {}`", tcx.def_path_str(principal.def_id())).into()
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}
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ty::Dynamic(..) => "trait object".into(),
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ty::Closure(..) => "closure".into(),
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ty::Generator(def_id, ..) => tcx.generator_kind(def_id).unwrap().descr().into(),
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ty::GeneratorWitness(..) => "generator witness".into(),
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ty::Tuple(..) => "tuple".into(),
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ty::Infer(ty::TyVar(_)) => "inferred type".into(),
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ty::Infer(ty::IntVar(_)) => "integer".into(),
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ty::Infer(ty::FloatVar(_)) => "floating-point number".into(),
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ty::Placeholder(..) => "placeholder type".into(),
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ty::Bound(..) => "bound type".into(),
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ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
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ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
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ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
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ty::Projection(_) => "associated type".into(),
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ty::Param(p) => format!("type parameter `{}`", p).into(),
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ty::Opaque(..) => "opaque type".into(),
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ty::Error(_) => "type error".into(),
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}
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}
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pub fn prefix_string(self, tcx: TyCtxt<'_>) -> Cow<'static, str> {
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match *self.kind() {
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ty::Infer(_)
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| ty::Error(_)
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| ty::Bool
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| ty::Char
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| ty::Int(_)
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| ty::Uint(_)
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| ty::Float(_)
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| ty::Str
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| ty::Never => "type".into(),
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ty::Tuple(ref tys) if tys.is_empty() => "unit type".into(),
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ty::Adt(def, _) => def.descr().into(),
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ty::Foreign(_) => "extern type".into(),
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ty::Array(..) => "array".into(),
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ty::Slice(_) => "slice".into(),
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ty::RawPtr(_) => "raw pointer".into(),
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ty::Ref(.., mutbl) => match mutbl {
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hir::Mutability::Mut => "mutable reference",
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_ => "reference",
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}
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.into(),
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ty::FnDef(..) => "fn item".into(),
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ty::FnPtr(_) => "fn pointer".into(),
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ty::Dynamic(..) => "trait object".into(),
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ty::Closure(..) => "closure".into(),
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ty::Generator(def_id, ..) => tcx.generator_kind(def_id).unwrap().descr().into(),
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ty::GeneratorWitness(..) => "generator witness".into(),
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ty::Tuple(..) => "tuple".into(),
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ty::Placeholder(..) => "higher-ranked type".into(),
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ty::Bound(..) => "bound type variable".into(),
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ty::Projection(_) => "associated type".into(),
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ty::Param(_) => "type parameter".into(),
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ty::Opaque(..) => "opaque type".into(),
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}
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}
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}
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impl<'tcx> TyCtxt<'tcx> {
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pub fn note_and_explain_type_err(
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self,
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diag: &mut Diagnostic,
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err: TypeError<'tcx>,
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cause: &ObligationCause<'tcx>,
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sp: Span,
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body_owner_def_id: DefId,
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) {
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use self::TypeError::*;
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debug!("note_and_explain_type_err err={:?} cause={:?}", err, cause);
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match err {
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ArgumentSorts(values, _) | Sorts(values) => {
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match (values.expected.kind(), values.found.kind()) {
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(ty::Closure(..), ty::Closure(..)) => {
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diag.note("no two closures, even if identical, have the same type");
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diag.help("consider boxing your closure and/or using it as a trait object");
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}
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(ty::Opaque(..), ty::Opaque(..)) => {
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// Issue #63167
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diag.note("distinct uses of `impl Trait` result in different opaque types");
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}
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(ty::Float(_), ty::Infer(ty::IntVar(_)))
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|
if let Ok(
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|
// Issue #53280
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|
snippet,
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|
) = self.sess.source_map().span_to_snippet(sp) =>
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{
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|
if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') {
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diag.span_suggestion(
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sp,
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"use a float literal",
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format!("{}.0", snippet),
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MachineApplicable,
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);
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}
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|
}
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|
(ty::Param(expected), ty::Param(found)) => {
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|
let generics = self.generics_of(body_owner_def_id);
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|
let e_span = self.def_span(generics.type_param(expected, self).def_id);
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|
if !sp.contains(e_span) {
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diag.span_label(e_span, "expected type parameter");
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}
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let f_span = self.def_span(generics.type_param(found, self).def_id);
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|
if !sp.contains(f_span) {
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diag.span_label(f_span, "found type parameter");
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}
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diag.note(
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"a type parameter was expected, but a different one was found; \
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you might be missing a type parameter or trait bound",
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);
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diag.note(
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|
"for more information, visit \
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https://doc.rust-lang.org/book/ch10-02-traits.html\
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#traits-as-parameters",
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|
);
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|
}
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|
(ty::Projection(_), ty::Projection(_)) => {
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|
diag.note("an associated type was expected, but a different one was found");
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}
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|
(ty::Param(p), ty::Projection(proj)) | (ty::Projection(proj), ty::Param(p)) => {
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|
let generics = self.generics_of(body_owner_def_id);
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|
let p_span = self.def_span(generics.type_param(p, self).def_id);
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|
if !sp.contains(p_span) {
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diag.span_label(p_span, "this type parameter");
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}
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|
let hir = self.hir();
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|
let mut note = true;
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|
if let Some(generics) = generics
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|
.type_param(p, self)
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|
.def_id
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|
.as_local()
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|
.map(|id| hir.local_def_id_to_hir_id(id))
|
|
.and_then(|id| self.hir().find(self.hir().get_parent_node(id)))
|
|
.as_ref()
|
|
.and_then(|node| node.generics())
|
|
{
|
|
// Synthesize the associated type restriction `Add<Output = Expected>`.
|
|
// FIXME: extract this logic for use in other diagnostics.
|
|
let (trait_ref, assoc_substs) = proj.trait_ref_and_own_substs(self);
|
|
let path =
|
|
self.def_path_str_with_substs(trait_ref.def_id, trait_ref.substs);
|
|
let item_name = self.item_name(proj.item_def_id);
|
|
let item_args = self.format_generic_args(assoc_substs);
|
|
|
|
let path = if path.ends_with('>') {
|
|
format!(
|
|
"{}, {}{} = {}>",
|
|
&path[..path.len() - 1],
|
|
item_name,
|
|
item_args,
|
|
p
|
|
)
|
|
} else {
|
|
format!("{}<{}{} = {}>", path, item_name, item_args, p)
|
|
};
|
|
note = !suggest_constraining_type_param(
|
|
self,
|
|
generics,
|
|
diag,
|
|
&format!("{}", proj.self_ty()),
|
|
&path,
|
|
None,
|
|
);
|
|
}
|
|
if note {
|
|
diag.note("you might be missing a type parameter or trait bound");
|
|
}
|
|
}
|
|
(ty::Param(p), ty::Dynamic(..) | ty::Opaque(..))
|
|
| (ty::Dynamic(..) | ty::Opaque(..), ty::Param(p)) => {
|
|
let generics = self.generics_of(body_owner_def_id);
|
|
let p_span = self.def_span(generics.type_param(p, self).def_id);
|
|
if !sp.contains(p_span) {
|
|
diag.span_label(p_span, "this type parameter");
|
|
}
|
|
diag.help("type parameters must be constrained to match other types");
|
|
if self.sess.teach(&diag.get_code().unwrap()) {
|
|
diag.help(
|
|
"given a type parameter `T` and a method `foo`:
|
|
```
|
|
trait Trait<T> { fn foo(&self) -> T; }
|
|
```
|
|
the only ways to implement method `foo` are:
|
|
- constrain `T` with an explicit type:
|
|
```
|
|
impl Trait<String> for X {
|
|
fn foo(&self) -> String { String::new() }
|
|
}
|
|
```
|
|
- add a trait bound to `T` and call a method on that trait that returns `Self`:
|
|
```
|
|
impl<T: std::default::Default> Trait<T> for X {
|
|
fn foo(&self) -> T { <T as std::default::Default>::default() }
|
|
}
|
|
```
|
|
- change `foo` to return an argument of type `T`:
|
|
```
|
|
impl<T> Trait<T> for X {
|
|
fn foo(&self, x: T) -> T { x }
|
|
}
|
|
```",
|
|
);
|
|
}
|
|
diag.note(
|
|
"for more information, visit \
|
|
https://doc.rust-lang.org/book/ch10-02-traits.html\
|
|
#traits-as-parameters",
|
|
);
|
|
}
|
|
(ty::Param(p), ty::Closure(..) | ty::Generator(..)) => {
|
|
let generics = self.generics_of(body_owner_def_id);
|
|
let p_span = self.def_span(generics.type_param(p, self).def_id);
|
|
if !sp.contains(p_span) {
|
|
diag.span_label(p_span, "this type parameter");
|
|
}
|
|
diag.help(&format!(
|
|
"every closure has a distinct type and so could not always match the \
|
|
caller-chosen type of parameter `{}`",
|
|
p
|
|
));
|
|
}
|
|
(ty::Param(p), _) | (_, ty::Param(p)) => {
|
|
let generics = self.generics_of(body_owner_def_id);
|
|
let p_span = self.def_span(generics.type_param(p, self).def_id);
|
|
if !sp.contains(p_span) {
|
|
diag.span_label(p_span, "this type parameter");
|
|
}
|
|
}
|
|
(ty::Projection(proj_ty), _) if self.def_kind(proj_ty.item_def_id) != DefKind::ImplTraitPlaceholder => {
|
|
self.expected_projection(
|
|
diag,
|
|
proj_ty,
|
|
values,
|
|
body_owner_def_id,
|
|
cause.code(),
|
|
);
|
|
}
|
|
(_, ty::Projection(proj_ty)) if self.def_kind(proj_ty.item_def_id) != DefKind::ImplTraitPlaceholder => {
|
|
let msg = format!(
|
|
"consider constraining the associated type `{}` to `{}`",
|
|
values.found, values.expected,
|
|
);
|
|
if !(self.suggest_constraining_opaque_associated_type(
|
|
diag,
|
|
&msg,
|
|
proj_ty,
|
|
values.expected,
|
|
) || self.suggest_constraint(
|
|
diag,
|
|
&msg,
|
|
body_owner_def_id,
|
|
proj_ty,
|
|
values.expected,
|
|
)) {
|
|
diag.help(&msg);
|
|
diag.note(
|
|
"for more information, visit \
|
|
https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
|
|
);
|
|
}
|
|
}
|
|
_ => {}
|
|
}
|
|
debug!(
|
|
"note_and_explain_type_err expected={:?} ({:?}) found={:?} ({:?})",
|
|
values.expected,
|
|
values.expected.kind(),
|
|
values.found,
|
|
values.found.kind(),
|
|
);
|
|
}
|
|
CyclicTy(ty) => {
|
|
// Watch out for various cases of cyclic types and try to explain.
|
|
if ty.is_closure() || ty.is_generator() {
|
|
diag.note(
|
|
"closures cannot capture themselves or take themselves as argument;\n\
|
|
this error may be the result of a recent compiler bug-fix,\n\
|
|
see issue #46062 <https://github.com/rust-lang/rust/issues/46062>\n\
|
|
for more information",
|
|
);
|
|
}
|
|
}
|
|
TargetFeatureCast(def_id) => {
|
|
let target_spans =
|
|
self.get_attrs(def_id, sym::target_feature).map(|attr| attr.span);
|
|
diag.note(
|
|
"functions with `#[target_feature]` can only be coerced to `unsafe` function pointers"
|
|
);
|
|
diag.span_labels(target_spans, "`#[target_feature]` added here");
|
|
}
|
|
_ => {}
|
|
}
|
|
}
|
|
|
|
fn suggest_constraint(
|
|
self,
|
|
diag: &mut Diagnostic,
|
|
msg: &str,
|
|
body_owner_def_id: DefId,
|
|
proj_ty: &ty::ProjectionTy<'tcx>,
|
|
ty: Ty<'tcx>,
|
|
) -> bool {
|
|
let assoc = self.associated_item(proj_ty.item_def_id);
|
|
let (trait_ref, assoc_substs) = proj_ty.trait_ref_and_own_substs(self);
|
|
if let Some(item) = self.hir().get_if_local(body_owner_def_id) {
|
|
if let Some(hir_generics) = item.generics() {
|
|
// Get the `DefId` for the type parameter corresponding to `A` in `<A as T>::Foo`.
|
|
// This will also work for `impl Trait`.
|
|
let def_id = if let ty::Param(param_ty) = proj_ty.self_ty().kind() {
|
|
let generics = self.generics_of(body_owner_def_id);
|
|
generics.type_param(param_ty, self).def_id
|
|
} else {
|
|
return false;
|
|
};
|
|
let Some(def_id) = def_id.as_local() else {
|
|
return false;
|
|
};
|
|
|
|
// First look in the `where` clause, as this might be
|
|
// `fn foo<T>(x: T) where T: Trait`.
|
|
for pred in hir_generics.bounds_for_param(def_id) {
|
|
if self.constrain_generic_bound_associated_type_structured_suggestion(
|
|
diag,
|
|
&trait_ref,
|
|
pred.bounds,
|
|
&assoc,
|
|
assoc_substs,
|
|
ty,
|
|
msg,
|
|
false,
|
|
) {
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
false
|
|
}
|
|
|
|
/// An associated type was expected and a different type was found.
|
|
///
|
|
/// We perform a few different checks to see what we can suggest:
|
|
///
|
|
/// - In the current item, look for associated functions that return the expected type and
|
|
/// suggest calling them. (Not a structured suggestion.)
|
|
/// - If any of the item's generic bounds can be constrained, we suggest constraining the
|
|
/// associated type to the found type.
|
|
/// - If the associated type has a default type and was expected inside of a `trait`, we
|
|
/// mention that this is disallowed.
|
|
/// - If all other things fail, and the error is not because of a mismatch between the `trait`
|
|
/// and the `impl`, we provide a generic `help` to constrain the assoc type or call an assoc
|
|
/// fn that returns the type.
|
|
fn expected_projection(
|
|
self,
|
|
diag: &mut Diagnostic,
|
|
proj_ty: &ty::ProjectionTy<'tcx>,
|
|
values: ExpectedFound<Ty<'tcx>>,
|
|
body_owner_def_id: DefId,
|
|
cause_code: &ObligationCauseCode<'_>,
|
|
) {
|
|
let msg = format!(
|
|
"consider constraining the associated type `{}` to `{}`",
|
|
values.expected, values.found
|
|
);
|
|
let body_owner = self.hir().get_if_local(body_owner_def_id);
|
|
let current_method_ident = body_owner.and_then(|n| n.ident()).map(|i| i.name);
|
|
|
|
// We don't want to suggest calling an assoc fn in a scope where that isn't feasible.
|
|
let callable_scope = matches!(
|
|
body_owner,
|
|
Some(
|
|
hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(..), .. })
|
|
| hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
|
|
| hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }),
|
|
)
|
|
);
|
|
let impl_comparison =
|
|
matches!(cause_code, ObligationCauseCode::CompareImplItemObligation { .. });
|
|
let assoc = self.associated_item(proj_ty.item_def_id);
|
|
if !callable_scope || impl_comparison {
|
|
// We do not want to suggest calling functions when the reason of the
|
|
// type error is a comparison of an `impl` with its `trait` or when the
|
|
// scope is outside of a `Body`.
|
|
} else {
|
|
// If we find a suitable associated function that returns the expected type, we don't
|
|
// want the more general suggestion later in this method about "consider constraining
|
|
// the associated type or calling a method that returns the associated type".
|
|
let point_at_assoc_fn = self.point_at_methods_that_satisfy_associated_type(
|
|
diag,
|
|
assoc.container_id(self),
|
|
current_method_ident,
|
|
proj_ty.item_def_id,
|
|
values.expected,
|
|
);
|
|
// Possibly suggest constraining the associated type to conform to the
|
|
// found type.
|
|
if self.suggest_constraint(diag, &msg, body_owner_def_id, proj_ty, values.found)
|
|
|| point_at_assoc_fn
|
|
{
|
|
return;
|
|
}
|
|
}
|
|
|
|
self.suggest_constraining_opaque_associated_type(diag, &msg, proj_ty, values.found);
|
|
|
|
if self.point_at_associated_type(diag, body_owner_def_id, values.found) {
|
|
return;
|
|
}
|
|
|
|
if !impl_comparison {
|
|
// Generic suggestion when we can't be more specific.
|
|
if callable_scope {
|
|
diag.help(&format!(
|
|
"{} or calling a method that returns `{}`",
|
|
msg, values.expected
|
|
));
|
|
} else {
|
|
diag.help(&msg);
|
|
}
|
|
diag.note(
|
|
"for more information, visit \
|
|
https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
|
|
);
|
|
}
|
|
if self.sess.teach(&diag.get_code().unwrap()) {
|
|
diag.help(
|
|
"given an associated type `T` and a method `foo`:
|
|
```
|
|
trait Trait {
|
|
type T;
|
|
fn foo(&self) -> Self::T;
|
|
}
|
|
```
|
|
the only way of implementing method `foo` is to constrain `T` with an explicit associated type:
|
|
```
|
|
impl Trait for X {
|
|
type T = String;
|
|
fn foo(&self) -> Self::T { String::new() }
|
|
}
|
|
```",
|
|
);
|
|
}
|
|
}
|
|
|
|
/// When the expected `impl Trait` is not defined in the current item, it will come from
|
|
/// a return type. This can occur when dealing with `TryStream` (#71035).
|
|
fn suggest_constraining_opaque_associated_type(
|
|
self,
|
|
diag: &mut Diagnostic,
|
|
msg: &str,
|
|
proj_ty: &ty::ProjectionTy<'tcx>,
|
|
ty: Ty<'tcx>,
|
|
) -> bool {
|
|
let assoc = self.associated_item(proj_ty.item_def_id);
|
|
if let ty::Opaque(def_id, _) = *proj_ty.self_ty().kind() {
|
|
let opaque_local_def_id = def_id.as_local();
|
|
let opaque_hir_ty = if let Some(opaque_local_def_id) = opaque_local_def_id {
|
|
match &self.hir().expect_item(opaque_local_def_id).kind {
|
|
hir::ItemKind::OpaqueTy(opaque_hir_ty) => opaque_hir_ty,
|
|
_ => bug!("The HirId comes from a `ty::Opaque`"),
|
|
}
|
|
} else {
|
|
return false;
|
|
};
|
|
|
|
let (trait_ref, assoc_substs) = proj_ty.trait_ref_and_own_substs(self);
|
|
|
|
self.constrain_generic_bound_associated_type_structured_suggestion(
|
|
diag,
|
|
&trait_ref,
|
|
opaque_hir_ty.bounds,
|
|
assoc,
|
|
assoc_substs,
|
|
ty,
|
|
msg,
|
|
true,
|
|
)
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
fn point_at_methods_that_satisfy_associated_type(
|
|
self,
|
|
diag: &mut Diagnostic,
|
|
assoc_container_id: DefId,
|
|
current_method_ident: Option<Symbol>,
|
|
proj_ty_item_def_id: DefId,
|
|
expected: Ty<'tcx>,
|
|
) -> bool {
|
|
let items = self.associated_items(assoc_container_id);
|
|
// Find all the methods in the trait that could be called to construct the
|
|
// expected associated type.
|
|
// FIXME: consider suggesting the use of associated `const`s.
|
|
let methods: Vec<(Span, String)> = items
|
|
.items
|
|
.iter()
|
|
.filter(|(name, item)| {
|
|
ty::AssocKind::Fn == item.kind && Some(**name) != current_method_ident
|
|
})
|
|
.filter_map(|(_, item)| {
|
|
let method = self.fn_sig(item.def_id);
|
|
match *method.output().skip_binder().kind() {
|
|
ty::Projection(ty::ProjectionTy { item_def_id, .. })
|
|
if item_def_id == proj_ty_item_def_id =>
|
|
{
|
|
Some((
|
|
self.def_span(item.def_id),
|
|
format!("consider calling `{}`", self.def_path_str(item.def_id)),
|
|
))
|
|
}
|
|
_ => None,
|
|
}
|
|
})
|
|
.collect();
|
|
if !methods.is_empty() {
|
|
// Use a single `help:` to show all the methods in the trait that can
|
|
// be used to construct the expected associated type.
|
|
let mut span: MultiSpan =
|
|
methods.iter().map(|(sp, _)| *sp).collect::<Vec<Span>>().into();
|
|
let msg = format!(
|
|
"{some} method{s} {are} available that return{r} `{ty}`",
|
|
some = if methods.len() == 1 { "a" } else { "some" },
|
|
s = pluralize!(methods.len()),
|
|
are = pluralize!("is", methods.len()),
|
|
r = if methods.len() == 1 { "s" } else { "" },
|
|
ty = expected
|
|
);
|
|
for (sp, label) in methods.into_iter() {
|
|
span.push_span_label(sp, label);
|
|
}
|
|
diag.span_help(span, &msg);
|
|
return true;
|
|
}
|
|
false
|
|
}
|
|
|
|
fn point_at_associated_type(
|
|
self,
|
|
diag: &mut Diagnostic,
|
|
body_owner_def_id: DefId,
|
|
found: Ty<'tcx>,
|
|
) -> bool {
|
|
let Some(hir_id) = body_owner_def_id.as_local() else {
|
|
return false;
|
|
};
|
|
let hir_id = self.hir().local_def_id_to_hir_id(hir_id);
|
|
// When `body_owner` is an `impl` or `trait` item, look in its associated types for
|
|
// `expected` and point at it.
|
|
let parent_id = self.hir().get_parent_item(hir_id);
|
|
let item = self.hir().find_by_def_id(parent_id.def_id);
|
|
debug!("expected_projection parent item {:?}", item);
|
|
match item {
|
|
Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Trait(.., items), .. })) => {
|
|
// FIXME: account for `#![feature(specialization)]`
|
|
for item in &items[..] {
|
|
match item.kind {
|
|
hir::AssocItemKind::Type => {
|
|
// FIXME: account for returning some type in a trait fn impl that has
|
|
// an assoc type as a return type (#72076).
|
|
if let hir::Defaultness::Default { has_value: true } =
|
|
self.impl_defaultness(item.id.def_id)
|
|
{
|
|
if self.type_of(item.id.def_id) == found {
|
|
diag.span_label(
|
|
item.span,
|
|
"associated type defaults can't be assumed inside the \
|
|
trait defining them",
|
|
);
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
_ => {}
|
|
}
|
|
}
|
|
}
|
|
Some(hir::Node::Item(hir::Item {
|
|
kind: hir::ItemKind::Impl(hir::Impl { items, .. }),
|
|
..
|
|
})) => {
|
|
for item in &items[..] {
|
|
if let hir::AssocItemKind::Type = item.kind {
|
|
if self.type_of(item.id.def_id) == found {
|
|
diag.span_label(item.span, "expected this associated type");
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
_ => {}
|
|
}
|
|
false
|
|
}
|
|
|
|
/// Given a slice of `hir::GenericBound`s, if any of them corresponds to the `trait_ref`
|
|
/// requirement, provide a structured suggestion to constrain it to a given type `ty`.
|
|
///
|
|
/// `is_bound_surely_present` indicates whether we know the bound we're looking for is
|
|
/// inside `bounds`. If that's the case then we can consider `bounds` containing only one
|
|
/// trait bound as the one we're looking for. This can help in cases where the associated
|
|
/// type is defined on a supertrait of the one present in the bounds.
|
|
fn constrain_generic_bound_associated_type_structured_suggestion(
|
|
self,
|
|
diag: &mut Diagnostic,
|
|
trait_ref: &ty::TraitRef<'tcx>,
|
|
bounds: hir::GenericBounds<'_>,
|
|
assoc: &ty::AssocItem,
|
|
assoc_substs: &[ty::GenericArg<'tcx>],
|
|
ty: Ty<'tcx>,
|
|
msg: &str,
|
|
is_bound_surely_present: bool,
|
|
) -> bool {
|
|
// FIXME: we would want to call `resolve_vars_if_possible` on `ty` before suggesting.
|
|
|
|
let trait_bounds = bounds.iter().filter_map(|bound| match bound {
|
|
hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::None) => Some(ptr),
|
|
_ => None,
|
|
});
|
|
|
|
let matching_trait_bounds = trait_bounds
|
|
.clone()
|
|
.filter(|ptr| ptr.trait_ref.trait_def_id() == Some(trait_ref.def_id))
|
|
.collect::<Vec<_>>();
|
|
|
|
let span = match &matching_trait_bounds[..] {
|
|
&[ptr] => ptr.span,
|
|
&[] if is_bound_surely_present => match &trait_bounds.collect::<Vec<_>>()[..] {
|
|
&[ptr] => ptr.span,
|
|
_ => return false,
|
|
},
|
|
_ => return false,
|
|
};
|
|
|
|
self.constrain_associated_type_structured_suggestion(
|
|
diag,
|
|
span,
|
|
assoc,
|
|
assoc_substs,
|
|
ty,
|
|
msg,
|
|
)
|
|
}
|
|
|
|
/// Given a span corresponding to a bound, provide a structured suggestion to set an
|
|
/// associated type to a given type `ty`.
|
|
fn constrain_associated_type_structured_suggestion(
|
|
self,
|
|
diag: &mut Diagnostic,
|
|
span: Span,
|
|
assoc: &ty::AssocItem,
|
|
assoc_substs: &[ty::GenericArg<'tcx>],
|
|
ty: Ty<'tcx>,
|
|
msg: &str,
|
|
) -> bool {
|
|
if let Ok(has_params) =
|
|
self.sess.source_map().span_to_snippet(span).map(|snippet| snippet.ends_with('>'))
|
|
{
|
|
let (span, sugg) = if has_params {
|
|
let pos = span.hi() - BytePos(1);
|
|
let span = Span::new(pos, pos, span.ctxt(), span.parent());
|
|
(span, format!(", {} = {}", assoc.ident(self), ty))
|
|
} else {
|
|
let item_args = self.format_generic_args(assoc_substs);
|
|
(span.shrink_to_hi(), format!("<{}{} = {}>", assoc.ident(self), item_args, ty))
|
|
};
|
|
diag.span_suggestion_verbose(span, msg, sugg, MaybeIncorrect);
|
|
return true;
|
|
}
|
|
false
|
|
}
|
|
|
|
fn format_generic_args(self, args: &[ty::GenericArg<'tcx>]) -> String {
|
|
FmtPrinter::new(self, hir::def::Namespace::TypeNS)
|
|
.path_generic_args(Ok, args)
|
|
.expect("could not write to `String`.")
|
|
.into_buffer()
|
|
}
|
|
}
|