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fuchsia / third_party / rust / 57e8fc56852e7728d7160242bf13c3ab6e066bd8 / . / compiler / rustc_typeck / src / check / fn_ctxt.rs
blob: 79d6c7dbfdae264e980b88b96c498bb6fb5e4ddf [file] [log] [blame]
// ignore-tidy-filelength
// FIXME: This file seems to have too much functionality wrapped into it,
// leading to it being too long.
// Splitting this file may involve abstracting functionality into other files.
use super::callee::{self, DeferredCallResolution};
use super::coercion::{CoerceMany, DynamicCoerceMany};
use super::method::{self, MethodCallee, SelfSource};
use super::Expectation::*;
use super::TupleArgumentsFlag::*;
use super::{
potentially_plural_count, struct_span_err, BreakableCtxt, Diverges, EnclosingBreakables,
Expectation, FallbackMode, Inherited, LocalTy, Needs, TupleArgumentsFlag, UnsafetyState,
};
use crate::astconv::{
AstConv, ExplicitLateBound, GenericArgCountMismatch, GenericArgCountResult, PathSeg,
};
use rustc_ast as ast;
use rustc_ast::util::parser::ExprPrecedence;
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::ErrorReported;
use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticId};
use rustc_hir as hir;
use rustc_hir::def::{CtorOf, DefKind, Res};
use rustc_hir::def_id::DefId;
use rustc_hir::lang_items::LangItem;
use rustc_hir::{ExprKind, GenericArg, ItemKind, Node, QPath};
use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_infer::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
use rustc_infer::infer::{self, InferOk, InferResult};
use rustc_middle::hir::map::blocks::FnLikeNode;
use rustc_middle::ty::adjustment::{
Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
};
use rustc_middle::ty::fold::TypeFoldable;
use rustc_middle::ty::subst::{
self, GenericArgKind, InternalSubsts, Subst, SubstsRef, UserSelfTy, UserSubsts,
};
use rustc_middle::ty::{
self, AdtKind, CanonicalUserType, Const, DefIdTree, GenericParamDefKind, ToPolyTraitRef,
ToPredicate, Ty, TyCtxt, UserType,
};
use rustc_session::{lint, Session};
use rustc_span::hygiene::DesugaringKind;
use rustc_span::source_map::{original_sp, DUMMY_SP};
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::{self, BytePos, MultiSpan, Span};
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::opaque_types::InferCtxtExt as _;
use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
use rustc_trait_selection::traits::{
self, ObligationCause, ObligationCauseCode, TraitEngine, TraitEngineExt,
};
use std::cell::{Cell, RefCell};
use std::collections::hash_map::Entry;
use std::iter;
use std::mem::replace;
use std::ops::Deref;
use std::slice;
pub struct FnCtxt<'a, 'tcx> {
pub(super) body_id: hir::HirId,
/// The parameter environment used for proving trait obligations
/// in this function. This can change when we descend into
/// closures (as they bring new things into scope), hence it is
/// not part of `Inherited` (as of the time of this writing,
/// closures do not yet change the environment, but they will
/// eventually).
pub(super) param_env: ty::ParamEnv<'tcx>,
/// Number of errors that had been reported when we started
/// checking this function. On exit, if we find that *more* errors
/// have been reported, we will skip regionck and other work that
/// expects the types within the function to be consistent.
// FIXME(matthewjasper) This should not exist, and it's not correct
// if type checking is run in parallel.
err_count_on_creation: usize,
/// If `Some`, this stores coercion information for returned
/// expressions. If `None`, this is in a context where return is
/// inappropriate, such as a const expression.
///
/// This is a `RefCell<DynamicCoerceMany>`, which means that we
/// can track all the return expressions and then use them to
/// compute a useful coercion from the set, similar to a match
/// expression or other branching context. You can use methods
/// like `expected_ty` to access the declared return type (if
/// any).
pub(super) ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
pub(super) ret_coercion_impl_trait: Option<Ty<'tcx>>,
pub(super) ret_type_span: Option<Span>,
/// Used exclusively to reduce cost of advanced evaluation used for
/// more helpful diagnostics.
pub(super) in_tail_expr: bool,
/// First span of a return site that we find. Used in error messages.
pub(super) ret_coercion_span: RefCell<Option<Span>>,
pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
pub(super) ps: RefCell<UnsafetyState>,
/// Whether the last checked node generates a divergence (e.g.,
/// `return` will set this to `Always`). In general, when entering
/// an expression or other node in the tree, the initial value
/// indicates whether prior parts of the containing expression may
/// have diverged. It is then typically set to `Maybe` (and the
/// old value remembered) for processing the subparts of the
/// current expression. As each subpart is processed, they may set
/// the flag to `Always`, etc. Finally, at the end, we take the
/// result and "union" it with the original value, so that when we
/// return the flag indicates if any subpart of the parent
/// expression (up to and including this part) has diverged. So,
/// if you read it after evaluating a subexpression `X`, the value
/// you get indicates whether any subexpression that was
/// evaluating up to and including `X` diverged.
///
/// We currently use this flag only for diagnostic purposes:
///
/// - To warn about unreachable code: if, after processing a
/// sub-expression but before we have applied the effects of the
/// current node, we see that the flag is set to `Always`, we
/// can issue a warning. This corresponds to something like
/// `foo(return)`; we warn on the `foo()` expression. (We then
/// update the flag to `WarnedAlways` to suppress duplicate
/// reports.) Similarly, if we traverse to a fresh statement (or
/// tail expression) from a `Always` setting, we will issue a
/// warning. This corresponds to something like `{return;
/// foo();}` or `{return; 22}`, where we would warn on the
/// `foo()` or `22`.
///
/// An expression represents dead code if, after checking it,
/// the diverges flag is set to something other than `Maybe`.
pub(super) diverges: Cell<Diverges>,
/// Whether any child nodes have any type errors.
pub(super) has_errors: Cell<bool>,
pub(super) enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
pub(super) inh: &'a Inherited<'a, 'tcx>,
}
impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
pub fn new(
inh: &'a Inherited<'a, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
body_id: hir::HirId,
) -> FnCtxt<'a, 'tcx> {
FnCtxt {
body_id,
param_env,
err_count_on_creation: inh.tcx.sess.err_count(),
ret_coercion: None,
ret_coercion_impl_trait: None,
ret_type_span: None,
in_tail_expr: false,
ret_coercion_span: RefCell::new(None),
resume_yield_tys: None,
ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
diverges: Cell::new(Diverges::Maybe),
has_errors: Cell::new(false),
enclosing_breakables: RefCell::new(EnclosingBreakables {
stack: Vec::new(),
by_id: Default::default(),
}),
inh,
}
}
pub fn sess(&self) -> &Session {
&self.tcx.sess
}
pub fn errors_reported_since_creation(&self) -> bool {
self.tcx.sess.err_count() > self.err_count_on_creation
}
/// Produces warning on the given node, if the current point in the
/// function is unreachable, and there hasn't been another warning.
pub(super) fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
// FIXME: Combine these two 'if' expressions into one once
// let chains are implemented
if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
// If span arose from a desugaring of `if` or `while`, then it is the condition itself,
// which diverges, that we are about to lint on. This gives suboptimal diagnostics.
// Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
if !span.is_desugaring(DesugaringKind::CondTemporary)
&& !span.is_desugaring(DesugaringKind::Async)
&& !orig_span.is_desugaring(DesugaringKind::Await)
{
self.diverges.set(Diverges::WarnedAlways);
debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, |lint| {
let msg = format!("unreachable {}", kind);
lint.build(&msg)
.span_label(span, &msg)
.span_label(
orig_span,
custom_note
.unwrap_or("any code following this expression is unreachable"),
)
.emit();
})
}
}
}
pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
ObligationCause::new(span, self.body_id, code)
}
pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
self.cause(span, ObligationCauseCode::MiscObligation)
}
/// Resolves type and const variables in `ty` if possible. Unlike the infcx
/// version (resolve_vars_if_possible), this version will
/// also select obligations if it seems useful, in an effort
/// to get more type information.
pub(super) fn resolve_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
debug!("resolve_vars_with_obligations(ty={:?})", ty);
// No Infer()? Nothing needs doing.
if !ty.has_infer_types_or_consts() {
debug!("resolve_vars_with_obligations: ty={:?}", ty);
return ty;
}
// If `ty` is a type variable, see whether we already know what it is.
ty = self.resolve_vars_if_possible(&ty);
if !ty.has_infer_types_or_consts() {
debug!("resolve_vars_with_obligations: ty={:?}", ty);
return ty;
}
// If not, try resolving pending obligations as much as
// possible. This can help substantially when there are
// indirect dependencies that don't seem worth tracking
// precisely.
self.select_obligations_where_possible(false, |_| {});
ty = self.resolve_vars_if_possible(&ty);
debug!("resolve_vars_with_obligations: ty={:?}", ty);
ty
}
pub(super) fn record_deferred_call_resolution(
&self,
closure_def_id: DefId,
r: DeferredCallResolution<'tcx>,
) {
let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
}
pub(super) fn remove_deferred_call_resolutions(
&self,
closure_def_id: DefId,
) -> Vec<DeferredCallResolution<'tcx>> {
let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
}
pub fn tag(&self) -> String {
format!("{:p}", self)
}
pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
self.locals.borrow().get(&nid).cloned().unwrap_or_else(|| {
span_bug!(span, "no type for local variable {}", self.tcx.hir().node_to_string(nid))
})
}
#[inline]
pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
debug!(
"write_ty({:?}, {:?}) in fcx {}",
id,
self.resolve_vars_if_possible(&ty),
self.tag()
);
self.typeck_results.borrow_mut().node_types_mut().insert(id, ty);
if ty.references_error() {
self.has_errors.set(true);
self.set_tainted_by_errors();
}
}
pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
self.typeck_results.borrow_mut().field_indices_mut().insert(hir_id, index);
}
fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
self.typeck_results.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
}
pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
self.write_resolution(hir_id, Ok((DefKind::AssocFn, method.def_id)));
self.write_substs(hir_id, method.substs);
// When the method is confirmed, the `method.substs` includes
// parameters from not just the method, but also the impl of
// the method -- in particular, the `Self` type will be fully
// resolved. However, those are not something that the "user
// specified" -- i.e., those types come from the inferred type
// of the receiver, not something the user wrote. So when we
// create the user-substs, we want to replace those earlier
// types with just the types that the user actually wrote --
// that is, those that appear on the *method itself*.
//
// As an example, if the user wrote something like
// `foo.bar::<u32>(...)` -- the `Self` type here will be the
// type of `foo` (possibly adjusted), but we don't want to
// include that. We want just the `[_, u32]` part.
if !method.substs.is_noop() {
let method_generics = self.tcx.generics_of(method.def_id);
if !method_generics.params.is_empty() {
let user_type_annotation = self.infcx.probe(|_| {
let user_substs = UserSubsts {
substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
let i = param.index as usize;
if i < method_generics.parent_count {
self.infcx.var_for_def(DUMMY_SP, param)
} else {
method.substs[i]
}
}),
user_self_ty: None, // not relevant here
};
self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
method.def_id,
user_substs,
))
});
debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
self.write_user_type_annotation(hir_id, user_type_annotation);
}
}
}
pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
if !substs.is_noop() {
debug!("write_substs({:?}, {:?}) in fcx {}", node_id, substs, self.tag());
self.typeck_results.borrow_mut().node_substs_mut().insert(node_id, substs);
}
}
/// Given the substs that we just converted from the HIR, try to
/// canonicalize them and store them as user-given substitutions
/// (i.e., substitutions that must be respected by the NLL check).
///
/// This should be invoked **before any unifications have
/// occurred**, so that annotations like `Vec<_>` are preserved
/// properly.
pub fn write_user_type_annotation_from_substs(
&self,
hir_id: hir::HirId,
def_id: DefId,
substs: SubstsRef<'tcx>,
user_self_ty: Option<UserSelfTy<'tcx>>,
) {
debug!(
"write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
user_self_ty={:?} in fcx {}",
hir_id,
def_id,
substs,
user_self_ty,
self.tag(),
);
if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
let canonicalized = self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
def_id,
UserSubsts { substs, user_self_ty },
));
debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
self.write_user_type_annotation(hir_id, canonicalized);
}
}
pub fn write_user_type_annotation(
&self,
hir_id: hir::HirId,
canonical_user_type_annotation: CanonicalUserType<'tcx>,
) {
debug!(
"write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
hir_id,
canonical_user_type_annotation,
self.tag(),
);
if !canonical_user_type_annotation.is_identity() {
self.typeck_results
.borrow_mut()
.user_provided_types_mut()
.insert(hir_id, canonical_user_type_annotation);
} else {
debug!("write_user_type_annotation: skipping identity substs");
}
}
pub fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment<'tcx>>) {
debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
if adj.is_empty() {
return;
}
let autoborrow_mut = adj.iter().any(|adj| {
matches!(adj, &Adjustment {
kind: Adjust::Borrow(AutoBorrow::Ref(_, AutoBorrowMutability::Mut { .. })),
..
})
});
match self.typeck_results.borrow_mut().adjustments_mut().entry(expr.hir_id) {
Entry::Vacant(entry) => {
entry.insert(adj);
}
Entry::Occupied(mut entry) => {
debug!(" - composing on top of {:?}", entry.get());
match (&entry.get()[..], &adj[..]) {
// Applying any adjustment on top of a NeverToAny
// is a valid NeverToAny adjustment, because it can't
// be reached.
(&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
(&[
Adjustment { kind: Adjust::Deref(_), .. },
Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
], &[
Adjustment { kind: Adjust::Deref(_), .. },
.. // Any following adjustments are allowed.
]) => {
// A reborrow has no effect before a dereference.
}
// FIXME: currently we never try to compose autoderefs
// and ReifyFnPointer/UnsafeFnPointer, but we could.
_ =>
bug!("while adjusting {:?}, can't compose {:?} and {:?}",
expr, entry.get(), adj)
};
*entry.get_mut() = adj;
}
}
// If there is an mutable auto-borrow, it is equivalent to `&mut <expr>`.
// In this case implicit use of `Deref` and `Index` within `<expr>` should
// instead be `DerefMut` and `IndexMut`, so fix those up.
if autoborrow_mut {
self.convert_place_derefs_to_mutable(expr);
}
}
/// Basically whenever we are converting from a type scheme into
/// the fn body space, we always want to normalize associated
/// types as well. This function combines the two.
fn instantiate_type_scheme<T>(&self, span: Span, substs: SubstsRef<'tcx>, value: &T) -> T
where
T: TypeFoldable<'tcx>,
{
let value = value.subst(self.tcx, substs);
let result = self.normalize_associated_types_in(span, &value);
debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}", value, substs, result);
result
}
/// As `instantiate_type_scheme`, but for the bounds found in a
/// generic type scheme.
fn instantiate_bounds(
&self,
span: Span,
def_id: DefId,
substs: SubstsRef<'tcx>,
) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
let bounds = self.tcx.predicates_of(def_id);
let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
let result = bounds.instantiate(self.tcx, substs);
let result = self.normalize_associated_types_in(span, &result);
debug!(
"instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
bounds, substs, result, spans,
);
(result, spans)
}
/// Replaces the opaque types from the given value with type variables,
/// and records the `OpaqueTypeMap` for later use during writeback. See
/// `InferCtxt::instantiate_opaque_types` for more details.
pub(super) fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
&self,
parent_id: hir::HirId,
value: &T,
value_span: Span,
) -> T {
let parent_def_id = self.tcx.hir().local_def_id(parent_id);
debug!(
"instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
parent_def_id, value
);
let (value, opaque_type_map) =
self.register_infer_ok_obligations(self.instantiate_opaque_types(
parent_def_id,
self.body_id,
self.param_env,
value,
value_span,
));
let mut opaque_types = self.opaque_types.borrow_mut();
let mut opaque_types_vars = self.opaque_types_vars.borrow_mut();
for (ty, decl) in opaque_type_map {
let _ = opaque_types.insert(ty, decl);
let _ = opaque_types_vars.insert(decl.concrete_ty, decl.opaque_type);
}
value
}
pub(super) fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
where
T: TypeFoldable<'tcx>,
{
self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
}
pub(super) fn normalize_associated_types_in_as_infer_ok<T>(
&self,
span: Span,
value: &T,
) -> InferOk<'tcx, T>
where
T: TypeFoldable<'tcx>,
{
self.inh.partially_normalize_associated_types_in(span, self.body_id, self.param_env, value)
}
pub fn require_type_meets(
&self,
ty: Ty<'tcx>,
span: Span,
code: traits::ObligationCauseCode<'tcx>,
def_id: DefId,
) {
self.register_bound(ty, def_id, traits::ObligationCause::new(span, self.body_id, code));
}
pub fn require_type_is_sized(
&self,
ty: Ty<'tcx>,
span: Span,
code: traits::ObligationCauseCode<'tcx>,
) {
if !ty.references_error() {
let lang_item = self.tcx.require_lang_item(LangItem::Sized, None);
self.require_type_meets(ty, span, code, lang_item);
}
}
pub fn require_type_is_sized_deferred(
&self,
ty: Ty<'tcx>,
span: Span,
code: traits::ObligationCauseCode<'tcx>,
) {
if !ty.references_error() {
self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
}
}
pub fn register_bound(
&self,
ty: Ty<'tcx>,
def_id: DefId,
cause: traits::ObligationCause<'tcx>,
) {
if !ty.references_error() {
self.fulfillment_cx.borrow_mut().register_bound(
self,
self.param_env,
ty,
def_id,
cause,
);
}
}
pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> {
let t = AstConv::ast_ty_to_ty(self, ast_t);
self.register_wf_obligation(t.into(), ast_t.span, traits::MiscObligation);
t
}
pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
let ty = self.to_ty(ast_ty);
debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
if Self::can_contain_user_lifetime_bounds(ty) {
let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
self.typeck_results.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
}
ty
}
pub fn to_const(&self, ast_c: &hir::AnonConst) -> &'tcx ty::Const<'tcx> {
let const_def_id = self.tcx.hir().local_def_id(ast_c.hir_id);
let c = ty::Const::from_anon_const(self.tcx, const_def_id);
self.register_wf_obligation(
c.into(),
self.tcx.hir().span(ast_c.hir_id),
ObligationCauseCode::MiscObligation,
);
c
}
pub fn const_arg_to_const(
&self,
ast_c: &hir::AnonConst,
param_def_id: DefId,
) -> &'tcx ty::Const<'tcx> {
let const_def = ty::WithOptConstParam {
did: self.tcx.hir().local_def_id(ast_c.hir_id),
const_param_did: Some(param_def_id),
};
let c = ty::Const::from_opt_const_arg_anon_const(self.tcx, const_def);
self.register_wf_obligation(
c.into(),
self.tcx.hir().span(ast_c.hir_id),
ObligationCauseCode::MiscObligation,
);
c
}
// If the type given by the user has free regions, save it for later, since
// NLL would like to enforce those. Also pass in types that involve
// projections, since those can resolve to `'static` bounds (modulo #54940,
// which hopefully will be fixed by the time you see this comment, dear
// reader, although I have my doubts). Also pass in types with inference
// types, because they may be repeated. Other sorts of things are already
// sufficiently enforced with erased regions. =)
fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
where
T: TypeFoldable<'tcx>,
{
t.has_free_regions() || t.has_projections() || t.has_infer_types()
}
pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
match self.typeck_results.borrow().node_types().get(id) {
Some(&t) => t,
None if self.is_tainted_by_errors() => self.tcx.ty_error(),
None => {
bug!(
"no type for node {}: {} in fcx {}",
id,
self.tcx.hir().node_to_string(id),
self.tag()
);
}
}
}
/// Registers an obligation for checking later, during regionck, that `arg` is well-formed.
pub fn register_wf_obligation(
&self,
arg: subst::GenericArg<'tcx>,
span: Span,
code: traits::ObligationCauseCode<'tcx>,
) {
// WF obligations never themselves fail, so no real need to give a detailed cause:
let cause = traits::ObligationCause::new(span, self.body_id, code);
self.register_predicate(traits::Obligation::new(
cause,
self.param_env,
ty::PredicateAtom::WellFormed(arg).to_predicate(self.tcx),
));
}
/// Registers obligations that all `substs` are well-formed.
pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr<'_>) {
for arg in substs.iter().filter(|arg| {
matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..))
}) {
self.register_wf_obligation(arg, expr.span, traits::MiscObligation);
}
}
/// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
/// type/region parameter was instantiated (`substs`), creates and registers suitable
/// trait/region obligations.
///
/// For example, if there is a function:
///
/// ```
/// fn foo<'a,T:'a>(...)
/// ```
///
/// and a reference:
///
/// ```
/// let f = foo;
/// ```
///
/// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
/// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
pub fn add_obligations_for_parameters(
&self,
cause: traits::ObligationCause<'tcx>,
predicates: ty::InstantiatedPredicates<'tcx>,
) {
assert!(!predicates.has_escaping_bound_vars());
debug!("add_obligations_for_parameters(predicates={:?})", predicates);
for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
self.register_predicate(obligation);
}
}
// FIXME(arielb1): use this instead of field.ty everywhere
// Only for fields! Returns <none> for methods>
// Indifferent to privacy flags
pub fn field_ty(
&self,
span: Span,
field: &'tcx ty::FieldDef,
substs: SubstsRef<'tcx>,
) -> Ty<'tcx> {
self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
}
pub(super) fn check_casts(&self) {
let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
for cast in deferred_cast_checks.drain(..) {
cast.check(self);
}
}
pub(super) fn resolve_generator_interiors(&self, def_id: DefId) {
let mut generators = self.deferred_generator_interiors.borrow_mut();
for (body_id, interior, kind) in generators.drain(..) {
self.select_obligations_where_possible(false, |_| {});
super::generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
}
}
// Tries to apply a fallback to `ty` if it is an unsolved variable.
//
// - Unconstrained ints are replaced with `i32`.
//
// - Unconstrained floats are replaced with with `f64`.
//
// - Non-numerics get replaced with `!` when `#![feature(never_type_fallback)]`
// is enabled. Otherwise, they are replaced with `()`.
//
// Fallback becomes very dubious if we have encountered type-checking errors.
// In that case, fallback to Error.
// The return value indicates whether fallback has occurred.
pub(super) fn fallback_if_possible(&self, ty: Ty<'tcx>, mode: FallbackMode) -> bool {
use rustc_middle::ty::error::UnconstrainedNumeric::Neither;
use rustc_middle::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt};
assert!(ty.is_ty_infer());
let fallback = match self.type_is_unconstrained_numeric(ty) {
_ if self.is_tainted_by_errors() => self.tcx().ty_error(),
UnconstrainedInt => self.tcx.types.i32,
UnconstrainedFloat => self.tcx.types.f64,
Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
Neither => {
// This type variable was created from the instantiation of an opaque
// type. The fact that we're attempting to perform fallback for it
// means that the function neither constrained it to a concrete
// type, nor to the opaque type itself.
//
// For example, in this code:
//
//```
// type MyType = impl Copy;
// fn defining_use() -> MyType { true }
// fn other_use() -> MyType { defining_use() }
// ```
//
// `defining_use` will constrain the instantiated inference
// variable to `bool`, while `other_use` will constrain
// the instantiated inference variable to `MyType`.
//
// When we process opaque types during writeback, we
// will handle cases like `other_use`, and not count
// them as defining usages
//
// However, we also need to handle cases like this:
//
// ```rust
// pub type Foo = impl Copy;
// fn produce() -> Option<Foo> {
// None
// }
// ```
//
// In the above snippet, the inference variable created by
// instantiating `Option<Foo>` will be completely unconstrained.
// We treat this as a non-defining use by making the inference
// variable fall back to the opaque type itself.
if let FallbackMode::All = mode {
if let Some(opaque_ty) = self.opaque_types_vars.borrow().get(ty) {
debug!(
"fallback_if_possible: falling back opaque type var {:?} to {:?}",
ty, opaque_ty
);
*opaque_ty
} else {
return false;
}
} else {
return false;
}
}
};
debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
self.demand_eqtype(rustc_span::DUMMY_SP, ty, fallback);
true
}
pub(super) fn select_all_obligations_or_error(&self) {
debug!("select_all_obligations_or_error");
if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
self.report_fulfillment_errors(&errors, self.inh.body_id, false);
}
}
/// Select as many obligations as we can at present.
pub(super) fn select_obligations_where_possible(
&self,
fallback_has_occurred: bool,
mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
) {
let result = self.fulfillment_cx.borrow_mut().select_where_possible(self);
if let Err(mut errors) = result {
mutate_fullfillment_errors(&mut errors);
self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
}
}
/// For the overloaded place expressions (`*x`, `x[3]`), the trait
/// returns a type of `&T`, but the actual type we assign to the
/// *expression* is `T`. So this function just peels off the return
/// type by one layer to yield `T`.
pub(super) fn make_overloaded_place_return_type(
&self,
method: MethodCallee<'tcx>,
) -> ty::TypeAndMut<'tcx> {
// extract method return type, which will be &T;
let ret_ty = method.sig.output();
// method returns &T, but the type as visible to user is T, so deref
ret_ty.builtin_deref(true).unwrap()
}
pub(super) fn check_method_argument_types(
&self,
sp: Span,
expr: &'tcx hir::Expr<'tcx>,
method: Result<MethodCallee<'tcx>, ()>,
args_no_rcvr: &'tcx [hir::Expr<'tcx>],
tuple_arguments: TupleArgumentsFlag,
expected: Expectation<'tcx>,
) -> Ty<'tcx> {
let has_error = match method {
Ok(method) => method.substs.references_error() || method.sig.references_error(),
Err(_) => true,
};
if has_error {
let err_inputs = self.err_args(args_no_rcvr.len());
let err_inputs = match tuple_arguments {
DontTupleArguments => err_inputs,
TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
};
self.check_argument_types(
sp,
expr,
&err_inputs[..],
&[],
args_no_rcvr,
false,
tuple_arguments,
None,
);
return self.tcx.ty_error();
}
let method = method.unwrap();
// HACK(eddyb) ignore self in the definition (see above).
let expected_arg_tys = self.expected_inputs_for_expected_output(
sp,
expected,
method.sig.output(),
&method.sig.inputs()[1..],
);
self.check_argument_types(
sp,
expr,
&method.sig.inputs()[1..],
&expected_arg_tys[..],
args_no_rcvr,
method.sig.c_variadic,
tuple_arguments,
self.tcx.hir().span_if_local(method.def_id),
);
method.sig.output()
}
fn self_type_matches_expected_vid(
&self,
trait_ref: ty::PolyTraitRef<'tcx>,
expected_vid: ty::TyVid,
) -> bool {
let self_ty = self.shallow_resolve(trait_ref.skip_binder().self_ty());
debug!(
"self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
trait_ref, self_ty, expected_vid
);
match *self_ty.kind() {
ty::Infer(ty::TyVar(found_vid)) => {
// FIXME: consider using `sub_root_var` here so we
// can see through subtyping.
let found_vid = self.root_var(found_vid);
debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
expected_vid == found_vid
}
_ => false,
}
}
pub(super) fn obligations_for_self_ty<'b>(
&'b self,
self_ty: ty::TyVid,
) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
+ Captures<'tcx>
+ 'b {
// FIXME: consider using `sub_root_var` here so we
// can see through subtyping.
let ty_var_root = self.root_var(self_ty);
debug!(
"obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
self_ty,
ty_var_root,
self.fulfillment_cx.borrow().pending_obligations()
);
self.fulfillment_cx
.borrow()
.pending_obligations()
.into_iter()
.filter_map(move |obligation| {
match obligation.predicate.skip_binders() {
ty::PredicateAtom::Projection(data) => {
Some((ty::Binder::bind(data).to_poly_trait_ref(self.tcx), obligation))
}
ty::PredicateAtom::Trait(data, _) => {
Some((ty::Binder::bind(data).to_poly_trait_ref(), obligation))
}
ty::PredicateAtom::Subtype(..) => None,
ty::PredicateAtom::RegionOutlives(..) => None,
ty::PredicateAtom::TypeOutlives(..) => None,
ty::PredicateAtom::WellFormed(..) => None,
ty::PredicateAtom::ObjectSafe(..) => None,
ty::PredicateAtom::ConstEvaluatable(..) => None,
ty::PredicateAtom::ConstEquate(..) => None,
// N.B., this predicate is created by breaking down a
// `ClosureType: FnFoo()` predicate, where
// `ClosureType` represents some `Closure`. It can't
// possibly be referring to the current closure,
// because we haven't produced the `Closure` for
// this closure yet; this is exactly why the other
// code is looking for a self type of a unresolved
// inference variable.
ty::PredicateAtom::ClosureKind(..) => None,
ty::PredicateAtom::TypeWellFormedFromEnv(..) => None,
}
})
.filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
}
pub(super) fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
self.obligations_for_self_ty(self_ty)
.any(|(tr, _)| Some(tr.def_id()) == self.tcx.lang_items().sized_trait())
}
/// Generic function that factors out common logic from function calls,
/// method calls and overloaded operators.
pub(super) fn check_argument_types(
&self,
sp: Span,
expr: &'tcx hir::Expr<'tcx>,
fn_inputs: &[Ty<'tcx>],
expected_arg_tys: &[Ty<'tcx>],
args: &'tcx [hir::Expr<'tcx>],
c_variadic: bool,
tuple_arguments: TupleArgumentsFlag,
def_span: Option<Span>,
) {
let tcx = self.tcx;
// Grab the argument types, supplying fresh type variables
// if the wrong number of arguments were supplied
let supplied_arg_count = if tuple_arguments == DontTupleArguments { args.len() } else { 1 };
// All the input types from the fn signature must outlive the call
// so as to validate implied bounds.
for (&fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
self.register_wf_obligation(fn_input_ty.into(), arg_expr.span, traits::MiscObligation);
}
let expected_arg_count = fn_inputs.len();
let param_count_error = |expected_count: usize,
arg_count: usize,
error_code: &str,
c_variadic: bool,
sugg_unit: bool| {
let (span, start_span, args) = match &expr.kind {
hir::ExprKind::Call(hir::Expr { span, .. }, args) => (*span, *span, &args[..]),
hir::ExprKind::MethodCall(path_segment, span, args, _) => (
*span,
// `sp` doesn't point at the whole `foo.bar()`, only at `bar`.
path_segment
.args
.and_then(|args| args.args.iter().last())
// Account for `foo.bar::<T>()`.
.map(|arg| {
// Skip the closing `>`.
tcx.sess
.source_map()
.next_point(tcx.sess.source_map().next_point(arg.span()))
})
.unwrap_or(*span),
&args[1..], // Skip the receiver.
),
k => span_bug!(sp, "checking argument types on a non-call: `{:?}`", k),
};
let arg_spans = if args.is_empty() {
// foo()
// ^^^-- supplied 0 arguments
// |
// expected 2 arguments
vec![tcx.sess.source_map().next_point(start_span).with_hi(sp.hi())]
} else {
// foo(1, 2, 3)
// ^^^ - - - supplied 3 arguments
// |
// expected 2 arguments
args.iter().map(|arg| arg.span).collect::<Vec<Span>>()
};
let mut err = tcx.sess.struct_span_err_with_code(
span,
&format!(
"this function takes {}{} but {} {} supplied",
if c_variadic { "at least " } else { "" },
potentially_plural_count(expected_count, "argument"),
potentially_plural_count(arg_count, "argument"),
if arg_count == 1 { "was" } else { "were" }
),
DiagnosticId::Error(error_code.to_owned()),
);
let label = format!("supplied {}", potentially_plural_count(arg_count, "argument"));
for (i, span) in arg_spans.into_iter().enumerate() {
err.span_label(
span,
if arg_count == 0 || i + 1 == arg_count { &label } else { "" },
);
}
if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().guess_head_span(sp)) {
err.span_label(def_s, "defined here");
}
if sugg_unit {
let sugg_span = tcx.sess.source_map().end_point(expr.span);
// remove closing `)` from the span
let sugg_span = sugg_span.shrink_to_lo();
err.span_suggestion(
sugg_span,
"expected the unit value `()`; create it with empty parentheses",
String::from("()"),
Applicability::MachineApplicable,
);
} else {
err.span_label(
span,
format!(
"expected {}{}",
if c_variadic { "at least " } else { "" },
potentially_plural_count(expected_count, "argument")
),
);
}
err.emit();
};
let mut expected_arg_tys = expected_arg_tys.to_vec();
let formal_tys = if tuple_arguments == TupleArguments {
let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
match tuple_type.kind() {
ty::Tuple(arg_types) if arg_types.len() != args.len() => {
param_count_error(arg_types.len(), args.len(), "E0057", false, false);
expected_arg_tys = vec![];
self.err_args(args.len())
}
ty::Tuple(arg_types) => {
expected_arg_tys = match expected_arg_tys.get(0) {
Some(&ty) => match ty.kind() {
ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
_ => vec![],
},
None => vec![],
};
arg_types.iter().map(|k| k.expect_ty()).collect()
}
_ => {
struct_span_err!(
tcx.sess,
sp,
E0059,
"cannot use call notation; the first type parameter \
for the function trait is neither a tuple nor unit"
)
.emit();
expected_arg_tys = vec![];
self.err_args(args.len())
}
}
} else if expected_arg_count == supplied_arg_count {
fn_inputs.to_vec()
} else if c_variadic {
if supplied_arg_count >= expected_arg_count {
fn_inputs.to_vec()
} else {
param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
expected_arg_tys = vec![];
self.err_args(supplied_arg_count)
}
} else {
// is the missing argument of type `()`?
let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
} else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
} else {
false
};
param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
expected_arg_tys = vec![];
self.err_args(supplied_arg_count)
};
debug!(
"check_argument_types: formal_tys={:?}",
formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>()
);
// If there is no expectation, expect formal_tys.
let expected_arg_tys =
if !expected_arg_tys.is_empty() { expected_arg_tys } else { formal_tys.clone() };
let mut final_arg_types: Vec<(usize, Ty<'_>, Ty<'_>)> = vec![];
// Check the arguments.
// We do this in a pretty awful way: first we type-check any arguments
// that are not closures, then we type-check the closures. This is so
// that we have more information about the types of arguments when we
// type-check the functions. This isn't really the right way to do this.
for &check_closures in &[false, true] {
debug!("check_closures={}", check_closures);
// More awful hacks: before we check argument types, try to do
// an "opportunistic" trait resolution of any trait bounds on
// the call. This helps coercions.
if check_closures {
self.select_obligations_where_possible(false, |errors| {
self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
self.point_at_arg_instead_of_call_if_possible(
errors,
&final_arg_types[..],
sp,
&args,
);
})
}
// For C-variadic functions, we don't have a declared type for all of
// the arguments hence we only do our usual type checking with
// the arguments who's types we do know.
let t = if c_variadic {
expected_arg_count
} else if tuple_arguments == TupleArguments {
args.len()
} else {
supplied_arg_count
};
for (i, arg) in args.iter().take(t).enumerate() {
// Warn only for the first loop (the "no closures" one).
// Closure arguments themselves can't be diverging, but
// a previous argument can, e.g., `foo(panic!(), || {})`.
if !check_closures {
self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
}
let is_closure = match arg.kind {
ExprKind::Closure(..) => true,
_ => false,
};
if is_closure != check_closures {
continue;
}
debug!("checking the argument");
let formal_ty = formal_tys[i];
// The special-cased logic below has three functions:
// 1. Provide as good of an expected type as possible.
let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
let checked_ty = self.check_expr_with_expectation(&arg, expected);
// 2. Coerce to the most detailed type that could be coerced
// to, which is `expected_ty` if `rvalue_hint` returns an
// `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
// We're processing function arguments so we definitely want to use
// two-phase borrows.
self.demand_coerce(&arg, checked_ty, coerce_ty, None, AllowTwoPhase::Yes);
final_arg_types.push((i, checked_ty, coerce_ty));
// 3. Relate the expected type and the formal one,
// if the expected type was used for the coercion.
self.demand_suptype(arg.span, formal_ty, coerce_ty);
}
}
// We also need to make sure we at least write the ty of the other
// arguments which we skipped above.
if c_variadic {
fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
use crate::structured_errors::{StructuredDiagnostic, VariadicError};
VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
}
for arg in args.iter().skip(expected_arg_count) {
let arg_ty = self.check_expr(&arg);
// There are a few types which get autopromoted when passed via varargs
// in C but we just error out instead and require explicit casts.
let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
match arg_ty.kind() {
ty::Float(ast::FloatTy::F32) => {
variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
}
ty::Int(ast::IntTy::I8 | ast::IntTy::I16) | ty::Bool => {
variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
}
ty::Uint(ast::UintTy::U8 | ast::UintTy::U16) => {
variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
}
ty::FnDef(..) => {
let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
}
_ => {}
}
}
}
}
pub(super) fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
vec![self.tcx.ty_error(); len]
}
/// Given a vec of evaluated `FulfillmentError`s and an `fn` call argument expressions, we walk
/// the checked and coerced types for each argument to see if any of the `FulfillmentError`s
/// reference a type argument. The reason to walk also the checked type is that the coerced type
/// can be not easily comparable with predicate type (because of coercion). If the types match
/// for either checked or coerced type, and there's only *one* argument that does, we point at
/// the corresponding argument's expression span instead of the `fn` call path span.
fn point_at_arg_instead_of_call_if_possible(
&self,
errors: &mut Vec<traits::FulfillmentError<'tcx>>,
final_arg_types: &[(usize, Ty<'tcx>, Ty<'tcx>)],
call_sp: Span,
args: &'tcx [hir::Expr<'tcx>],
) {
// We *do not* do this for desugared call spans to keep good diagnostics when involving
// the `?` operator.
if call_sp.desugaring_kind().is_some() {
return;
}
for error in errors {
// Only if the cause is somewhere inside the expression we want try to point at arg.
// Otherwise, it means that the cause is somewhere else and we should not change
// anything because we can break the correct span.
if !call_sp.contains(error.obligation.cause.span) {
continue;
}
if let ty::PredicateAtom::Trait(predicate, _) =
error.obligation.predicate.skip_binders()
{
// Collect the argument position for all arguments that could have caused this
// `FulfillmentError`.
let mut referenced_in = final_arg_types
.iter()
.map(|&(i, checked_ty, _)| (i, checked_ty))
.chain(final_arg_types.iter().map(|&(i, _, coerced_ty)| (i, coerced_ty)))
.flat_map(|(i, ty)| {
let ty = self.resolve_vars_if_possible(&ty);
// We walk the argument type because the argument's type could have
// been `Option<T>`, but the `FulfillmentError` references `T`.
if ty.walk().any(|arg| arg == predicate.self_ty().into()) {
Some(i)
} else {
None
}
})
.collect::<Vec<usize>>();
// Both checked and coerced types could have matched, thus we need to remove
// duplicates.
// We sort primitive type usize here and can use unstable sort
referenced_in.sort_unstable();
referenced_in.dedup();
if let (Some(ref_in), None) = (referenced_in.pop(), referenced_in.pop()) {
// We make sure that only *one* argument matches the obligation failure
// and we assign the obligation's span to its expression's.
error.obligation.cause.make_mut().span = args[ref_in].span;
error.points_at_arg_span = true;
}
}
}
}
/// Given a vec of evaluated `FulfillmentError`s and an `fn` call expression, we walk the
/// `PathSegment`s and resolve their type parameters to see if any of the `FulfillmentError`s
/// were caused by them. If they were, we point at the corresponding type argument's span
/// instead of the `fn` call path span.
fn point_at_type_arg_instead_of_call_if_possible(
&self,
errors: &mut Vec<traits::FulfillmentError<'tcx>>,
call_expr: &'tcx hir::Expr<'tcx>,
) {
if let hir::ExprKind::Call(path, _) = &call_expr.kind {
if let hir::ExprKind::Path(qpath) = &path.kind {
if let hir::QPath::Resolved(_, path) = &qpath {
for error in errors {
if let ty::PredicateAtom::Trait(predicate, _) =
error.obligation.predicate.skip_binders()
{
// If any of the type arguments in this path segment caused the
// `FullfillmentError`, point at its span (#61860).
for arg in path
.segments
.iter()
.filter_map(|seg| seg.args.as_ref())
.flat_map(|a| a.args.iter())
{
if let hir::GenericArg::Type(hir_ty) = &arg {
if let hir::TyKind::Path(hir::QPath::TypeRelative(..)) =
&hir_ty.kind
{
// Avoid ICE with associated types. As this is best
// effort only, it's ok to ignore the case. It
// would trigger in `is_send::<T::AssocType>();`
// from `typeck-default-trait-impl-assoc-type.rs`.
} else {
let ty = AstConv::ast_ty_to_ty(self, hir_ty);
let ty = self.resolve_vars_if_possible(&ty);
if ty == predicate.self_ty() {
error.obligation.cause.make_mut().span = hir_ty.span;
}
}
}
}
}
}
}
}
}
}
// AST fragment checking
pub(super) fn check_lit(&self, lit: &hir::Lit, expected: Expectation<'tcx>) -> Ty<'tcx> {
let tcx = self.tcx;
match lit.node {
ast::LitKind::Str(..) => tcx.mk_static_str(),
ast::LitKind::ByteStr(ref v) => {
tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.u8, v.len() as u64))
}
ast::LitKind::Byte(_) => tcx.types.u8,
ast::LitKind::Char(_) => tcx.types.char,
ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() {
ty::Int(_) | ty::Uint(_) => Some(ty),
ty::Char => Some(tcx.types.u8),
ty::RawPtr(..) => Some(tcx.types.usize),
ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
_ => None,
});
opt_ty.unwrap_or_else(|| self.next_int_var())
}
ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => tcx.mk_mach_float(t),
ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => {
let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() {
ty::Float(_) => Some(ty),
_ => None,
});
opt_ty.unwrap_or_else(|| self.next_float_var())
}
ast::LitKind::Bool(_) => tcx.types.bool,
ast::LitKind::Err(_) => tcx.ty_error(),
}
}
/// Unifies the output type with the expected type early, for more coercions
/// and forward type information on the input expressions.
pub(super) fn expected_inputs_for_expected_output(
&self,
call_span: Span,
expected_ret: Expectation<'tcx>,
formal_ret: Ty<'tcx>,
formal_args: &[Ty<'tcx>],
) -> Vec<Ty<'tcx>> {
let formal_ret = self.resolve_vars_with_obligations(formal_ret);
let ret_ty = match expected_ret.only_has_type(self) {
Some(ret) => ret,
None => return Vec::new(),
};
let expect_args = self
.fudge_inference_if_ok(|| {
// Attempt to apply a subtyping relationship between the formal
// return type (likely containing type variables if the function
// is polymorphic) and the expected return type.
// No argument expectations are produced if unification fails.
let origin = self.misc(call_span);
let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
// FIXME(#27336) can't use ? here, Try::from_error doesn't default
// to identity so the resulting type is not constrained.
match ures {
Ok(ok) => {
// Process any obligations locally as much as
// we can. We don't care if some things turn
// out unconstrained or ambiguous, as we're
// just trying to get hints here.
self.save_and_restore_in_snapshot_flag(|_| {
let mut fulfill = TraitEngine::new(self.tcx);
for obligation in ok.obligations {
fulfill.register_predicate_obligation(self, obligation);
}
fulfill.select_where_possible(self)
})
.map_err(|_| ())?;
}
Err(_) => return Err(()),
}
// Record all the argument types, with the substitutions
// produced from the above subtyping unification.
Ok(formal_args.iter().map(|ty| self.resolve_vars_if_possible(ty)).collect())
})
.unwrap_or_default();
debug!(
"expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
formal_args, formal_ret, expect_args, expected_ret
);
expect_args
}
pub fn check_struct_path(
&self,
qpath: &QPath<'_>,
hir_id: hir::HirId,
) -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
let path_span = qpath.qself_span();
let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
let variant = match def {
Res::Err => {
self.set_tainted_by_errors();
return None;
}
Res::Def(DefKind::Variant, _) => match ty.kind() {
ty::Adt(adt, substs) => Some((adt.variant_of_res(def), adt.did, substs)),
_ => bug!("unexpected type: {:?}", ty),
},
Res::Def(DefKind::Struct | DefKind::Union | DefKind::TyAlias | DefKind::AssocTy, _)
| Res::SelfTy(..) => match ty.kind() {
ty::Adt(adt, substs) if !adt.is_enum() => {
Some((adt.non_enum_variant(), adt.did, substs))
}
_ => None,
},
_ => bug!("unexpected definition: {:?}", def),
};
if let Some((variant, did, substs)) = variant {
debug!("check_struct_path: did={:?} substs={:?}", did, substs);
self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
// Check bounds on type arguments used in the path.
let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
let cause =
traits::ObligationCause::new(path_span, self.body_id, traits::ItemObligation(did));
self.add_obligations_for_parameters(cause, bounds);
Some((variant, ty))
} else {
struct_span_err!(
self.tcx.sess,
path_span,
E0071,
"expected struct, variant or union type, found {}",
ty.sort_string(self.tcx)
)
.span_label(path_span, "not a struct")
.emit();
None
}
}
// Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
// The newly resolved definition is written into `type_dependent_defs`.
fn finish_resolving_struct_path(
&self,
qpath: &QPath<'_>,
path_span: Span,
hir_id: hir::HirId,
) -> (Res, Ty<'tcx>) {
match *qpath {
QPath::Resolved(ref maybe_qself, ref path) => {
let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
let ty = AstConv::res_to_ty(self, self_ty, path, true);
(path.res, ty)
}
QPath::TypeRelative(ref qself, ref segment) => {
let ty = self.to_ty(qself);
let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
path.res
} else {
Res::Err
};
let result =
AstConv::associated_path_to_ty(self, hir_id, path_span, ty, res, segment, true);
let ty = result.map(|(ty, _, _)| ty).unwrap_or_else(|_| self.tcx().ty_error());
let result = result.map(|(_, kind, def_id)| (kind, def_id));
// Write back the new resolution.
self.write_resolution(hir_id, result);
(result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
}
QPath::LangItem(lang_item, span) => {
self.resolve_lang_item_path(lang_item, span, hir_id)
}
}
}
pub(super) fn resolve_lang_item_path(
&self,
lang_item: hir::LangItem,
span: Span,
hir_id: hir::HirId,
) -> (Res, Ty<'tcx>) {
let def_id = self.tcx.require_lang_item(lang_item, Some(span));
let def_kind = self.tcx.def_kind(def_id);
let item_ty = if let DefKind::Variant = def_kind {
self.tcx.type_of(self.tcx.parent(def_id).expect("variant w/out parent"))
} else {
self.tcx.type_of(def_id)
};
let substs = self.infcx.fresh_substs_for_item(span, def_id);
let ty = item_ty.subst(self.tcx, substs);
self.write_resolution(hir_id, Ok((def_kind, def_id)));
self.add_required_obligations(span, def_id, &substs);
(Res::Def(def_kind, def_id), ty)
}
/// Resolves an associated value path into a base type and associated constant, or method
/// resolution. The newly resolved definition is written into `type_dependent_defs`.
pub fn resolve_ty_and_res_ufcs<'b>(
&self,
qpath: &'b QPath<'b>,
hir_id: hir::HirId,
span: Span,
) -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment<'b>]) {
debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
let (ty, qself, item_segment) = match *qpath {
QPath::Resolved(ref opt_qself, ref path) => {
return (
path.res,
opt_qself.as_ref().map(|qself| self.to_ty(qself)),
&path.segments[..],
);
}
QPath::TypeRelative(ref qself, ref segment) => (self.to_ty(qself), qself, segment),
QPath::LangItem(..) => bug!("`resolve_ty_and_res_ufcs` called on `LangItem`"),
};
if let Some(&cached_result) = self.typeck_results.borrow().type_dependent_defs().get(hir_id)
{
// Return directly on cache hit. This is useful to avoid doubly reporting
// errors with default match binding modes. See #44614.
let def =
cached_result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err);
return (def, Some(ty), slice::from_ref(&**item_segment));
}
let item_name = item_segment.ident;
let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
let result = match error {
method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
_ => Err(ErrorReported),
};
if item_name.name != kw::Invalid {
if let Some(mut e) = self.report_method_error(
span,
ty,
item_name,
SelfSource::QPath(qself),
error,
None,
) {
e.emit();
}
}
result
});
// Write back the new resolution.
self.write_resolution(hir_id, result);
(
result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
Some(ty),
slice::from_ref(&**item_segment),
)
}
pub fn check_decl_initializer(
&self,
local: &'tcx hir::Local<'tcx>,
init: &'tcx hir::Expr<'tcx>,
) -> Ty<'tcx> {
// FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
// for #42640 (default match binding modes).
//
// See #44848.
let ref_bindings = local.pat.contains_explicit_ref_binding();
let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
if let Some(m) = ref_bindings {
// Somewhat subtle: if we have a `ref` binding in the pattern,
// we want to avoid introducing coercions for the RHS. This is
// both because it helps preserve sanity and, in the case of
// ref mut, for soundness (issue #23116). In particular, in
// the latter case, we need to be clear that the type of the
// referent for the reference that results is *equal to* the
// type of the place it is referencing, and not some
// supertype thereof.
let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
self.demand_eqtype(init.span, local_ty, init_ty);
init_ty
} else {
self.check_expr_coercable_to_type(init, local_ty, None)
}
}
/// Type check a `let` statement.
pub fn check_decl_local(&self, local: &'tcx hir::Local<'tcx>) {
// Determine and write the type which we'll check the pattern against.
let ty = self.local_ty(local.span, local.hir_id).decl_ty;
self.write_ty(local.hir_id, ty);
// Type check the initializer.
if let Some(ref init) = local.init {
let init_ty = self.check_decl_initializer(local, &init);
self.overwrite_local_ty_if_err(local, ty, init_ty);
}
// Does the expected pattern type originate from an expression and what is the span?
let (origin_expr, ty_span) = match (local.ty, local.init) {
(Some(ty), _) => (false, Some(ty.span)), // Bias towards the explicit user type.
(_, Some(init)) => (true, Some(init.span)), // No explicit type; so use the scrutinee.
_ => (false, None), // We have `let $pat;`, so the expected type is unconstrained.
};
// Type check the pattern. Override if necessary to avoid knock-on errors.
self.check_pat_top(&local.pat, ty, ty_span, origin_expr);
let pat_ty = self.node_ty(local.pat.hir_id);
self.overwrite_local_ty_if_err(local, ty, pat_ty);
}
fn overwrite_local_ty_if_err(
&self,
local: &'tcx hir::Local<'tcx>,
decl_ty: Ty<'tcx>,
ty: Ty<'tcx>,
) {
if ty.references_error() {
// Override the types everywhere with `err()` to avoid knock on errors.
self.write_ty(local.hir_id, ty);
self.write_ty(local.pat.hir_id, ty);
let local_ty = LocalTy { decl_ty, revealed_ty: ty };
self.locals.borrow_mut().insert(local.hir_id, local_ty);
self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
}
}
pub(super) fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
err.span_suggestion_short(
span.shrink_to_hi(),
"consider using a semicolon here",
";".to_string(),
Applicability::MachineApplicable,
);
}
pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>) {
// Don't do all the complex logic below for `DeclItem`.
match stmt.kind {
hir::StmtKind::Item(..) => return,
hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
}
self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
// Hide the outer diverging and `has_errors` flags.
let old_diverges = self.diverges.replace(Diverges::Maybe);
let old_has_errors = self.has_errors.replace(false);
match stmt.kind {
hir::StmtKind::Local(ref l) => {
self.check_decl_local(&l);
}
// Ignore for now.
hir::StmtKind::Item(_) => {}
hir::StmtKind::Expr(ref expr) => {
// Check with expected type of `()`.
self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
self.suggest_semicolon_at_end(expr.span, err);
});
}
hir::StmtKind::Semi(ref expr) => {
self.check_expr(&expr);
}
}
// Combine the diverging and `has_error` flags.
self.diverges.set(self.diverges.get() | old_diverges);
self.has_errors.set(self.has_errors.get() | old_has_errors);
}
pub fn check_block_no_value(&self, blk: &'tcx hir::Block<'tcx>) {
let unit = self.tcx.mk_unit();
let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
// if the block produces a `!` value, that can always be
// (effectively) coerced to unit.
if !ty.is_never() {
self.demand_suptype(blk.span, unit, ty);
}
}
/// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
/// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
/// when given code like the following:
/// ```text
/// if false { return 0i32; } else { 1u32 }
/// // ^^^^ point at this instead of the whole `if` expression
/// ```
fn get_expr_coercion_span(&self, expr: &hir::Expr<'_>) -> rustc_span::Span {
if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
let arm_spans: Vec<Span> = arms
.iter()
.filter_map(|arm| {
self.in_progress_typeck_results
.and_then(|typeck_results| {
typeck_results.borrow().node_type_opt(arm.body.hir_id)
})
.and_then(|arm_ty| {
if arm_ty.is_never() {
None
} else {
Some(match &arm.body.kind {
// Point at the tail expression when possible.
hir::ExprKind::Block(block, _) => {
block.expr.as_ref().map(|e| e.span).unwrap_or(block.span)
}
_ => arm.body.span,
})
}
})
})
.collect();
if arm_spans.len() == 1 {
return arm_spans[0];
}
}
expr.span
}
pub(super) fn check_block_with_expected(
&self,
blk: &'tcx hir::Block<'tcx>,
expected: Expectation<'tcx>,
) -> Ty<'tcx> {
let prev = {
let mut fcx_ps = self.ps.borrow_mut();
let unsafety_state = fcx_ps.recurse(blk);
replace(&mut *fcx_ps, unsafety_state)
};
// In some cases, blocks have just one exit, but other blocks
// can be targeted by multiple breaks. This can happen both
// with labeled blocks as well as when we desugar
// a `try { ... }` expression.
//
// Example 1:
//
// 'a: { if true { break 'a Err(()); } Ok(()) }
//
// Here we would wind up with two coercions, one from
// `Err(())` and the other from the tail expression
// `Ok(())`. If the tail expression is omitted, that's a
// "forced unit" -- unless the block diverges, in which
// case we can ignore the tail expression (e.g., `'a: {
// break 'a 22; }` would not force the type of the block
// to be `()`).
let tail_expr = blk.expr.as_ref();
let coerce_to_ty = expected.coercion_target_type(self, blk.span);
let coerce = if blk.targeted_by_break {
CoerceMany::new(coerce_to_ty)
} else {
let tail_expr: &[&hir::Expr<'_>] = match tail_expr {
Some(e) => slice::from_ref(e),
None => &[],
};
CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
};
let prev_diverges = self.diverges.get();
let ctxt = BreakableCtxt { coerce: Some(coerce), may_break: false };
let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
for s in blk.stmts {
self.check_stmt(s);
}
// check the tail expression **without** holding the
// `enclosing_breakables` lock below.
let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
let coerce = ctxt.coerce.as_mut().unwrap();
if let Some(tail_expr_ty) = tail_expr_ty {
let tail_expr = tail_expr.unwrap();
let span = self.get_expr_coercion_span(tail_expr);
let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
} else {
// Subtle: if there is no explicit tail expression,
// that is typically equivalent to a tail expression
// of `()` -- except if the block diverges. In that
// case, there is no value supplied from the tail
// expression (assuming there are no other breaks,
// this implies that the type of the block will be
// `!`).
//
// #41425 -- label the implicit `()` as being the
// "found type" here, rather than the "expected type".
if !self.diverges.get().is_always() {
// #50009 -- Do not point at the entire fn block span, point at the return type
// span, as it is the cause of the requirement, and
// `consider_hint_about_removing_semicolon` will point at the last expression
// if it were a relevant part of the error. This improves usability in editors
// that highlight errors inline.
let mut sp = blk.span;
let mut fn_span = None;
if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
let ret_sp = decl.output.span();
if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
// HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
// output would otherwise be incorrect and even misleading. Make sure
// the span we're aiming at correspond to a `fn` body.
if block_sp == blk.span {
sp = ret_sp;
fn_span = Some(ident.span);
}
}
}
coerce.coerce_forced_unit(
self,
&self.misc(sp),
&mut |err| {
if let Some(expected_ty) = expected.only_has_type(self) {
self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
}
if let Some(fn_span) = fn_span {
err.span_label(
fn_span,
"implicitly returns `()` as its body has no tail or `return` \
expression",
);
}
},
false,
);
}
}
});
if ctxt.may_break {
// If we can break from the block, then the block's exit is always reachable
// (... as long as the entry is reachable) - regardless of the tail of the block.
self.diverges.set(prev_diverges);
}
let mut ty = ctxt.coerce.unwrap().complete(self);
if self.has_errors.get() || ty.references_error() {
ty = self.tcx.ty_error()
}
self.write_ty(blk.hir_id, ty);
*self.ps.borrow_mut() = prev;
ty
}
fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
match node {
Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })
| Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(_, body_id), .. }) => {
let body = self.tcx.hir().body(body_id);
if let ExprKind::Block(block, _) = &body.value.kind {
return Some(block.span);
}
}
_ => {}
}
None
}
/// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, Ident)> {
let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
}
/// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
pub(super) fn get_node_fn_decl(
&self,
node: Node<'tcx>,
) -> Option<(&'tcx hir::FnDecl<'tcx>, Ident, bool)> {
match node {
Node::Item(&hir::Item { ident, kind: hir::ItemKind::Fn(ref sig, ..), .. }) => {
// This is less than ideal, it will not suggest a return type span on any
// method called `main`, regardless of whether it is actually the entry point,
// but it will still present it as the reason for the expected type.
Some((&sig.decl, ident, ident.name != sym::main))
}
Node::TraitItem(&hir::TraitItem {
ident,
kind: hir::TraitItemKind::Fn(ref sig, ..),
..
}) => Some((&sig.decl, ident, true)),
Node::ImplItem(&hir::ImplItem {
ident,
kind: hir::ImplItemKind::Fn(ref sig, ..),
..
}) => Some((&sig.decl, ident, false)),
_ => None,
}
}
/// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
/// suggestion can be made, `None` otherwise.
pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, bool)> {
// Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
// `while` before reaching it, as block tail returns are not available in them.
self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
let parent = self.tcx.hir().get(blk_id);
self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
})
}
/// On implicit return expressions with mismatched types, provides the following suggestions:
///
/// - Points out the method's return type as the reason for the expected type.
/// - Possible missing semicolon.
/// - Possible missing return type if the return type is the default, and not `fn main()`.
pub fn suggest_mismatched_types_on_tail(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &'tcx hir::Expr<'tcx>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
cause_span: Span,
blk_id: hir::HirId,
) -> bool {
let expr = expr.peel_drop_temps();
self.suggest_missing_semicolon(err, expr, expected, cause_span);
let mut pointing_at_return_type = false;
if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
pointing_at_return_type =
self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest);
}
pointing_at_return_type
}
/// When encountering an fn-like ctor that needs to unify with a value, check whether calling
/// the ctor would successfully solve the type mismatch and if so, suggest it:
/// ```
/// fn foo(x: usize) -> usize { x }
/// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
/// ```
fn suggest_fn_call(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr<'_>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
) -> bool {
let hir = self.tcx.hir();
let (def_id, sig) = match *found.kind() {
ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig()),
_ => return false,
};
let sig = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig).0;
let sig = self.normalize_associated_types_in(expr.span, &sig);
if self.can_coerce(sig.output(), expected) {
let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
(String::new(), Applicability::MachineApplicable)
} else {
("...".to_string(), Applicability::HasPlaceholders)
};
let mut msg = "call this function";
match hir.get_if_local(def_id) {
Some(
Node::Item(hir::Item { kind: ItemKind::Fn(.., body_id), .. })
| Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::Fn(_, body_id), ..
})
| Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Provided(body_id)),
..
}),
) => {
let body = hir.body(*body_id);
sugg_call = body
.params
.iter()
.map(|param| match &param.pat.kind {
hir::PatKind::Binding(_, _, ident, None)
if ident.name != kw::SelfLower =>
{
ident.to_string()
}
_ => "_".to_string(),
})
.collect::<Vec<_>>()
.join(", ");
}
Some(Node::Expr(hir::Expr {
kind: ExprKind::Closure(_, _, body_id, _, _),
span: full_closure_span,
..
})) => {
if *full_closure_span == expr.span {
return false;
}
msg = "call this closure";
let body = hir.body(*body_id);
sugg_call = body
.params
.iter()
.map(|param| match &param.pat.kind {
hir::PatKind::Binding(_, _, ident, None)
if ident.name != kw::SelfLower =>
{
ident.to_string()
}
_ => "_".to_string(),
})
.collect::<Vec<_>>()
.join(", ");
}
Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
match def_id.as_local().map(|def_id| hir.def_kind(def_id)) {
Some(DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
msg = "instantiate this tuple variant";
}
Some(DefKind::Ctor(CtorOf::Struct, _)) => {
msg = "instantiate this tuple struct";
}
_ => {}
}
}
Some(Node::ForeignItem(hir::ForeignItem {
kind: hir::ForeignItemKind::Fn(_, idents, _),
..
})) => {
sugg_call = idents
.iter()
.map(|ident| {
if ident.name != kw::SelfLower {
ident.to_string()
} else {
"_".to_string()
}
})
.collect::<Vec<_>>()
.join(", ")
}
Some(Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Required(idents)),
..
})) => {
sugg_call = idents
.iter()
.map(|ident| {
if ident.name != kw::SelfLower {
ident.to_string()
} else {
"_".to_string()
}
})
.collect::<Vec<_>>()
.join(", ")
}
_ => {}
}
err.span_suggestion_verbose(
expr.span.shrink_to_hi(),
&format!("use parentheses to {}", msg),
format!("({})", sugg_call),
applicability,
);
return true;
}
false
}
pub fn suggest_deref_ref_or_into(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr<'_>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
) {
if let Some((sp, msg, suggestion, applicability)) = self.check_ref(expr, found, expected) {
err.span_suggestion(sp, msg, suggestion, applicability);
} else if let (ty::FnDef(def_id, ..), true) =
(&found.kind(), self.suggest_fn_call(err, expr, expected, found))
{
if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
let sp = self.sess().source_map().guess_head_span(sp);
err.span_label(sp, &format!("{} defined here", found));
}
} else if !self.check_for_cast(err, expr, found, expected, expected_ty_expr) {
let is_struct_pat_shorthand_field =
self.is_hir_id_from_struct_pattern_shorthand_field(expr.hir_id, expr.span);
let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id);
if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
let mut suggestions = iter::repeat(&expr_text)
.zip(methods.iter())
.filter_map(|(receiver, method)| {
let method_call = format!(".{}()", method.ident);
if receiver.ends_with(&method_call) {
None // do not suggest code that is already there (#53348)
} else {
let method_call_list = [".to_vec()", ".to_string()"];
let sugg = if receiver.ends_with(".clone()")
&& method_call_list.contains(&method_call.as_str())
{
let max_len = receiver.rfind('.').unwrap();
format!("{}{}", &receiver[..max_len], method_call)
} else {
if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
format!("({}){}", receiver, method_call)
} else {
format!("{}{}", receiver, method_call)
}
};
Some(if is_struct_pat_shorthand_field {
format!("{}: {}", receiver, sugg)
} else {
sugg
})
}
})
.peekable();
if suggestions.peek().is_some() {
err.span_suggestions(
expr.span,
"try using a conversion method",
suggestions,
Applicability::MaybeIncorrect,
);
}
}
}
}
/// When encountering the expected boxed value allocated in the stack, suggest allocating it
/// in the heap by calling `Box::new()`.
pub(super) fn suggest_boxing_when_appropriate(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr<'_>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
) {
if self.tcx.hir().is_inside_const_context(expr.hir_id) {
// Do not suggest `Box::new` in const context.
return;
}
if !expected.is_box() || found.is_box() {
return;
}
let boxed_found = self.tcx.mk_box(found);
if let (true, Ok(snippet)) = (
self.can_coerce(boxed_found, expected),
self.sess().source_map().span_to_snippet(expr.span),
) {
err.span_suggestion(
expr.span,
"store this in the heap by calling `Box::new`",
format!("Box::new({})", snippet),
Applicability::MachineApplicable,
);
err.note(
"for more on the distinction between the stack and the heap, read \
https://doc.rust-lang.org/book/ch15-01-box.html, \
https://doc.rust-lang.org/rust-by-example/std/box.html, and \
https://doc.rust-lang.org/std/boxed/index.html",
);
}
}
pub(super) fn note_internal_mutation_in_method(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr<'_>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
) {
if found != self.tcx.types.unit {
return;
}
if let ExprKind::MethodCall(path_segment, _, [rcvr, ..], _) = expr.kind {
if self
.typeck_results
.borrow()
.expr_ty_adjusted_opt(rcvr)
.map_or(true, |ty| expected.peel_refs() != ty.peel_refs())
{
return;
}
let mut sp = MultiSpan::from_span(path_segment.ident.span);
sp.push_span_label(
path_segment.ident.span,
format!(
"this call modifies {} in-place",
match rcvr.kind {
ExprKind::Path(QPath::Resolved(
None,
hir::Path { segments: [segment], .. },
)) => format!("`{}`", segment.ident),
_ => "its receiver".to_string(),
}
),
);
sp.push_span_label(
rcvr.span,
"you probably want to use this value after calling the method...".to_string(),
);
err.span_note(
sp,
&format!("method `{}` modifies its receiver in-place", path_segment.ident),
);
err.note(&format!("...instead of the `()` output of method `{}`", path_segment.ident));
}
}
/// When encountering an `impl Future` where `BoxFuture` is expected, suggest `Box::pin`.
pub(super) fn suggest_calling_boxed_future_when_appropriate(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr<'_>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
) -> bool {
// Handle #68197.
if self.tcx.hir().is_inside_const_context(expr.hir_id) {
// Do not suggest `Box::new` in const context.
return false;
}
let pin_did = self.tcx.lang_items().pin_type();
match expected.kind() {
ty::Adt(def, _) if Some(def.did) != pin_did => return false,
// This guards the `unwrap` and `mk_box` below.
_ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return false,
_ => {}
}
let boxed_found = self.tcx.mk_box(found);
let new_found = self.tcx.mk_lang_item(boxed_found, LangItem::Pin).unwrap();
if let (true, Ok(snippet)) = (
self.can_coerce(new_found, expected),
self.sess().source_map().span_to_snippet(expr.span),
) {
match found.kind() {
ty::Adt(def, _) if def.is_box() => {
err.help("use `Box::pin`");
}
_ => {
err.span_suggestion(
expr.span,
"you need to pin and box this expression",
format!("Box::pin({})", snippet),
Applicability::MachineApplicable,
);
}
}
true
} else {
false
}
}
/// A common error is to forget to add a semicolon at the end of a block, e.g.,
///
/// ```
/// fn foo() {
/// bar_that_returns_u32()
/// }
/// ```
///
/// This routine checks if the return expression in a block would make sense on its own as a
/// statement and the return type has been left as default or has been specified as `()`. If so,
/// it suggests adding a semicolon.
fn suggest_missing_semicolon(
&self,
err: &mut DiagnosticBuilder<'_>,
expression: &'tcx hir::Expr<'tcx>,
expected: Ty<'tcx>,
cause_span: Span,
) {
if expected.is_unit() {
// `BlockTailExpression` only relevant if the tail expr would be
// useful on its own.
match expression.kind {
ExprKind::Call(..)
| ExprKind::MethodCall(..)
| ExprKind::Loop(..)
| ExprKind::Match(..)
| ExprKind::Block(..) => {
err.span_suggestion(
cause_span.shrink_to_hi(),
"try adding a semicolon",
";".to_string(),
Applicability::MachineApplicable,
);
}
_ => (),
}
}
}
/// A possible error is to forget to add a return type that is needed:
///
/// ```
/// fn foo() {
/// bar_that_returns_u32()
/// }
/// ```
///
/// This routine checks if the return type is left as default, the method is not part of an
/// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
/// type.
pub(super) fn suggest_missing_return_type(
&self,
err: &mut DiagnosticBuilder<'_>,
fn_decl: &hir::FnDecl<'_>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
can_suggest: bool,
) -> bool {
// Only suggest changing the return type for methods that
// haven't set a return type at all (and aren't `fn main()` or an impl).
match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
(&hir::FnRetTy::DefaultReturn(span), true, true, true) => {
err.span_suggestion(
span,
"try adding a return type",
format!("-> {} ", self.resolve_vars_with_obligations(found)),
Applicability::MachineApplicable,
);
true
}
(&hir::FnRetTy::DefaultReturn(span), false, true, true) => {
err.span_label(span, "possibly return type missing here?");
true
}
(&hir::FnRetTy::DefaultReturn(span), _, false, true) => {
// `fn main()` must return `()`, do not suggest changing return type
err.span_label(span, "expected `()` because of default return type");
true
}
// expectation was caused by something else, not the default return
(&hir::FnRetTy::DefaultReturn(_), _, _, false) => false,
(&hir::FnRetTy::Return(ref ty), _, _, _) => {
// Only point to return type if the expected type is the return type, as if they
// are not, the expectation must have been caused by something else.
debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
let sp = ty.span;
let ty = AstConv::ast_ty_to_ty(self, ty);
debug!("suggest_missing_return_type: return type {:?}", ty);
debug!("suggest_missing_return_type: expected type {:?}", ty);
if ty.kind() == expected.kind() {
err.span_label(sp, format!("expected `{}` because of return type", expected));
return true;
}
false
}
}
}
/// A possible error is to forget to add `.await` when using futures:
///
/// ```
/// async fn make_u32() -> u32 {
/// 22
/// }
///
/// fn take_u32(x: u32) {}
///
/// async fn foo() {
/// let x = make_u32();
/// take_u32(x);
/// }
/// ```
///
/// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
/// expected type. If this is the case, and we are inside of an async body, it suggests adding
/// `.await` to the tail of the expression.
pub(super) fn suggest_missing_await(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr<'_>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
) {
debug!("suggest_missing_await: expr={:?} expected={:?}, found={:?}", expr, expected, found);
// `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
// body isn't `async`.
let item_id = self.tcx().hir().get_parent_node(self.body_id);
if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
let body = self.tcx().hir().body(body_id);
if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
let sp = expr.span;
// Check for `Future` implementations by constructing a predicate to
// prove: `<T as Future>::Output == U`
let future_trait = self.tcx.require_lang_item(LangItem::Future, Some(sp));
let item_def_id = self
.tcx
.associated_items(future_trait)
.in_definition_order()
.next()
.unwrap()
.def_id;
// `<T as Future>::Output`
let projection_ty = ty::ProjectionTy {
// `T`
substs: self
.tcx
.mk_substs_trait(found, self.fresh_substs_for_item(sp, item_def_id)),
// `Future::Output`
item_def_id,
};
let predicate = ty::PredicateAtom::Projection(ty::ProjectionPredicate {
projection_ty,
ty: expected,
})
.potentially_quantified(self.tcx, ty::PredicateKind::ForAll);
let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
debug!("suggest_missing_await: trying obligation {:?}", obligation);
if self.infcx.predicate_may_hold(&obligation) {
debug!("suggest_missing_await: obligation held: {:?}", obligation);
if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
err.span_suggestion(
sp,
"consider using `.await` here",
format!("{}.await", code),
Applicability::MaybeIncorrect,
);
} else {
debug!("suggest_missing_await: no snippet for {:?}", sp);
}
} else {
debug!("suggest_missing_await: obligation did not hold: {:?}", obligation)
}
}
}
}
pub(super) fn suggest_missing_parentheses(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr<'_>,
) {
let sp = self.tcx.sess.source_map().start_point(expr.span);
if let Some(sp) = self.tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp) {
// `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`
self.tcx.sess.parse_sess.expr_parentheses_needed(err, *sp, None);
}
}
pub(super) fn note_need_for_fn_pointer(
&self,
err: &mut DiagnosticBuilder<'_>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
) {
let (sig, did, substs) = match (&expected.kind(), &found.kind()) {
(ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
let sig1 = self.tcx.fn_sig(*did1).subst(self.tcx, substs1);
let sig2 = self.tcx.fn_sig(*did2).subst(self.tcx, substs2);
if sig1 != sig2 {
return;
}
err.note(
"different `fn` items always have unique types, even if their signatures are \
the same",
);
(sig1, *did1, substs1)
}
(ty::FnDef(did, substs), ty::FnPtr(sig2)) => {
let sig1 = self.tcx.fn_sig(*did).subst(self.tcx, substs);
if sig1 != *sig2 {
return;
}
(sig1, *did, substs)
}
_ => return,
};
err.help(&format!("change the expected type to be function pointer `{}`", sig));
err.help(&format!(
"if the expected type is due to type inference, cast the expected `fn` to a function \
pointer: `{} as {}`",
self.tcx.def_path_str_with_substs(did, substs),
sig
));
}
/// A common error is to add an extra semicolon:
///
/// ```
/// fn foo() -> usize {
/// 22;
/// }
/// ```
///
/// This routine checks if the final statement in a block is an
/// expression with an explicit semicolon whose type is compatible
/// with `expected_ty`. If so, it suggests removing the semicolon.
fn consider_hint_about_removing_semicolon(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
err: &mut DiagnosticBuilder<'_>,
) {
if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
err.span_suggestion(
span_semi,
"consider removing this semicolon",
String::new(),
Applicability::MachineApplicable,
);
}
}
pub(super) fn could_remove_semicolon(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
) -> Option<Span> {
// Be helpful when the user wrote `{... expr;}` and
// taking the `;` off is enough to fix the error.
let last_stmt = blk.stmts.last()?;
let last_expr = match last_stmt.kind {
hir::StmtKind::Semi(ref e) => e,
_ => return None,
};
let last_expr_ty = self.node_ty(last_expr.hir_id);
if matches!(last_expr_ty.kind(), ty::Error(_))
|| self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err()
{
return None;
}
let original_span = original_sp(last_stmt.span, blk.span);
Some(original_span.with_lo(original_span.hi() - BytePos(1)))
}
// Instantiates the given path, which must refer to an item with the given
// number of type parameters and type.
pub fn instantiate_value_path(
&self,
segments: &[hir::PathSegment<'_>],
self_ty: Option<Ty<'tcx>>,
res: Res,
span: Span,
hir_id: hir::HirId,
) -> (Ty<'tcx>, Res) {
debug!(
"instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
segments, self_ty, res, hir_id,
);
let tcx = self.tcx;
let path_segs = match res {
Res::Local(_) | Res::SelfCtor(_) => vec![],
Res::Def(kind, def_id) => {
AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id)
}
_ => bug!("instantiate_value_path on {:?}", res),
};
let mut user_self_ty = None;
let mut is_alias_variant_ctor = false;
match res {
Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
if let Some(self_ty) = self_ty {
let adt_def = self_ty.ty_adt_def().unwrap();
user_self_ty = Some(UserSelfTy { impl_def_id: adt_def.did, self_ty });
is_alias_variant_ctor = true;
}
}
Res::Def(DefKind::AssocFn | DefKind::AssocConst, def_id) => {
let container = tcx.associated_item(def_id).container;
debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
match container {
ty::TraitContainer(trait_did) => {
callee::check_legal_trait_for_method_call(tcx, span, None, trait_did)
}
ty::ImplContainer(impl_def_id) => {
if segments.len() == 1 {
// `<T>::assoc` will end up here, and so
// can `T::assoc`. It this came from an
// inherent impl, we need to record the
// `T` for posterity (see `UserSelfTy` for
// details).
let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
user_self_ty = Some(UserSelfTy { impl_def_id, self_ty });
}
}
}
}
_ => {}
}
// Now that we have categorized what space the parameters for each
// segment belong to, let's sort out the parameters that the user
// provided (if any) into their appropriate spaces. We'll also report
// errors if type parameters are provided in an inappropriate place.
let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
let generics_has_err = AstConv::prohibit_generics(
self,
segments.iter().enumerate().filter_map(|(index, seg)| {
if !generic_segs.contains(&index) || is_alias_variant_ctor {
Some(seg)
} else {
None
}
}),
);
if let Res::Local(hid) = res {
let ty = self.local_ty(span, hid).decl_ty;
let ty = self.normalize_associated_types_in(span, &ty);
self.write_ty(hir_id, ty);
return (ty, res);
}
if generics_has_err {
// Don't try to infer type parameters when prohibited generic arguments were given.
user_self_ty = None;
}
// Now we have to compare the types that the user *actually*
// provided against the types that were *expected*. If the user
// did not provide any types, then we want to substitute inference
// variables. If the user provided some types, we may still need
// to add defaults. If the user provided *too many* types, that's
// a problem.
let mut infer_args_for_err = FxHashSet::default();
for &PathSeg(def_id, index) in &path_segs {
let seg = &segments[index];
let generics = tcx.generics_of(def_id);
// Argument-position `impl Trait` is treated as a normal generic
// parameter internally, but we don't allow users to specify the
// parameter's value explicitly, so we have to do some error-
// checking here.
if let GenericArgCountResult {
correct: Err(GenericArgCountMismatch { reported: Some(ErrorReported), .. }),
..
} = AstConv::check_generic_arg_count_for_call(
tcx, span, &generics, &seg, false, // `is_method_call`
) {
infer_args_for_err.insert(index);
self.set_tainted_by_errors(); // See issue #53251.
}
}
let has_self = path_segs
.last()
.map(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self)
.unwrap_or(false);
let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id));
match *ty.kind() {
ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
let variant = adt_def.non_enum_variant();
let ctor_def_id = variant.ctor_def_id.unwrap();
(
Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
Some(substs),
)
}
_ => {
let mut err = tcx.sess.struct_span_err(
span,
"the `Self` constructor can only be used with tuple or unit structs",
);
if let Some(adt_def) = ty.ty_adt_def() {
match adt_def.adt_kind() {
AdtKind::Enum => {
err.help("did you mean to use one of the enum's variants?");
}
AdtKind::Struct | AdtKind::Union => {
err.span_suggestion(
span,
"use curly brackets",
String::from("Self { /* fields */ }"),
Applicability::HasPlaceholders,
);
}
}
}
err.emit();
return (tcx.ty_error(), res);
}
}
} else {
(res, None)
};
let def_id = res.def_id();
// The things we are substituting into the type should not contain
// escaping late-bound regions, and nor should the base type scheme.
let ty = tcx.type_of(def_id);
let arg_count = GenericArgCountResult {
explicit_late_bound: ExplicitLateBound::No,
correct: if infer_args_for_err.is_empty() {
Ok(())
} else {
Err(GenericArgCountMismatch::default())
},
};
let substs = self_ctor_substs.unwrap_or_else(|| {
AstConv::create_substs_for_generic_args(
tcx,
def_id,
&[][..],
has_self,
self_ty,
arg_count,
// Provide the generic args, and whether types should be inferred.
|def_id| {
if let Some(&PathSeg(_, index)) =
path_segs.iter().find(|&PathSeg(did, _)| *did == def_id)
{
// If we've encountered an `impl Trait`-related error, we're just
// going to infer the arguments for better error messages.
if !infer_args_for_err.contains(&index) {
// Check whether the user has provided generic arguments.
if let Some(ref data) = segments[index].args {
return (Some(data), segments[index].infer_args);
}
}
return (None, segments[index].infer_args);
}
(None, true)
},
// Provide substitutions for parameters for which (valid) arguments have been provided.
|param, arg| match (&param.kind, arg) {
(GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
AstConv::ast_region_to_region(self, lt, Some(param)).into()
}
(GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
self.to_ty(ty).into()
}
(GenericParamDefKind::Const, GenericArg::Const(ct)) => {
self.const_arg_to_const(&ct.value, param.def_id).into()
}
_ => unreachable!(),
},
// Provide substitutions for parameters for which arguments are inferred.
|substs, param, infer_args| {
match param.kind {
GenericParamDefKind::Lifetime => {
self.re_infer(Some(param), span).unwrap().into()
}
GenericParamDefKind::Type { has_default, .. } => {
if !infer_args && has_default {
// If we have a default, then we it doesn't matter that we're not
// inferring the type arguments: we provide the default where any
// is missing.
let default = tcx.type_of(param.def_id);
self.normalize_ty(
span,
default.subst_spanned(tcx, substs.unwrap(), Some(span)),
)
.into()
} else {
// If no type arguments were provided, we have to infer them.
// This case also occurs as a result of some malformed input, e.g.
// a lifetime argument being given instead of a type parameter.
// Using inference instead of `Error` gives better error messages.
self.var_for_def(span, param)
}
}
GenericParamDefKind::Const => {
// FIXME(const_generics:defaults)
// No const parameters were provided, we have to infer them.
self.var_for_def(span, param)
}
}
},
)
});
assert!(!substs.has_escaping_bound_vars());
assert!(!ty.has_escaping_bound_vars());
// First, store the "user substs" for later.
self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
self.add_required_obligations(span, def_id, &substs);
// Substitute the values for the type parameters into the type of
// the referenced item.
let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
// In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
// is inherent, there is no `Self` parameter; instead, the impl needs
// type parameters, which we can infer by unifying the provided `Self`
// with the substituted impl type.
// This also occurs for an enum variant on a type alias.
let ty = tcx.type_of(impl_def_id);
let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
Ok(ok) => self.register_infer_ok_obligations(ok),
Err(_) => {
self.tcx.sess.delay_span_bug(
span,
&format!(
"instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
self_ty,
impl_ty,
),
);
}
}
}
self.check_rustc_args_require_const(def_id, hir_id, span);
debug!("instantiate_value_path: type of {:?} is {:?}", hir_id, ty_substituted);
self.write_substs(hir_id, substs);
(ty_substituted, res)
}
/// Add all the obligations that are required, substituting and normalized appropriately.
fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
for (i, mut obligation) in traits::predicates_for_generics(
traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
self.param_env,
bounds,
)
.enumerate()
{
// This makes the error point at the bound, but we want to point at the argument
if let Some(span) = spans.get(i) {
obligation.cause.make_mut().code = traits::BindingObligation(def_id, *span);
}
self.register_predicate(obligation);
}
}
fn check_rustc_args_require_const(&self, def_id: DefId, hir_id: hir::HirId, span: Span) {
// We're only interested in functions tagged with
// #[rustc_args_required_const], so ignore anything that's not.
if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
return;
}
// If our calling expression is indeed the function itself, we're good!
// If not, generate an error that this can only be called directly.
if let Node::Expr(expr) = self.tcx.hir().get(self.tcx.hir().get_parent_node(hir_id)) {
if let ExprKind::Call(ref callee, ..) = expr.kind {
if callee.hir_id == hir_id {
return;
}
}
}
self.tcx.sess.span_err(
span,
"this function can only be invoked directly, not through a function pointer",
);
}
/// Resolves `typ` by a single level if `typ` is a type variable.
/// If no resolution is possible, then an error is reported.
/// Numeric inference variables may be left unresolved.
pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
let ty = self.resolve_vars_with_obligations(ty);
if !ty.is_ty_var() {
ty
} else {
if !self.is_tainted_by_errors() {
self.emit_inference_failure_err((**self).body_id, sp, ty.into(), E0282)
.note("type must be known at this point")
.emit();
}
let err = self.tcx.ty_error();
self.demand_suptype(sp, err, ty);
err
}
}
pub(super) fn with_breakable_ctxt<F: FnOnce() -> R, R>(
&self,
id: hir::HirId,
ctxt: BreakableCtxt<'tcx>,
f: F,
) -> (BreakableCtxt<'tcx>, R) {
let index;
{
let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
index = enclosing_breakables.stack.len();
enclosing_breakables.by_id.insert(id, index);
enclosing_breakables.stack.push(ctxt);
}
let result = f();
let ctxt = {
let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
debug_assert!(enclosing_breakables.stack.len() == index + 1);
enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
enclosing_breakables.stack.pop().expect("missing breakable context")
};
(ctxt, result)
}
/// Instantiate a QueryResponse in a probe context, without a
/// good ObligationCause.
pub(super) fn probe_instantiate_query_response(
&self,
span: Span,
original_values: &OriginalQueryValues<'tcx>,
query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
) -> InferResult<'tcx, Ty<'tcx>> {
self.instantiate_query_response_and_region_obligations(
&traits::ObligationCause::misc(span, self.body_id),
self.param_env,
original_values,
query_result,
)
}
/// Returns `true` if an expression is contained inside the LHS of an assignment expression.
pub(super) fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
let mut contained_in_place = false;
while let hir::Node::Expr(parent_expr) =
self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
{
match &parent_expr.kind {
hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
if lhs.hir_id == expr_id {
contained_in_place = true;
break;
}
}
_ => (),
}
expr_id = parent_expr.hir_id;
}
contained_in_place
}
}
impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
type Target = Inherited<'a, 'tcx>;
fn deref(&self) -> &Self::Target {
&self.inh
}
}
impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
self.tcx
}
fn item_def_id(&self) -> Option<DefId> {
None
}
fn default_constness_for_trait_bounds(&self) -> hir::Constness {
// FIXME: refactor this into a method
let node = self.tcx.hir().get(self.body_id);
if let Some(fn_like) = FnLikeNode::from_node(node) {
fn_like.constness()
} else {
hir::Constness::NotConst
}
}
fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
let tcx = self.tcx;
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
let item_id = tcx.hir().ty_param_owner(hir_id);
let item_def_id = tcx.hir().local_def_id(item_id);
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id];
ty::GenericPredicates {
parent: None,
predicates: tcx.arena.alloc_from_iter(
self.param_env.caller_bounds().iter().filter_map(|predicate| {
match predicate.skip_binders() {
ty::PredicateAtom::Trait(data, _) if data.self_ty().is_param(index) => {
// HACK(eddyb) should get the original `Span`.
let span = tcx.def_span(def_id);
Some((predicate, span))
}
_ => None,
}
}),
),
}
}
fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
let v = match def {
Some(def) => infer::EarlyBoundRegion(span, def.name),
None => infer::MiscVariable(span),
};
Some(self.next_region_var(v))
}
fn allow_ty_infer(&self) -> bool {
true
}
fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
if let Some(param) = param {
if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
return ty;
}
unreachable!()
} else {
self.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::TypeInference,
span,
})
}
}
fn ct_infer(
&self,
ty: Ty<'tcx>,
param: Option<&ty::GenericParamDef>,
span: Span,
) -> &'tcx Const<'tcx> {
if let Some(param) = param {
if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
return ct;
}
unreachable!()
} else {
self.next_const_var(
ty,
ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
)
}
}
fn projected_ty_from_poly_trait_ref(
&self,
span: Span,
item_def_id: DefId,
item_segment: &hir::PathSegment<'_>,
poly_trait_ref: ty::PolyTraitRef<'tcx>,
) -> Ty<'tcx> {
let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
span,
infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
&poly_trait_ref,
);
let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
self,
self.tcx,
span,
item_def_id,
item_segment,
trait_ref.substs,
);
self.tcx().mk_projection(item_def_id, item_substs)
}
fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
if ty.has_escaping_bound_vars() {
ty // FIXME: normalization and escaping regions
} else {
self.normalize_associated_types_in(span, &ty)
}
}
fn set_tainted_by_errors(&self) {
self.infcx.set_tainted_by_errors()
}
fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
self.write_ty(hir_id, ty)
}
}