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::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;
21 /// Checks that it is legal to call methods of the trait corresponding
22 /// to `trait_id` (this only cares about the trait, not the specific
23 /// method that is called).
24 pub fn check_legal_trait_for_method_call(
27 receiver: Option<Span>,
31 if tcx.lang_items().drop_trait() == Some(trait_id) {
32 let mut err = struct_span_err!(tcx.sess, span, E0040, "explicit use of destructor method");
33 err.span_label(span, "explicit destructor calls not allowed");
35 let (sp, suggestion) = receiver
36 .and_then(|s| tcx.sess.source_map().span_to_snippet(s).ok())
37 .filter(|snippet| !snippet.is_empty())
38 .map(|snippet| (expr_span, format!("drop({})", snippet)))
39 .unwrap_or_else(|| (span, "drop".to_string()));
43 "consider using `drop` function",
45 Applicability::MaybeIncorrect,
54 DeferredClosure(ty::FnSig<'tcx>),
55 /// E.g., enum variant constructors.
56 Overloaded(MethodCallee<'tcx>),
59 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
62 call_expr: &'tcx hir::Expr<'tcx>,
63 callee_expr: &'tcx hir::Expr<'tcx>,
64 arg_exprs: &'tcx [hir::Expr<'tcx>],
65 expected: Expectation<'tcx>,
67 let original_callee_ty = self.check_expr(callee_expr);
68 let expr_ty = self.structurally_resolved_type(call_expr.span, original_callee_ty);
70 let mut autoderef = self.autoderef(callee_expr.span, expr_ty);
71 let mut result = None;
72 while result.is_none() && autoderef.next().is_some() {
73 result = self.try_overloaded_call_step(call_expr, callee_expr, arg_exprs, &autoderef);
75 self.register_predicates(autoderef.into_obligations());
77 let output = match result {
79 // this will report an error since original_callee_ty is not a fn
80 self.confirm_builtin_call(call_expr, original_callee_ty, arg_exprs, expected)
83 Some(CallStep::Builtin(callee_ty)) => {
84 self.confirm_builtin_call(call_expr, callee_ty, arg_exprs, expected)
87 Some(CallStep::DeferredClosure(fn_sig)) => {
88 self.confirm_deferred_closure_call(call_expr, arg_exprs, expected, fn_sig)
91 Some(CallStep::Overloaded(method_callee)) => {
92 self.confirm_overloaded_call(call_expr, arg_exprs, expected, method_callee)
96 // we must check that return type of called functions is WF:
97 self.register_wf_obligation(output.into(), call_expr.span, traits::MiscObligation);
102 fn try_overloaded_call_step(
104 call_expr: &'tcx hir::Expr<'tcx>,
105 callee_expr: &'tcx hir::Expr<'tcx>,
106 arg_exprs: &'tcx [hir::Expr<'tcx>],
107 autoderef: &Autoderef<'a, 'tcx>,
108 ) -> Option<CallStep<'tcx>> {
110 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
112 "try_overloaded_call_step(call_expr={:?}, adjusted_ty={:?})",
113 call_expr, adjusted_ty
116 // If the callee is a bare function or a closure, then we're all set.
117 match *adjusted_ty.kind() {
118 ty::FnDef(..) | ty::FnPtr(_) => {
119 let adjustments = self.adjust_steps(autoderef);
120 self.apply_adjustments(callee_expr, adjustments);
121 return Some(CallStep::Builtin(adjusted_ty));
124 ty::Closure(def_id, substs) => {
125 assert_eq!(def_id.krate, LOCAL_CRATE);
127 // Check whether this is a call to a closure where we
128 // haven't yet decided on whether the closure is fn vs
129 // fnmut vs fnonce. If so, we have to defer further processing.
130 if self.closure_kind(substs).is_none() {
131 let closure_sig = substs.as_closure().sig();
132 let closure_sig = self
133 .replace_bound_vars_with_fresh_vars(
139 let adjustments = self.adjust_steps(autoderef);
140 self.record_deferred_call_resolution(
142 DeferredCallResolution {
148 closure_substs: substs,
151 return Some(CallStep::DeferredClosure(closure_sig));
155 // Hack: we know that there are traits implementing Fn for &F
156 // where F:Fn and so forth. In the particular case of types
157 // like `x: &mut FnMut()`, if there is a call `x()`, we would
158 // normally translate to `FnMut::call_mut(&mut x, ())`, but
159 // that winds up requiring `mut x: &mut FnMut()`. A little
160 // over the top. The simplest fix by far is to just ignore
161 // this case and deref again, so we wind up with
162 // `FnMut::call_mut(&mut *x, ())`.
163 ty::Ref(..) if autoderef.step_count() == 0 => {
170 // Now, we look for the implementation of a Fn trait on the object's type.
171 // We first do it with the explicit instruction to look for an impl of
172 // `Fn<Tuple>`, with the tuple `Tuple` having an arity corresponding
173 // to the number of call parameters.
174 // If that fails (or_else branch), we try again without specifying the
175 // shape of the tuple (hence the None). This allows to detect an Fn trait
176 // is implemented, and use this information for diagnostic.
177 self.try_overloaded_call_traits(call_expr, adjusted_ty, Some(arg_exprs))
178 .or_else(|| self.try_overloaded_call_traits(call_expr, adjusted_ty, None))
179 .map(|(autoref, method)| {
180 let mut adjustments = self.adjust_steps(autoderef);
181 adjustments.extend(autoref);
182 self.apply_adjustments(callee_expr, adjustments);
183 CallStep::Overloaded(method)
187 fn try_overloaded_call_traits(
189 call_expr: &hir::Expr<'_>,
190 adjusted_ty: Ty<'tcx>,
191 opt_arg_exprs: Option<&'tcx [hir::Expr<'tcx>]>,
192 ) -> Option<(Option<Adjustment<'tcx>>, MethodCallee<'tcx>)> {
193 // Try the options that are least restrictive on the caller first.
194 for &(opt_trait_def_id, method_name, borrow) in &[
195 (self.tcx.lang_items().fn_trait(), Ident::with_dummy_span(sym::call), true),
196 (self.tcx.lang_items().fn_mut_trait(), Ident::with_dummy_span(sym::call_mut), true),
197 (self.tcx.lang_items().fn_once_trait(), Ident::with_dummy_span(sym::call_once), false),
199 let trait_def_id = match opt_trait_def_id {
200 Some(def_id) => def_id,
204 let opt_input_types = opt_arg_exprs.map(|arg_exprs| {
205 [self.tcx.mk_tup(arg_exprs.iter().map(|e| {
206 self.next_ty_var(TypeVariableOrigin {
207 kind: TypeVariableOriginKind::TypeInference,
212 let opt_input_types = opt_input_types.as_ref().map(AsRef::as_ref);
214 if let Some(ok) = self.lookup_method_in_trait(
221 let method = self.register_infer_ok_obligations(ok);
222 let mut autoref = None;
224 // Check for &self vs &mut self in the method signature. Since this is either
225 // the Fn or FnMut trait, it should be one of those.
226 let (region, mutbl) =
227 if let ty::Ref(r, _, mutbl) = method.sig.inputs()[0].kind() {
230 span_bug!(call_expr.span, "input to call/call_mut is not a ref?");
233 let mutbl = match mutbl {
234 hir::Mutability::Not => AutoBorrowMutability::Not,
235 hir::Mutability::Mut => AutoBorrowMutability::Mut {
236 // For initial two-phase borrow
237 // deployment, conservatively omit
238 // overloaded function call ops.
239 allow_two_phase_borrow: AllowTwoPhase::No,
242 autoref = Some(Adjustment {
243 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
244 target: method.sig.inputs()[0],
247 return Some((autoref, method));
254 /// Give appropriate suggestion when encountering `||{/* not callable */}()`, where the
255 /// likely intention is to call the closure, suggest `(||{})()`. (#55851)
256 fn identify_bad_closure_def_and_call(
258 err: &mut DiagnosticBuilder<'a>,
260 callee_node: &hir::ExprKind<'_>,
263 let hir_id = self.tcx.hir().get_parent_node(hir_id);
264 let parent_node = self.tcx.hir().get(hir_id);
266 hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(_, _, _, sp, ..), .. }),
267 hir::ExprKind::Block(..),
268 ) = (parent_node, callee_node)
270 let start = sp.shrink_to_lo();
271 let end = callee_span.shrink_to_hi();
272 err.multipart_suggestion(
273 "if you meant to create this closure and immediately call it, surround the \
274 closure with parenthesis",
275 vec![(start, "(".to_string()), (end, ")".to_string())],
276 Applicability::MaybeIncorrect,
281 fn confirm_builtin_call(
283 call_expr: &'tcx hir::Expr<'tcx>,
285 arg_exprs: &'tcx [hir::Expr<'tcx>],
286 expected: Expectation<'tcx>,
288 let (fn_sig, def_id) = match *callee_ty.kind() {
289 ty::FnDef(def_id, _) => (callee_ty.fn_sig(self.tcx), Some(def_id)),
290 ty::FnPtr(sig) => (sig, None),
292 let mut unit_variant = None;
293 if let ty::Adt(adt_def, ..) = t {
294 if adt_def.is_enum() {
295 if let hir::ExprKind::Call(expr, _) = call_expr.kind {
297 self.tcx.sess.source_map().span_to_snippet(expr.span).ok();
302 if let hir::ExprKind::Call(callee, _) = call_expr.kind {
303 let mut err = type_error_struct!(
308 "expected function, found {}",
310 Some(ref path) => format!("enum variant `{}`", path),
311 None => format!("`{}`", callee_ty),
315 self.identify_bad_closure_def_and_call(
322 if let Some(ref path) = unit_variant {
326 "`{}` is a unit variant, you need to write it \
327 without the parenthesis",
331 Applicability::MachineApplicable,
335 let mut inner_callee_path = None;
336 let def = match callee.kind {
337 hir::ExprKind::Path(ref qpath) => {
338 self.typeck_results.borrow().qpath_res(qpath, callee.hir_id)
340 hir::ExprKind::Call(ref inner_callee, _) => {
341 // If the call spans more than one line and the callee kind is
342 // itself another `ExprCall`, that's a clue that we might just be
343 // missing a semicolon (Issue #51055)
344 let call_is_multiline =
345 self.tcx.sess.source_map().is_multiline(call_expr.span);
346 if call_is_multiline {
348 callee.span.shrink_to_hi(),
349 "consider using a semicolon here",
351 Applicability::MaybeIncorrect,
354 if let hir::ExprKind::Path(ref inner_qpath) = inner_callee.kind {
355 inner_callee_path = Some(inner_qpath);
358 .qpath_res(inner_qpath, inner_callee.hir_id)
366 err.span_label(call_expr.span, "call expression requires function");
368 if let Some(span) = self.tcx.hir().res_span(def) {
369 let callee_ty = callee_ty.to_string();
370 let label = match (unit_variant, inner_callee_path) {
371 (Some(path), _) => Some(format!("`{}` defined here", path)),
372 (_, Some(hir::QPath::Resolved(_, path))) => {
373 self.tcx.sess.source_map().span_to_snippet(path.span).ok().map(
374 |p| format!("`{}` defined here returns `{}`", p, callee_ty),
377 _ => Some(format!("`{}` defined here", callee_ty)),
379 if let Some(label) = label {
380 err.span_label(span, label);
385 bug!("call_expr.kind should be an ExprKind::Call, got {:?}", call_expr.kind);
388 // This is the "default" function signature, used in case of error.
389 // In that case, we check each argument against "error" in order to
390 // set up all the node type bindings.
392 ty::Binder::dummy(self.tcx.mk_fn_sig(
393 self.err_args(arg_exprs.len()).into_iter(),
396 hir::Unsafety::Normal,
404 // Replace any late-bound regions that appear in the function
405 // signature with region variables. We also have to
406 // renormalize the associated types at this point, since they
407 // previously appeared within a `Binder<>` and hence would not
408 // have been normalized before.
410 self.replace_bound_vars_with_fresh_vars(call_expr.span, infer::FnCall, fn_sig).0;
411 let fn_sig = self.normalize_associated_types_in(call_expr.span, fn_sig);
413 // Call the generic checker.
414 let expected_arg_tys = self.expected_inputs_for_expected_output(
420 self.check_argument_types(
424 &expected_arg_tys[..],
427 TupleArgumentsFlag::DontTupleArguments,
434 fn confirm_deferred_closure_call(
436 call_expr: &'tcx hir::Expr<'tcx>,
437 arg_exprs: &'tcx [hir::Expr<'tcx>],
438 expected: Expectation<'tcx>,
439 fn_sig: ty::FnSig<'tcx>,
441 // `fn_sig` is the *signature* of the cosure being called. We
442 // don't know the full details yet (`Fn` vs `FnMut` etc), but we
443 // do know the types expected for each argument and the return
446 let expected_arg_tys = self.expected_inputs_for_expected_output(
449 fn_sig.output().clone(),
453 self.check_argument_types(
460 TupleArgumentsFlag::TupleArguments,
467 fn confirm_overloaded_call(
469 call_expr: &'tcx hir::Expr<'tcx>,
470 arg_exprs: &'tcx [hir::Expr<'tcx>],
471 expected: Expectation<'tcx>,
472 method_callee: MethodCallee<'tcx>,
474 let output_type = self.check_method_argument_types(
479 TupleArgumentsFlag::TupleArguments,
483 self.write_method_call(call_expr.hir_id, method_callee);
489 pub struct DeferredCallResolution<'tcx> {
490 call_expr: &'tcx hir::Expr<'tcx>,
491 callee_expr: &'tcx hir::Expr<'tcx>,
492 adjusted_ty: Ty<'tcx>,
493 adjustments: Vec<Adjustment<'tcx>>,
494 fn_sig: ty::FnSig<'tcx>,
495 closure_substs: SubstsRef<'tcx>,
498 impl<'a, 'tcx> DeferredCallResolution<'tcx> {
499 pub fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) {
500 debug!("DeferredCallResolution::resolve() {:?}", self);
502 // we should not be invoked until the closure kind has been
503 // determined by upvar inference
504 assert!(fcx.closure_kind(self.closure_substs).is_some());
506 // We may now know enough to figure out fn vs fnmut etc.
507 match fcx.try_overloaded_call_traits(self.call_expr, self.adjusted_ty, None) {
508 Some((autoref, method_callee)) => {
509 // One problem is that when we get here, we are going
510 // to have a newly instantiated function signature
511 // from the call trait. This has to be reconciled with
512 // the older function signature we had before. In
513 // principle we *should* be able to fn_sigs(), but we
514 // can't because of the annoying need for a TypeTrace.
515 // (This always bites me, should find a way to
517 let method_sig = method_callee.sig;
519 debug!("attempt_resolution: method_callee={:?}", method_callee);
521 for (method_arg_ty, self_arg_ty) in
522 method_sig.inputs().iter().skip(1).zip(self.fn_sig.inputs())
524 fcx.demand_eqtype(self.call_expr.span, &self_arg_ty, &method_arg_ty);
527 fcx.demand_eqtype(self.call_expr.span, method_sig.output(), self.fn_sig.output());
529 let mut adjustments = self.adjustments;
530 adjustments.extend(autoref);
531 fcx.apply_adjustments(self.callee_expr, adjustments);
533 fcx.write_method_call(self.call_expr.hir_id, method_callee);
538 "failed to find an overloaded call trait for closure call"