use std::cell::RefCell;
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::intravisit::Visitor;
use rustc_hir::lang_items::LangItem;
use rustc_hir_analysis::check::{check_function_signature, forbid_intrinsic_abi};
use rustc_infer::infer::RegionVariableOrigin;
use rustc_infer::traits::WellFormedLoc;
use rustc_middle::ty::{self, Binder, Ty, TyCtxt};
use rustc_span::def_id::LocalDefId;
use rustc_span::symbol::sym;
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
use tracing::{debug, instrument};
use crate::coercion::CoerceMany;
use crate::gather_locals::GatherLocalsVisitor;
use crate::{CoroutineTypes, Diverges, FnCtxt};
#[instrument(skip(fcx, body), level = "debug")]
pub(super) fn check_fn<'a, 'tcx>(
fcx: &mut FnCtxt<'a, 'tcx>,
fn_sig: ty::FnSig<'tcx>,
coroutine_types: Option<CoroutineTypes<'tcx>>,
decl: &'tcx hir::FnDecl<'tcx>,
fn_def_id: LocalDefId,
body: &'tcx hir::Body<'tcx>,
params_can_be_unsized: bool,
) -> Option<CoroutineTypes<'tcx>> {
let fn_id = fcx.tcx.local_def_id_to_hir_id(fn_def_id);
let tcx = fcx.tcx;
let hir = tcx.hir();
let declared_ret_ty = fn_sig.output();
let ret_ty =
fcx.register_infer_ok_obligations(fcx.infcx.replace_opaque_types_with_inference_vars(
declared_ret_ty,
fn_def_id,
decl.output.span(),
fcx.param_env,
));
fcx.coroutine_types = coroutine_types;
fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
let span = body.value.span;
forbid_intrinsic_abi(tcx, span, fn_sig.abi);
GatherLocalsVisitor::new(fcx).visit_body(body);
let maybe_va_list = fn_sig.c_variadic.then(|| {
let span = body.params.last().unwrap().span;
let va_list_did = tcx.require_lang_item(LangItem::VaList, Some(span));
let region = fcx.next_region_var(RegionVariableOrigin::MiscVariable(span));
tcx.type_of(va_list_did).instantiate(tcx, &[region.into()])
});
let inputs_hir = hir.fn_decl_by_hir_id(fn_id).map(|decl| &decl.inputs);
let inputs_fn = fn_sig.inputs().iter().copied();
for (idx, (param_ty, param)) in inputs_fn.chain(maybe_va_list).zip(body.params).enumerate() {
if fcx.tcx.is_typeck_child(fn_def_id.to_def_id()) {
fcx.register_wf_obligation(
param_ty.into(),
param.span,
ObligationCauseCode::WellFormed(Some(WellFormedLoc::Param {
function: fn_def_id,
param_idx: idx,
})),
);
}
let ty: Option<&hir::Ty<'_>> = inputs_hir.and_then(|h| h.get(idx));
let ty_span = ty.map(|ty| ty.span);
fcx.check_pat_top(param.pat, param_ty, ty_span, None, None);
if param.pat.is_never_pattern() {
fcx.function_diverges_because_of_empty_arguments.set(Diverges::Always {
span: param.pat.span,
custom_note: Some("any code following a never pattern is unreachable"),
});
}
if !params_can_be_unsized {
fcx.require_type_is_sized(
param_ty,
param.pat.span,
ObligationCauseCode::SizedArgumentType(
if ty_span == Some(param.span) && tcx.is_closure_like(fn_def_id.into()) {
None
} else {
ty.map(|ty| ty.hir_id)
},
),
);
}
fcx.write_ty(param.hir_id, param_ty);
}
fcx.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
let return_or_body_span = match decl.output {
hir::FnRetTy::DefaultReturn(_) => body.value.span,
hir::FnRetTy::Return(ty) => ty.span,
};
fcx.require_type_is_sized(
declared_ret_ty,
return_or_body_span,
ObligationCauseCode::SizedReturnType,
);
if fcx.tcx.is_typeck_child(fn_def_id.to_def_id()) {
fcx.require_type_is_sized(
declared_ret_ty,
return_or_body_span,
ObligationCauseCode::WellFormed(None),
);
}
fcx.is_whole_body.set(true);
fcx.check_return_expr(body.value, false);
let coercion = fcx.ret_coercion.take().unwrap().into_inner();
let mut actual_return_ty = coercion.complete(fcx);
debug!("actual_return_ty = {:?}", actual_return_ty);
if let ty::Dynamic(..) = declared_ret_ty.kind() {
actual_return_ty = fcx.next_ty_var(span);
debug!("actual_return_ty replaced with {:?}", actual_return_ty);
}
fcx.demand_suptype(span, ret_ty, actual_return_ty);
if tcx.is_lang_item(fn_def_id.to_def_id(), LangItem::PanicImpl) {
check_panic_info_fn(tcx, fn_def_id, fn_sig);
}
if tcx.is_lang_item(fn_def_id.to_def_id(), LangItem::Start) {
check_lang_start_fn(tcx, fn_sig, fn_def_id);
}
fcx.coroutine_types
}
fn check_panic_info_fn(tcx: TyCtxt<'_>, fn_id: LocalDefId, fn_sig: ty::FnSig<'_>) {
let span = tcx.def_span(fn_id);
let DefKind::Fn = tcx.def_kind(fn_id) else {
tcx.dcx().span_err(span, "should be a function");
return;
};
let generic_counts = tcx.generics_of(fn_id).own_counts();
if generic_counts.types != 0 {
tcx.dcx().span_err(span, "should have no type parameters");
}
if generic_counts.consts != 0 {
tcx.dcx().span_err(span, "should have no const parameters");
}
let panic_info_did = tcx.require_lang_item(hir::LangItem::PanicInfo, Some(span));
let panic_info_ty = tcx.type_of(panic_info_did).instantiate(
tcx,
&[ty::GenericArg::from(ty::Region::new_bound(
tcx,
ty::INNERMOST,
ty::BoundRegion { var: ty::BoundVar::from_u32(1), kind: ty::BrAnon },
))],
);
let panic_info_ref_ty = Ty::new_imm_ref(
tcx,
ty::Region::new_bound(
tcx,
ty::INNERMOST,
ty::BoundRegion { var: ty::BoundVar::ZERO, kind: ty::BrAnon },
),
panic_info_ty,
);
let bounds = tcx.mk_bound_variable_kinds(&[
ty::BoundVariableKind::Region(ty::BrAnon),
ty::BoundVariableKind::Region(ty::BrAnon),
]);
let expected_sig = ty::Binder::bind_with_vars(
tcx.mk_fn_sig([panic_info_ref_ty], tcx.types.never, false, fn_sig.safety, Abi::Rust),
bounds,
);
let _ = check_function_signature(
tcx,
ObligationCause::new(span, fn_id, ObligationCauseCode::LangFunctionType(sym::panic_impl)),
fn_id.into(),
expected_sig,
);
}
fn check_lang_start_fn<'tcx>(tcx: TyCtxt<'tcx>, fn_sig: ty::FnSig<'tcx>, def_id: LocalDefId) {
let generics = tcx.generics_of(def_id);
let fn_generic = generics.param_at(0, tcx);
let generic_ty = Ty::new_param(tcx, fn_generic.index, fn_generic.name);
let main_fn_ty = Ty::new_fn_ptr(
tcx,
Binder::dummy(tcx.mk_fn_sig([], generic_ty, false, hir::Safety::Safe, Abi::Rust)),
);
let expected_sig = ty::Binder::dummy(tcx.mk_fn_sig(
[
main_fn_ty,
tcx.types.isize,
Ty::new_imm_ptr(tcx, Ty::new_imm_ptr(tcx, tcx.types.u8)),
tcx.types.u8,
],
tcx.types.isize,
false,
fn_sig.safety,
Abi::Rust,
));
let _ = check_function_signature(
tcx,
ObligationCause::new(
tcx.def_span(def_id),
def_id,
ObligationCauseCode::LangFunctionType(sym::start),
),
def_id.into(),
expected_sig,
);
}