1 use crate::coercion::CoerceMany;
2 use crate::gather_locals::GatherLocalsVisitor;
4 use crate::GeneratorTypes;
6 use rustc_hir::def::DefKind;
7 use rustc_hir::intravisit::Visitor;
8 use rustc_hir::lang_items::LangItem;
9 use rustc_hir_analysis::check::fn_maybe_err;
10 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
11 use rustc_infer::infer::RegionVariableOrigin;
12 use rustc_middle::ty::{self, Ty, TyCtxt};
13 use rustc_span::def_id::LocalDefId;
14 use rustc_trait_selection::traits;
15 use std::cell::RefCell;
17 /// Helper used for fns and closures. Does the grungy work of checking a function
18 /// body and returns the function context used for that purpose, since in the case of a fn item
19 /// there is still a bit more to do.
22 /// * inherited: other fields inherited from the enclosing fn (if any)
23 #[instrument(skip(fcx, body), level = "debug")]
24 pub(super) fn check_fn<'a, 'tcx>(
25 fcx: &mut FnCtxt<'a, 'tcx>,
26 fn_sig: ty::FnSig<'tcx>,
27 decl: &'tcx hir::FnDecl<'tcx>,
28 fn_def_id: LocalDefId,
29 body: &'tcx hir::Body<'tcx>,
30 can_be_generator: Option<hir::Movability>,
31 ) -> Option<GeneratorTypes<'tcx>> {
32 let fn_id = fcx.tcx.hir().local_def_id_to_hir_id(fn_def_id);
37 let declared_ret_ty = fn_sig.output();
40 fcx.register_infer_ok_obligations(fcx.infcx.replace_opaque_types_with_inference_vars(
47 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
49 let span = body.value.span;
51 fn_maybe_err(tcx, span, fn_sig.abi);
53 if let Some(kind) = body.generator_kind && can_be_generator.is_some() {
54 let yield_ty = if kind == hir::GeneratorKind::Gen {
56 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
57 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
63 // Resume type defaults to `()` if the generator has no argument.
64 let resume_ty = fn_sig.inputs().get(0).copied().unwrap_or_else(|| tcx.mk_unit());
66 fcx.resume_yield_tys = Some((resume_ty, yield_ty));
69 GatherLocalsVisitor::new(&fcx).visit_body(body);
71 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
72 // (as it's created inside the body itself, not passed in from outside).
73 let maybe_va_list = if fn_sig.c_variadic {
74 let span = body.params.last().unwrap().span;
75 let va_list_did = tcx.require_lang_item(LangItem::VaList, Some(span));
76 let region = fcx.next_region_var(RegionVariableOrigin::MiscVariable(span));
78 Some(tcx.bound_type_of(va_list_did).subst(tcx, &[region.into()]))
83 // Add formal parameters.
84 let inputs_hir = hir.fn_decl_by_hir_id(fn_id).map(|decl| &decl.inputs);
85 let inputs_fn = fn_sig.inputs().iter().copied();
86 for (idx, (param_ty, param)) in inputs_fn.chain(maybe_va_list).zip(body.params).enumerate() {
88 let ty_span = try { inputs_hir?.get(idx)?.span };
89 fcx.check_pat_top(¶m.pat, param_ty, ty_span, false);
91 // Check that argument is Sized.
92 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
93 // for simple cases like `fn foo(x: Trait)`,
94 // where we would error once on the parameter as a whole, and once on the binding `x`.
95 if param.pat.simple_ident().is_none() && !tcx.features().unsized_fn_params {
96 fcx.require_type_is_sized(param_ty, param.pat.span, traits::SizedArgumentType(ty_span));
99 fcx.write_ty(param.hir_id, param_ty);
102 fcx.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
104 if let ty::Dynamic(_, _, ty::Dyn) = declared_ret_ty.kind() {
105 // FIXME: We need to verify that the return type is `Sized` after the return expression has
106 // been evaluated so that we have types available for all the nodes being returned, but that
107 // requires the coerced evaluated type to be stored. Moving `check_return_expr` before this
108 // causes unsized errors caused by the `declared_ret_ty` to point at the return expression,
109 // while keeping the current ordering we will ignore the tail expression's type because we
110 // don't know it yet. We can't do `check_expr_kind` while keeping `check_return_expr`
111 // because we will trigger "unreachable expression" lints unconditionally.
112 // Because of all of this, we perform a crude check to know whether the simplest `!Sized`
113 // case that a newcomer might make, returning a bare trait, and in that case we populate
114 // the tail expression's type so that the suggestion will be correct, but ignore all other
116 fcx.check_expr(&body.value);
117 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
119 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
120 fcx.check_return_expr(&body.value, false);
123 // We insert the deferred_generator_interiors entry after visiting the body.
124 // This ensures that all nested generators appear before the entry of this generator.
125 // resolve_generator_interiors relies on this property.
126 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
128 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span });
129 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
131 let (resume_ty, yield_ty) = fcx.resume_yield_tys.unwrap();
132 Some(GeneratorTypes {
136 movability: can_be_generator.unwrap(),
142 // Finalize the return check by taking the LUB of the return types
143 // we saw and assigning it to the expected return type. This isn't
144 // really expected to fail, since the coercions would have failed
145 // earlier when trying to find a LUB.
146 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
147 let mut actual_return_ty = coercion.complete(&fcx);
148 debug!("actual_return_ty = {:?}", actual_return_ty);
149 if let ty::Dynamic(..) = declared_ret_ty.kind() {
150 // We have special-cased the case where the function is declared
151 // `-> dyn Foo` and we don't actually relate it to the
152 // `fcx.ret_coercion`, so just substitute a type variable.
154 fcx.next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::DynReturnFn, span });
155 debug!("actual_return_ty replaced with {:?}", actual_return_ty);
158 // HACK(oli-obk, compiler-errors): We should be comparing this against
159 // `declared_ret_ty`, but then anything uninferred would be inferred to
160 // the opaque type itself. That again would cause writeback to assume
161 // we have a recursive call site and do the sadly stabilized fallback to `()`.
162 fcx.demand_suptype(span, ret_ty, actual_return_ty);
164 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
165 if let Some(panic_impl_did) = tcx.lang_items().panic_impl()
166 && panic_impl_did == hir.local_def_id(fn_id).to_def_id()
168 check_panic_info_fn(tcx, panic_impl_did.expect_local(), fn_sig, decl, declared_ret_ty);
174 fn check_panic_info_fn(
177 fn_sig: ty::FnSig<'_>,
178 decl: &hir::FnDecl<'_>,
179 declared_ret_ty: Ty<'_>,
181 let Some(panic_info_did) = tcx.lang_items().panic_info() else {
182 tcx.sess.err("language item required, but not found: `panic_info`");
186 if *declared_ret_ty.kind() != ty::Never {
187 tcx.sess.span_err(decl.output.span(), "return type should be `!`");
190 let inputs = fn_sig.inputs();
191 if inputs.len() != 1 {
192 tcx.sess.span_err(tcx.def_span(fn_id), "function should have one argument");
196 let arg_is_panic_info = match *inputs[0].kind() {
197 ty::Ref(region, ty, mutbl) => match *ty.kind() {
198 ty::Adt(ref adt, _) => {
199 adt.did() == panic_info_did && mutbl.is_not() && !region.is_static()
206 if !arg_is_panic_info {
207 tcx.sess.span_err(decl.inputs[0].span, "argument should be `&PanicInfo`");
210 let DefKind::Fn = tcx.def_kind(fn_id) else {
211 let span = tcx.def_span(fn_id);
212 tcx.sess.span_err(span, "should be a function");
216 let generic_counts = tcx.generics_of(fn_id).own_counts();
217 if generic_counts.types != 0 {
218 let span = tcx.def_span(fn_id);
219 tcx.sess.span_err(span, "should have no type parameters");
221 if generic_counts.consts != 0 {
222 let span = tcx.def_span(fn_id);
223 tcx.sess.span_err(span, "should have no const parameters");