516 lines
20 KiB
Rust
516 lines
20 KiB
Rust
use super::autoderef::Autoderef;
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use super::method::MethodCallee;
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use super::{Expectation, FnCtxt, Needs, TupleArgumentsFlag};
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use crate::type_error_struct;
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use errors::{struct_span_err, Applicability, DiagnosticBuilder};
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use hir::def::Res;
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use hir::def_id::{DefId, LOCAL_CRATE};
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use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
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use rustc::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
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use rustc::ty::subst::SubstsRef;
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use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
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use rustc::{infer, traits};
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use rustc_span::Span;
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use rustc_target::spec::abi;
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use syntax::ast::Ident;
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use rustc_hir as hir;
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use rustc_error_codes::*;
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/// Checks that it is legal to call methods of the trait corresponding
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/// to `trait_id` (this only cares about the trait, not the specific
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/// method that is called).
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pub fn check_legal_trait_for_method_call(tcx: TyCtxt<'_>, span: Span, trait_id: DefId) {
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if tcx.lang_items().drop_trait() == Some(trait_id) {
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struct_span_err!(tcx.sess, span, E0040, "explicit use of destructor method")
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.span_label(span, "explicit destructor calls not allowed")
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.emit();
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}
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}
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enum CallStep<'tcx> {
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Builtin(Ty<'tcx>),
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DeferredClosure(ty::FnSig<'tcx>),
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/// E.g., enum variant constructors.
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Overloaded(MethodCallee<'tcx>),
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}
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impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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pub fn check_call(
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&self,
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call_expr: &'tcx hir::Expr<'tcx>,
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callee_expr: &'tcx hir::Expr<'tcx>,
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arg_exprs: &'tcx [hir::Expr<'tcx>],
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expected: Expectation<'tcx>,
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) -> Ty<'tcx> {
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let original_callee_ty = self.check_expr(callee_expr);
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let expr_ty = self.structurally_resolved_type(call_expr.span, original_callee_ty);
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let mut autoderef = self.autoderef(callee_expr.span, expr_ty);
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let mut result = None;
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while result.is_none() && autoderef.next().is_some() {
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result = self.try_overloaded_call_step(call_expr, callee_expr, arg_exprs, &autoderef);
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}
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autoderef.finalize(self);
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let output = match result {
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None => {
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// this will report an error since original_callee_ty is not a fn
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self.confirm_builtin_call(call_expr, original_callee_ty, arg_exprs, expected)
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}
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Some(CallStep::Builtin(callee_ty)) => {
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self.confirm_builtin_call(call_expr, callee_ty, arg_exprs, expected)
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}
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Some(CallStep::DeferredClosure(fn_sig)) => {
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self.confirm_deferred_closure_call(call_expr, arg_exprs, expected, fn_sig)
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}
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Some(CallStep::Overloaded(method_callee)) => {
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self.confirm_overloaded_call(call_expr, arg_exprs, expected, method_callee)
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}
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};
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// we must check that return type of called functions is WF:
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self.register_wf_obligation(output, call_expr.span, traits::MiscObligation);
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output
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}
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fn try_overloaded_call_step(
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&self,
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call_expr: &'tcx hir::Expr<'tcx>,
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callee_expr: &'tcx hir::Expr<'tcx>,
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arg_exprs: &'tcx [hir::Expr<'tcx>],
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autoderef: &Autoderef<'a, 'tcx>,
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) -> Option<CallStep<'tcx>> {
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let adjusted_ty = autoderef.unambiguous_final_ty(self);
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debug!(
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"try_overloaded_call_step(call_expr={:?}, adjusted_ty={:?})",
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call_expr, adjusted_ty
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);
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// If the callee is a bare function or a closure, then we're all set.
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match adjusted_ty.kind {
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ty::FnDef(..) | ty::FnPtr(_) => {
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let adjustments = autoderef.adjust_steps(self, Needs::None);
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self.apply_adjustments(callee_expr, adjustments);
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return Some(CallStep::Builtin(adjusted_ty));
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}
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ty::Closure(def_id, substs) => {
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assert_eq!(def_id.krate, LOCAL_CRATE);
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// Check whether this is a call to a closure where we
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// haven't yet decided on whether the closure is fn vs
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// fnmut vs fnonce. If so, we have to defer further processing.
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if self.closure_kind(def_id, substs).is_none() {
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let closure_ty = self.closure_sig(def_id, substs);
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let fn_sig = self
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.replace_bound_vars_with_fresh_vars(
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call_expr.span,
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infer::FnCall,
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&closure_ty,
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)
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.0;
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let adjustments = autoderef.adjust_steps(self, Needs::None);
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self.record_deferred_call_resolution(
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def_id,
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DeferredCallResolution {
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call_expr,
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callee_expr,
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adjusted_ty,
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adjustments,
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fn_sig,
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closure_def_id: def_id,
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closure_substs: substs,
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},
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);
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return Some(CallStep::DeferredClosure(fn_sig));
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}
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}
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// Hack: we know that there are traits implementing Fn for &F
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// where F:Fn and so forth. In the particular case of types
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// like `x: &mut FnMut()`, if there is a call `x()`, we would
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// normally translate to `FnMut::call_mut(&mut x, ())`, but
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// that winds up requiring `mut x: &mut FnMut()`. A little
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// over the top. The simplest fix by far is to just ignore
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// this case and deref again, so we wind up with
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// `FnMut::call_mut(&mut *x, ())`.
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ty::Ref(..) if autoderef.step_count() == 0 => {
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return None;
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}
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_ => {}
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}
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// Now, we look for the implementation of a Fn trait on the object's type.
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// We first do it with the explicit instruction to look for an impl of
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// `Fn<Tuple>`, with the tuple `Tuple` having an arity corresponding
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// to the number of call parameters.
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// If that fails (or_else branch), we try again without specifying the
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// shape of the tuple (hence the None). This allows to detect an Fn trait
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// is implemented, and use this information for diagnostic.
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self.try_overloaded_call_traits(call_expr, adjusted_ty, Some(arg_exprs))
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.or_else(|| self.try_overloaded_call_traits(call_expr, adjusted_ty, None))
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.map(|(autoref, method)| {
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let mut adjustments = autoderef.adjust_steps(self, Needs::None);
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adjustments.extend(autoref);
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self.apply_adjustments(callee_expr, adjustments);
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CallStep::Overloaded(method)
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})
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}
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fn try_overloaded_call_traits(
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&self,
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call_expr: &hir::Expr<'_>,
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adjusted_ty: Ty<'tcx>,
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opt_arg_exprs: Option<&'tcx [hir::Expr<'tcx>]>,
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) -> Option<(Option<Adjustment<'tcx>>, MethodCallee<'tcx>)> {
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// Try the options that are least restrictive on the caller first.
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for &(opt_trait_def_id, method_name, borrow) in &[
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(self.tcx.lang_items().fn_trait(), Ident::from_str("call"), true),
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(self.tcx.lang_items().fn_mut_trait(), Ident::from_str("call_mut"), true),
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(self.tcx.lang_items().fn_once_trait(), Ident::from_str("call_once"), false),
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] {
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let trait_def_id = match opt_trait_def_id {
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Some(def_id) => def_id,
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None => continue,
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};
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let opt_input_types = opt_arg_exprs.map(|arg_exprs| {
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[self.tcx.mk_tup(arg_exprs.iter().map(|e| {
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self.next_ty_var(TypeVariableOrigin {
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kind: TypeVariableOriginKind::TypeInference,
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span: e.span,
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})
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}))]
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});
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let opt_input_types = opt_input_types.as_ref().map(AsRef::as_ref);
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if let Some(ok) = self.lookup_method_in_trait(
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call_expr.span,
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method_name,
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trait_def_id,
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adjusted_ty,
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opt_input_types,
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) {
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let method = self.register_infer_ok_obligations(ok);
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let mut autoref = None;
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if borrow {
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if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind {
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let mutbl = match mutbl {
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hir::Mutability::Not => AutoBorrowMutability::Not,
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hir::Mutability::Mut => AutoBorrowMutability::Mut {
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// For initial two-phase borrow
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// deployment, conservatively omit
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// overloaded function call ops.
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allow_two_phase_borrow: AllowTwoPhase::No,
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},
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};
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autoref = Some(Adjustment {
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kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
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target: method.sig.inputs()[0],
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});
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}
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}
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return Some((autoref, method));
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}
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}
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None
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}
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/// Give appropriate suggestion when encountering `||{/* not callable */}()`, where the
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/// likely intention is to call the closure, suggest `(||{})()`. (#55851)
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fn identify_bad_closure_def_and_call(
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&self,
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err: &mut DiagnosticBuilder<'a>,
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hir_id: hir::HirId,
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callee_node: &hir::ExprKind<'_>,
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callee_span: Span,
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) {
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let hir_id = self.tcx.hir().get_parent_node(hir_id);
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let parent_node = self.tcx.hir().get(hir_id);
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if let (
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hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(_, _, _, sp, ..), .. }),
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hir::ExprKind::Block(..),
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) = (parent_node, callee_node)
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{
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let start = sp.shrink_to_lo();
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let end = self.tcx.sess.source_map().next_point(callee_span);
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err.multipart_suggestion(
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"if you meant to create this closure and immediately call it, surround the \
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closure with parenthesis",
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vec![(start, "(".to_string()), (end, ")".to_string())],
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Applicability::MaybeIncorrect,
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);
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}
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}
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fn confirm_builtin_call(
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&self,
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call_expr: &'tcx hir::Expr<'tcx>,
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callee_ty: Ty<'tcx>,
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arg_exprs: &'tcx [hir::Expr<'tcx>],
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expected: Expectation<'tcx>,
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) -> Ty<'tcx> {
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let (fn_sig, def_span) = match callee_ty.kind {
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ty::FnDef(def_id, _) => {
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(callee_ty.fn_sig(self.tcx), self.tcx.hir().span_if_local(def_id))
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}
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ty::FnPtr(sig) => (sig, None),
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ref t => {
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let mut unit_variant = None;
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if let &ty::Adt(adt_def, ..) = t {
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if adt_def.is_enum() {
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if let hir::ExprKind::Call(ref expr, _) = call_expr.kind {
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unit_variant = Some(self.tcx.hir().hir_to_pretty_string(expr.hir_id))
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}
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}
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}
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if let hir::ExprKind::Call(ref callee, _) = call_expr.kind {
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let mut err = type_error_struct!(
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self.tcx.sess,
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callee.span,
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callee_ty,
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E0618,
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"expected function, found {}",
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match unit_variant {
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Some(ref path) => format!("enum variant `{}`", path),
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None => format!("`{}`", callee_ty),
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}
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);
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self.identify_bad_closure_def_and_call(
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&mut err,
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call_expr.hir_id,
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&callee.kind,
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callee.span,
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);
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if let Some(ref path) = unit_variant {
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err.span_suggestion(
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call_expr.span,
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&format!(
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"`{}` is a unit variant, you need to write it \
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without the parenthesis",
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path
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),
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path.to_string(),
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Applicability::MachineApplicable,
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);
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}
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let mut inner_callee_path = None;
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let def = match callee.kind {
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hir::ExprKind::Path(ref qpath) => {
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self.tables.borrow().qpath_res(qpath, callee.hir_id)
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}
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hir::ExprKind::Call(ref inner_callee, _) => {
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// If the call spans more than one line and the callee kind is
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// itself another `ExprCall`, that's a clue that we might just be
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// missing a semicolon (Issue #51055)
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let call_is_multiline =
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self.tcx.sess.source_map().is_multiline(call_expr.span);
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if call_is_multiline {
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let span = self.tcx.sess.source_map().next_point(callee.span);
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err.span_suggestion(
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span,
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"try adding a semicolon",
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";".to_owned(),
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Applicability::MaybeIncorrect,
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);
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}
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if let hir::ExprKind::Path(ref inner_qpath) = inner_callee.kind {
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inner_callee_path = Some(inner_qpath);
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self.tables.borrow().qpath_res(inner_qpath, inner_callee.hir_id)
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} else {
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Res::Err
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}
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}
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_ => Res::Err,
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};
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err.span_label(call_expr.span, "call expression requires function");
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if let Some(span) = self.tcx.hir().res_span(def) {
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let label = match (unit_variant, inner_callee_path) {
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(Some(path), _) => format!("`{}` defined here", path),
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(_, Some(hir::QPath::Resolved(_, path))) => format!(
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"`{}` defined here returns `{}`",
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path,
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callee_ty.to_string()
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),
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_ => format!("`{}` defined here", callee_ty.to_string()),
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};
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err.span_label(span, label);
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}
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err.emit();
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} else {
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bug!("call_expr.kind should be an ExprKind::Call, got {:?}", call_expr.kind);
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}
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// This is the "default" function signature, used in case of error.
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// In that case, we check each argument against "error" in order to
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// set up all the node type bindings.
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(
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ty::Binder::bind(self.tcx.mk_fn_sig(
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self.err_args(arg_exprs.len()).into_iter(),
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self.tcx.types.err,
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false,
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hir::Unsafety::Normal,
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abi::Abi::Rust,
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)),
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None,
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)
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}
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};
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// Replace any late-bound regions that appear in the function
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// signature with region variables. We also have to
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// renormalize the associated types at this point, since they
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// previously appeared within a `Binder<>` and hence would not
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// have been normalized before.
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let fn_sig =
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self.replace_bound_vars_with_fresh_vars(call_expr.span, infer::FnCall, &fn_sig).0;
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let fn_sig = self.normalize_associated_types_in(call_expr.span, &fn_sig);
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// Call the generic checker.
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let expected_arg_tys = self.expected_inputs_for_expected_output(
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call_expr.span,
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expected,
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fn_sig.output(),
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fn_sig.inputs(),
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);
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self.check_argument_types(
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call_expr.span,
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call_expr,
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fn_sig.inputs(),
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&expected_arg_tys[..],
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arg_exprs,
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fn_sig.c_variadic,
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TupleArgumentsFlag::DontTupleArguments,
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def_span,
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);
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fn_sig.output()
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}
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fn confirm_deferred_closure_call(
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&self,
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call_expr: &'tcx hir::Expr<'tcx>,
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arg_exprs: &'tcx [hir::Expr<'tcx>],
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expected: Expectation<'tcx>,
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fn_sig: ty::FnSig<'tcx>,
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) -> Ty<'tcx> {
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// `fn_sig` is the *signature* of the cosure being called. We
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// don't know the full details yet (`Fn` vs `FnMut` etc), but we
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// do know the types expected for each argument and the return
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// type.
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let expected_arg_tys = self.expected_inputs_for_expected_output(
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call_expr.span,
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expected,
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fn_sig.output().clone(),
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fn_sig.inputs(),
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);
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self.check_argument_types(
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call_expr.span,
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call_expr,
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fn_sig.inputs(),
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&expected_arg_tys,
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arg_exprs,
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fn_sig.c_variadic,
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TupleArgumentsFlag::TupleArguments,
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None,
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);
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fn_sig.output()
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}
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fn confirm_overloaded_call(
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&self,
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call_expr: &'tcx hir::Expr<'tcx>,
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arg_exprs: &'tcx [hir::Expr<'tcx>],
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expected: Expectation<'tcx>,
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method_callee: MethodCallee<'tcx>,
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) -> Ty<'tcx> {
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let output_type = self.check_method_argument_types(
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call_expr.span,
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call_expr,
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Ok(method_callee),
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arg_exprs,
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TupleArgumentsFlag::TupleArguments,
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expected,
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);
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self.write_method_call(call_expr.hir_id, method_callee);
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output_type
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}
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}
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#[derive(Debug)]
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pub struct DeferredCallResolution<'tcx> {
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call_expr: &'tcx hir::Expr<'tcx>,
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callee_expr: &'tcx hir::Expr<'tcx>,
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adjusted_ty: Ty<'tcx>,
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adjustments: Vec<Adjustment<'tcx>>,
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fn_sig: ty::FnSig<'tcx>,
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closure_def_id: DefId,
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closure_substs: SubstsRef<'tcx>,
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}
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impl<'a, 'tcx> DeferredCallResolution<'tcx> {
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pub fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) {
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debug!("DeferredCallResolution::resolve() {:?}", self);
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|
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// we should not be invoked until the closure kind has been
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|
// determined by upvar inference
|
|
assert!(fcx.closure_kind(self.closure_def_id, self.closure_substs).is_some());
|
|
|
|
// We may now know enough to figure out fn vs fnmut etc.
|
|
match fcx.try_overloaded_call_traits(self.call_expr, self.adjusted_ty, None) {
|
|
Some((autoref, method_callee)) => {
|
|
// One problem is that when we get here, we are going
|
|
// to have a newly instantiated function signature
|
|
// from the call trait. This has to be reconciled with
|
|
// the older function signature we had before. In
|
|
// principle we *should* be able to fn_sigs(), but we
|
|
// can't because of the annoying need for a TypeTrace.
|
|
// (This always bites me, should find a way to
|
|
// refactor it.)
|
|
let method_sig = method_callee.sig;
|
|
|
|
debug!("attempt_resolution: method_callee={:?}", method_callee);
|
|
|
|
for (method_arg_ty, self_arg_ty) in
|
|
method_sig.inputs().iter().skip(1).zip(self.fn_sig.inputs())
|
|
{
|
|
fcx.demand_eqtype(self.call_expr.span, &self_arg_ty, &method_arg_ty);
|
|
}
|
|
|
|
fcx.demand_eqtype(self.call_expr.span, method_sig.output(), self.fn_sig.output());
|
|
|
|
let mut adjustments = self.adjustments;
|
|
adjustments.extend(autoref);
|
|
fcx.apply_adjustments(self.callee_expr, adjustments);
|
|
|
|
fcx.write_method_call(self.call_expr.hir_id, method_callee);
|
|
}
|
|
None => {
|
|
span_bug!(
|
|
self.call_expr.span,
|
|
"failed to find an overloaded call trait for closure call"
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|