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rust/rust/8ae423e5e8db47b8233ad657b8d84247f94de179/./compiler/rustc_hir_analysis/src/check/check.rs
blob: 06ccf61a1620309f9ffc31ad61ce441d77eed468 [file]
use std::cell::LazyCell;
use std::ops::ControlFlow;
use rustc_abi::{ExternAbi, FieldIdx, ScalableElt};
use rustc_data_structures::unord::{UnordMap, UnordSet};
use rustc_errors::codes::*;
use rustc_errors::{Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level, MultiSpan};
use rustc_hir as hir;
use rustc_hir::attrs::ReprAttr::ReprPacked;
use rustc_hir::def::{CtorKind, DefKind};
use rustc_hir::{LangItem, Node, find_attr, intravisit};
use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
use rustc_infer::traits::{Obligation, ObligationCauseCode, WellFormedLoc};
use rustc_lint_defs::builtin::{REPR_TRANSPARENT_NON_ZST_FIELDS, UNSUPPORTED_CALLING_CONVENTIONS};
use rustc_macros::Diagnostic;
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
use rustc_middle::middle::stability::EvalResult;
use rustc_middle::ty::error::TypeErrorToStringExt;
use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES};
use rustc_middle::ty::util::Discr;
use rustc_middle::ty::{
AdtDef, BottomUpFolder, FnSig, GenericArgKind, RegionKind, TypeFoldable, TypeSuperVisitable,
TypeVisitable, TypeVisitableExt, fold_regions,
};
use rustc_session::lint::builtin::UNINHABITED_STATIC;
use rustc_target::spec::{AbiMap, AbiMapping};
use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
use rustc_trait_selection::traits;
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
use tracing::{debug, instrument};
use ty::TypingMode;
use super::compare_impl_item::check_type_bounds;
use super::*;
use crate::check::wfcheck::{
check_associated_item, check_trait_item, check_variances_for_type_defn, check_where_clauses,
enter_wf_checking_ctxt,
};
fn add_abi_diag_help<T: EmissionGuarantee>(abi: ExternAbi, diag: &mut Diag<'_, T>) {
if let ExternAbi::Cdecl { unwind } = abi {
let c_abi = ExternAbi::C { unwind };
diag.help(format!("use `extern {c_abi}` instead",));
} else if let ExternAbi::Stdcall { unwind } = abi {
let c_abi = ExternAbi::C { unwind };
let system_abi = ExternAbi::System { unwind };
diag.help(format!(
"if you need `extern {abi}` on win32 and `extern {c_abi}` everywhere else, \
use `extern {system_abi}`"
));
}
}
pub fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: ExternAbi) {
struct UnsupportedCallingConventions {
abi: ExternAbi,
}
impl<'a> Diagnostic<'a, ()> for UnsupportedCallingConventions {
fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, ()> {
let Self { abi } = self;
let mut lint = Diag::new(
dcx,
level,
format!("{abi} is not a supported ABI for the current target"),
);
add_abi_diag_help(abi, &mut lint);
lint
}
}
// FIXME: This should be checked earlier, e.g. in `rustc_ast_lowering`, as this
// currently only guards function imports, function definitions, and function pointer types.
// Functions in trait declarations can still use "deprecated" ABIs without any warning.
match AbiMap::from_target(&tcx.sess.target).canonize_abi(abi, false) {
AbiMapping::Direct(..) => (),
// already erred in rustc_ast_lowering
AbiMapping::Invalid => {
tcx.dcx().span_delayed_bug(span, format!("{abi} should be rejected in ast_lowering"));
}
AbiMapping::Deprecated(..) => {
tcx.emit_node_span_lint(
UNSUPPORTED_CALLING_CONVENTIONS,
hir_id,
span,
UnsupportedCallingConventions { abi },
);
}
}
}
pub fn check_custom_abi(tcx: TyCtxt<'_>, def_id: LocalDefId, fn_sig: FnSig<'_>, fn_sig_span: Span) {
if fn_sig.abi == ExternAbi::Custom {
// Function definitions that use `extern "custom"` must be naked functions.
if !find_attr!(tcx, def_id, Naked(_)) {
tcx.dcx().emit_err(crate::errors::AbiCustomClothedFunction {
span: fn_sig_span,
naked_span: tcx.def_span(def_id).shrink_to_lo(),
});
}
}
}
fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) {
let def = tcx.adt_def(def_id);
let span = tcx.def_span(def_id);
def.destructor(tcx); // force the destructor to be evaluated
if let Some(scalable) = def.repr().scalable {
check_scalable_vector(tcx, span, def_id, scalable);
} else if def.repr().simd() {
check_simd(tcx, span, def_id);
}
check_transparent(tcx, def);
check_packed(tcx, span, def);
}
fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) {
let def = tcx.adt_def(def_id);
let span = tcx.def_span(def_id);
def.destructor(tcx); // force the destructor to be evaluated
check_transparent(tcx, def);
check_union_fields(tcx, span, def_id);
check_packed(tcx, span, def);
}
fn allowed_union_or_unsafe_field<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
span: Span,
) -> bool {
// HACK (not that bad of a hack don't worry): Some codegen tests don't even define proper
// impls for `Copy`. Let's short-circuit here for this validity check, since a lot of them
// use unions. We should eventually fix all the tests to define that lang item or use
// minicore stubs.
if ty.is_trivially_pure_clone_copy() {
return true;
}
// If `BikeshedGuaranteedNoDrop` is not defined in a `#[no_core]` test, fall back to `Copy`.
// This is an underapproximation of `BikeshedGuaranteedNoDrop`,
let def_id = tcx
.lang_items()
.get(LangItem::BikeshedGuaranteedNoDrop)
.unwrap_or_else(|| tcx.require_lang_item(LangItem::Copy, span));
let Ok(ty) = tcx.try_normalize_erasing_regions(typing_env, ty) else {
tcx.dcx().span_delayed_bug(span, "could not normalize field type");
return true;
};
let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(typing_env);
infcx.predicate_must_hold_modulo_regions(&Obligation::new(
tcx,
ObligationCause::dummy_with_span(span),
param_env,
ty::TraitRef::new(tcx, def_id, [ty]),
))
}
/// Check that the fields of the `union` do not need dropping.
fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> bool {
let def = tcx.adt_def(item_def_id);
assert!(def.is_union());
let typing_env = ty::TypingEnv::non_body_analysis(tcx, item_def_id);
let args = ty::GenericArgs::identity_for_item(tcx, item_def_id);
for field in &def.non_enum_variant().fields {
if !allowed_union_or_unsafe_field(tcx, field.ty(tcx, args), typing_env, span) {
let (field_span, ty_span) = match tcx.hir_get_if_local(field.did) {
// We are currently checking the type this field came from, so it must be local.
Some(Node::Field(field)) => (field.span, field.ty.span),
_ => unreachable!("mir field has to correspond to hir field"),
};
tcx.dcx().emit_err(errors::InvalidUnionField {
field_span,
sugg: errors::InvalidUnionFieldSuggestion {
lo: ty_span.shrink_to_lo(),
hi: ty_span.shrink_to_hi(),
},
note: (),
});
return false;
}
}
true
}
/// Check that a `static` is inhabited.
fn check_static_inhabited(tcx: TyCtxt<'_>, def_id: LocalDefId) {
#[derive(Diagnostic)]
#[diag("static of uninhabited type")]
#[note("uninhabited statics cannot be initialized, and any access would be an immediate error")]
struct StaticOfUninhabitedType;
// Make sure statics are inhabited.
// Other parts of the compiler assume that there are no uninhabited places. In principle it
// would be enough to check this for `extern` statics, as statics with an initializer will
// have UB during initialization if they are uninhabited, but there also seems to be no good
// reason to allow any statics to be uninhabited.
let ty = tcx.type_of(def_id).instantiate_identity();
let span = tcx.def_span(def_id);
let layout = match tcx.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(ty)) {
Ok(l) => l,
// Foreign statics that overflow their allowed size should emit an error
Err(LayoutError::SizeOverflow(_))
if matches!(tcx.def_kind(def_id), DefKind::Static{ .. }
if tcx.def_kind(tcx.local_parent(def_id)) == DefKind::ForeignMod) =>
{
tcx.dcx().emit_err(errors::TooLargeStatic { span });
return;
}
// SIMD types with invalid layout (e.g., zero-length) should emit an error
Err(e @ LayoutError::InvalidSimd { .. }) => {
let ty_span = tcx.ty_span(def_id);
tcx.dcx().span_err(ty_span, e.to_string());
return;
}
// Generic statics are rejected, but we still reach this case.
Err(e) => {
tcx.dcx().span_delayed_bug(span, format!("{e:?}"));
return;
}
};
if layout.is_uninhabited() {
tcx.emit_node_span_lint(
UNINHABITED_STATIC,
tcx.local_def_id_to_hir_id(def_id),
span,
StaticOfUninhabitedType,
);
}
}
/// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
/// projections that would result in "inheriting lifetimes".
fn check_opaque(tcx: TyCtxt<'_>, def_id: LocalDefId) {
let hir::OpaqueTy { origin, .. } = *tcx.hir_expect_opaque_ty(def_id);
// HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
// `async-std` (and `pub async fn` in general).
// Since rustdoc doesn't care about the hidden type behind `impl Trait`, just don't look at it!
// See https://github.com/rust-lang/rust/issues/75100
if tcx.sess.opts.actually_rustdoc {
return;
}
if tcx.type_of(def_id).instantiate_identity().references_error() {
return;
}
if check_opaque_for_cycles(tcx, def_id).is_err() {
return;
}
let _ = check_opaque_meets_bounds(tcx, def_id, origin);
}
/// Checks that an opaque type does not contain cycles.
pub(super) fn check_opaque_for_cycles<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
) -> Result<(), ErrorGuaranteed> {
let args = GenericArgs::identity_for_item(tcx, def_id);
// First, try to look at any opaque expansion cycles, considering coroutine fields
// (even though these aren't necessarily true errors).
if tcx.try_expand_impl_trait_type(def_id.to_def_id(), args).is_err() {
let reported = opaque_type_cycle_error(tcx, def_id);
return Err(reported);
}
Ok(())
}
/// Check that the hidden type behind `impl Trait` actually implements `Trait`.
///
/// This is mostly checked at the places that specify the opaque type, but we
/// check those cases in the `param_env` of that function, which may have
/// bounds not on this opaque type:
///
/// ```ignore (illustrative)
/// type X<T> = impl Clone;
/// fn f<T: Clone>(t: T) -> X<T> {
/// t
/// }
/// ```
///
/// Without this check the above code is incorrectly accepted: we would ICE if
/// some tried, for example, to clone an `Option<X<&mut ()>>`.
#[instrument(level = "debug", skip(tcx))]
fn check_opaque_meets_bounds<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
origin: hir::OpaqueTyOrigin<LocalDefId>,
) -> Result<(), ErrorGuaranteed> {
let (span, definition_def_id) =
if let Some((span, def_id)) = best_definition_site_of_opaque(tcx, def_id, origin) {
(span, Some(def_id))
} else {
(tcx.def_span(def_id), None)
};
let defining_use_anchor = match origin {
hir::OpaqueTyOrigin::FnReturn { parent, .. }
| hir::OpaqueTyOrigin::AsyncFn { parent, .. }
| hir::OpaqueTyOrigin::TyAlias { parent, .. } => parent,
};
let param_env = tcx.param_env(defining_use_anchor);
// FIXME(#132279): Once `PostBorrowckAnalysis` is supported in the old solver, this branch should be removed.
let infcx = tcx.infer_ctxt().build(if tcx.next_trait_solver_globally() {
TypingMode::post_borrowck_analysis(tcx, defining_use_anchor)
} else {
TypingMode::analysis_in_body(tcx, defining_use_anchor)
});
let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
let args = match origin {
hir::OpaqueTyOrigin::FnReturn { parent, .. }
| hir::OpaqueTyOrigin::AsyncFn { parent, .. }
| hir::OpaqueTyOrigin::TyAlias { parent, .. } => GenericArgs::identity_for_item(
tcx, parent,
)
.extend_to(tcx, def_id.to_def_id(), |param, _| {
tcx.map_opaque_lifetime_to_parent_lifetime(param.def_id.expect_local()).into()
}),
};
let opaque_ty = Ty::new_opaque(tcx, def_id.to_def_id(), args);
// `ReErased` regions appear in the "parent_args" of closures/coroutines.
// We're ignoring them here and replacing them with fresh region variables.
// See tests in ui/type-alias-impl-trait/closure_{parent_args,wf_outlives}.rs.
//
// FIXME: Consider wrapping the hidden type in an existential `Binder` and instantiating it
// here rather than using ReErased.
let hidden_ty = tcx.type_of(def_id.to_def_id()).instantiate(tcx, args);
let hidden_ty = fold_regions(tcx, hidden_ty, |re, _dbi| match re.kind() {
ty::ReErased => infcx.next_region_var(RegionVariableOrigin::Misc(span)),
_ => re,
});
// HACK: We eagerly instantiate some bounds to report better errors for them...
// This isn't necessary for correctness, since we register these bounds when
// equating the opaque below, but we should clean this up in the new solver.
for (predicate, pred_span) in
tcx.explicit_item_bounds(def_id).iter_instantiated_copied(tcx, args)
{
let predicate = predicate.fold_with(&mut BottomUpFolder {
tcx,
ty_op: |ty| if ty == opaque_ty { hidden_ty } else { ty },
lt_op: |lt| lt,
ct_op: |ct| ct,
});
ocx.register_obligation(Obligation::new(
tcx,
ObligationCause::new(
span,
def_id,
ObligationCauseCode::OpaqueTypeBound(pred_span, definition_def_id),
),
param_env,
predicate,
));
}
let misc_cause = ObligationCause::misc(span, def_id);
// FIXME: We should just register the item bounds here, rather than equating.
// FIXME(const_trait_impl): When we do that, please make sure to also register
// the `[const]` bounds.
match ocx.eq(&misc_cause, param_env, opaque_ty, hidden_ty) {
Ok(()) => {}
Err(ty_err) => {
// Some types may be left "stranded" if they can't be reached
// from a lowered rustc_middle bound but they're mentioned in the HIR.
// This will happen, e.g., when a nested opaque is inside of a non-
// existent associated type, like `impl Trait<Missing = impl Trait>`.
// See <tests/ui/impl-trait/stranded-opaque.rs>.
let ty_err = ty_err.to_string(tcx);
let guar = tcx.dcx().span_delayed_bug(
span,
format!("could not unify `{hidden_ty}` with revealed type:\n{ty_err}"),
);
return Err(guar);
}
}
// Additionally require the hidden type to be well-formed with only the generics of the opaque type.
// Defining use functions may have more bounds than the opaque type, which is ok, as long as the
// hidden type is well formed even without those bounds.
let predicate =
ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(hidden_ty.into())));
ocx.register_obligation(Obligation::new(tcx, misc_cause.clone(), param_env, predicate));
// Check that all obligations are satisfied by the implementation's
// version.
let errors = ocx.evaluate_obligations_error_on_ambiguity();
if !errors.is_empty() {
let guar = infcx.err_ctxt().report_fulfillment_errors(errors);
return Err(guar);
}
let wf_tys = ocx.assumed_wf_types_and_report_errors(param_env, defining_use_anchor)?;
ocx.resolve_regions_and_report_errors(defining_use_anchor, param_env, wf_tys)?;
if infcx.next_trait_solver() {
Ok(())
} else if let hir::OpaqueTyOrigin::FnReturn { .. } | hir::OpaqueTyOrigin::AsyncFn { .. } =
origin
{
// HACK: this should also fall through to the hidden type check below, but the original
// implementation had a bug where equivalent lifetimes are not identical. This caused us
// to reject existing stable code that is otherwise completely fine. The real fix is to
// compare the hidden types via our type equivalence/relation infra instead of doing an
// identity check.
let _ = infcx.take_opaque_types();
Ok(())
} else {
// Check that any hidden types found during wf checking match the hidden types that `type_of` sees.
for (mut key, mut ty) in infcx.take_opaque_types() {
ty.ty = infcx.resolve_vars_if_possible(ty.ty);
key = infcx.resolve_vars_if_possible(key);
sanity_check_found_hidden_type(tcx, key, ty)?;
}
Ok(())
}
}
fn best_definition_site_of_opaque<'tcx>(
tcx: TyCtxt<'tcx>,
opaque_def_id: LocalDefId,
origin: hir::OpaqueTyOrigin<LocalDefId>,
) -> Option<(Span, LocalDefId)> {
struct TaitConstraintLocator<'tcx> {
opaque_def_id: LocalDefId,
tcx: TyCtxt<'tcx>,
}
impl<'tcx> TaitConstraintLocator<'tcx> {
fn check(&self, item_def_id: LocalDefId) -> ControlFlow<(Span, LocalDefId)> {
if !self.tcx.has_typeck_results(item_def_id) {
return ControlFlow::Continue(());
}
let opaque_types_defined_by = self.tcx.opaque_types_defined_by(item_def_id);
// Don't try to check items that cannot possibly constrain the type.
if !opaque_types_defined_by.contains(&self.opaque_def_id) {
return ControlFlow::Continue(());
}
if let Some(hidden_ty) = self
.tcx
.mir_borrowck(item_def_id)
.ok()
.and_then(|opaque_types| opaque_types.get(&self.opaque_def_id))
{
ControlFlow::Break((hidden_ty.span, item_def_id))
} else {
ControlFlow::Continue(())
}
}
}
impl<'tcx> intravisit::Visitor<'tcx> for TaitConstraintLocator<'tcx> {
type NestedFilter = nested_filter::All;
type Result = ControlFlow<(Span, LocalDefId)>;
fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
self.tcx
}
fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) -> Self::Result {
intravisit::walk_expr(self, ex)
}
fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) -> Self::Result {
self.check(it.owner_id.def_id)?;
intravisit::walk_item(self, it)
}
fn visit_impl_item(&mut self, it: &'tcx hir::ImplItem<'tcx>) -> Self::Result {
self.check(it.owner_id.def_id)?;
intravisit::walk_impl_item(self, it)
}
fn visit_trait_item(&mut self, it: &'tcx hir::TraitItem<'tcx>) -> Self::Result {
self.check(it.owner_id.def_id)?;
intravisit::walk_trait_item(self, it)
}
fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) -> Self::Result {
intravisit::walk_foreign_item(self, it)
}
}
let mut locator = TaitConstraintLocator { tcx, opaque_def_id };
match origin {
hir::OpaqueTyOrigin::FnReturn { parent, .. }
| hir::OpaqueTyOrigin::AsyncFn { parent, .. } => locator.check(parent).break_value(),
hir::OpaqueTyOrigin::TyAlias { parent, in_assoc_ty: true } => {
let impl_def_id = tcx.local_parent(parent);
for assoc in tcx.associated_items(impl_def_id).in_definition_order() {
match assoc.kind {
ty::AssocKind::Const { .. } | ty::AssocKind::Fn { .. } => {
if let ControlFlow::Break(span) = locator.check(assoc.def_id.expect_local())
{
return Some(span);
}
}
ty::AssocKind::Type { .. } => {}
}
}
None
}
hir::OpaqueTyOrigin::TyAlias { in_assoc_ty: false, .. } => {
tcx.hir_walk_toplevel_module(&mut locator).break_value()
}
}
}
fn sanity_check_found_hidden_type<'tcx>(
tcx: TyCtxt<'tcx>,
key: ty::OpaqueTypeKey<'tcx>,
mut ty: ty::ProvisionalHiddenType<'tcx>,
) -> Result<(), ErrorGuaranteed> {
if ty.ty.is_ty_var() {
// Nothing was actually constrained.
return Ok(());
}
if let ty::Alias(ty::Opaque, alias) = ty.ty.kind() {
if alias.def_id == key.def_id.to_def_id() && alias.args == key.args {
// Nothing was actually constrained, this is an opaque usage that was
// only discovered to be opaque after inference vars resolved.
return Ok(());
}
}
let erase_re_vars = |ty: Ty<'tcx>| {
fold_regions(tcx, ty, |r, _| match r.kind() {
RegionKind::ReVar(_) => tcx.lifetimes.re_erased,
_ => r,
})
};
// Closures frequently end up containing erased lifetimes in their final representation.
// These correspond to lifetime variables that never got resolved, so we patch this up here.
ty.ty = erase_re_vars(ty.ty);
// Get the hidden type.
let hidden_ty = tcx.type_of(key.def_id).instantiate(tcx, key.args);
let hidden_ty = erase_re_vars(hidden_ty);
// If the hidden types differ, emit a type mismatch diagnostic.
if hidden_ty == ty.ty {
Ok(())
} else {
let span = tcx.def_span(key.def_id);
let other = ty::ProvisionalHiddenType { ty: hidden_ty, span };
Err(ty.build_mismatch_error(&other, tcx)?.emit())
}
}
/// Check that the opaque's precise captures list is valid (if present).
/// We check this for regular `impl Trait`s and also RPITITs, even though the latter
/// are technically GATs.
///
/// This function is responsible for:
/// 1. Checking that all type/const params are mention in the captures list.
/// 2. Checking that all lifetimes that are implicitly captured are mentioned.
/// 3. Asserting that all parameters mentioned in the captures list are invariant.
fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDefId) {
let hir::OpaqueTy { bounds, .. } = *tcx.hir_node_by_def_id(opaque_def_id).expect_opaque_ty();
let Some(precise_capturing_args) = bounds.iter().find_map(|bound| match *bound {
hir::GenericBound::Use(bounds, ..) => Some(bounds),
_ => None,
}) else {
// No precise capturing args; nothing to validate
return;
};
let mut expected_captures = UnordSet::default();
let mut shadowed_captures = UnordSet::default();
let mut seen_params = UnordMap::default();
let mut prev_non_lifetime_param = None;
for arg in precise_capturing_args {
let (hir_id, ident) = match *arg {
hir::PreciseCapturingArg::Param(hir::PreciseCapturingNonLifetimeArg {
hir_id,
ident,
..
}) => {
if prev_non_lifetime_param.is_none() {
prev_non_lifetime_param = Some(ident);
}
(hir_id, ident)
}
hir::PreciseCapturingArg::Lifetime(&hir::Lifetime { hir_id, ident, .. }) => {
if let Some(prev_non_lifetime_param) = prev_non_lifetime_param {
tcx.dcx().emit_err(errors::LifetimesMustBeFirst {
lifetime_span: ident.span,
name: ident.name,
other_span: prev_non_lifetime_param.span,
});
}
(hir_id, ident)
}
};
let ident = ident.normalize_to_macros_2_0();
if let Some(span) = seen_params.insert(ident, ident.span) {
tcx.dcx().emit_err(errors::DuplicatePreciseCapture {
name: ident.name,
first_span: span,
second_span: ident.span,
});
}
match tcx.named_bound_var(hir_id) {
Some(ResolvedArg::EarlyBound(def_id)) => {
expected_captures.insert(def_id.to_def_id());
// Make sure we allow capturing these lifetimes through `Self` and
// `T::Assoc` projection syntax, too. These will occur when we only
// see lifetimes are captured after hir-lowering -- this aligns with
// the cases that were stabilized with the `impl_trait_projection`
// feature -- see <https://github.com/rust-lang/rust/pull/115659>.
if let DefKind::LifetimeParam = tcx.def_kind(def_id)
&& let Some(def_id) = tcx
.map_opaque_lifetime_to_parent_lifetime(def_id)
.opt_param_def_id(tcx, tcx.parent(opaque_def_id.to_def_id()))
{
shadowed_captures.insert(def_id);
}
}
_ => {
tcx.dcx()
.span_delayed_bug(tcx.hir_span(hir_id), "parameter should have been resolved");
}
}
}
let variances = tcx.variances_of(opaque_def_id);
let mut def_id = Some(opaque_def_id.to_def_id());
while let Some(generics) = def_id {
let generics = tcx.generics_of(generics);
def_id = generics.parent;
for param in &generics.own_params {
if expected_captures.contains(&param.def_id) {
assert_eq!(
variances[param.index as usize],
ty::Invariant,
"precise captured param should be invariant"
);
continue;
}
// If a param is shadowed by a early-bound (duplicated) lifetime, then
// it may or may not be captured as invariant, depending on if it shows
// up through `Self` or `T::Assoc` syntax.
if shadowed_captures.contains(&param.def_id) {
continue;
}
match param.kind {
ty::GenericParamDefKind::Lifetime => {
let use_span = tcx.def_span(param.def_id);
let opaque_span = tcx.def_span(opaque_def_id);
// Check if the lifetime param was captured but isn't named in the precise captures list.
if variances[param.index as usize] == ty::Invariant {
if let DefKind::OpaqueTy = tcx.def_kind(tcx.parent(param.def_id))
&& let Some(def_id) = tcx
.map_opaque_lifetime_to_parent_lifetime(param.def_id.expect_local())
.opt_param_def_id(tcx, tcx.parent(opaque_def_id.to_def_id()))
{
tcx.dcx().emit_err(errors::LifetimeNotCaptured {
opaque_span,
use_span,
param_span: tcx.def_span(def_id),
});
} else {
if tcx.def_kind(tcx.parent(param.def_id)) == DefKind::Trait {
tcx.dcx().emit_err(errors::LifetimeImplicitlyCaptured {
opaque_span,
param_span: tcx.def_span(param.def_id),
});
} else {
// If the `use_span` is actually just the param itself, then we must
// have not duplicated the lifetime but captured the original.
// The "effective" `use_span` will be the span of the opaque itself,
// and the param span will be the def span of the param.
tcx.dcx().emit_err(errors::LifetimeNotCaptured {
opaque_span,
use_span: opaque_span,
param_span: use_span,
});
}
}
continue;
}
}
ty::GenericParamDefKind::Type { .. } => {
if matches!(tcx.def_kind(param.def_id), DefKind::Trait | DefKind::TraitAlias) {
// FIXME(precise_capturing): Structured suggestion for this would be useful
tcx.dcx().emit_err(errors::SelfTyNotCaptured {
trait_span: tcx.def_span(param.def_id),
opaque_span: tcx.def_span(opaque_def_id),
});
} else {
// FIXME(precise_capturing): Structured suggestion for this would be useful
tcx.dcx().emit_err(errors::ParamNotCaptured {
param_span: tcx.def_span(param.def_id),
opaque_span: tcx.def_span(opaque_def_id),
kind: "type",
});
}
}
ty::GenericParamDefKind::Const { .. } => {
// FIXME(precise_capturing): Structured suggestion for this would be useful
tcx.dcx().emit_err(errors::ParamNotCaptured {
param_span: tcx.def_span(param.def_id),
opaque_span: tcx.def_span(opaque_def_id),
kind: "const",
});
}
}
}
}
}
fn is_enum_of_nonnullable_ptr<'tcx>(
tcx: TyCtxt<'tcx>,
adt_def: AdtDef<'tcx>,
args: GenericArgsRef<'tcx>,
) -> bool {
if adt_def.repr().inhibit_enum_layout_opt() {
return false;
}
let [var_one, var_two] = &adt_def.variants().raw[..] else {
return false;
};
let (([], [field]) | ([field], [])) = (&var_one.fields.raw[..], &var_two.fields.raw[..]) else {
return false;
};
matches!(field.ty(tcx, args).kind(), ty::FnPtr(..) | ty::Ref(..))
}
fn check_static_linkage(tcx: TyCtxt<'_>, def_id: LocalDefId) {
if tcx.codegen_fn_attrs(def_id).import_linkage.is_some() {
if match tcx.type_of(def_id).instantiate_identity().kind() {
ty::RawPtr(_, _) => false,
ty::Adt(adt_def, args) => !is_enum_of_nonnullable_ptr(tcx, *adt_def, *args),
_ => true,
} {
tcx.dcx().emit_err(errors::LinkageType { span: tcx.def_span(def_id) });
}
}
}
pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGuaranteed> {
let mut res = Ok(());
let generics = tcx.generics_of(def_id);
for param in &generics.own_params {
match param.kind {
ty::GenericParamDefKind::Lifetime { .. } => {}
ty::GenericParamDefKind::Type { has_default, .. } => {
if has_default {
tcx.ensure_ok().type_of(param.def_id);
}
}
ty::GenericParamDefKind::Const { has_default, .. } => {
tcx.ensure_ok().type_of(param.def_id);
if has_default {
// need to store default and type of default
let ct = tcx.const_param_default(param.def_id).skip_binder();
if let ty::ConstKind::Unevaluated(uv) = ct.kind() {
tcx.ensure_ok().type_of(uv.def);
}
}
}
}
}
match tcx.def_kind(def_id) {
DefKind::Static { .. } => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
check_static_inhabited(tcx, def_id);
check_static_linkage(tcx, def_id);
let ty = tcx.type_of(def_id).instantiate_identity();
res = res.and(wfcheck::check_static_item(
tcx, def_id, ty, /* should_check_for_sync */ true,
));
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
return res;
}
DefKind::Enum => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
crate::collect::lower_enum_variant_types(tcx, def_id);
check_enum(tcx, def_id);
check_variances_for_type_defn(tcx, def_id);
}
DefKind::Fn => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
tcx.ensure_ok().fn_sig(def_id);
tcx.ensure_ok().codegen_fn_attrs(def_id);
if let Some(i) = tcx.intrinsic(def_id) {
intrinsic::check_intrinsic_type(
tcx,
def_id,
tcx.def_ident_span(def_id).unwrap(),
i.name,
)
}
}
DefKind::Impl { of_trait } => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
tcx.ensure_ok().associated_items(def_id);
if of_trait {
let impl_trait_header = tcx.impl_trait_header(def_id);
res = res.and(
tcx.ensure_result()
.coherent_trait(impl_trait_header.trait_ref.instantiate_identity().def_id),
);
if res.is_ok() {
// Checking this only makes sense if the all trait impls satisfy basic
// requirements (see `coherent_trait` query), otherwise
// we run into infinite recursions a lot.
check_impl_items_against_trait(tcx, def_id, impl_trait_header);
}
}
}
DefKind::Trait => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().trait_def(def_id);
tcx.ensure_ok().explicit_super_predicates_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
tcx.ensure_ok().associated_items(def_id);
let assoc_items = tcx.associated_items(def_id);
for &assoc_item in assoc_items.in_definition_order() {
match assoc_item.kind {
ty::AssocKind::Type { .. } if assoc_item.defaultness(tcx).has_value() => {
let trait_args = GenericArgs::identity_for_item(tcx, def_id);
let _: Result<_, rustc_errors::ErrorGuaranteed> = check_type_bounds(
tcx,
assoc_item,
assoc_item,
ty::TraitRef::new_from_args(tcx, def_id.to_def_id(), trait_args),
);
}
_ => {}
}
}
}
DefKind::TraitAlias => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().explicit_implied_predicates_of(def_id);
tcx.ensure_ok().explicit_super_predicates_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
}
def_kind @ (DefKind::Struct | DefKind::Union) => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
let adt = tcx.adt_def(def_id).non_enum_variant();
for f in adt.fields.iter() {
tcx.ensure_ok().generics_of(f.did);
tcx.ensure_ok().type_of(f.did);
tcx.ensure_ok().predicates_of(f.did);
}
if let Some((_, ctor_def_id)) = adt.ctor {
crate::collect::lower_variant_ctor(tcx, ctor_def_id.expect_local());
}
match def_kind {
DefKind::Struct => check_struct(tcx, def_id),
DefKind::Union => check_union(tcx, def_id),
_ => unreachable!(),
}
check_variances_for_type_defn(tcx, def_id);
}
DefKind::OpaqueTy => {
check_opaque_precise_captures(tcx, def_id);
let origin = tcx.local_opaque_ty_origin(def_id);
if let hir::OpaqueTyOrigin::FnReturn { parent: fn_def_id, .. }
| hir::OpaqueTyOrigin::AsyncFn { parent: fn_def_id, .. } = origin
&& let hir::Node::TraitItem(trait_item) = tcx.hir_node_by_def_id(fn_def_id)
&& let (_, hir::TraitFn::Required(..)) = trait_item.expect_fn()
{
// Skip opaques from RPIT in traits with no default body.
} else {
check_opaque(tcx, def_id);
}
tcx.ensure_ok().predicates_of(def_id);
tcx.ensure_ok().explicit_item_bounds(def_id);
tcx.ensure_ok().explicit_item_self_bounds(def_id);
if tcx.is_conditionally_const(def_id) {
tcx.ensure_ok().explicit_implied_const_bounds(def_id);
tcx.ensure_ok().const_conditions(def_id);
}
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
return res;
}
DefKind::Const { .. } => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
res = res.and(enter_wf_checking_ctxt(tcx, def_id, |wfcx| {
let ty = tcx.type_of(def_id).instantiate_identity();
let ty_span = tcx.ty_span(def_id);
let ty = wfcx.deeply_normalize(ty_span, Some(WellFormedLoc::Ty(def_id)), ty);
wfcx.register_wf_obligation(ty_span, Some(WellFormedLoc::Ty(def_id)), ty.into());
wfcx.register_bound(
traits::ObligationCause::new(
ty_span,
def_id,
ObligationCauseCode::SizedConstOrStatic,
),
tcx.param_env(def_id),
ty,
tcx.require_lang_item(LangItem::Sized, ty_span),
);
check_where_clauses(wfcx, def_id);
if tcx.is_type_const(def_id) {
wfcheck::check_type_const(wfcx, def_id, ty, true)?;
}
Ok(())
}));
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
return res;
}
DefKind::TyAlias => {
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
check_type_alias_type_params_are_used(tcx, def_id);
let ty = tcx.type_of(def_id).instantiate_identity();
let span = tcx.def_span(def_id);
if tcx.type_alias_is_lazy(def_id) {
res = res.and(enter_wf_checking_ctxt(tcx, def_id, |wfcx| {
let item_ty = wfcx.deeply_normalize(span, Some(WellFormedLoc::Ty(def_id)), ty);
wfcx.register_wf_obligation(
span,
Some(WellFormedLoc::Ty(def_id)),
item_ty.into(),
);
check_where_clauses(wfcx, def_id);
Ok(())
}));
check_variances_for_type_defn(tcx, def_id);
} else {
res = res.and(enter_wf_checking_ctxt(tcx, def_id, |wfcx| {
// HACK: We sometimes incidentally check that const arguments have the correct
// type as a side effect of the anon const desugaring. To make this "consistent"
// for users we explicitly check `ConstArgHasType` clauses so that const args
// that don't go through an anon const still have their types checked.
//
// We use the unnormalized type as this mirrors the behaviour that we previously
// would have had when all const arguments were anon consts.
//
// Changing this to normalized obligations is a breaking change:
// `type Bar = [(); panic!()];` would become an error
if let Some(unnormalized_obligations) = wfcx.unnormalized_obligations(span, ty)
{
let filtered_obligations =
unnormalized_obligations.into_iter().filter(|o| {
matches!(o.predicate.kind().skip_binder(),
ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, _))
if matches!(ct.kind(), ty::ConstKind::Param(..)))
});
wfcx.ocx.register_obligations(filtered_obligations)
}
Ok(())
}));
}
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
return res;
}
DefKind::ForeignMod => {
let it = tcx.hir_expect_item(def_id);
let hir::ItemKind::ForeignMod { abi, items } = it.kind else {
return Ok(());
};
check_abi(tcx, it.hir_id(), it.span, abi);
for &item in items {
let def_id = item.owner_id.def_id;
let generics = tcx.generics_of(def_id);
let own_counts = generics.own_counts();
if generics.own_params.len() - own_counts.lifetimes != 0 {
let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
(_, 0) => ("type", "types", Some("u32")),
// We don't specify an example value, because we can't generate
// a valid value for any type.
(0, _) => ("const", "consts", None),
_ => ("type or const", "types or consts", None),
};
let name = if find_attr!(tcx, def_id, RustcEiiForeignItem) {
"externally implementable items"
} else {
"foreign items"
};
let span = tcx.def_span(def_id);
struct_span_code_err!(
tcx.dcx(),
span,
E0044,
"{name} may not have {kinds} parameters",
)
.with_span_label(span, format!("can't have {kinds} parameters"))
.with_help(
// FIXME: once we start storing spans for type arguments, turn this
// into a suggestion.
format!(
"replace the {} parameters with concrete {}{}",
kinds,
kinds_pl,
egs.map(|egs| format!(" like `{egs}`")).unwrap_or_default(),
),
)
.emit();
}
tcx.ensure_ok().generics_of(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
if tcx.is_conditionally_const(def_id) {
tcx.ensure_ok().explicit_implied_const_bounds(def_id);
tcx.ensure_ok().const_conditions(def_id);
}
match tcx.def_kind(def_id) {
DefKind::Fn => {
tcx.ensure_ok().codegen_fn_attrs(def_id);
tcx.ensure_ok().fn_sig(def_id);
let item = tcx.hir_foreign_item(item);
let hir::ForeignItemKind::Fn(sig, ..) = item.kind else { bug!() };
check_c_variadic_abi(tcx, sig.decl, abi, item.span);
}
DefKind::Static { .. } => {
tcx.ensure_ok().codegen_fn_attrs(def_id);
}
_ => (),
}
}
}
DefKind::Closure => {
// This is guaranteed to be called by metadata encoding,
// we still call it in wfcheck eagerly to ensure errors in codegen
// attrs prevent lints from spamming the output.
tcx.ensure_ok().codegen_fn_attrs(def_id);
// We do not call `type_of` for closures here as that
// depends on typecheck and would therefore hide
// any further errors in case one typeck fails.
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
return res;
}
DefKind::AssocFn => {
tcx.ensure_ok().codegen_fn_attrs(def_id);
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().fn_sig(def_id);
tcx.ensure_ok().predicates_of(def_id);
res = res.and(check_associated_item(tcx, def_id));
let assoc_item = tcx.associated_item(def_id);
match assoc_item.container {
ty::AssocContainer::InherentImpl | ty::AssocContainer::TraitImpl(_) => {}
ty::AssocContainer::Trait => {
res = res.and(check_trait_item(tcx, def_id));
}
}
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
return res;
}
DefKind::AssocConst { .. } => {
tcx.ensure_ok().type_of(def_id);
tcx.ensure_ok().predicates_of(def_id);
res = res.and(check_associated_item(tcx, def_id));
let assoc_item = tcx.associated_item(def_id);
match assoc_item.container {
ty::AssocContainer::InherentImpl | ty::AssocContainer::TraitImpl(_) => {}
ty::AssocContainer::Trait => {
res = res.and(check_trait_item(tcx, def_id));
}
}
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
return res;
}
DefKind::AssocTy => {
tcx.ensure_ok().predicates_of(def_id);
res = res.and(check_associated_item(tcx, def_id));
let assoc_item = tcx.associated_item(def_id);
let has_type = match assoc_item.container {
ty::AssocContainer::InherentImpl | ty::AssocContainer::TraitImpl(_) => true,
ty::AssocContainer::Trait => {
tcx.ensure_ok().explicit_item_bounds(def_id);
tcx.ensure_ok().explicit_item_self_bounds(def_id);
if tcx.is_conditionally_const(def_id) {
tcx.ensure_ok().explicit_implied_const_bounds(def_id);
tcx.ensure_ok().const_conditions(def_id);
}
res = res.and(check_trait_item(tcx, def_id));
assoc_item.defaultness(tcx).has_value()
}
};
if has_type {
tcx.ensure_ok().type_of(def_id);
}
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
return res;
}
// Only `Node::Item` and `Node::ForeignItem` still have HIR based
// checks. Returning early here does not miss any checks and
// avoids this query from having a direct dependency edge on the HIR
DefKind::AnonConst | DefKind::InlineConst => return res,
_ => {}
}
let node = tcx.hir_node_by_def_id(def_id);
res.and(match node {
hir::Node::Crate(_) => bug!("check_well_formed cannot be applied to the crate root"),
hir::Node::Item(item) => wfcheck::check_item(tcx, item),
hir::Node::ForeignItem(item) => wfcheck::check_foreign_item(tcx, item),
_ => unreachable!("{node:?}"),
})
}
pub(super) fn check_specialization_validity<'tcx>(
tcx: TyCtxt<'tcx>,
trait_def: &ty::TraitDef,
trait_item: ty::AssocItem,
impl_id: DefId,
impl_item: DefId,
) {
let Ok(ancestors) = trait_def.ancestors(tcx, impl_id) else { return };
let mut ancestor_impls = ancestors.skip(1).filter_map(|parent| {
if parent.is_from_trait() {
None
} else {
Some((parent, parent.item(tcx, trait_item.def_id)))
}
});
let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
match parent_item {
// Parent impl exists, and contains the parent item we're trying to specialize, but
// doesn't mark it `default`.
Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
Some(Err(parent_impl.def_id()))
}
// Parent impl contains item and makes it specializable.
Some(_) => Some(Ok(())),
// Parent impl doesn't mention the item. This means it's inherited from the
// grandparent. In that case, if parent is a `default impl`, inherited items use the
// "defaultness" from the grandparent, else they are final.
None => {
if tcx.defaultness(parent_impl.def_id()).is_default() {
None
} else {
Some(Err(parent_impl.def_id()))
}
}
}
});
// If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the
// item. This is allowed, the item isn't actually getting specialized here.
let result = opt_result.unwrap_or(Ok(()));
if let Err(parent_impl) = result {
if !tcx.is_impl_trait_in_trait(impl_item) {
let span = tcx.def_span(impl_item);
let ident = tcx.item_ident(impl_item);
let err = match tcx.span_of_impl(parent_impl) {
Ok(sp) => errors::ImplNotMarkedDefault::Ok { span, ident, ok_label: sp },
Err(cname) => errors::ImplNotMarkedDefault::Err { span, ident, cname },
};
tcx.dcx().emit_err(err);
} else {
tcx.dcx().delayed_bug(format!("parent item: {parent_impl:?} not marked as default"));
}
}
}
fn check_overriding_final_trait_item<'tcx>(
tcx: TyCtxt<'tcx>,
trait_item: ty::AssocItem,
impl_item: ty::AssocItem,
) {
if trait_item.defaultness(tcx).is_final() {
tcx.dcx().emit_err(errors::OverridingFinalTraitFunction {
impl_span: tcx.def_span(impl_item.def_id),
trait_span: tcx.def_span(trait_item.def_id),
ident: tcx.item_ident(impl_item.def_id),
});
}
}
fn check_impl_items_against_trait<'tcx>(
tcx: TyCtxt<'tcx>,
impl_id: LocalDefId,
impl_trait_header: ty::ImplTraitHeader<'tcx>,
) {
let trait_ref = impl_trait_header.trait_ref.instantiate_identity();
// If the trait reference itself is erroneous (so the compilation is going
// to fail), skip checking the items here -- the `impl_item` table in `tcx`
// isn't populated for such impls.
if trait_ref.references_error() {
return;
}
let impl_item_refs = tcx.associated_item_def_ids(impl_id);
// Negative impls are not expected to have any items
match impl_trait_header.polarity {
ty::ImplPolarity::Reservation | ty::ImplPolarity::Positive => {}
ty::ImplPolarity::Negative => {
if let [first_item_ref, ..] = *impl_item_refs {
let first_item_span = tcx.def_span(first_item_ref);
struct_span_code_err!(
tcx.dcx(),
first_item_span,
E0749,
"negative impls cannot have any items"
)
.emit();
}
return;
}
}
let trait_def = tcx.trait_def(trait_ref.def_id);
let self_is_guaranteed_unsize_self = tcx.impl_self_is_guaranteed_unsized(impl_id);
for &impl_item in impl_item_refs {
let ty_impl_item = tcx.associated_item(impl_item);
let ty_trait_item = match ty_impl_item.expect_trait_impl() {
Ok(trait_item_id) => tcx.associated_item(trait_item_id),
Err(ErrorGuaranteed { .. }) => continue,
};
let res = tcx.ensure_result().compare_impl_item(impl_item.expect_local());
if res.is_ok() {
match ty_impl_item.kind {
ty::AssocKind::Fn { .. } => {
compare_impl_item::refine::check_refining_return_position_impl_trait_in_trait(
tcx,
ty_impl_item,
ty_trait_item,
tcx.impl_trait_ref(ty_impl_item.container_id(tcx)).instantiate_identity(),
);
}
ty::AssocKind::Const { .. } => {}
ty::AssocKind::Type { .. } => {}
}
}
if self_is_guaranteed_unsize_self && tcx.generics_require_sized_self(ty_trait_item.def_id) {
tcx.emit_node_span_lint(
rustc_lint_defs::builtin::DEAD_CODE,
tcx.local_def_id_to_hir_id(ty_impl_item.def_id.expect_local()),
tcx.def_span(ty_impl_item.def_id),
errors::UselessImplItem,
)
}
check_specialization_validity(
tcx,
trait_def,
ty_trait_item,
impl_id.to_def_id(),
impl_item,
);
check_overriding_final_trait_item(tcx, ty_trait_item, ty_impl_item);
}
if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id.to_def_id()) {
// Check for missing items from trait
let mut missing_items = Vec::new();
let mut must_implement_one_of: Option<&[Ident]> =
trait_def.must_implement_one_of.as_deref();
for &trait_item_id in tcx.associated_item_def_ids(trait_ref.def_id) {
let leaf_def = ancestors.leaf_def(tcx, trait_item_id);
let is_implemented = leaf_def
.as_ref()
.is_some_and(|node_item| node_item.item.defaultness(tcx).has_value());
if !is_implemented
&& tcx.defaultness(impl_id).is_final()
// unsized types don't need to implement methods that have `Self: Sized` bounds.
&& !(self_is_guaranteed_unsize_self && tcx.generics_require_sized_self(trait_item_id))
{
missing_items.push(tcx.associated_item(trait_item_id));
}
// true if this item is specifically implemented in this impl
let is_implemented_here =
leaf_def.as_ref().is_some_and(|node_item| !node_item.defining_node.is_from_trait());
if !is_implemented_here {
let full_impl_span = tcx.hir_span_with_body(tcx.local_def_id_to_hir_id(impl_id));
match tcx.eval_default_body_stability(trait_item_id, full_impl_span) {
EvalResult::Deny { feature, reason, issue, .. } => default_body_is_unstable(
tcx,
full_impl_span,
trait_item_id,
feature,
reason,
issue,
),
// Unmarked default bodies are considered stable (at least for now).
EvalResult::Allow | EvalResult::Unmarked => {}
}
}
if let Some(required_items) = &must_implement_one_of {
if is_implemented_here {
let trait_item = tcx.associated_item(trait_item_id);
if required_items.contains(&trait_item.ident(tcx)) {
must_implement_one_of = None;
}
}
}
if let Some(leaf_def) = &leaf_def
&& !leaf_def.is_final()
&& let def_id = leaf_def.item.def_id
&& tcx.impl_method_has_trait_impl_trait_tys(def_id)
{
let def_kind = tcx.def_kind(def_id);
let descr = tcx.def_kind_descr(def_kind, def_id);
let (msg, feature) = if tcx.asyncness(def_id).is_async() {
(
format!("async {descr} in trait cannot be specialized"),
"async functions in traits",
)
} else {
(
format!(
"{descr} with return-position `impl Trait` in trait cannot be specialized"
),
"return position `impl Trait` in traits",
)
};
tcx.dcx()
.struct_span_err(tcx.def_span(def_id), msg)
.with_note(format!(
"specialization behaves in inconsistent and surprising ways with \
{feature}, and for now is disallowed"
))
.emit();
}
}
if !missing_items.is_empty() {
let full_impl_span = tcx.hir_span_with_body(tcx.local_def_id_to_hir_id(impl_id));
missing_items_err(tcx, impl_id, &missing_items, full_impl_span);
}
if let Some(missing_items) = must_implement_one_of {
let attr_span = find_attr!(tcx, trait_ref.def_id, RustcMustImplementOneOf {attr_span, ..} => *attr_span);
missing_items_must_implement_one_of_err(
tcx,
tcx.def_span(impl_id),
missing_items,
attr_span,
);
}
}
}
fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
let t = tcx.type_of(def_id).instantiate_identity();
if let ty::Adt(def, args) = t.kind()
&& def.is_struct()
{
let fields = &def.non_enum_variant().fields;
if fields.is_empty() {
struct_span_code_err!(tcx.dcx(), sp, E0075, "SIMD vector cannot be empty").emit();
return;
}
let array_field = &fields[FieldIdx::ZERO];
let array_ty = array_field.ty(tcx, args);
let ty::Array(element_ty, len_const) = array_ty.kind() else {
struct_span_code_err!(
tcx.dcx(),
sp,
E0076,
"SIMD vector's only field must be an array"
)
.with_span_label(tcx.def_span(array_field.did), "not an array")
.emit();
return;
};
if let Some(second_field) = fields.get(FieldIdx::ONE) {
struct_span_code_err!(tcx.dcx(), sp, E0075, "SIMD vector cannot have multiple fields")
.with_span_label(tcx.def_span(second_field.did), "excess field")
.emit();
return;
}
// FIXME(repr_simd): This check is nice, but perhaps unnecessary due to the fact
// we do not expect users to implement their own `repr(simd)` types. If they could,
// this check is easily side-steppable by hiding the const behind normalization.
// The consequence is that the error is, in general, only observable post-mono.
if let Some(len) = len_const.try_to_target_usize(tcx) {
if len == 0 {
struct_span_code_err!(tcx.dcx(), sp, E0075, "SIMD vector cannot be empty").emit();
return;
} else if len > MAX_SIMD_LANES {
struct_span_code_err!(
tcx.dcx(),
sp,
E0075,
"SIMD vector cannot have more than {MAX_SIMD_LANES} elements",
)
.emit();
return;
}
}
// Check that we use types valid for use in the lanes of a SIMD "vector register"
// These are scalar types which directly match a "machine" type
// Yes: Integers, floats, "thin" pointers
// No: char, "wide" pointers, compound types
match element_ty.kind() {
ty::Param(_) => (), // pass struct<T>([T; 4]) through, let monomorphization catch errors
ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_, _) => (), // struct([u8; 4]) is ok
_ => {
struct_span_code_err!(
tcx.dcx(),
sp,
E0077,
"SIMD vector element type should be a \
primitive scalar (integer/float/pointer) type"
)
.emit();
return;
}
}
}
}
#[tracing::instrument(skip(tcx), level = "debug")]
fn check_scalable_vector(tcx: TyCtxt<'_>, span: Span, def_id: LocalDefId, scalable: ScalableElt) {
let ty = tcx.type_of(def_id).instantiate_identity();
let ty::Adt(def, args) = ty.kind() else { return };
if !def.is_struct() {
tcx.dcx().delayed_bug("`rustc_scalable_vector` applied to non-struct");
return;
}
let fields = &def.non_enum_variant().fields;
match scalable {
ScalableElt::ElementCount(..) if fields.is_empty() => {
let mut err =
tcx.dcx().struct_span_err(span, "scalable vectors must have a single field");
err.help("scalable vector types' only field must be a primitive scalar type");
err.emit();
return;
}
ScalableElt::ElementCount(..) if fields.len() >= 2 => {
tcx.dcx().struct_span_err(span, "scalable vectors cannot have multiple fields").emit();
return;
}
ScalableElt::Container if fields.is_empty() => {
let mut err = tcx
.dcx()
.struct_span_err(span, "scalable vector tuples must have at least one field");
err.help("tuples of scalable vectors can only contain multiple of the same scalable vector type");
err.emit();
return;
}
ScalableElt::Container if fields.len() > 8 => {
let mut err = tcx
.dcx()
.struct_span_err(span, "scalable vector tuples can have at most eight fields");
err.help("tuples of scalable vectors can only contain multiple of the same scalable vector type");
err.emit();
return;
}
_ => {}
}
match scalable {
ScalableElt::ElementCount(..) => {
let element_ty = &fields[FieldIdx::ZERO].ty(tcx, args);
// Check that `element_ty` only uses types valid in the lanes of a scalable vector
// register: scalar types which directly match a "machine" type - integers, floats and
// bools
match element_ty.kind() {
ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Bool => (),
_ => {
let mut err = tcx.dcx().struct_span_err(
span,
"element type of a scalable vector must be a primitive scalar",
);
err.help("only `u*`, `i*`, `f*` and `bool` types are accepted");
err.emit();
}
}
}
ScalableElt::Container => {
let mut prev_field_ty = None;
for field in fields.iter() {
let element_ty = field.ty(tcx, args);
if let ty::Adt(def, _) = element_ty.kind()
&& def.repr().scalable()
{
match def
.repr()
.scalable
.expect("`repr().scalable.is_some()` != `repr().scalable()`")
{
ScalableElt::ElementCount(_) => { /* expected field */ }
ScalableElt::Container => {
tcx.dcx().span_err(
tcx.def_span(field.did),
"scalable vector structs cannot contain other scalable vector structs",
);
break;
}
}
} else {
tcx.dcx().span_err(
tcx.def_span(field.did),
"scalable vector structs can only have scalable vector fields",
);
break;
}
if let Some(prev_ty) = prev_field_ty.replace(element_ty)
&& prev_ty != element_ty
{
tcx.dcx().span_err(
tcx.def_span(field.did),
"all fields in a scalable vector struct must be the same type",
);
break;
}
}
}
}
}
pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: ty::AdtDef<'_>) {
let repr = def.repr();
if repr.packed() {
if let Some(reprs) = find_attr!(tcx, def.did(), Repr { reprs, .. } => reprs) {
for (r, _) in reprs {
if let ReprPacked(pack) = r
&& let Some(repr_pack) = repr.pack
&& pack != &repr_pack
{
struct_span_code_err!(
tcx.dcx(),
sp,
E0634,
"type has conflicting packed representation hints"
)
.emit();
}
}
}
if repr.align.is_some() {
struct_span_code_err!(
tcx.dcx(),
sp,
E0587,
"type has conflicting packed and align representation hints"
)
.emit();
} else if let Some(def_spans) = check_packed_inner(tcx, def.did(), &mut vec![]) {
let mut err = struct_span_code_err!(
tcx.dcx(),
sp,
E0588,
"packed type cannot transitively contain a `#[repr(align)]` type"
);
err.span_note(
tcx.def_span(def_spans[0].0),
format!("`{}` has a `#[repr(align)]` attribute", tcx.item_name(def_spans[0].0)),
);
if def_spans.len() > 2 {
let mut first = true;
for (adt_def, span) in def_spans.iter().skip(1).rev() {
let ident = tcx.item_name(*adt_def);
err.span_note(
*span,
if first {
format!(
"`{}` contains a field of type `{}`",
tcx.type_of(def.did()).instantiate_identity(),
ident
)
} else {
format!("...which contains a field of type `{ident}`")
},
);
first = false;
}
}
err.emit();
}
}
}
pub(super) fn check_packed_inner(
tcx: TyCtxt<'_>,
def_id: DefId,
stack: &mut Vec<DefId>,
) -> Option<Vec<(DefId, Span)>> {
if let ty::Adt(def, args) = tcx.type_of(def_id).instantiate_identity().kind() {
if def.is_struct() || def.is_union() {
if def.repr().align.is_some() {
return Some(vec![(def.did(), DUMMY_SP)]);
}
stack.push(def_id);
for field in &def.non_enum_variant().fields {
if let ty::Adt(def, _) = field.ty(tcx, args).kind()
&& !stack.contains(&def.did())
&& let Some(mut defs) = check_packed_inner(tcx, def.did(), stack)
{
defs.push((def.did(), field.ident(tcx).span));
return Some(defs);
}
}
stack.pop();
}
}
None
}
pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>) {
struct ZeroSizedFieldReprTransparentIncompatibility<'tcx> {
unsuited: UnsuitedInfo<'tcx>,
}
impl<'a, 'tcx> Diagnostic<'a, ()> for ZeroSizedFieldReprTransparentIncompatibility<'tcx> {
fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, ()> {
let Self { unsuited } = self;
let (title, note) = match unsuited.reason {
UnsuitedReason::NonExhaustive => (
"external non-exhaustive types",
"is marked with `#[non_exhaustive]`, so it could become non-zero-sized in the future.",
),
UnsuitedReason::PrivateField => (
"external types with private fields",
"contains private fields, so it could become non-zero-sized in the future.",
),
UnsuitedReason::ReprC => (
"`repr(C)` types",
"is a `#[repr(C)]` type, so it is not guaranteed to be zero-sized on all targets.",
),
};
Diag::new(
dcx,
level,
format!("zero-sized fields in `repr(transparent)` cannot contain {title}"),
)
.with_note(format!(
"this field contains `{field_ty}`, which {note}",
field_ty = unsuited.ty,
))
}
}
if !adt.repr().transparent() {
return;
}
if adt.is_union() && !tcx.features().transparent_unions() {
feature_err(
&tcx.sess,
sym::transparent_unions,
tcx.def_span(adt.did()),
"transparent unions are unstable",
)
.emit();
}
if adt.variants().len() != 1 {
bad_variant_count(tcx, adt, tcx.def_span(adt.did()), adt.did());
// Don't bother checking the fields.
return;
}
let typing_env = ty::TypingEnv::non_body_analysis(tcx, adt.did());
// For each field, figure out if it has "trivial" layout (i.e., is a 1-ZST).
struct FieldInfo<'tcx> {
span: Span,
trivial: bool,
ty: Ty<'tcx>,
}
let field_infos = adt.all_fields().map(|field| {
let ty = field.ty(tcx, GenericArgs::identity_for_item(tcx, field.did));
let layout = tcx.layout_of(typing_env.as_query_input(ty));
// We are currently checking the type this field came from, so it must be local
let span = tcx.hir_span_if_local(field.did).unwrap();
let trivial = layout.is_ok_and(|layout| layout.is_1zst());
FieldInfo { span, trivial, ty }
});
let non_trivial_fields = field_infos
.clone()
.filter_map(|field| if !field.trivial { Some(field.span) } else { None });
let non_trivial_count = non_trivial_fields.clone().count();
if non_trivial_count >= 2 {
bad_non_zero_sized_fields(
tcx,
adt,
non_trivial_count,
non_trivial_fields,
tcx.def_span(adt.did()),
);
return;
}
// Even some 1-ZST fields are not allowed though, if they have `non_exhaustive` or private
// fields or `repr(C)`. We call those fields "unsuited".
struct UnsuitedInfo<'tcx> {
/// The source of the problem, a type that is found somewhere within the field type.
ty: Ty<'tcx>,
reason: UnsuitedReason,
}
enum UnsuitedReason {
NonExhaustive,
PrivateField,
ReprC,
}
fn check_unsuited<'tcx>(
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
ty: Ty<'tcx>,
) -> ControlFlow<UnsuitedInfo<'tcx>> {
// We can encounter projections during traversal, so ensure the type is normalized.
let ty = tcx.try_normalize_erasing_regions(typing_env, ty).unwrap_or(ty);
match ty.kind() {
ty::Tuple(list) => list.iter().try_for_each(|t| check_unsuited(tcx, typing_env, t)),
ty::Array(ty, _) => check_unsuited(tcx, typing_env, *ty),
ty::Adt(def, args) => {
if !def.did().is_local() && !find_attr!(tcx, def.did(), RustcPubTransparent(_)) {
let non_exhaustive = def.is_variant_list_non_exhaustive()
|| def.variants().iter().any(ty::VariantDef::is_field_list_non_exhaustive);
let has_priv = def.all_fields().any(|f| !f.vis.is_public());
if non_exhaustive || has_priv {
return ControlFlow::Break(UnsuitedInfo {
ty,
reason: if non_exhaustive {
UnsuitedReason::NonExhaustive
} else {
UnsuitedReason::PrivateField
},
});
}
}
if def.repr().c() {
return ControlFlow::Break(UnsuitedInfo { ty, reason: UnsuitedReason::ReprC });
}
def.all_fields()
.map(|field| field.ty(tcx, args))
.try_for_each(|t| check_unsuited(tcx, typing_env, t))
}
_ => ControlFlow::Continue(()),
}
}
let mut prev_unsuited_1zst = false;
for field in field_infos {
if field.trivial
&& let Some(unsuited) = check_unsuited(tcx, typing_env, field.ty).break_value()
{
// If there are any non-trivial fields, then there can be no non-exhaustive 1-zsts.
// Otherwise, it's only an issue if there's >1 non-exhaustive 1-zst.
if non_trivial_count > 0 || prev_unsuited_1zst {
tcx.emit_node_span_lint(
REPR_TRANSPARENT_NON_ZST_FIELDS,
tcx.local_def_id_to_hir_id(adt.did().expect_local()),
field.span,
ZeroSizedFieldReprTransparentIncompatibility { unsuited },
);
} else {
prev_unsuited_1zst = true;
}
}
}
}
#[allow(trivial_numeric_casts)]
fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) {
let def = tcx.adt_def(def_id);
def.destructor(tcx); // force the destructor to be evaluated
if def.variants().is_empty() {
find_attr!(tcx, def_id, Repr { reprs, first_span } => {
struct_span_code_err!(
tcx.dcx(),
reprs.first().map(|repr| repr.1).unwrap_or(*first_span),
E0084,
"unsupported representation for zero-variant enum"
)
.with_span_label(tcx.def_span(def_id), "zero-variant enum")
.emit();
});
}
for v in def.variants() {
if let ty::VariantDiscr::Explicit(discr_def_id) = v.discr {
tcx.ensure_ok().typeck(discr_def_id.expect_local());
}
}
if def.repr().int.is_none() {
let is_unit = |var: &ty::VariantDef| matches!(var.ctor_kind(), Some(CtorKind::Const));
let get_disr = |var: &ty::VariantDef| match var.discr {
ty::VariantDiscr::Explicit(disr) => Some(disr),
ty::VariantDiscr::Relative(_) => None,
};
let non_unit = def.variants().iter().find(|var| !is_unit(var));
let disr_unit =
def.variants().iter().filter(|var| is_unit(var)).find_map(|var| get_disr(var));
let disr_non_unit =
def.variants().iter().filter(|var| !is_unit(var)).find_map(|var| get_disr(var));
if disr_non_unit.is_some() || (disr_unit.is_some() && non_unit.is_some()) {
let mut err = struct_span_code_err!(
tcx.dcx(),
tcx.def_span(def_id),
E0732,
"`#[repr(inttype)]` must be specified for enums with explicit discriminants and non-unit variants"
);
if let Some(disr_non_unit) = disr_non_unit {
err.span_label(
tcx.def_span(disr_non_unit),
"explicit discriminant on non-unit variant specified here",
);
} else {
err.span_label(
tcx.def_span(disr_unit.unwrap()),
"explicit discriminant specified here",
);
err.span_label(
tcx.def_span(non_unit.unwrap().def_id),
"non-unit discriminant declared here",
);
}
err.emit();
}
}
detect_discriminant_duplicate(tcx, def);
check_transparent(tcx, def);
}
/// Part of enum check. Given the discriminants of an enum, errors if two or more discriminants are equal
fn detect_discriminant_duplicate<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>) {
// Helper closure to reduce duplicate code. This gets called everytime we detect a duplicate.
// Here `idx` refers to the order of which the discriminant appears, and its index in `vs`
let report = |dis: Discr<'tcx>, idx, err: &mut Diag<'_>| {
let var = adt.variant(idx); // HIR for the duplicate discriminant
let (span, display_discr) = match var.discr {
ty::VariantDiscr::Explicit(discr_def_id) => {
// In the case the discriminant is both a duplicate and overflowed, let the user know
if let hir::Node::AnonConst(expr) =
tcx.hir_node_by_def_id(discr_def_id.expect_local())
&& let hir::ExprKind::Lit(lit) = &tcx.hir_body(expr.body).value.kind
&& let rustc_ast::LitKind::Int(lit_value, _int_kind) = &lit.node
&& *lit_value != dis.val
{
(tcx.def_span(discr_def_id), format!("`{dis}` (overflowed from `{lit_value}`)"))
} else {
// Otherwise, format the value as-is
(tcx.def_span(discr_def_id), format!("`{dis}`"))
}
}
// This should not happen.
ty::VariantDiscr::Relative(0) => (tcx.def_span(var.def_id), format!("`{dis}`")),
ty::VariantDiscr::Relative(distance_to_explicit) => {
// At this point we know this discriminant is a duplicate, and was not explicitly
// assigned by the user. Here we iterate backwards to fetch the HIR for the last
// explicitly assigned discriminant, and letting the user know that this was the
// increment startpoint, and how many steps from there leading to the duplicate
if let Some(explicit_idx) =
idx.as_u32().checked_sub(distance_to_explicit).map(VariantIdx::from_u32)
{
let explicit_variant = adt.variant(explicit_idx);
let ve_ident = var.name;
let ex_ident = explicit_variant.name;
let sp = if distance_to_explicit > 1 { "variants" } else { "variant" };
err.span_label(
tcx.def_span(explicit_variant.def_id),
format!(
"discriminant for `{ve_ident}` incremented from this startpoint \
(`{ex_ident}` + {distance_to_explicit} {sp} later \
=> `{ve_ident}` = {dis})"
),
);
}
(tcx.def_span(var.def_id), format!("`{dis}`"))
}
};
err.span_label(span, format!("{display_discr} assigned here"));
};
let mut discrs = adt.discriminants(tcx).collect::<Vec<_>>();
// Here we loop through the discriminants, comparing each discriminant to another.
// When a duplicate is detected, we instantiate an error and point to both
// initial and duplicate value. The duplicate discriminant is then discarded by swapping
// it with the last element and decrementing the `vec.len` (which is why we have to evaluate
// `discrs.len()` anew every iteration, and why this could be tricky to do in a functional
// style as we are mutating `discrs` on the fly).
let mut i = 0;
while i < discrs.len() {
let var_i_idx = discrs[i].0;
let mut error: Option<Diag<'_, _>> = None;
let mut o = i + 1;
while o < discrs.len() {
let var_o_idx = discrs[o].0;
if discrs[i].1.val == discrs[o].1.val {
let err = error.get_or_insert_with(|| {
let mut ret = struct_span_code_err!(
tcx.dcx(),
tcx.def_span(adt.did()),
E0081,
"discriminant value `{}` assigned more than once",
discrs[i].1,
);
report(discrs[i].1, var_i_idx, &mut ret);
ret
});
report(discrs[o].1, var_o_idx, err);
// Safe to unwrap here, as we wouldn't reach this point if `discrs` was empty
discrs[o] = *discrs.last().unwrap();
discrs.pop();
} else {
o += 1;
}
}
if let Some(e) = error {
e.emit();
}
i += 1;
}
}
fn check_type_alias_type_params_are_used<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) {
if tcx.type_alias_is_lazy(def_id) {
// Since we compute the variances for lazy type aliases and already reject bivariant
// parameters as unused, we can and should skip this check for lazy type aliases.
return;
}
let generics = tcx.generics_of(def_id);
if generics.own_counts().types == 0 {
return;
}
let ty = tcx.type_of(def_id).instantiate_identity();
if ty.references_error() {
// If there is already another error, do not emit an error for not using a type parameter.
return;
}
// Lazily calculated because it is only needed in case of an error.
let bounded_params = LazyCell::new(|| {
tcx.explicit_predicates_of(def_id)
.predicates
.iter()
.filter_map(|(predicate, span)| {
let bounded_ty = match predicate.kind().skip_binder() {
ty::ClauseKind::Trait(pred) => pred.trait_ref.self_ty(),
ty::ClauseKind::TypeOutlives(pred) => pred.0,
_ => return None,
};
if let ty::Param(param) = bounded_ty.kind() {
Some((param.index, span))
} else {
None
}
})
// FIXME: This assumes that elaborated `Sized` bounds come first (which does hold at the
// time of writing). This is a bit fragile since we later use the span to detect elaborated
// `Sized` bounds. If they came last for example, this would break `Trait + /*elab*/Sized`
// since it would overwrite the span of the user-written bound. This could be fixed by
// folding the spans with `Span::to` which requires a bit of effort I think.
.collect::<FxIndexMap<_, _>>()
});
let mut params_used = DenseBitSet::new_empty(generics.own_params.len());
for leaf in ty.walk() {
if let GenericArgKind::Type(leaf_ty) = leaf.kind()
&& let ty::Param(param) = leaf_ty.kind()
{
debug!("found use of ty param {:?}", param);
params_used.insert(param.index);
}
}
for param in &generics.own_params {
if !params_used.contains(param.index)
&& let ty::GenericParamDefKind::Type { .. } = param.kind
{
let span = tcx.def_span(param.def_id);
let param_name = Ident::new(param.name, span);
// The corresponding predicates are post-`Sized`-elaboration. Therefore we
// * check for emptiness to detect lone user-written `?Sized` bounds
// * compare the param span to the pred span to detect lone user-written `Sized` bounds
let has_explicit_bounds = bounded_params.is_empty()
|| (*bounded_params).get(&param.index).is_some_and(|&&pred_sp| pred_sp != span);
let const_param_help = !has_explicit_bounds;
let mut diag = tcx.dcx().create_err(errors::UnusedGenericParameter {
span,
param_name,
param_def_kind: tcx.def_descr(param.def_id),
help: errors::UnusedGenericParameterHelp::TyAlias { param_name },
usage_spans: vec![],
const_param_help,
});
diag.code(E0091);
diag.emit();
}
}
}
/// Emit an error for recursive opaque types.
///
/// If this is a return `impl Trait`, find the item's return expressions and point at them. For
/// direct recursion this is enough, but for indirect recursion also point at the last intermediary
/// `impl Trait`.
///
/// If all the return expressions evaluate to `!`, then we explain that the error will go away
/// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder.
fn opaque_type_cycle_error(tcx: TyCtxt<'_>, opaque_def_id: LocalDefId) -> ErrorGuaranteed {
let span = tcx.def_span(opaque_def_id);
let mut err = struct_span_code_err!(tcx.dcx(), span, E0720, "cannot resolve opaque type");
let mut label = false;
if let Some((def_id, visitor)) = get_owner_return_paths(tcx, opaque_def_id) {
let typeck_results = tcx.typeck(def_id);
if visitor
.returns
.iter()
.filter_map(|expr| typeck_results.node_type_opt(expr.hir_id))
.all(|ty| matches!(ty.kind(), ty::Never))
{
let spans = visitor
.returns
.iter()
.filter(|expr| typeck_results.node_type_opt(expr.hir_id).is_some())
.map(|expr| expr.span)
.collect::<Vec<Span>>();
let span_len = spans.len();
if span_len == 1 {
err.span_label(spans[0], "this returned value is of `!` type");
} else {
let mut multispan: MultiSpan = spans.clone().into();
for span in spans {
multispan.push_span_label(span, "this returned value is of `!` type");
}
err.span_note(multispan, "these returned values have a concrete \"never\" type");
}
err.help("this error will resolve once the item's body returns a concrete type");
} else {
let mut seen = FxHashSet::default();
seen.insert(span);
err.span_label(span, "recursive opaque type");
label = true;
for (sp, ty) in visitor
.returns
.iter()
.filter_map(|e| typeck_results.node_type_opt(e.hir_id).map(|t| (e.span, t)))
.filter(|(_, ty)| !matches!(ty.kind(), ty::Never))
{
#[derive(Default)]
struct OpaqueTypeCollector {
opaques: Vec<DefId>,
closures: Vec<DefId>,
}
impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector {
fn visit_ty(&mut self, t: Ty<'tcx>) {
match *t.kind() {
ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => {
self.opaques.push(def);
}
ty::Closure(def_id, ..) | ty::Coroutine(def_id, ..) => {
self.closures.push(def_id);
t.super_visit_with(self);
}
_ => t.super_visit_with(self),
}
}
}
let mut visitor = OpaqueTypeCollector::default();
ty.visit_with(&mut visitor);
for def_id in visitor.opaques {
let ty_span = tcx.def_span(def_id);
if !seen.contains(&ty_span) {
let descr = if ty.is_impl_trait() { "opaque " } else { "" };
err.span_label(ty_span, format!("returning this {descr}type `{ty}`"));
seen.insert(ty_span);
}
err.span_label(sp, format!("returning here with type `{ty}`"));
}
for closure_def_id in visitor.closures {
let Some(closure_local_did) = closure_def_id.as_local() else {
continue;
};
let typeck_results = tcx.typeck(closure_local_did);
let mut label_match = |ty: Ty<'_>, span| {
for arg in ty.walk() {
if let ty::GenericArgKind::Type(ty) = arg.kind()
&& let ty::Alias(
ty::Opaque,
ty::AliasTy { def_id: captured_def_id, .. },
) = *ty.kind()
&& captured_def_id == opaque_def_id.to_def_id()
{
err.span_label(
span,
format!(
"{} captures itself here",
tcx.def_descr(closure_def_id)
),
);
}
}
};
// Label any closure upvars that capture the opaque
for capture in typeck_results.closure_min_captures_flattened(closure_local_did)
{
label_match(capture.place.ty(), capture.get_path_span(tcx));
}
// Label any coroutine locals that capture the opaque
if tcx.is_coroutine(closure_def_id)
&& let Some(coroutine_layout) = tcx.mir_coroutine_witnesses(closure_def_id)
{
for interior_ty in &coroutine_layout.field_tys {
label_match(interior_ty.ty, interior_ty.source_info.span);
}
}
}
}
}
}
if !label {
err.span_label(span, "cannot resolve opaque type");
}
err.emit()
}
pub(super) fn check_coroutine_obligations(
tcx: TyCtxt<'_>,
def_id: LocalDefId,
) -> Result<(), ErrorGuaranteed> {
debug_assert!(!tcx.is_typeck_child(def_id.to_def_id()));
let typeck_results = tcx.typeck(def_id);
let param_env = tcx.param_env(def_id);
debug!(?typeck_results.coroutine_stalled_predicates);
let mode = if tcx.next_trait_solver_globally() {
// This query is conceptually between HIR typeck and
// MIR borrowck. We use the opaque types defined by HIR
// and ignore region constraints.
TypingMode::borrowck(tcx, def_id)
} else {
TypingMode::analysis_in_body(tcx, def_id)
};
// Typeck writeback gives us predicates with their regions erased.
// We only need to check the goals while ignoring lifetimes to give good
// error message and to avoid breaking the assumption of `mir_borrowck`
// that all obligations already hold modulo regions.
let infcx = tcx.infer_ctxt().ignoring_regions().build(mode);
let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
for (predicate, cause) in &typeck_results.coroutine_stalled_predicates {
ocx.register_obligation(Obligation::new(tcx, cause.clone(), param_env, *predicate));
}
let errors = ocx.evaluate_obligations_error_on_ambiguity();
debug!(?errors);
if !errors.is_empty() {
return Err(infcx.err_ctxt().report_fulfillment_errors(errors));
}
if !tcx.next_trait_solver_globally() {
// Check that any hidden types found when checking these stalled coroutine obligations
// are valid.
for (key, ty) in infcx.take_opaque_types() {
let hidden_type = infcx.resolve_vars_if_possible(ty);
let key = infcx.resolve_vars_if_possible(key);
sanity_check_found_hidden_type(tcx, key, hidden_type)?;
}
} else {
// We're not checking region constraints here, so we can simply drop the
// added opaque type uses in `TypingMode::Borrowck`.
let _ = infcx.take_opaque_types();
}
Ok(())
}
pub(super) fn check_potentially_region_dependent_goals<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
) -> Result<(), ErrorGuaranteed> {
if !tcx.next_trait_solver_globally() {
return Ok(());
}
let typeck_results = tcx.typeck(def_id);
let param_env = tcx.param_env(def_id);
// We use `TypingMode::Borrowck` as we want to use the opaque types computed by HIR typeck.
let typing_mode = TypingMode::borrowck(tcx, def_id);
let infcx = tcx.infer_ctxt().ignoring_regions().build(typing_mode);
let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
for (predicate, cause) in &typeck_results.potentially_region_dependent_goals {
let predicate = fold_regions(tcx, *predicate, |_, _| {
infcx.next_region_var(RegionVariableOrigin::Misc(cause.span))
});
ocx.register_obligation(Obligation::new(tcx, cause.clone(), param_env, predicate));
}
let errors = ocx.evaluate_obligations_error_on_ambiguity();
debug!(?errors);
if errors.is_empty() { Ok(()) } else { Err(infcx.err_ctxt().report_fulfillment_errors(errors)) }
}