1 #![allow(non_snake_case)]
3 use rustc::hir::{ExprKind, Node};
4 use crate::hir::def_id::DefId;
5 use rustc::hir::lowering::is_range_literal;
6 use rustc::ty::subst::SubstsRef;
7 use rustc::ty::{self, AdtKind, ParamEnv, Ty, TyCtxt};
8 use rustc::ty::layout::{self, IntegerExt, LayoutOf, VariantIdx, SizeSkeleton};
9 use rustc::{lint, util};
10 use rustc_index::vec::Idx;
11 use util::nodemap::FxHashSet;
12 use lint::{LateContext, LintContext, LintArray};
13 use lint::{LintPass, LateLintPass};
16 use std::{i8, i16, i32, i64, u8, u16, u32, u64, f32, f64};
18 use syntax::{ast, attr, source_map};
19 use syntax::errors::Applicability;
20 use syntax::symbol::sym;
21 use rustc_target::spec::abi::Abi;
26 use rustc::mir::interpret::{sign_extend, truncate};
33 "comparisons made useless by limits of the types involved"
39 "literal out of range for its type"
43 VARIANT_SIZE_DIFFERENCES,
45 "detects enums with widely varying variant sizes"
48 #[derive(Copy, Clone)]
49 pub struct TypeLimits {
50 /// Id of the last visited negated expression
51 negated_expr_id: hir::HirId,
54 impl_lint_pass!(TypeLimits => [UNUSED_COMPARISONS, OVERFLOWING_LITERALS]);
57 pub fn new() -> TypeLimits {
58 TypeLimits { negated_expr_id: hir::DUMMY_HIR_ID }
62 /// Attempts to special-case the overflowing literal lint when it occurs as a range endpoint.
63 /// Returns `true` iff the lint was overridden.
64 fn lint_overflowing_range_endpoint<'a, 'tcx>(
65 cx: &LateContext<'a, 'tcx>,
69 expr: &'tcx hir::Expr,
70 parent_expr: &'tcx hir::Expr,
73 // We only want to handle exclusive (`..`) ranges,
74 // which are represented as `ExprKind::Struct`.
75 if let ExprKind::Struct(_, eps, _) = &parent_expr.kind {
79 // We can suggest using an inclusive range
80 // (`..=`) instead only if it is the `end` that is
81 // overflowing and only by 1.
82 if eps[1].expr.hir_id == expr.hir_id && lit_val - 1 == max {
83 let mut err = cx.struct_span_lint(
86 &format!("range endpoint is out of range for `{}`", ty),
88 if let Ok(start) = cx.sess().source_map().span_to_snippet(eps[0].span) {
89 use ast::{LitKind, LitIntType};
90 // We need to preserve the literal's suffix,
91 // as it may determine typing information.
92 let suffix = match lit.node {
93 LitKind::Int(_, LitIntType::Signed(s)) => format!("{}", s.name_str()),
94 LitKind::Int(_, LitIntType::Unsigned(s)) => format!("{}", s.name_str()),
95 LitKind::Int(_, LitIntType::Unsuffixed) => "".to_owned(),
98 let suggestion = format!("{}..={}{}", start, lit_val - 1, suffix);
101 &"use an inclusive range instead",
103 Applicability::MachineApplicable,
114 // For `isize` & `usize`, be conservative with the warnings, so that the
115 // warnings are consistent between 32- and 64-bit platforms.
116 fn int_ty_range(int_ty: ast::IntTy) -> (i128, i128) {
118 ast::IntTy::Isize => (i64::min_value() as i128, i64::max_value() as i128),
119 ast::IntTy::I8 => (i8::min_value() as i64 as i128, i8::max_value() as i128),
120 ast::IntTy::I16 => (i16::min_value() as i64 as i128, i16::max_value() as i128),
121 ast::IntTy::I32 => (i32::min_value() as i64 as i128, i32::max_value() as i128),
122 ast::IntTy::I64 => (i64::min_value() as i128, i64::max_value() as i128),
123 ast::IntTy::I128 =>(i128::min_value() as i128, i128::max_value()),
127 fn uint_ty_range(uint_ty: ast::UintTy) -> (u128, u128) {
129 ast::UintTy::Usize => (u64::min_value() as u128, u64::max_value() as u128),
130 ast::UintTy::U8 => (u8::min_value() as u128, u8::max_value() as u128),
131 ast::UintTy::U16 => (u16::min_value() as u128, u16::max_value() as u128),
132 ast::UintTy::U32 => (u32::min_value() as u128, u32::max_value() as u128),
133 ast::UintTy::U64 => (u64::min_value() as u128, u64::max_value() as u128),
134 ast::UintTy::U128 => (u128::min_value(), u128::max_value()),
138 fn get_bin_hex_repr(cx: &LateContext<'_, '_>, lit: &hir::Lit) -> Option<String> {
139 let src = cx.sess().source_map().span_to_snippet(lit.span).ok()?;
140 let firstch = src.chars().next()?;
143 match src.chars().nth(1) {
144 Some('x') | Some('b') => return Some(src),
152 fn report_bin_hex_error(
153 cx: &LateContext<'_, '_>,
160 let size = layout::Integer::from_attr(&cx.tcx, ty).size();
161 let (t, actually) = match ty {
162 attr::IntType::SignedInt(t) => {
163 let actually = sign_extend(val, size) as i128;
164 (t.name_str(), actually.to_string())
166 attr::IntType::UnsignedInt(t) => {
167 let actually = truncate(val, size);
168 (t.name_str(), actually.to_string())
171 let mut err = cx.struct_span_lint(
172 OVERFLOWING_LITERALS,
174 &format!("literal out of range for {}", t),
177 "the literal `{}` (decimal `{}`) does not fit into \
178 an `{}` and will become `{}{}`",
179 repr_str, val, t, actually, t
181 if let Some(sugg_ty) =
182 get_type_suggestion(&cx.tables.node_type(expr.hir_id), val, negative)
184 if let Some(pos) = repr_str.chars().position(|c| c == 'i' || c == 'u') {
185 let (sans_suffix, _) = repr_str.split_at(pos);
188 &format!("consider using `{}` instead", sugg_ty),
189 format!("{}{}", sans_suffix, sugg_ty),
190 Applicability::MachineApplicable
193 err.help(&format!("consider using `{}` instead", sugg_ty));
200 // This function finds the next fitting type and generates a suggestion string.
201 // It searches for fitting types in the following way (`X < Y`):
202 // - `iX`: if literal fits in `uX` => `uX`, else => `iY`
206 // No suggestion for: `isize`, `usize`.
207 fn get_type_suggestion(t: Ty<'_>, val: u128, negative: bool) -> Option<&'static str> {
208 use syntax::ast::IntTy::*;
209 use syntax::ast::UintTy::*;
210 macro_rules! find_fit {
211 ($ty:expr, $val:expr, $negative:expr,
212 $($type:ident => [$($utypes:expr),*] => [$($itypes:expr),*]),+) => {
214 let _neg = if negative { 1 } else { 0 };
217 $(if !negative && val <= uint_ty_range($utypes).1 {
218 return Some($utypes.name_str())
220 $(if val <= int_ty_range($itypes).1 as u128 + _neg {
221 return Some($itypes.name_str())
231 ty::Int(i) => find_fit!(i, val, negative,
232 I8 => [U8] => [I16, I32, I64, I128],
233 I16 => [U16] => [I32, I64, I128],
234 I32 => [U32] => [I64, I128],
235 I64 => [U64] => [I128],
236 I128 => [U128] => []),
237 ty::Uint(u) => find_fit!(u, val, negative,
238 U8 => [U8, U16, U32, U64, U128] => [],
239 U16 => [U16, U32, U64, U128] => [],
240 U32 => [U32, U64, U128] => [],
241 U64 => [U64, U128] => [],
242 U128 => [U128] => []),
247 fn lint_int_literal<'a, 'tcx>(
248 cx: &LateContext<'a, 'tcx>,
249 type_limits: &TypeLimits,
255 let int_type = if let ast::IntTy::Isize = t {
256 cx.sess().target.isize_ty
261 let (_, max) = int_ty_range(int_type);
262 let max = max as u128;
263 let negative = type_limits.negated_expr_id == e.hir_id;
265 // Detect literal value out of range [min, max] inclusive
266 // avoiding use of -min to prevent overflow/panic
267 if (negative && v > max + 1) || (!negative && v > max) {
268 if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
269 report_bin_hex_error(
272 attr::IntType::SignedInt(t),
280 let par_id = cx.tcx.hir().get_parent_node(e.hir_id);
281 if let Node::Expr(par_e) = cx.tcx.hir().get(par_id) {
282 if let hir::ExprKind::Struct(..) = par_e.kind {
283 if is_range_literal(cx.sess(), par_e)
284 && lint_overflowing_range_endpoint(cx, lit, v, max, e, par_e, t.name_str())
286 // The overflowing literal lint was overridden.
293 OVERFLOWING_LITERALS,
295 &format!("literal out of range for `{}`", t.name_str()),
300 fn lint_uint_literal<'a, 'tcx>(
301 cx: &LateContext<'a, 'tcx>,
306 let uint_type = if let ast::UintTy::Usize = t {
307 cx.sess().target.usize_ty
311 let (min, max) = uint_ty_range(uint_type);
312 let lit_val: u128 = match lit.node {
313 // _v is u8, within range by definition
314 ast::LitKind::Byte(_v) => return,
315 ast::LitKind::Int(v, _) => v,
318 if lit_val < min || lit_val > max {
319 let parent_id = cx.tcx.hir().get_parent_node(e.hir_id);
320 if let Node::Expr(par_e) = cx.tcx.hir().get(parent_id) {
322 hir::ExprKind::Cast(..) => {
323 if let ty::Char = cx.tables.expr_ty(par_e).kind {
324 let mut err = cx.struct_span_lint(
325 OVERFLOWING_LITERALS,
327 "only `u8` can be cast into `char`",
331 &"use a `char` literal instead",
332 format!("'\\u{{{:X}}}'", lit_val),
333 Applicability::MachineApplicable,
339 hir::ExprKind::Struct(..)
340 if is_range_literal(cx.sess(), par_e) => {
341 let t = t.name_str();
342 if lint_overflowing_range_endpoint(cx, lit, lit_val, max, e, par_e, t) {
343 // The overflowing literal lint was overridden.
350 if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
351 report_bin_hex_error(cx, e, attr::IntType::UnsignedInt(t), repr_str, lit_val, false);
355 OVERFLOWING_LITERALS,
357 &format!("literal out of range for `{}`", t.name_str()),
362 fn lint_literal<'a, 'tcx>(
363 cx: &LateContext<'a, 'tcx>,
364 type_limits: &TypeLimits,
368 match cx.tables.node_type(e.hir_id).kind {
371 ast::LitKind::Int(v, ast::LitIntType::Signed(_)) |
372 ast::LitKind::Int(v, ast::LitIntType::Unsuffixed) => {
373 lint_int_literal(cx, type_limits, e, lit, t, v)
379 lint_uint_literal(cx, e, lit, t)
382 let is_infinite = match lit.node {
383 ast::LitKind::Float(v, _) => {
385 ast::FloatTy::F32 => v.as_str().parse().map(f32::is_infinite),
386 ast::FloatTy::F64 => v.as_str().parse().map(f64::is_infinite),
391 if is_infinite == Ok(true) {
393 OVERFLOWING_LITERALS,
395 &format!("literal out of range for `{}`", t.name_str()),
403 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeLimits {
404 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx hir::Expr) {
406 hir::ExprKind::Unary(hir::UnNeg, ref expr) => {
407 // propagate negation, if the negation itself isn't negated
408 if self.negated_expr_id != e.hir_id {
409 self.negated_expr_id = expr.hir_id;
412 hir::ExprKind::Binary(binop, ref l, ref r) => {
413 if is_comparison(binop) && !check_limits(cx, binop, &l, &r) {
414 cx.span_lint(UNUSED_COMPARISONS,
416 "comparison is useless due to type limits");
419 hir::ExprKind::Lit(ref lit) => lint_literal(cx, self, e, lit),
423 fn is_valid<T: cmp::PartialOrd>(binop: hir::BinOp, v: T, min: T, max: T) -> bool {
425 hir::BinOpKind::Lt => v > min && v <= max,
426 hir::BinOpKind::Le => v >= min && v < max,
427 hir::BinOpKind::Gt => v >= min && v < max,
428 hir::BinOpKind::Ge => v > min && v <= max,
429 hir::BinOpKind::Eq | hir::BinOpKind::Ne => v >= min && v <= max,
434 fn rev_binop(binop: hir::BinOp) -> hir::BinOp {
435 source_map::respan(binop.span,
437 hir::BinOpKind::Lt => hir::BinOpKind::Gt,
438 hir::BinOpKind::Le => hir::BinOpKind::Ge,
439 hir::BinOpKind::Gt => hir::BinOpKind::Lt,
440 hir::BinOpKind::Ge => hir::BinOpKind::Le,
445 fn check_limits(cx: &LateContext<'_, '_>,
450 let (lit, expr, swap) = match (&l.kind, &r.kind) {
451 (&hir::ExprKind::Lit(_), _) => (l, r, true),
452 (_, &hir::ExprKind::Lit(_)) => (r, l, false),
455 // Normalize the binop so that the literal is always on the RHS in
457 let norm_binop = if swap { rev_binop(binop) } else { binop };
458 match cx.tables.node_type(expr.hir_id).kind {
460 let (min, max) = int_ty_range(int_ty);
461 let lit_val: i128 = match lit.kind {
462 hir::ExprKind::Lit(ref li) => {
464 ast::LitKind::Int(v, ast::LitIntType::Signed(_)) |
465 ast::LitKind::Int(v, ast::LitIntType::Unsuffixed) => v as i128,
471 is_valid(norm_binop, lit_val, min, max)
473 ty::Uint(uint_ty) => {
474 let (min, max) :(u128, u128) = uint_ty_range(uint_ty);
475 let lit_val: u128 = match lit.kind {
476 hir::ExprKind::Lit(ref li) => {
478 ast::LitKind::Int(v, _) => v,
484 is_valid(norm_binop, lit_val, min, max)
490 fn is_comparison(binop: hir::BinOp) -> bool {
497 hir::BinOpKind::Gt => true,
507 "proper use of libc types in foreign modules"
510 declare_lint_pass!(ImproperCTypes => [IMPROPER_CTYPES]);
512 struct ImproperCTypesVisitor<'a, 'tcx> {
513 cx: &'a LateContext<'a, 'tcx>,
516 enum FfiResult<'tcx> {
518 FfiPhantom(Ty<'tcx>),
521 reason: &'static str,
522 help: Option<&'static str>,
526 fn is_zst<'tcx>(tcx: TyCtxt<'tcx>, did: DefId, ty: Ty<'tcx>) -> bool {
527 tcx.layout_of(tcx.param_env(did).and(ty)).map(|layout| layout.is_zst()).unwrap_or(false)
530 fn ty_is_known_nonnull<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
532 ty::FnPtr(_) => true,
534 ty::Adt(field_def, substs) if field_def.repr.transparent() && !field_def.is_union() => {
535 for field in field_def.all_fields() {
536 let field_ty = tcx.normalize_erasing_regions(
537 ParamEnv::reveal_all(),
538 field.ty(tcx, substs),
540 if is_zst(tcx, field.did, field_ty) {
544 let attrs = tcx.get_attrs(field_def.did);
545 if attrs.iter().any(|a| a.check_name(sym::rustc_nonnull_optimization_guaranteed)) ||
546 ty_is_known_nonnull(tcx, field_ty) {
557 /// Check if this enum can be safely exported based on the
558 /// "nullable pointer optimization". Currently restricted
559 /// to function pointers, references, core::num::NonZero*,
560 /// core::ptr::NonNull, and #[repr(transparent)] newtypes.
561 /// FIXME: This duplicates code in codegen.
562 fn is_repr_nullable_ptr<'tcx>(
565 ty_def: &'tcx ty::AdtDef,
566 substs: SubstsRef<'tcx>,
568 if ty_def.variants.len() != 2 {
572 let get_variant_fields = |index| &ty_def.variants[VariantIdx::new(index)].fields;
573 let variant_fields = [get_variant_fields(0), get_variant_fields(1)];
574 let fields = if variant_fields[0].is_empty() {
576 } else if variant_fields[1].is_empty() {
582 if fields.len() != 1 {
586 let field_ty = fields[0].ty(tcx, substs);
587 if !ty_is_known_nonnull(tcx, field_ty) {
591 // At this point, the field's type is known to be nonnull and the parent enum is Option-like.
592 // If the computed size for the field and the enum are different, the nonnull optimization isn't
593 // being applied (and we've got a problem somewhere).
594 let compute_size_skeleton = |t| SizeSkeleton::compute(t, tcx, ParamEnv::reveal_all()).unwrap();
595 if !compute_size_skeleton(ty).same_size(compute_size_skeleton(field_ty)) {
596 bug!("improper_ctypes: Option nonnull optimization not applied?");
602 impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
603 /// Checks if the given type is "ffi-safe" (has a stable, well-defined
604 /// representation which can be exported to C code).
605 fn check_type_for_ffi(&self,
606 cache: &mut FxHashSet<Ty<'tcx>>,
607 ty: Ty<'tcx>) -> FfiResult<'tcx> {
610 let cx = self.cx.tcx;
612 // Protect against infinite recursion, for example
613 // `struct S(*mut S);`.
614 // FIXME: A recursion limit is necessary as well, for irregular
616 if !cache.insert(ty) {
621 ty::Adt(def, substs) => {
622 if def.is_phantom_data() {
623 return FfiPhantom(ty);
625 match def.adt_kind() {
627 if !def.repr.c() && !def.repr.transparent() {
630 reason: "this struct has unspecified layout",
631 help: Some("consider adding a `#[repr(C)]` or \
632 `#[repr(transparent)]` attribute to this struct"),
636 let is_non_exhaustive =
637 def.non_enum_variant().is_field_list_non_exhaustive();
638 if is_non_exhaustive && !def.did.is_local() {
641 reason: "this struct is non-exhaustive",
646 if def.non_enum_variant().fields.is_empty() {
649 reason: "this struct has no fields",
650 help: Some("consider adding a member to this struct"),
654 // We can't completely trust repr(C) and repr(transparent) markings;
655 // make sure the fields are actually safe.
656 let mut all_phantom = true;
657 for field in &def.non_enum_variant().fields {
658 let field_ty = cx.normalize_erasing_regions(
659 ParamEnv::reveal_all(),
660 field.ty(cx, substs),
662 // repr(transparent) types are allowed to have arbitrary ZSTs, not just
663 // PhantomData -- skip checking all ZST fields
664 if def.repr.transparent() && is_zst(cx, field.did, field_ty) {
667 let r = self.check_type_for_ffi(cache, field_ty);
673 FfiUnsafe { .. } => {
679 if all_phantom { FfiPhantom(ty) } else { FfiSafe }
682 if !def.repr.c() && !def.repr.transparent() {
685 reason: "this union has unspecified layout",
686 help: Some("consider adding a `#[repr(C)]` or \
687 `#[repr(transparent)]` attribute to this union"),
691 if def.non_enum_variant().fields.is_empty() {
694 reason: "this union has no fields",
695 help: Some("consider adding a field to this union"),
699 let mut all_phantom = true;
700 for field in &def.non_enum_variant().fields {
701 let field_ty = cx.normalize_erasing_regions(
702 ParamEnv::reveal_all(),
703 field.ty(cx, substs),
705 // repr(transparent) types are allowed to have arbitrary ZSTs, not just
706 // PhantomData -- skip checking all ZST fields.
707 if def.repr.transparent() && is_zst(cx, field.did, field_ty) {
710 let r = self.check_type_for_ffi(cache, field_ty);
716 FfiUnsafe { .. } => {
722 if all_phantom { FfiPhantom(ty) } else { FfiSafe }
725 if def.variants.is_empty() {
726 // Empty enums are okay... although sort of useless.
730 // Check for a repr() attribute to specify the size of the
732 if !def.repr.c() && !def.repr.transparent() && def.repr.int.is_none() {
733 // Special-case types like `Option<extern fn()>`.
734 if !is_repr_nullable_ptr(cx, ty, def, substs) {
737 reason: "enum has no representation hint",
738 help: Some("consider adding a `#[repr(C)]`, \
739 `#[repr(transparent)]`, or integer `#[repr(...)]` \
740 attribute to this enum"),
745 if def.is_variant_list_non_exhaustive() && !def.did.is_local() {
748 reason: "this enum is non-exhaustive",
753 // Check the contained variants.
754 for variant in &def.variants {
755 let is_non_exhaustive = variant.is_field_list_non_exhaustive();
756 if is_non_exhaustive && !variant.def_id.is_local() {
759 reason: "this enum has non-exhaustive variants",
764 for field in &variant.fields {
765 let field_ty = cx.normalize_erasing_regions(
766 ParamEnv::reveal_all(),
767 field.ty(cx, substs),
769 // repr(transparent) types are allowed to have arbitrary ZSTs, not
770 // just PhantomData -- skip checking all ZST fields.
771 if def.repr.transparent() && is_zst(cx, field.did, field_ty) {
774 let r = self.check_type_for_ffi(cache, field_ty);
777 FfiUnsafe { .. } => {
783 reason: "this enum contains a PhantomData field",
795 ty::Char => FfiUnsafe {
797 reason: "the `char` type has no C equivalent",
798 help: Some("consider using `u32` or `libc::wchar_t` instead"),
801 ty::Int(ast::IntTy::I128) | ty::Uint(ast::UintTy::U128) => FfiUnsafe {
803 reason: "128-bit integers don't currently have a known stable ABI",
807 // Primitive types with a stable representation.
808 ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
810 ty::Slice(_) => FfiUnsafe {
812 reason: "slices have no C equivalent",
813 help: Some("consider using a raw pointer instead"),
816 ty::Dynamic(..) => FfiUnsafe {
818 reason: "trait objects have no C equivalent",
822 ty::Str => FfiUnsafe {
824 reason: "string slices have no C equivalent",
825 help: Some("consider using `*const u8` and a length instead"),
828 ty::Tuple(..) => FfiUnsafe {
830 reason: "tuples have unspecified layout",
831 help: Some("consider using a struct instead"),
834 ty::RawPtr(ty::TypeAndMut { ty, .. }) |
835 ty::Ref(_, ty, _) => self.check_type_for_ffi(cache, ty),
837 ty::Array(ty, _) => self.check_type_for_ffi(cache, ty),
841 Abi::Rust | Abi::RustIntrinsic | Abi::PlatformIntrinsic | Abi::RustCall => {
844 reason: "this function pointer has Rust-specific calling convention",
845 help: Some("consider using an `extern fn(...) -> ...` \
846 function pointer instead"),
852 let sig = cx.erase_late_bound_regions(&sig);
853 if !sig.output().is_unit() {
854 let r = self.check_type_for_ffi(cache, sig.output());
862 for arg in sig.inputs() {
863 let r = self.check_type_for_ffi(cache, arg);
874 ty::Foreign(..) => FfiSafe,
882 ty::GeneratorWitness(..) |
883 ty::Placeholder(..) |
884 ty::UnnormalizedProjection(..) |
887 ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
891 fn emit_ffi_unsafe_type_lint(
898 let mut diag = self.cx.struct_span_lint(
901 &format!("`extern` block uses type `{}`, which is not FFI-safe", ty),
903 diag.span_label(sp, "not FFI-safe");
904 if let Some(help) = help {
908 if let ty::Adt(def, _) = ty.kind {
909 if let Some(sp) = self.cx.tcx.hir().span_if_local(def.did) {
910 diag.span_note(sp, "type defined here");
916 fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
917 use crate::rustc::ty::TypeFoldable;
919 struct ProhibitOpaqueTypes<'tcx> {
920 ty: Option<Ty<'tcx>>,
923 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueTypes<'tcx> {
924 fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool {
925 if let ty::Opaque(..) = ty.kind {
929 ty.super_visit_with(self)
934 let mut visitor = ProhibitOpaqueTypes { ty: None };
935 ty.visit_with(&mut visitor);
936 if let Some(ty) = visitor.ty {
937 self.emit_ffi_unsafe_type_lint(
940 "opaque types have no C equivalent",
949 fn check_type_for_ffi_and_report_errors(&mut self, sp: Span, ty: Ty<'tcx>) {
950 // We have to check for opaque types before `normalize_erasing_regions`,
951 // which will replace opaque types with their underlying concrete type.
952 if self.check_for_opaque_ty(sp, ty) {
953 // We've already emitted an error due to an opaque type.
957 // it is only OK to use this function because extern fns cannot have
958 // any generic types right now:
959 let ty = self.cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), ty);
961 match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
962 FfiResult::FfiSafe => {}
963 FfiResult::FfiPhantom(ty) => {
964 self.emit_ffi_unsafe_type_lint(ty, sp, "composed only of `PhantomData`", None);
966 FfiResult::FfiUnsafe { ty, reason, help } => {
967 self.emit_ffi_unsafe_type_lint(ty, sp, reason, help);
972 fn check_foreign_fn(&mut self, id: hir::HirId, decl: &hir::FnDecl) {
973 let def_id = self.cx.tcx.hir().local_def_id(id);
974 let sig = self.cx.tcx.fn_sig(def_id);
975 let sig = self.cx.tcx.erase_late_bound_regions(&sig);
977 for (input_ty, input_hir) in sig.inputs().iter().zip(&decl.inputs) {
978 self.check_type_for_ffi_and_report_errors(input_hir.span, input_ty);
981 if let hir::Return(ref ret_hir) = decl.output {
982 let ret_ty = sig.output();
983 if !ret_ty.is_unit() {
984 self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty);
989 fn check_foreign_static(&mut self, id: hir::HirId, span: Span) {
990 let def_id = self.cx.tcx.hir().local_def_id(id);
991 let ty = self.cx.tcx.type_of(def_id);
992 self.check_type_for_ffi_and_report_errors(span, ty);
996 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImproperCTypes {
997 fn check_foreign_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::ForeignItem) {
998 let mut vis = ImproperCTypesVisitor { cx };
999 let abi = cx.tcx.hir().get_foreign_abi(it.hir_id);
1000 if let Abi::Rust | Abi::RustCall | Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1001 // Don't worry about types in internal ABIs.
1004 hir::ForeignItemKind::Fn(ref decl, _, _) => {
1005 vis.check_foreign_fn(it.hir_id, decl);
1007 hir::ForeignItemKind::Static(ref ty, _) => {
1008 vis.check_foreign_static(it.hir_id, ty.span);
1010 hir::ForeignItemKind::Type => ()
1016 declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
1018 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for VariantSizeDifferences {
1019 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
1020 if let hir::ItemKind::Enum(ref enum_definition, _) = it.kind {
1021 let item_def_id = cx.tcx.hir().local_def_id(it.hir_id);
1022 let t = cx.tcx.type_of(item_def_id);
1023 let ty = cx.tcx.erase_regions(&t);
1024 let layout = match cx.layout_of(ty) {
1025 Ok(layout) => layout,
1026 Err(ty::layout::LayoutError::Unknown(_)) => return,
1027 Err(err @ ty::layout::LayoutError::SizeOverflow(_)) => {
1028 bug!("failed to get layout for `{}`: {}", t, err);
1031 let (variants, tag) = match layout.variants {
1032 layout::Variants::Multiple {
1033 discr_kind: layout::DiscriminantKind::Tag,
1037 } => (variants, discr),
1041 let discr_size = tag.value.size(&cx.tcx).bytes();
1043 debug!("enum `{}` is {} bytes large with layout:\n{:#?}",
1044 t, layout.size.bytes(), layout);
1046 let (largest, slargest, largest_index) = enum_definition.variants
1049 .map(|(variant, variant_layout)| {
1050 // Subtract the size of the enum discriminant.
1051 let bytes = variant_layout.size.bytes().saturating_sub(discr_size);
1053 debug!("- variant `{}` is {} bytes large",
1059 .fold((0, 0, 0), |(l, s, li), (idx, size)| if size > l {
1061 } else if size > s {
1067 // We only warn if the largest variant is at least thrice as large as
1068 // the second-largest.
1069 if largest > slargest * 3 && slargest > 0 {
1070 cx.span_lint(VARIANT_SIZE_DIFFERENCES,
1071 enum_definition.variants[largest_index].span,
1072 &format!("enum variant is more than three times \
1073 larger ({} bytes) than the next largest",