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, DiagnosticBuilder};
7 use rustc_hir::def::{Namespace, Res};
8 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
9 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
10 use rustc_infer::{infer, traits};
11 use rustc_middle::ty::adjustment::{
12 Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
14 use rustc_middle::ty::subst::SubstsRef;
15 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
16 use rustc_span::symbol::{sym, Ident};
18 use rustc_target::spec::abi;
19 use rustc_trait_selection::autoderef::Autoderef;
22 /// Checks that it is legal to call methods of the trait corresponding
23 /// to `trait_id` (this only cares about the trait, not the specific
24 /// method that is called).
25 pub fn check_legal_trait_for_method_call(
28 receiver: Option<Span>,
32 if tcx.lang_items().drop_trait() == Some(trait_id) {
33 let mut err = struct_span_err!(tcx.sess, span, E0040, "explicit use of destructor method");
34 err.span_label(span, "explicit destructor calls not allowed");
36 let (sp, suggestion) = receiver
37 .and_then(|s| tcx.sess.source_map().span_to_snippet(s).ok())
38 .filter(|snippet| !snippet.is_empty())
39 .map(|snippet| (expr_span, format!("drop({})", snippet)))
40 .unwrap_or_else(|| (span, "drop".to_string()));
44 "consider using `drop` function",
46 Applicability::MaybeIncorrect,
55 DeferredClosure(ty::FnSig<'tcx>),
56 /// E.g., enum variant constructors.
57 Overloaded(MethodCallee<'tcx>),
60 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
63 call_expr: &'tcx hir::Expr<'tcx>,
64 callee_expr: &'tcx hir::Expr<'tcx>,
65 arg_exprs: &'tcx [hir::Expr<'tcx>],
66 expected: Expectation<'tcx>,
68 let original_callee_ty = self.check_expr(callee_expr);
69 let expr_ty = self.structurally_resolved_type(call_expr.span, original_callee_ty);
71 let mut autoderef = self.autoderef(callee_expr.span, expr_ty);
72 let mut result = None;
73 while result.is_none() && autoderef.next().is_some() {
74 result = self.try_overloaded_call_step(call_expr, callee_expr, arg_exprs, &autoderef);
76 self.register_predicates(autoderef.into_obligations());
78 let output = match result {
80 // this will report an error since original_callee_ty is not a fn
81 self.confirm_builtin_call(
90 Some(CallStep::Builtin(callee_ty)) => {
91 self.confirm_builtin_call(call_expr, callee_expr, callee_ty, arg_exprs, expected)
94 Some(CallStep::DeferredClosure(fn_sig)) => {
95 self.confirm_deferred_closure_call(call_expr, arg_exprs, expected, fn_sig)
98 Some(CallStep::Overloaded(method_callee)) => {
99 self.confirm_overloaded_call(call_expr, arg_exprs, expected, method_callee)
103 // we must check that return type of called functions is WF:
104 self.register_wf_obligation(output.into(), call_expr.span, traits::MiscObligation);
109 fn try_overloaded_call_step(
111 call_expr: &'tcx hir::Expr<'tcx>,
112 callee_expr: &'tcx hir::Expr<'tcx>,
113 arg_exprs: &'tcx [hir::Expr<'tcx>],
114 autoderef: &Autoderef<'a, 'tcx>,
115 ) -> Option<CallStep<'tcx>> {
117 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
119 "try_overloaded_call_step(call_expr={:?}, adjusted_ty={:?})",
120 call_expr, adjusted_ty
123 // If the callee is a bare function or a closure, then we're all set.
124 match *adjusted_ty.kind() {
125 ty::FnDef(..) | ty::FnPtr(_) => {
126 let adjustments = self.adjust_steps(autoderef);
127 self.apply_adjustments(callee_expr, adjustments);
128 return Some(CallStep::Builtin(adjusted_ty));
131 ty::Closure(def_id, substs) => {
132 assert_eq!(def_id.krate, LOCAL_CRATE);
134 // Check whether this is a call to a closure where we
135 // haven't yet decided on whether the closure is fn vs
136 // fnmut vs fnonce. If so, we have to defer further processing.
137 if self.closure_kind(substs).is_none() {
138 let closure_sig = substs.as_closure().sig();
139 let closure_sig = self
140 .replace_bound_vars_with_fresh_vars(
146 let adjustments = self.adjust_steps(autoderef);
147 self.record_deferred_call_resolution(
149 DeferredCallResolution {
155 closure_substs: substs,
158 return Some(CallStep::DeferredClosure(closure_sig));
162 // Hack: we know that there are traits implementing Fn for &F
163 // where F:Fn and so forth. In the particular case of types
164 // like `x: &mut FnMut()`, if there is a call `x()`, we would
165 // normally translate to `FnMut::call_mut(&mut x, ())`, but
166 // that winds up requiring `mut x: &mut FnMut()`. A little
167 // over the top. The simplest fix by far is to just ignore
168 // this case and deref again, so we wind up with
169 // `FnMut::call_mut(&mut *x, ())`.
170 ty::Ref(..) if autoderef.step_count() == 0 => {
177 // Now, we look for the implementation of a Fn trait on the object's type.
178 // We first do it with the explicit instruction to look for an impl of
179 // `Fn<Tuple>`, with the tuple `Tuple` having an arity corresponding
180 // to the number of call parameters.
181 // If that fails (or_else branch), we try again without specifying the
182 // shape of the tuple (hence the None). This allows to detect an Fn trait
183 // is implemented, and use this information for diagnostic.
184 self.try_overloaded_call_traits(call_expr, adjusted_ty, Some(arg_exprs))
185 .or_else(|| self.try_overloaded_call_traits(call_expr, adjusted_ty, None))
186 .map(|(autoref, method)| {
187 let mut adjustments = self.adjust_steps(autoderef);
188 adjustments.extend(autoref);
189 self.apply_adjustments(callee_expr, adjustments);
190 CallStep::Overloaded(method)
194 fn try_overloaded_call_traits(
196 call_expr: &hir::Expr<'_>,
197 adjusted_ty: Ty<'tcx>,
198 opt_arg_exprs: Option<&'tcx [hir::Expr<'tcx>]>,
199 ) -> Option<(Option<Adjustment<'tcx>>, MethodCallee<'tcx>)> {
200 // Try the options that are least restrictive on the caller first.
201 for &(opt_trait_def_id, method_name, borrow) in &[
202 (self.tcx.lang_items().fn_trait(), Ident::with_dummy_span(sym::call), true),
203 (self.tcx.lang_items().fn_mut_trait(), Ident::with_dummy_span(sym::call_mut), true),
204 (self.tcx.lang_items().fn_once_trait(), Ident::with_dummy_span(sym::call_once), false),
206 let trait_def_id = match opt_trait_def_id {
207 Some(def_id) => def_id,
211 let opt_input_types = opt_arg_exprs.map(|arg_exprs| {
212 [self.tcx.mk_tup(arg_exprs.iter().map(|e| {
213 self.next_ty_var(TypeVariableOrigin {
214 kind: TypeVariableOriginKind::TypeInference,
219 let opt_input_types = opt_input_types.as_ref().map(AsRef::as_ref);
221 if let Some(ok) = self.lookup_method_in_trait(
228 let method = self.register_infer_ok_obligations(ok);
229 let mut autoref = None;
231 // Check for &self vs &mut self in the method signature. Since this is either
232 // the Fn or FnMut trait, it should be one of those.
233 let (region, mutbl) =
234 if let ty::Ref(r, _, mutbl) = method.sig.inputs()[0].kind() {
237 span_bug!(call_expr.span, "input to call/call_mut is not a ref?");
240 let mutbl = match mutbl {
241 hir::Mutability::Not => AutoBorrowMutability::Not,
242 hir::Mutability::Mut => AutoBorrowMutability::Mut {
243 // For initial two-phase borrow
244 // deployment, conservatively omit
245 // overloaded function call ops.
246 allow_two_phase_borrow: AllowTwoPhase::No,
249 autoref = Some(Adjustment {
250 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
251 target: method.sig.inputs()[0],
254 return Some((autoref, method));
261 /// Give appropriate suggestion when encountering `||{/* not callable */}()`, where the
262 /// likely intention is to call the closure, suggest `(||{})()`. (#55851)
263 fn identify_bad_closure_def_and_call(
265 err: &mut DiagnosticBuilder<'a>,
267 callee_node: &hir::ExprKind<'_>,
270 let hir_id = self.tcx.hir().get_parent_node(hir_id);
271 let parent_node = self.tcx.hir().get(hir_id);
273 hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(_, _, _, sp, ..), .. }),
274 hir::ExprKind::Block(..),
275 ) = (parent_node, callee_node)
277 let start = sp.shrink_to_lo();
278 let end = callee_span.shrink_to_hi();
279 err.multipart_suggestion(
280 "if you meant to create this closure and immediately call it, surround the \
281 closure with parenthesis",
282 vec![(start, "(".to_string()), (end, ")".to_string())],
283 Applicability::MaybeIncorrect,
288 fn confirm_builtin_call(
290 call_expr: &'tcx hir::Expr<'tcx>,
291 callee_expr: &'tcx hir::Expr<'tcx>,
293 arg_exprs: &'tcx [hir::Expr<'tcx>],
294 expected: Expectation<'tcx>,
296 let (fn_sig, def_id) = match *callee_ty.kind() {
297 ty::FnDef(def_id, _) => (callee_ty.fn_sig(self.tcx), Some(def_id)),
298 ty::FnPtr(sig) => (sig, None),
300 let mut unit_variant = None;
301 if let ty::Adt(adt_def, ..) = t {
302 if adt_def.is_enum() {
303 if let hir::ExprKind::Call(expr, _) = call_expr.kind {
305 self.tcx.sess.source_map().span_to_snippet(expr.span).ok();
310 let mut err = type_error_struct!(
315 "expected function, found {}",
317 Some(ref path) => format!("enum variant `{}`", path),
318 None => format!("`{}`", callee_ty),
322 self.identify_bad_closure_def_and_call(
329 if let Some(ref path) = unit_variant {
333 "`{}` is a unit variant, you need to write it \
334 without the parenthesis",
338 Applicability::MachineApplicable,
342 let mut inner_callee_path = None;
343 let def = match callee_expr.kind {
344 hir::ExprKind::Path(ref qpath) => {
345 self.typeck_results.borrow().qpath_res(qpath, callee_expr.hir_id)
347 hir::ExprKind::Call(ref inner_callee, _) => {
348 // If the call spans more than one line and the callee kind is
349 // itself another `ExprCall`, that's a clue that we might just be
350 // missing a semicolon (Issue #51055)
351 let call_is_multiline =
352 self.tcx.sess.source_map().is_multiline(call_expr.span);
353 if call_is_multiline {
355 callee_expr.span.shrink_to_hi(),
356 "consider using a semicolon here",
358 Applicability::MaybeIncorrect,
361 if let hir::ExprKind::Path(ref inner_qpath) = inner_callee.kind {
362 inner_callee_path = Some(inner_qpath);
363 self.typeck_results.borrow().qpath_res(inner_qpath, inner_callee.hir_id)
371 err.span_label(call_expr.span, "call expression requires function");
373 if let Some(span) = self.tcx.hir().res_span(def) {
374 let callee_ty = callee_ty.to_string();
375 let label = match (unit_variant, inner_callee_path) {
376 (Some(path), _) => Some(format!("`{}` defined here", path)),
377 (_, Some(hir::QPath::Resolved(_, path))) => self
381 .span_to_snippet(path.span)
383 .map(|p| format!("`{}` defined here returns `{}`", p, callee_ty)),
386 // Emit a different diagnostic for local variables, as they are not
387 // type definitions themselves, but rather variables *of* that type.
388 Res::Local(hir_id) => Some(format!(
389 "`{}` has type `{}`",
390 self.tcx.hir().name(hir_id),
393 Res::Def(kind, def_id) if kind.ns() == Some(Namespace::ValueNS) => {
396 self.tcx.def_path_str(def_id),
399 _ => Some(format!("`{}` defined here", callee_ty)),
403 if let Some(label) = label {
404 err.span_label(span, label);
409 // This is the "default" function signature, used in case of error.
410 // In that case, we check each argument against "error" in order to
411 // set up all the node type bindings.
413 ty::Binder::dummy(self.tcx.mk_fn_sig(
414 self.err_args(arg_exprs.len()).into_iter(),
417 hir::Unsafety::Normal,
425 // Replace any late-bound regions that appear in the function
426 // signature with region variables. We also have to
427 // renormalize the associated types at this point, since they
428 // previously appeared within a `Binder<>` and hence would not
429 // have been normalized before.
431 self.replace_bound_vars_with_fresh_vars(call_expr.span, infer::FnCall, fn_sig).0;
432 let fn_sig = self.normalize_associated_types_in(call_expr.span, fn_sig);
434 // Call the generic checker.
435 let expected_arg_tys = self.expected_inputs_for_expected_output(
441 self.check_argument_types(
445 &expected_arg_tys[..],
448 TupleArgumentsFlag::DontTupleArguments,
455 fn confirm_deferred_closure_call(
457 call_expr: &'tcx hir::Expr<'tcx>,
458 arg_exprs: &'tcx [hir::Expr<'tcx>],
459 expected: Expectation<'tcx>,
460 fn_sig: ty::FnSig<'tcx>,
462 // `fn_sig` is the *signature* of the cosure being called. We
463 // don't know the full details yet (`Fn` vs `FnMut` etc), but we
464 // do know the types expected for each argument and the return
467 let expected_arg_tys = self.expected_inputs_for_expected_output(
474 self.check_argument_types(
481 TupleArgumentsFlag::TupleArguments,
488 fn confirm_overloaded_call(
490 call_expr: &'tcx hir::Expr<'tcx>,
491 arg_exprs: &'tcx [hir::Expr<'tcx>],
492 expected: Expectation<'tcx>,
493 method_callee: MethodCallee<'tcx>,
495 let output_type = self.check_method_argument_types(
500 TupleArgumentsFlag::TupleArguments,
504 self.write_method_call(call_expr.hir_id, method_callee);
510 pub struct DeferredCallResolution<'tcx> {
511 call_expr: &'tcx hir::Expr<'tcx>,
512 callee_expr: &'tcx hir::Expr<'tcx>,
513 adjusted_ty: Ty<'tcx>,
514 adjustments: Vec<Adjustment<'tcx>>,
515 fn_sig: ty::FnSig<'tcx>,
516 closure_substs: SubstsRef<'tcx>,
519 impl<'a, 'tcx> DeferredCallResolution<'tcx> {
520 pub fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) {
521 debug!("DeferredCallResolution::resolve() {:?}", self);
523 // we should not be invoked until the closure kind has been
524 // determined by upvar inference
525 assert!(fcx.closure_kind(self.closure_substs).is_some());
527 // We may now know enough to figure out fn vs fnmut etc.
528 match fcx.try_overloaded_call_traits(self.call_expr, self.adjusted_ty, None) {
529 Some((autoref, method_callee)) => {
530 // One problem is that when we get here, we are going
531 // to have a newly instantiated function signature
532 // from the call trait. This has to be reconciled with
533 // the older function signature we had before. In
534 // principle we *should* be able to fn_sigs(), but we
535 // can't because of the annoying need for a TypeTrace.
536 // (This always bites me, should find a way to
538 let method_sig = method_callee.sig;
540 debug!("attempt_resolution: method_callee={:?}", method_callee);
542 for (method_arg_ty, self_arg_ty) in
543 iter::zip(method_sig.inputs().iter().skip(1), self.fn_sig.inputs())
545 fcx.demand_eqtype(self.call_expr.span, &self_arg_ty, &method_arg_ty);
548 fcx.demand_eqtype(self.call_expr.span, method_sig.output(), self.fn_sig.output());
550 let mut adjustments = self.adjustments;
551 adjustments.extend(autoref);
552 fcx.apply_adjustments(self.callee_expr, adjustments);
554 fcx.write_method_call(self.call_expr.hir_id, method_callee);
559 "failed to find an overloaded call trait for closure call"