1 use super::method
::MethodCallee
;
2 use super::{Expectation, FnCtxt, TupleArgumentsFlag}
;
3 use crate::type_error_struct
;
5 use rustc_errors
::{struct_span_err, Applicability, Diagnostic}
;
7 use rustc_hir
::def
::{self, Namespace, Res}
;
8 use rustc_hir
::def_id
::DefId
;
11 traits
::{self, Obligation}
,
14 infer
::type_variable
::{TypeVariableOrigin, TypeVariableOriginKind}
,
15 traits
::ObligationCause
,
17 use rustc_middle
::ty
::adjustment
::{
18 Adjust
, Adjustment
, AllowTwoPhase
, AutoBorrow
, AutoBorrowMutability
,
20 use rustc_middle
::ty
::subst
::{Subst, SubstsRef}
;
21 use rustc_middle
::ty
::{self, Ty, TyCtxt, TypeVisitable}
;
22 use rustc_span
::def_id
::LocalDefId
;
23 use rustc_span
::symbol
::{sym, Ident}
;
25 use rustc_target
::spec
::abi
;
26 use rustc_trait_selection
::autoderef
::Autoderef
;
27 use rustc_trait_selection
::traits
::query
::evaluate_obligation
::InferCtxtExt
;
31 /// Checks that it is legal to call methods of the trait corresponding
32 /// to `trait_id` (this only cares about the trait, not the specific
33 /// method that is called).
34 pub fn check_legal_trait_for_method_call(
37 receiver
: Option
<Span
>,
41 if tcx
.lang_items().drop_trait() == Some(trait_id
) {
42 let mut err
= struct_span_err
!(tcx
.sess
, span
, E0040
, "explicit use of destructor method");
43 err
.span_label(span
, "explicit destructor calls not allowed");
45 let (sp
, suggestion
) = receiver
46 .and_then(|s
| tcx
.sess
.source_map().span_to_snippet(s
).ok())
47 .filter(|snippet
| !snippet
.is_empty())
48 .map(|snippet
| (expr_span
, format
!("drop({snippet})")))
49 .unwrap_or_else(|| (span
, "drop".to_string()));
53 "consider using `drop` function",
55 Applicability
::MaybeIncorrect
,
64 DeferredClosure(LocalDefId
, ty
::FnSig
<'tcx
>),
65 /// E.g., enum variant constructors.
66 Overloaded(MethodCallee
<'tcx
>),
69 impl<'a
, 'tcx
> FnCtxt
<'a
, 'tcx
> {
72 call_expr
: &'tcx hir
::Expr
<'tcx
>,
73 callee_expr
: &'tcx hir
::Expr
<'tcx
>,
74 arg_exprs
: &'tcx
[hir
::Expr
<'tcx
>],
75 expected
: Expectation
<'tcx
>,
77 let original_callee_ty
= match &callee_expr
.kind
{
78 hir
::ExprKind
::Path(hir
::QPath
::Resolved(..) | hir
::QPath
::TypeRelative(..)) => self
79 .check_expr_with_expectation_and_args(
81 Expectation
::NoExpectation
,
84 _
=> self.check_expr(callee_expr
),
87 let expr_ty
= self.structurally_resolved_type(call_expr
.span
, original_callee_ty
);
89 let mut autoderef
= self.autoderef(callee_expr
.span
, expr_ty
);
90 let mut result
= None
;
91 while result
.is_none() && autoderef
.next().is_some() {
92 result
= self.try_overloaded_call_step(call_expr
, callee_expr
, arg_exprs
, &autoderef
);
94 self.register_predicates(autoderef
.into_obligations());
96 let output
= match result
{
98 // this will report an error since original_callee_ty is not a fn
99 self.confirm_builtin_call(
108 Some(CallStep
::Builtin(callee_ty
)) => {
109 self.confirm_builtin_call(call_expr
, callee_expr
, callee_ty
, arg_exprs
, expected
)
112 Some(CallStep
::DeferredClosure(def_id
, fn_sig
)) => {
113 self.confirm_deferred_closure_call(call_expr
, arg_exprs
, expected
, def_id
, fn_sig
)
116 Some(CallStep
::Overloaded(method_callee
)) => {
117 self.confirm_overloaded_call(call_expr
, arg_exprs
, expected
, method_callee
)
121 // we must check that return type of called functions is WF:
122 self.register_wf_obligation(output
.into(), call_expr
.span
, traits
::WellFormed(None
));
127 fn try_overloaded_call_step(
129 call_expr
: &'tcx hir
::Expr
<'tcx
>,
130 callee_expr
: &'tcx hir
::Expr
<'tcx
>,
131 arg_exprs
: &'tcx
[hir
::Expr
<'tcx
>],
132 autoderef
: &Autoderef
<'a
, 'tcx
>,
133 ) -> Option
<CallStep
<'tcx
>> {
135 self.structurally_resolved_type(autoderef
.span(), autoderef
.final_ty(false));
137 "try_overloaded_call_step(call_expr={:?}, adjusted_ty={:?})",
138 call_expr
, adjusted_ty
141 // If the callee is a bare function or a closure, then we're all set.
142 match *adjusted_ty
.kind() {
143 ty
::FnDef(..) | ty
::FnPtr(_
) => {
144 let adjustments
= self.adjust_steps(autoderef
);
145 self.apply_adjustments(callee_expr
, adjustments
);
146 return Some(CallStep
::Builtin(adjusted_ty
));
149 ty
::Closure(def_id
, substs
) => {
150 let def_id
= def_id
.expect_local();
152 // Check whether this is a call to a closure where we
153 // haven't yet decided on whether the closure is fn vs
154 // fnmut vs fnonce. If so, we have to defer further processing.
155 if self.closure_kind(substs
).is_none() {
156 let closure_sig
= substs
.as_closure().sig();
157 let closure_sig
= self.replace_bound_vars_with_fresh_vars(
162 let adjustments
= self.adjust_steps(autoderef
);
163 self.record_deferred_call_resolution(
165 DeferredCallResolution
{
171 closure_substs
: substs
,
174 return Some(CallStep
::DeferredClosure(def_id
, closure_sig
));
178 // Hack: we know that there are traits implementing Fn for &F
179 // where F:Fn and so forth. In the particular case of types
180 // like `x: &mut FnMut()`, if there is a call `x()`, we would
181 // normally translate to `FnMut::call_mut(&mut x, ())`, but
182 // that winds up requiring `mut x: &mut FnMut()`. A little
183 // over the top. The simplest fix by far is to just ignore
184 // this case and deref again, so we wind up with
185 // `FnMut::call_mut(&mut *x, ())`.
186 ty
::Ref(..) if autoderef
.step_count() == 0 => {
193 // Now, we look for the implementation of a Fn trait on the object's type.
194 // We first do it with the explicit instruction to look for an impl of
195 // `Fn<Tuple>`, with the tuple `Tuple` having an arity corresponding
196 // to the number of call parameters.
197 // If that fails (or_else branch), we try again without specifying the
198 // shape of the tuple (hence the None). This allows to detect an Fn trait
199 // is implemented, and use this information for diagnostic.
200 self.try_overloaded_call_traits(call_expr
, adjusted_ty
, Some(arg_exprs
))
201 .or_else(|| self.try_overloaded_call_traits(call_expr
, adjusted_ty
, None
))
202 .map(|(autoref
, method
)| {
203 let mut adjustments
= self.adjust_steps(autoderef
);
204 adjustments
.extend(autoref
);
205 self.apply_adjustments(callee_expr
, adjustments
);
206 CallStep
::Overloaded(method
)
210 fn try_overloaded_call_traits(
212 call_expr
: &hir
::Expr
<'_
>,
213 adjusted_ty
: Ty
<'tcx
>,
214 opt_arg_exprs
: Option
<&'tcx
[hir
::Expr
<'tcx
>]>,
215 ) -> Option
<(Option
<Adjustment
<'tcx
>>, MethodCallee
<'tcx
>)> {
216 // Try the options that are least restrictive on the caller first.
217 for (opt_trait_def_id
, method_name
, borrow
) in [
218 (self.tcx
.lang_items().fn_trait(), Ident
::with_dummy_span(sym
::call
), true),
219 (self.tcx
.lang_items().fn_mut_trait(), Ident
::with_dummy_span(sym
::call_mut
), true),
220 (self.tcx
.lang_items().fn_once_trait(), Ident
::with_dummy_span(sym
::call_once
), false),
222 let Some(trait_def_id
) = opt_trait_def_id
else { continue }
;
224 let opt_input_types
= opt_arg_exprs
.map(|arg_exprs
| {
225 [self.tcx
.mk_tup(arg_exprs
.iter().map(|e
| {
226 self.next_ty_var(TypeVariableOrigin
{
227 kind
: TypeVariableOriginKind
::TypeInference
,
232 let opt_input_types
= opt_input_types
.as_ref().map(AsRef
::as_ref
);
234 if let Some(ok
) = self.lookup_method_in_trait(
241 let method
= self.register_infer_ok_obligations(ok
);
242 let mut autoref
= None
;
244 // Check for &self vs &mut self in the method signature. Since this is either
245 // the Fn or FnMut trait, it should be one of those.
246 let ty
::Ref(region
, _
, mutbl
) = method
.sig
.inputs()[0].kind() else {
247 // The `fn`/`fn_mut` lang item is ill-formed, which should have
248 // caused an error elsewhere.
251 .delay_span_bug(call_expr
.span
, "input to call/call_mut is not a ref?");
255 let mutbl
= match mutbl
{
256 hir
::Mutability
::Not
=> AutoBorrowMutability
::Not
,
257 hir
::Mutability
::Mut
=> AutoBorrowMutability
::Mut
{
258 // For initial two-phase borrow
259 // deployment, conservatively omit
260 // overloaded function call ops.
261 allow_two_phase_borrow
: AllowTwoPhase
::No
,
264 autoref
= Some(Adjustment
{
265 kind
: Adjust
::Borrow(AutoBorrow
::Ref(*region
, mutbl
)),
266 target
: method
.sig
.inputs()[0],
269 return Some((autoref
, method
));
276 /// Give appropriate suggestion when encountering `||{/* not callable */}()`, where the
277 /// likely intention is to call the closure, suggest `(||{})()`. (#55851)
278 fn identify_bad_closure_def_and_call(
280 err
: &mut Diagnostic
,
282 callee_node
: &hir
::ExprKind
<'_
>,
285 let hir
= self.tcx
.hir();
286 let parent_hir_id
= hir
.get_parent_node(hir_id
);
287 let parent_node
= hir
.get(parent_hir_id
);
289 hir
::Node
::Expr(hir
::Expr
{
290 kind
: hir
::ExprKind
::Closure(&hir
::Closure { fn_decl_span, body, .. }
),
293 hir
::ExprKind
::Block(..),
294 ) = (parent_node
, callee_node
)
296 let fn_decl_span
= if hir
.body(body
).generator_kind
297 == Some(hir
::GeneratorKind
::Async(hir
::AsyncGeneratorKind
::Closure
))
299 // Actually need to unwrap a few more layers of HIR to get to
300 // the _real_ closure...
301 let async_closure
= hir
.get_parent_node(hir
.get_parent_node(parent_hir_id
));
302 if let hir
::Node
::Expr(hir
::Expr
{
303 kind
: hir
::ExprKind
::Closure(&hir
::Closure { fn_decl_span, .. }
),
305 }) = hir
.get(async_closure
)
315 let start
= fn_decl_span
.shrink_to_lo();
316 let end
= callee_span
.shrink_to_hi();
317 err
.multipart_suggestion(
318 "if you meant to create this closure and immediately call it, surround the \
319 closure with parentheses",
320 vec
![(start
, "(".to_string()), (end
, ")".to_string())],
321 Applicability
::MaybeIncorrect
,
326 /// Give appropriate suggestion when encountering `[("a", 0) ("b", 1)]`, where the
327 /// likely intention is to create an array containing tuples.
328 fn maybe_suggest_bad_array_definition(
330 err
: &mut Diagnostic
,
331 call_expr
: &'tcx hir
::Expr
<'tcx
>,
332 callee_expr
: &'tcx hir
::Expr
<'tcx
>,
334 let hir_id
= self.tcx
.hir().get_parent_node(call_expr
.hir_id
);
335 let parent_node
= self.tcx
.hir().get(hir_id
);
337 hir
::Node
::Expr(hir
::Expr { kind: hir::ExprKind::Array(_), .. }
),
338 hir
::ExprKind
::Tup(exp
),
339 hir
::ExprKind
::Call(_
, args
),
340 ) = (parent_node
, &callee_expr
.kind
, &call_expr
.kind
)
341 && args
.len() == exp
.len()
343 let start
= callee_expr
.span
.shrink_to_hi();
346 "consider separating array elements with a comma",
348 Applicability
::MaybeIncorrect
,
355 fn confirm_builtin_call(
357 call_expr
: &'tcx hir
::Expr
<'tcx
>,
358 callee_expr
: &'tcx hir
::Expr
<'tcx
>,
360 arg_exprs
: &'tcx
[hir
::Expr
<'tcx
>],
361 expected
: Expectation
<'tcx
>,
363 let (fn_sig
, def_id
) = match *callee_ty
.kind() {
364 ty
::FnDef(def_id
, subst
) => {
365 let fn_sig
= self.tcx
.bound_fn_sig(def_id
).subst(self.tcx
, subst
);
367 // Unit testing: function items annotated with
368 // `#[rustc_evaluate_where_clauses]` trigger special output
369 // to let us test the trait evaluation system.
370 if self.tcx
.has_attr(def_id
, sym
::rustc_evaluate_where_clauses
) {
371 let predicates
= self.tcx
.predicates_of(def_id
);
372 let predicates
= predicates
.instantiate(self.tcx
, subst
);
373 for (predicate
, predicate_span
) in
374 predicates
.predicates
.iter().zip(&predicates
.spans
)
376 let obligation
= Obligation
::new(
377 ObligationCause
::dummy_with_span(callee_expr
.span
),
381 let result
= self.evaluate_obligation(&obligation
);
386 &format
!("evaluate({:?}) = {:?}", predicate
, result
),
388 .span_label(*predicate_span
, "predicate")
392 (fn_sig
, Some(def_id
))
394 ty
::FnPtr(sig
) => (sig
, None
),
396 let mut unit_variant
= None
;
397 if let hir
::ExprKind
::Path(qpath
) = &callee_expr
.kind
398 && let Res
::Def(def
::DefKind
::Ctor(kind
, def
::CtorKind
::Const
), _
)
399 = self.typeck_results
.borrow().qpath_res(qpath
, callee_expr
.hir_id
)
400 // Only suggest removing parens if there are no arguments
401 && arg_exprs
.is_empty()
403 let descr
= match kind
{
404 def
::CtorOf
::Struct
=> "struct",
405 def
::CtorOf
::Variant
=> "enum variant",
408 callee_expr
.span
.shrink_to_hi().to(call_expr
.span
.shrink_to_hi());
410 Some((removal_span
, descr
, rustc_hir_pretty
::qpath_to_string(qpath
)));
413 let callee_ty
= self.resolve_vars_if_possible(callee_ty
);
414 let mut err
= type_error_struct
!(
419 "expected function, found {}",
420 match &unit_variant
{
421 Some((_
, kind
, path
)) => format
!("{kind} `{path}`"),
422 None
=> format
!("`{callee_ty}`"),
426 self.identify_bad_closure_def_and_call(
433 if let Some((removal_span
, kind
, path
)) = &unit_variant
{
434 err
.span_suggestion_verbose(
437 "`{path}` is a unit {kind}, and does not take parentheses to be constructed",
440 Applicability
::MachineApplicable
,
444 let mut inner_callee_path
= None
;
445 let def
= match callee_expr
.kind
{
446 hir
::ExprKind
::Path(ref qpath
) => {
447 self.typeck_results
.borrow().qpath_res(qpath
, callee_expr
.hir_id
)
449 hir
::ExprKind
::Call(ref inner_callee
, _
) => {
450 // If the call spans more than one line and the callee kind is
451 // itself another `ExprCall`, that's a clue that we might just be
452 // missing a semicolon (Issue #51055)
453 let call_is_multiline
=
454 self.tcx
.sess
.source_map().is_multiline(call_expr
.span
);
455 if call_is_multiline
{
457 callee_expr
.span
.shrink_to_hi(),
458 "consider using a semicolon here",
460 Applicability
::MaybeIncorrect
,
463 if let hir
::ExprKind
::Path(ref inner_qpath
) = inner_callee
.kind
{
464 inner_callee_path
= Some(inner_qpath
);
465 self.typeck_results
.borrow().qpath_res(inner_qpath
, inner_callee
.hir_id
)
473 if !self.maybe_suggest_bad_array_definition(&mut err
, call_expr
, callee_expr
) {
474 err
.span_label(call_expr
.span
, "call expression requires function");
477 if let Some(span
) = self.tcx
.hir().res_span(def
) {
478 let callee_ty
= callee_ty
.to_string();
479 let label
= match (unit_variant
, inner_callee_path
) {
480 (Some((_
, kind
, path
)), _
) => Some(format
!("{kind} `{path}` defined here")),
481 (_
, Some(hir
::QPath
::Resolved(_
, path
))) => self
485 .span_to_snippet(path
.span
)
487 .map(|p
| format
!("`{p}` defined here returns `{callee_ty}`")),
490 // Emit a different diagnostic for local variables, as they are not
491 // type definitions themselves, but rather variables *of* that type.
492 Res
::Local(hir_id
) => Some(format
!(
493 "`{}` has type `{}`",
494 self.tcx
.hir().name(hir_id
),
497 Res
::Def(kind
, def_id
) if kind
.ns() == Some(Namespace
::ValueNS
) => {
500 self.tcx
.def_path_str(def_id
),
503 _
=> Some(format
!("`{callee_ty}` defined here")),
507 if let Some(label
) = label
{
508 err
.span_label(span
, label
);
513 // This is the "default" function signature, used in case of error.
514 // In that case, we check each argument against "error" in order to
515 // set up all the node type bindings.
517 ty
::Binder
::dummy(self.tcx
.mk_fn_sig(
518 self.err_args(arg_exprs
.len()).into_iter(),
521 hir
::Unsafety
::Normal
,
529 // Replace any late-bound regions that appear in the function
530 // signature with region variables. We also have to
531 // renormalize the associated types at this point, since they
532 // previously appeared within a `Binder<>` and hence would not
533 // have been normalized before.
534 let fn_sig
= self.replace_bound_vars_with_fresh_vars(call_expr
.span
, infer
::FnCall
, fn_sig
);
535 let fn_sig
= self.normalize_associated_types_in(call_expr
.span
, fn_sig
);
537 // Call the generic checker.
538 let expected_arg_tys
= self.expected_inputs_for_expected_output(
544 self.check_argument_types(
551 TupleArgumentsFlag
::DontTupleArguments
,
558 fn confirm_deferred_closure_call(
560 call_expr
: &'tcx hir
::Expr
<'tcx
>,
561 arg_exprs
: &'tcx
[hir
::Expr
<'tcx
>],
562 expected
: Expectation
<'tcx
>,
563 closure_def_id
: LocalDefId
,
564 fn_sig
: ty
::FnSig
<'tcx
>,
566 // `fn_sig` is the *signature* of the closure being called. We
567 // don't know the full details yet (`Fn` vs `FnMut` etc), but we
568 // do know the types expected for each argument and the return
571 let expected_arg_tys
= self.expected_inputs_for_expected_output(
578 self.check_argument_types(
585 TupleArgumentsFlag
::TupleArguments
,
586 Some(closure_def_id
.to_def_id()),
592 fn confirm_overloaded_call(
594 call_expr
: &'tcx hir
::Expr
<'tcx
>,
595 arg_exprs
: &'tcx
[hir
::Expr
<'tcx
>],
596 expected
: Expectation
<'tcx
>,
597 method_callee
: MethodCallee
<'tcx
>,
599 let output_type
= self.check_method_argument_types(
604 TupleArgumentsFlag
::TupleArguments
,
608 self.write_method_call(call_expr
.hir_id
, method_callee
);
614 pub struct DeferredCallResolution
<'tcx
> {
615 call_expr
: &'tcx hir
::Expr
<'tcx
>,
616 callee_expr
: &'tcx hir
::Expr
<'tcx
>,
617 adjusted_ty
: Ty
<'tcx
>,
618 adjustments
: Vec
<Adjustment
<'tcx
>>,
619 fn_sig
: ty
::FnSig
<'tcx
>,
620 closure_substs
: SubstsRef
<'tcx
>,
623 impl<'a
, 'tcx
> DeferredCallResolution
<'tcx
> {
624 pub fn resolve(self, fcx
: &FnCtxt
<'a
, 'tcx
>) {
625 debug
!("DeferredCallResolution::resolve() {:?}", self);
627 // we should not be invoked until the closure kind has been
628 // determined by upvar inference
629 assert
!(fcx
.closure_kind(self.closure_substs
).is_some());
631 // We may now know enough to figure out fn vs fnmut etc.
632 match fcx
.try_overloaded_call_traits(self.call_expr
, self.adjusted_ty
, None
) {
633 Some((autoref
, method_callee
)) => {
634 // One problem is that when we get here, we are going
635 // to have a newly instantiated function signature
636 // from the call trait. This has to be reconciled with
637 // the older function signature we had before. In
638 // principle we *should* be able to fn_sigs(), but we
639 // can't because of the annoying need for a TypeTrace.
640 // (This always bites me, should find a way to
642 let method_sig
= method_callee
.sig
;
644 debug
!("attempt_resolution: method_callee={:?}", method_callee
);
646 for (method_arg_ty
, self_arg_ty
) in
647 iter
::zip(method_sig
.inputs().iter().skip(1), self.fn_sig
.inputs())
649 fcx
.demand_eqtype(self.call_expr
.span
, *self_arg_ty
, *method_arg_ty
);
652 fcx
.demand_eqtype(self.call_expr
.span
, method_sig
.output(), self.fn_sig
.output());
654 let mut adjustments
= self.adjustments
;
655 adjustments
.extend(autoref
);
656 fcx
.apply_adjustments(self.callee_expr
, adjustments
);
658 fcx
.write_method_call(self.call_expr
.hir_id
, method_callee
);
661 // This can happen if `#![no_core]` is used and the `fn/fn_mut/fn_once`
662 // lang items are not defined (issue #86238).
663 let mut err
= fcx
.inh
.tcx
.sess
.struct_span_err(
665 "failed to find an overloaded call trait for closure call",
668 "make sure the `fn`/`fn_mut`/`fn_once` lang items are defined \
669 and have associated `call`/`call_mut`/`call_once` functions",