1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use super::{Expectation, FnCtxt, Needs, TupleArgumentsFlag};
12 use super::autoderef::Autoderef;
13 use super::method::MethodCallee;
16 use hir::def_id::{DefId, LOCAL_CRATE};
17 use rustc::{infer, traits};
18 use rustc::ty::{self, TyCtxt, TypeFoldable, Ty};
19 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow};
21 use syntax::symbol::Symbol;
26 /// Check that it is legal to call methods of the trait corresponding
27 /// to `trait_id` (this only cares about the trait, not the specific
28 /// method that is called)
29 pub fn check_legal_trait_for_method_call(tcx: TyCtxt, span: Span, trait_id: DefId) {
30 if tcx.lang_items().drop_trait() == Some(trait_id) {
31 struct_span_err!(tcx.sess, span, E0040, "explicit use of destructor method")
32 .span_label(span, "explicit destructor calls not allowed")
39 DeferredClosure(ty::FnSig<'tcx>),
40 /// e.g. enum variant constructors
41 Overloaded(MethodCallee<'tcx>),
44 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
45 pub fn check_call(&self,
46 call_expr: &'gcx hir::Expr,
47 callee_expr: &'gcx hir::Expr,
48 arg_exprs: &'gcx [hir::Expr],
49 expected: Expectation<'tcx>)
51 let original_callee_ty = self.check_expr(callee_expr);
52 let expr_ty = self.structurally_resolved_type(call_expr.span, original_callee_ty);
54 let mut autoderef = self.autoderef(callee_expr.span, expr_ty);
55 let mut result = None;
56 while result.is_none() && autoderef.next().is_some() {
57 result = self.try_overloaded_call_step(call_expr, callee_expr, &autoderef);
61 let output = match result {
63 // this will report an error since original_callee_ty is not a fn
64 self.confirm_builtin_call(call_expr, original_callee_ty, arg_exprs, expected)
67 Some(CallStep::Builtin(callee_ty)) => {
68 self.confirm_builtin_call(call_expr, callee_ty, arg_exprs, expected)
71 Some(CallStep::DeferredClosure(fn_sig)) => {
72 self.confirm_deferred_closure_call(call_expr, arg_exprs, expected, fn_sig)
75 Some(CallStep::Overloaded(method_callee)) => {
76 self.confirm_overloaded_call(call_expr, arg_exprs, expected, method_callee)
80 // we must check that return type of called functions is WF:
81 self.register_wf_obligation(output, call_expr.span, traits::MiscObligation);
86 fn try_overloaded_call_step(&self,
87 call_expr: &'gcx hir::Expr,
88 callee_expr: &'gcx hir::Expr,
89 autoderef: &Autoderef<'a, 'gcx, 'tcx>)
90 -> Option<CallStep<'tcx>> {
91 let adjusted_ty = autoderef.unambiguous_final_ty();
92 debug!("try_overloaded_call_step(call_expr={:?}, adjusted_ty={:?})",
96 // If the callee is a bare function or a closure, then we're all set.
97 match adjusted_ty.sty {
98 ty::TyFnDef(..) | ty::TyFnPtr(_) => {
99 let adjustments = autoderef.adjust_steps(Needs::None);
100 self.apply_adjustments(callee_expr, adjustments);
101 return Some(CallStep::Builtin(adjusted_ty));
104 ty::TyClosure(def_id, substs) => {
105 assert_eq!(def_id.krate, LOCAL_CRATE);
107 // Check whether this is a call to a closure where we
108 // haven't yet decided on whether the closure is fn vs
109 // fnmut vs fnonce. If so, we have to defer further processing.
110 if self.closure_kind(def_id, substs).is_none() {
111 let closure_ty = self.closure_sig(def_id, substs);
112 let fn_sig = self.replace_late_bound_regions_with_fresh_var(call_expr.span,
116 let adjustments = autoderef.adjust_steps(Needs::None);
117 self.record_deferred_call_resolution(def_id, DeferredCallResolution {
123 closure_def_id: def_id,
124 closure_substs: substs,
126 return Some(CallStep::DeferredClosure(fn_sig));
130 // Hack: we know that there are traits implementing Fn for &F
131 // where F:Fn and so forth. In the particular case of types
132 // like `x: &mut FnMut()`, if there is a call `x()`, we would
133 // normally translate to `FnMut::call_mut(&mut x, ())`, but
134 // that winds up requiring `mut x: &mut FnMut()`. A little
135 // over the top. The simplest fix by far is to just ignore
136 // this case and deref again, so we wind up with
137 // `FnMut::call_mut(&mut *x, ())`.
138 ty::TyRef(..) if autoderef.step_count() == 0 => {
145 self.try_overloaded_call_traits(call_expr, adjusted_ty).map(|(autoref, method)| {
146 let mut adjustments = autoderef.adjust_steps(Needs::None);
147 adjustments.extend(autoref);
148 self.apply_adjustments(callee_expr, adjustments);
149 CallStep::Overloaded(method)
153 fn try_overloaded_call_traits(&self,
154 call_expr: &hir::Expr,
155 adjusted_ty: Ty<'tcx>)
156 -> Option<(Option<Adjustment<'tcx>>,
157 MethodCallee<'tcx>)> {
158 // Try the options that are least restrictive on the caller first.
159 for &(opt_trait_def_id, method_name, borrow) in
160 &[(self.tcx.lang_items().fn_trait(), Symbol::intern("call"), true),
161 (self.tcx.lang_items().fn_mut_trait(), Symbol::intern("call_mut"), true),
162 (self.tcx.lang_items().fn_once_trait(), Symbol::intern("call_once"), false)] {
163 let trait_def_id = match opt_trait_def_id {
164 Some(def_id) => def_id,
168 match self.lookup_method_in_trait(call_expr.span,
175 let method = self.register_infer_ok_obligations(ok);
176 let mut autoref = None;
178 if let ty::TyRef(region, mt) = method.sig.inputs()[0].sty {
179 autoref = Some(Adjustment {
180 kind: Adjust::Borrow(AutoBorrow::Ref(region, mt.mutbl)),
181 target: method.sig.inputs()[0]
185 return Some((autoref, method));
193 fn confirm_builtin_call(&self,
194 call_expr: &hir::Expr,
196 arg_exprs: &'gcx [hir::Expr],
197 expected: Expectation<'tcx>)
199 let (fn_sig, def_span) = match callee_ty.sty {
200 ty::TyFnDef(def_id, _) => {
201 (callee_ty.fn_sig(self.tcx), self.tcx.hir.span_if_local(def_id))
203 ty::TyFnPtr(sig) => (sig, None),
205 let mut unit_variant = None;
206 if let &ty::TyAdt(adt_def, ..) = t {
207 if adt_def.is_enum() {
208 if let hir::ExprCall(ref expr, _) = call_expr.node {
209 unit_variant = Some(self.tcx.hir.node_to_pretty_string(expr.id))
214 let mut err = type_error_struct!(
219 "expected function, found {}",
221 Some(ref path) => format!("enum variant `{}`", path),
222 None => format!("`{}`", callee_ty),
225 err.span_label(call_expr.span, "not a function");
227 if let Some(ref path) = unit_variant {
228 err.span_suggestion(call_expr.span,
229 &format!("`{}` is a unit variant, you need to write it \
230 without the parenthesis", path),
234 if let hir::ExprCall(ref expr, _) = call_expr.node {
235 let def = if let hir::ExprPath(ref qpath) = expr.node {
236 self.tables.borrow().qpath_def(qpath, expr.hir_id)
240 let def_span = match def {
242 Def::Local(id) | Def::Upvar(id, ..) => {
243 Some(self.tcx.hir.span(id))
245 _ => self.tcx.hir.span_if_local(def.def_id())
247 if let Some(span) = def_span {
248 let name = match unit_variant {
250 None => callee_ty.to_string(),
252 err.span_label(span, format!("`{}` defined here", name));
258 // This is the "default" function signature, used in case of error.
259 // In that case, we check each argument against "error" in order to
260 // set up all the node type bindings.
261 (ty::Binder(self.tcx.mk_fn_sig(
262 self.err_args(arg_exprs.len()).into_iter(),
265 hir::Unsafety::Normal,
271 // Replace any late-bound regions that appear in the function
272 // signature with region variables. We also have to
273 // renormalize the associated types at this point, since they
274 // previously appeared within a `Binder<>` and hence would not
275 // have been normalized before.
277 self.replace_late_bound_regions_with_fresh_var(call_expr.span, infer::FnCall, &fn_sig)
279 let fn_sig = self.normalize_associated_types_in(call_expr.span, &fn_sig);
281 // Call the generic checker.
282 let expected_arg_tys =
283 self.expected_inputs_for_expected_output(call_expr.span,
287 self.check_argument_types(call_expr.span,
290 &expected_arg_tys[..],
293 TupleArgumentsFlag::DontTupleArguments,
299 fn confirm_deferred_closure_call(&self,
300 call_expr: &hir::Expr,
301 arg_exprs: &'gcx [hir::Expr],
302 expected: Expectation<'tcx>,
303 fn_sig: ty::FnSig<'tcx>)
305 // `fn_sig` is the *signature* of the cosure being called. We
306 // don't know the full details yet (`Fn` vs `FnMut` etc), but we
307 // do know the types expected for each argument and the return
310 let expected_arg_tys = self.expected_inputs_for_expected_output(call_expr.span,
312 fn_sig.output().clone(),
315 self.check_argument_types(call_expr.span,
321 TupleArgumentsFlag::TupleArguments,
327 fn confirm_overloaded_call(&self,
328 call_expr: &hir::Expr,
329 arg_exprs: &'gcx [hir::Expr],
330 expected: Expectation<'tcx>,
331 method_callee: MethodCallee<'tcx>)
333 let output_type = self.check_method_argument_types(call_expr.span,
337 TupleArgumentsFlag::TupleArguments,
340 self.write_method_call(call_expr.hir_id, method_callee);
346 pub struct DeferredCallResolution<'gcx: 'tcx, 'tcx> {
347 call_expr: &'gcx hir::Expr,
348 callee_expr: &'gcx hir::Expr,
349 adjusted_ty: Ty<'tcx>,
350 adjustments: Vec<Adjustment<'tcx>>,
351 fn_sig: ty::FnSig<'tcx>,
352 closure_def_id: DefId,
353 closure_substs: ty::ClosureSubsts<'tcx>,
356 impl<'a, 'gcx, 'tcx> DeferredCallResolution<'gcx, 'tcx> {
357 pub fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) {
358 debug!("DeferredCallResolution::resolve() {:?}", self);
360 // we should not be invoked until the closure kind has been
361 // determined by upvar inference
362 assert!(fcx.closure_kind(self.closure_def_id, self.closure_substs).is_some());
364 // We may now know enough to figure out fn vs fnmut etc.
365 match fcx.try_overloaded_call_traits(self.call_expr,
367 Some((autoref, method_callee)) => {
368 // One problem is that when we get here, we are going
369 // to have a newly instantiated function signature
370 // from the call trait. This has to be reconciled with
371 // the older function signature we had before. In
372 // principle we *should* be able to fn_sigs(), but we
373 // can't because of the annoying need for a TypeTrace.
374 // (This always bites me, should find a way to
376 let method_sig = method_callee.sig;
378 debug!("attempt_resolution: method_callee={:?}", method_callee);
380 for (method_arg_ty, self_arg_ty) in
381 method_sig.inputs().iter().skip(1).zip(self.fn_sig.inputs()) {
382 fcx.demand_eqtype(self.call_expr.span, &self_arg_ty, &method_arg_ty);
385 fcx.demand_eqtype(self.call_expr.span, method_sig.output(), self.fn_sig.output());
387 let mut adjustments = self.adjustments;
388 adjustments.extend(autoref);
389 fcx.apply_adjustments(self.callee_expr, adjustments);
391 fcx.write_method_call(self.call_expr.hir_id,
395 span_bug!(self.call_expr.span,
396 "failed to find an overloaded call trait for closure call");