diff options
Diffstat (limited to 'compiler/rustc_hir_analysis/src/check/callee.rs')
| -rw-r--r-- | compiler/rustc_hir_analysis/src/check/callee.rs | 694 |
1 files changed, 694 insertions, 0 deletions
diff --git a/compiler/rustc_hir_analysis/src/check/callee.rs b/compiler/rustc_hir_analysis/src/check/callee.rs new file mode 100644 index 00000000000..c82a31e65cf --- /dev/null +++ b/compiler/rustc_hir_analysis/src/check/callee.rs @@ -0,0 +1,694 @@ +use super::method::MethodCallee; +use super::{DefIdOrName, Expectation, FnCtxt, TupleArgumentsFlag}; +use crate::type_error_struct; + +use rustc_errors::{struct_span_err, Applicability, Diagnostic}; +use rustc_hir as hir; +use rustc_hir::def::{self, Namespace, Res}; +use rustc_hir::def_id::DefId; +use rustc_infer::{ + infer, + traits::{self, Obligation}, +}; +use rustc_infer::{ + infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}, + traits::ObligationCause, +}; +use rustc_middle::ty::adjustment::{ + Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, +}; +use rustc_middle::ty::SubstsRef; +use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitable}; +use rustc_span::def_id::LocalDefId; +use rustc_span::symbol::{sym, Ident}; +use rustc_span::Span; +use rustc_target::spec::abi; +use rustc_trait_selection::autoderef::Autoderef; +use rustc_trait_selection::infer::InferCtxtExt as _; +use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _; + +use std::iter; + +/// Checks that it is legal to call methods of the trait corresponding +/// to `trait_id` (this only cares about the trait, not the specific +/// method that is called). +pub fn check_legal_trait_for_method_call( + tcx: TyCtxt<'_>, + span: Span, + receiver: Option<Span>, + expr_span: Span, + trait_id: DefId, +) { + if tcx.lang_items().drop_trait() == Some(trait_id) { + let mut err = struct_span_err!(tcx.sess, span, E0040, "explicit use of destructor method"); + err.span_label(span, "explicit destructor calls not allowed"); + + let (sp, suggestion) = receiver + .and_then(|s| tcx.sess.source_map().span_to_snippet(s).ok()) + .filter(|snippet| !snippet.is_empty()) + .map(|snippet| (expr_span, format!("drop({snippet})"))) + .unwrap_or_else(|| (span, "drop".to_string())); + + err.span_suggestion( + sp, + "consider using `drop` function", + suggestion, + Applicability::MaybeIncorrect, + ); + + err.emit(); + } +} + +enum CallStep<'tcx> { + Builtin(Ty<'tcx>), + DeferredClosure(LocalDefId, ty::FnSig<'tcx>), + /// E.g., enum variant constructors. + Overloaded(MethodCallee<'tcx>), +} + +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + pub fn check_call( + &self, + call_expr: &'tcx hir::Expr<'tcx>, + callee_expr: &'tcx hir::Expr<'tcx>, + arg_exprs: &'tcx [hir::Expr<'tcx>], + expected: Expectation<'tcx>, + ) -> Ty<'tcx> { + let original_callee_ty = match &callee_expr.kind { + hir::ExprKind::Path(hir::QPath::Resolved(..) | hir::QPath::TypeRelative(..)) => self + .check_expr_with_expectation_and_args( + callee_expr, + Expectation::NoExpectation, + arg_exprs, + ), + _ => self.check_expr(callee_expr), + }; + + let expr_ty = self.structurally_resolved_type(call_expr.span, original_callee_ty); + + let mut autoderef = self.autoderef(callee_expr.span, expr_ty); + let mut result = None; + while result.is_none() && autoderef.next().is_some() { + result = self.try_overloaded_call_step(call_expr, callee_expr, arg_exprs, &autoderef); + } + self.register_predicates(autoderef.into_obligations()); + + let output = match result { + None => { + // this will report an error since original_callee_ty is not a fn + self.confirm_builtin_call( + call_expr, + callee_expr, + original_callee_ty, + arg_exprs, + expected, + ) + } + + Some(CallStep::Builtin(callee_ty)) => { + self.confirm_builtin_call(call_expr, callee_expr, callee_ty, arg_exprs, expected) + } + + Some(CallStep::DeferredClosure(def_id, fn_sig)) => { + self.confirm_deferred_closure_call(call_expr, arg_exprs, expected, def_id, fn_sig) + } + + Some(CallStep::Overloaded(method_callee)) => { + self.confirm_overloaded_call(call_expr, arg_exprs, expected, method_callee) + } + }; + + // we must check that return type of called functions is WF: + self.register_wf_obligation(output.into(), call_expr.span, traits::WellFormed(None)); + + output + } + + fn try_overloaded_call_step( + &self, + call_expr: &'tcx hir::Expr<'tcx>, + callee_expr: &'tcx hir::Expr<'tcx>, + arg_exprs: &'tcx [hir::Expr<'tcx>], + autoderef: &Autoderef<'a, 'tcx>, + ) -> Option<CallStep<'tcx>> { + let adjusted_ty = + self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false)); + debug!( + "try_overloaded_call_step(call_expr={:?}, adjusted_ty={:?})", + call_expr, adjusted_ty + ); + + // If the callee is a bare function or a closure, then we're all set. + match *adjusted_ty.kind() { + ty::FnDef(..) | ty::FnPtr(_) => { + let adjustments = self.adjust_steps(autoderef); + self.apply_adjustments(callee_expr, adjustments); + return Some(CallStep::Builtin(adjusted_ty)); + } + + ty::Closure(def_id, substs) => { + let def_id = def_id.expect_local(); + + // Check whether this is a call to a closure where we + // haven't yet decided on whether the closure is fn vs + // fnmut vs fnonce. If so, we have to defer further processing. + if self.closure_kind(substs).is_none() { + let closure_sig = substs.as_closure().sig(); + let closure_sig = self.replace_bound_vars_with_fresh_vars( + call_expr.span, + infer::FnCall, + closure_sig, + ); + let adjustments = self.adjust_steps(autoderef); + self.record_deferred_call_resolution( + def_id, + DeferredCallResolution { + call_expr, + callee_expr, + adjusted_ty, + adjustments, + fn_sig: closure_sig, + closure_substs: substs, + }, + ); + return Some(CallStep::DeferredClosure(def_id, closure_sig)); + } + } + + // Hack: we know that there are traits implementing Fn for &F + // where F:Fn and so forth. In the particular case of types + // like `x: &mut FnMut()`, if there is a call `x()`, we would + // normally translate to `FnMut::call_mut(&mut x, ())`, but + // that winds up requiring `mut x: &mut FnMut()`. A little + // over the top. The simplest fix by far is to just ignore + // this case and deref again, so we wind up with + // `FnMut::call_mut(&mut *x, ())`. + ty::Ref(..) if autoderef.step_count() == 0 => { + return None; + } + + _ => {} + } + + // Now, we look for the implementation of a Fn trait on the object's type. + // We first do it with the explicit instruction to look for an impl of + // `Fn<Tuple>`, with the tuple `Tuple` having an arity corresponding + // to the number of call parameters. + // If that fails (or_else branch), we try again without specifying the + // shape of the tuple (hence the None). This allows to detect an Fn trait + // is implemented, and use this information for diagnostic. + self.try_overloaded_call_traits(call_expr, adjusted_ty, Some(arg_exprs)) + .or_else(|| self.try_overloaded_call_traits(call_expr, adjusted_ty, None)) + .map(|(autoref, method)| { + let mut adjustments = self.adjust_steps(autoderef); + adjustments.extend(autoref); + self.apply_adjustments(callee_expr, adjustments); + CallStep::Overloaded(method) + }) + } + + fn try_overloaded_call_traits( + &self, + call_expr: &hir::Expr<'_>, + adjusted_ty: Ty<'tcx>, + opt_arg_exprs: Option<&'tcx [hir::Expr<'tcx>]>, + ) -> Option<(Option<Adjustment<'tcx>>, MethodCallee<'tcx>)> { + // Try the options that are least restrictive on the caller first. + for (opt_trait_def_id, method_name, borrow) in [ + (self.tcx.lang_items().fn_trait(), Ident::with_dummy_span(sym::call), true), + (self.tcx.lang_items().fn_mut_trait(), Ident::with_dummy_span(sym::call_mut), true), + (self.tcx.lang_items().fn_once_trait(), Ident::with_dummy_span(sym::call_once), false), + ] { + let Some(trait_def_id) = opt_trait_def_id else { continue }; + + let opt_input_types = opt_arg_exprs.map(|arg_exprs| { + [self.tcx.mk_tup(arg_exprs.iter().map(|e| { + self.next_ty_var(TypeVariableOrigin { + kind: TypeVariableOriginKind::TypeInference, + span: e.span, + }) + }))] + }); + let opt_input_types = opt_input_types.as_ref().map(AsRef::as_ref); + + if let Some(ok) = self.lookup_method_in_trait( + call_expr.span, + method_name, + trait_def_id, + adjusted_ty, + opt_input_types, + ) { + let method = self.register_infer_ok_obligations(ok); + let mut autoref = None; + if borrow { + // Check for &self vs &mut self in the method signature. Since this is either + // the Fn or FnMut trait, it should be one of those. + let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind() else { + // The `fn`/`fn_mut` lang item is ill-formed, which should have + // caused an error elsewhere. + self.tcx + .sess + .delay_span_bug(call_expr.span, "input to call/call_mut is not a ref?"); + return None; + }; + + let mutbl = match mutbl { + hir::Mutability::Not => AutoBorrowMutability::Not, + hir::Mutability::Mut => AutoBorrowMutability::Mut { + // For initial two-phase borrow + // deployment, conservatively omit + // overloaded function call ops. + allow_two_phase_borrow: AllowTwoPhase::No, + }, + }; + autoref = Some(Adjustment { + kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)), + target: method.sig.inputs()[0], + }); + } + return Some((autoref, method)); + } + } + + None + } + + /// Give appropriate suggestion when encountering `||{/* not callable */}()`, where the + /// likely intention is to call the closure, suggest `(||{})()`. (#55851) + fn identify_bad_closure_def_and_call( + &self, + err: &mut Diagnostic, + hir_id: hir::HirId, + callee_node: &hir::ExprKind<'_>, + callee_span: Span, + ) { + let hir = self.tcx.hir(); + let parent_hir_id = hir.get_parent_node(hir_id); + let parent_node = hir.get(parent_hir_id); + if let ( + hir::Node::Expr(hir::Expr { + kind: hir::ExprKind::Closure(&hir::Closure { fn_decl_span, body, .. }), + .. + }), + hir::ExprKind::Block(..), + ) = (parent_node, callee_node) + { + let fn_decl_span = if hir.body(body).generator_kind + == Some(hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Closure)) + { + // Actually need to unwrap a few more layers of HIR to get to + // the _real_ closure... + let async_closure = hir.get_parent_node(hir.get_parent_node(parent_hir_id)); + if let hir::Node::Expr(hir::Expr { + kind: hir::ExprKind::Closure(&hir::Closure { fn_decl_span, .. }), + .. + }) = hir.get(async_closure) + { + fn_decl_span + } else { + return; + } + } else { + fn_decl_span + }; + + let start = fn_decl_span.shrink_to_lo(); + let end = callee_span.shrink_to_hi(); + err.multipart_suggestion( + "if you meant to create this closure and immediately call it, surround the \ + closure with parentheses", + vec![(start, "(".to_string()), (end, ")".to_string())], + Applicability::MaybeIncorrect, + ); + } + } + + /// Give appropriate suggestion when encountering `[("a", 0) ("b", 1)]`, where the + /// likely intention is to create an array containing tuples. + fn maybe_suggest_bad_array_definition( + &self, + err: &mut Diagnostic, + call_expr: &'tcx hir::Expr<'tcx>, + callee_expr: &'tcx hir::Expr<'tcx>, + ) -> bool { + let hir_id = self.tcx.hir().get_parent_node(call_expr.hir_id); + let parent_node = self.tcx.hir().get(hir_id); + if let ( + hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Array(_), .. }), + hir::ExprKind::Tup(exp), + hir::ExprKind::Call(_, args), + ) = (parent_node, &callee_expr.kind, &call_expr.kind) + && args.len() == exp.len() + { + let start = callee_expr.span.shrink_to_hi(); + err.span_suggestion( + start, + "consider separating array elements with a comma", + ",", + Applicability::MaybeIncorrect, + ); + return true; + } + false + } + + fn confirm_builtin_call( + &self, + call_expr: &'tcx hir::Expr<'tcx>, + callee_expr: &'tcx hir::Expr<'tcx>, + callee_ty: Ty<'tcx>, + arg_exprs: &'tcx [hir::Expr<'tcx>], + expected: Expectation<'tcx>, + ) -> Ty<'tcx> { + let (fn_sig, def_id) = match *callee_ty.kind() { + ty::FnDef(def_id, subst) => { + let fn_sig = self.tcx.bound_fn_sig(def_id).subst(self.tcx, subst); + + // Unit testing: function items annotated with + // `#[rustc_evaluate_where_clauses]` trigger special output + // to let us test the trait evaluation system. + if self.tcx.has_attr(def_id, sym::rustc_evaluate_where_clauses) { + let predicates = self.tcx.predicates_of(def_id); + let predicates = predicates.instantiate(self.tcx, subst); + for (predicate, predicate_span) in + predicates.predicates.iter().zip(&predicates.spans) + { + let obligation = Obligation::new( + ObligationCause::dummy_with_span(callee_expr.span), + self.param_env, + *predicate, + ); + let result = self.evaluate_obligation(&obligation); + self.tcx + .sess + .struct_span_err( + callee_expr.span, + &format!("evaluate({:?}) = {:?}", predicate, result), + ) + .span_label(*predicate_span, "predicate") + .emit(); + } + } + (fn_sig, Some(def_id)) + } + ty::FnPtr(sig) => (sig, None), + _ => { + let mut unit_variant = None; + if let hir::ExprKind::Path(qpath) = &callee_expr.kind + && let Res::Def(def::DefKind::Ctor(kind, def::CtorKind::Const), _) + = self.typeck_results.borrow().qpath_res(qpath, callee_expr.hir_id) + // Only suggest removing parens if there are no arguments + && arg_exprs.is_empty() + { + let descr = match kind { + def::CtorOf::Struct => "struct", + def::CtorOf::Variant => "enum variant", + }; + let removal_span = + callee_expr.span.shrink_to_hi().to(call_expr.span.shrink_to_hi()); + unit_variant = + Some((removal_span, descr, rustc_hir_pretty::qpath_to_string(qpath))); + } + + let callee_ty = self.resolve_vars_if_possible(callee_ty); + let mut err = type_error_struct!( + self.tcx.sess, + callee_expr.span, + callee_ty, + E0618, + "expected function, found {}", + match &unit_variant { + Some((_, kind, path)) => format!("{kind} `{path}`"), + None => format!("`{callee_ty}`"), + } + ); + + self.identify_bad_closure_def_and_call( + &mut err, + call_expr.hir_id, + &callee_expr.kind, + callee_expr.span, + ); + + if let Some((removal_span, kind, path)) = &unit_variant { + err.span_suggestion_verbose( + *removal_span, + &format!( + "`{path}` is a unit {kind}, and does not take parentheses to be constructed", + ), + "", + Applicability::MachineApplicable, + ); + } + + let mut inner_callee_path = None; + let def = match callee_expr.kind { + hir::ExprKind::Path(ref qpath) => { + self.typeck_results.borrow().qpath_res(qpath, callee_expr.hir_id) + } + hir::ExprKind::Call(ref inner_callee, _) => { + // If the call spans more than one line and the callee kind is + // itself another `ExprCall`, that's a clue that we might just be + // missing a semicolon (Issue #51055) + let call_is_multiline = + self.tcx.sess.source_map().is_multiline(call_expr.span); + if call_is_multiline { + err.span_suggestion( + callee_expr.span.shrink_to_hi(), + "consider using a semicolon here", + ";", + Applicability::MaybeIncorrect, + ); + } + if let hir::ExprKind::Path(ref inner_qpath) = inner_callee.kind { + inner_callee_path = Some(inner_qpath); + self.typeck_results.borrow().qpath_res(inner_qpath, inner_callee.hir_id) + } else { + Res::Err + } + } + _ => Res::Err, + }; + + if !self.maybe_suggest_bad_array_definition(&mut err, call_expr, callee_expr) { + if let Some((maybe_def, output_ty, _)) = self.extract_callable_info(callee_expr, callee_ty) + && !self.type_is_sized_modulo_regions(self.param_env, output_ty, callee_expr.span) + { + let descr = match maybe_def { + DefIdOrName::DefId(def_id) => self.tcx.def_kind(def_id).descr(def_id), + DefIdOrName::Name(name) => name, + }; + err.span_label( + callee_expr.span, + format!("this {descr} returns an unsized value `{output_ty}`, so it cannot be called") + ); + if let DefIdOrName::DefId(def_id) = maybe_def + && let Some(def_span) = self.tcx.hir().span_if_local(def_id) + { + err.span_label(def_span, "the callable type is defined here"); + } + } else { + err.span_label(call_expr.span, "call expression requires function"); + } + } + + if let Some(span) = self.tcx.hir().res_span(def) { + let callee_ty = callee_ty.to_string(); + let label = match (unit_variant, inner_callee_path) { + (Some((_, kind, path)), _) => Some(format!("{kind} `{path}` defined here")), + (_, Some(hir::QPath::Resolved(_, path))) => self + .tcx + .sess + .source_map() + .span_to_snippet(path.span) + .ok() + .map(|p| format!("`{p}` defined here returns `{callee_ty}`")), + _ => { + match def { + // Emit a different diagnostic for local variables, as they are not + // type definitions themselves, but rather variables *of* that type. + Res::Local(hir_id) => Some(format!( + "`{}` has type `{}`", + self.tcx.hir().name(hir_id), + callee_ty + )), + Res::Def(kind, def_id) if kind.ns() == Some(Namespace::ValueNS) => { + Some(format!( + "`{}` defined here", + self.tcx.def_path_str(def_id), + )) + } + _ => Some(format!("`{callee_ty}` defined here")), + } + } + }; + if let Some(label) = label { + err.span_label(span, label); + } + } + err.emit(); + + // This is the "default" function signature, used in case of error. + // In that case, we check each argument against "error" in order to + // set up all the node type bindings. + ( + ty::Binder::dummy(self.tcx.mk_fn_sig( + self.err_args(arg_exprs.len()).into_iter(), + self.tcx.ty_error(), + false, + hir::Unsafety::Normal, + abi::Abi::Rust, + )), + None, + ) + } + }; + + // Replace any late-bound regions that appear in the function + // signature with region variables. We also have to + // renormalize the associated types at this point, since they + // previously appeared within a `Binder<>` and hence would not + // have been normalized before. + let fn_sig = self.replace_bound_vars_with_fresh_vars(call_expr.span, infer::FnCall, fn_sig); + let fn_sig = self.normalize_associated_types_in(call_expr.span, fn_sig); + + // Call the generic checker. + let expected_arg_tys = self.expected_inputs_for_expected_output( + call_expr.span, + expected, + fn_sig.output(), + fn_sig.inputs(), + ); + self.check_argument_types( + call_expr.span, + call_expr, + fn_sig.inputs(), + expected_arg_tys, + arg_exprs, + fn_sig.c_variadic, + TupleArgumentsFlag::DontTupleArguments, + def_id, + ); + + fn_sig.output() + } + + fn confirm_deferred_closure_call( + &self, + call_expr: &'tcx hir::Expr<'tcx>, + arg_exprs: &'tcx [hir::Expr<'tcx>], + expected: Expectation<'tcx>, + closure_def_id: LocalDefId, + fn_sig: ty::FnSig<'tcx>, + ) -> Ty<'tcx> { + // `fn_sig` is the *signature* of the closure being called. We + // don't know the full details yet (`Fn` vs `FnMut` etc), but we + // do know the types expected for each argument and the return + // type. + + let expected_arg_tys = self.expected_inputs_for_expected_output( + call_expr.span, + expected, + fn_sig.output(), + fn_sig.inputs(), + ); + + self.check_argument_types( + call_expr.span, + call_expr, + fn_sig.inputs(), + expected_arg_tys, + arg_exprs, + fn_sig.c_variadic, + TupleArgumentsFlag::TupleArguments, + Some(closure_def_id.to_def_id()), + ); + + fn_sig.output() + } + + fn confirm_overloaded_call( + &self, + call_expr: &'tcx hir::Expr<'tcx>, + arg_exprs: &'tcx [hir::Expr<'tcx>], + expected: Expectation<'tcx>, + method_callee: MethodCallee<'tcx>, + ) -> Ty<'tcx> { + let output_type = self.check_method_argument_types( + call_expr.span, + call_expr, + Ok(method_callee), + arg_exprs, + TupleArgumentsFlag::TupleArguments, + expected, + ); + + self.write_method_call(call_expr.hir_id, method_callee); + output_type + } +} + +#[derive(Debug)] +pub struct DeferredCallResolution<'tcx> { + call_expr: &'tcx hir::Expr<'tcx>, + callee_expr: &'tcx hir::Expr<'tcx>, + adjusted_ty: Ty<'tcx>, + adjustments: Vec<Adjustment<'tcx>>, + fn_sig: ty::FnSig<'tcx>, + closure_substs: SubstsRef<'tcx>, +} + +impl<'a, 'tcx> DeferredCallResolution<'tcx> { + pub fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) { + debug!("DeferredCallResolution::resolve() {:?}", self); + + // we should not be invoked until the closure kind has been + // determined by upvar inference + assert!(fcx.closure_kind(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 + iter::zip(method_sig.inputs().iter().skip(1), 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 => { + // This can happen if `#![no_core]` is used and the `fn/fn_mut/fn_once` + // lang items are not defined (issue #86238). + let mut err = fcx.inh.tcx.sess.struct_span_err( + self.call_expr.span, + "failed to find an overloaded call trait for closure call", + ); + err.help( + "make sure the `fn`/`fn_mut`/`fn_once` lang items are defined \ + and have associated `call`/`call_mut`/`call_once` functions", + ); + err.emit(); + } + } + } +} |