1 use rustc_errors::Applicability;
2 use rustc_hir::def_id::DefId;
3 use rustc_middle::mir::visit::Visitor;
4 use rustc_middle::mir::*;
5 use rustc_middle::ty::{
7 subst::{GenericArgKind, Subst, SubstsRef},
8 PredicateKind, Ty, TyCtxt, TyS,
10 use rustc_session::lint::builtin::FUNCTION_ITEM_REFERENCES;
11 use rustc_span::{symbol::sym, Span};
12 use rustc_target::spec::abi::Abi;
14 use crate::transform::MirPass;
16 pub struct FunctionItemReferences;
18 impl<'tcx> MirPass<'tcx> for FunctionItemReferences {
19 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
20 let mut checker = FunctionItemRefChecker { tcx, body };
21 checker.visit_body(&body);
25 struct FunctionItemRefChecker<'a, 'tcx> {
30 impl<'a, 'tcx> Visitor<'tcx> for FunctionItemRefChecker<'a, 'tcx> {
31 /// Emits a lint for function reference arguments bound by `fmt::Pointer` or passed to
32 /// `transmute`. This only handles arguments in calls outside macro expansions to avoid double
33 /// counting function references formatted as pointers by macros.
34 fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
35 if let TerminatorKind::Call {
44 let source_info = *self.body.source_info(location);
45 // Only handle function calls outside macros
46 if !source_info.span.from_expansion() {
47 let func_ty = func.ty(self.body, self.tcx);
48 if let ty::FnDef(def_id, substs_ref) = *func_ty.kind() {
49 // Handle calls to `transmute`
50 if self.tcx.is_diagnostic_item(sym::transmute, def_id) {
51 let arg_ty = args[0].ty(self.body, self.tcx);
52 for generic_inner_ty in arg_ty.walk() {
53 if let GenericArgKind::Type(inner_ty) = generic_inner_ty.unpack() {
54 if let Some((fn_id, fn_substs)) =
55 FunctionItemRefChecker::is_fn_ref(inner_ty)
57 let span = self.nth_arg_span(&args, 0);
58 self.emit_lint(fn_id, fn_substs, source_info, span);
63 self.check_bound_args(def_id, substs_ref, &args, source_info);
68 self.super_terminator(terminator, location);
71 /// Emits a lint for function references formatted with `fmt::Pointer::fmt` by macros. These
72 /// cases are handled as operands instead of call terminators to avoid any dependence on
73 /// unstable, internal formatting details like whether `fmt` is called directly or not.
74 fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) {
75 let source_info = *self.body.source_info(location);
76 if source_info.span.from_expansion() {
77 let op_ty = operand.ty(self.body, self.tcx);
78 if let ty::FnDef(def_id, substs_ref) = *op_ty.kind() {
79 if self.tcx.is_diagnostic_item(sym::pointer_trait_fmt, def_id) {
80 let param_ty = substs_ref.type_at(0);
81 if let Some((fn_id, fn_substs)) = FunctionItemRefChecker::is_fn_ref(param_ty) {
82 // The operand's ctxt wouldn't display the lint since it's inside a macro so
83 // we have to use the callsite's ctxt.
84 let callsite_ctxt = source_info.span.source_callsite().ctxt();
85 let span = source_info.span.with_ctxt(callsite_ctxt);
86 self.emit_lint(fn_id, fn_substs, source_info, span);
91 self.super_operand(operand, location);
95 impl<'a, 'tcx> FunctionItemRefChecker<'a, 'tcx> {
96 /// Emits a lint for function reference arguments bound by `fmt::Pointer` in calls to the
97 /// function defined by `def_id` with the substitutions `substs_ref`.
101 substs_ref: SubstsRef<'tcx>,
102 args: &[Operand<'tcx>],
103 source_info: SourceInfo,
105 let param_env = self.tcx.param_env(def_id);
106 let bounds = param_env.caller_bounds();
107 for bound in bounds {
108 if let Some(bound_ty) = self.is_pointer_trait(&bound.kind().skip_binder()) {
109 // Get the argument types as they appear in the function signature.
110 let arg_defs = self.tcx.fn_sig(def_id).skip_binder().inputs();
111 for (arg_num, arg_def) in arg_defs.iter().enumerate() {
112 // For all types reachable from the argument type in the fn sig
113 for generic_inner_ty in arg_def.walk() {
114 if let GenericArgKind::Type(inner_ty) = generic_inner_ty.unpack() {
115 // If the inner type matches the type bound by `Pointer`
116 if TyS::same_type(inner_ty, bound_ty) {
117 // Do a substitution using the parameters from the callsite
118 let subst_ty = inner_ty.subst(self.tcx, substs_ref);
119 if let Some((fn_id, fn_substs)) =
120 FunctionItemRefChecker::is_fn_ref(subst_ty)
122 let span = self.nth_arg_span(args, arg_num);
123 self.emit_lint(fn_id, fn_substs, source_info, span);
133 /// If the given predicate is the trait `fmt::Pointer`, returns the bound parameter type.
134 fn is_pointer_trait(&self, bound: &PredicateKind<'tcx>) -> Option<Ty<'tcx>> {
135 if let ty::PredicateKind::Trait(predicate, _) = bound {
136 if self.tcx.is_diagnostic_item(sym::pointer_trait, predicate.def_id()) {
137 Some(predicate.trait_ref.self_ty())
146 /// If a type is a reference or raw pointer to the anonymous type of a function definition,
147 /// returns that function's `DefId` and `SubstsRef`.
148 fn is_fn_ref(ty: Ty<'tcx>) -> Option<(DefId, SubstsRef<'tcx>)> {
149 let referent_ty = match ty.kind() {
150 ty::Ref(_, referent_ty, _) => Some(referent_ty),
151 ty::RawPtr(ty_and_mut) => Some(&ty_and_mut.ty),
156 if let ty::FnDef(def_id, substs_ref) = *ref_ty.kind() {
157 Some((def_id, substs_ref))
165 fn nth_arg_span(&self, args: &[Operand<'tcx>], n: usize) -> Span {
167 Operand::Copy(place) | Operand::Move(place) => {
168 self.body.local_decls[place.local].source_info.span
170 Operand::Constant(constant) => constant.span,
177 fn_substs: SubstsRef<'tcx>,
178 source_info: SourceInfo,
181 let lint_root = self.body.source_scopes[source_info.scope]
184 .assert_crate_local()
186 let fn_sig = self.tcx.fn_sig(fn_id);
187 let unsafety = fn_sig.unsafety().prefix_str();
188 let abi = match fn_sig.abi() {
189 Abi::Rust => String::from(""),
191 let mut s = String::from("extern \"");
192 s.push_str(other_abi.name());
197 let ident = self.tcx.item_name(fn_id).to_ident_string();
198 let ty_params = fn_substs.types().map(|ty| format!("{}", ty));
199 let const_params = fn_substs.consts().map(|c| format!("{}", c));
200 let params = ty_params.chain(const_params).collect::<Vec<String>>().join(", ");
201 let num_args = fn_sig.inputs().map_bound(|inputs| inputs.len()).skip_binder();
202 let variadic = if fn_sig.c_variadic() { ", ..." } else { "" };
203 let ret = if fn_sig.output().skip_binder().is_unit() { "" } else { " -> _" };
204 self.tcx.struct_span_lint_hir(FUNCTION_ITEM_REFERENCES, lint_root, span, |lint| {
205 lint.build("taking a reference to a function item does not give a function pointer")
208 &format!("cast `{}` to obtain a function pointer", ident),
210 "{} as {}{}fn({}{}){}",
211 if params.is_empty() { ident } else { format!("{}::<{}>", ident, params) },
214 vec!["_"; num_args].join(", "),
218 Applicability::Unspecified,