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Tidy comments + tests; revert 'size-is-zero' detection

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This commit is contained in:
Nathaniel Hamovitz 2021-10-16 22:03:08 -07:00
parent 9b3f55ee61
commit a3420f7004
3 changed files with 75 additions and 93 deletions
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35
clippy_lints/src/trailing_zero_sized_array_without_repr_c.rs
View File

@ -36,16 +36,15 @@
}
declare_lint_pass!(TrailingZeroSizedArrayWithoutReprC => [TRAILING_ZERO_SIZED_ARRAY_WITHOUT_REPR_C]);
// TESTNAME=trailing_zero_sized_array_without_repr_c cargo uitest
impl<'tcx> LateLintPass<'tcx> for TrailingZeroSizedArrayWithoutReprC {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
if is_struct_with_trailing_zero_sized_array(cx, item) {
// NOTE: This is to include attributes on the definition when we print the lint. If the convention
// is to not do that with struct definitions (I'm not sure), then this isn't necessary.
let attrs = cx.tcx.get_attrs(item.def_id.to_def_id());
let first_attr = attrs.first(); // Actually, I've no idea if this is guaranteed to be the first one in the source code.
let first_attr = attrs.iter().min_by_key(|attr| attr.span.lo());
let lint_span = if let Some(first_attr) = first_attr {
first_attr.span.until(item.span)
first_attr.span.to(item.span)
} else {
item.span
};
@ -66,18 +65,29 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
fn is_struct_with_trailing_zero_sized_array(cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) -> bool {
if_chain! {
// Check if last field is an array
// First check if last field is an array
if let ItemKind::Struct(data, _) = &item.kind;
if let VariantData::Struct(field_defs, _) = data;
if let Some(last_field) = field_defs.last();
if let rustc_hir::TyKind::Array(_, length) = last_field.ty.kind;
// Check if that that array zero-sized.
let length_ldid = cx.tcx.hir().local_def_id(length.hir_id);
let length = Const::from_anon_const(cx.tcx, length_ldid);
if let Some(Constant::Int(length)) = miri_to_const(length);
if length == 0;
// Then check if that that array zero-sized
// This is pretty much copied from `enum_clike.rs` and I don't fully understand it, so let me know
// if there's a better way. I tried `Const::from_anon_const` but it didn't fold in the values
// on the `ZeroSizedWithConst` and `ZeroSizedWithConstFunction` tests.
// This line in particular seems convoluted.
let length_did = cx.tcx.hir().body_owner_def_id(length.body).to_def_id();
let length_ty = cx.tcx.type_of(length_did);
let length = cx
.tcx
.const_eval_poly(length_did)
.ok()
.map(|val| Const::from_value(cx.tcx, val, length_ty))
.and_then(miri_to_const);
if let Some(Constant::Int(length)) = length;
if length == 0;
then {
true
} else {
@ -88,7 +98,8 @@ fn is_struct_with_trailing_zero_sized_array(cx: &LateContext<'tcx>, item: &'tcx
fn has_repr_attr(cx: &LateContext<'tcx>, attrs: &[Attribute]) -> bool {
// NOTE: there's at least four other ways to do this but I liked this one the best. (All five agreed
// on all testcases.) Happy to use another; they're in the commit history.
// on all testcases.) Happy to use another; they're in the commit history if you want to look (or I
// can go find them).
attrs
.iter()
.any(|attr| !rustc_attr::find_repr_attrs(cx.tcx.sess(), attr).is_empty())

36
tests/ui/trailing_zero_sized_array_without_repr_c.rs
View File

@ -1,5 +1,4 @@
#![warn(clippy::trailing_zero_sized_array_without_repr_c)]
#![feature(const_generics_defaults)] // see below
// Do lint:
@ -17,14 +16,16 @@ struct GenericArrayType<T> {
last: [T; 0],
}
#[derive(Debug)]
struct OnlyAnotherAttributeDerive {
#[must_use]
struct OnlyAnotherAttributeMustUse {
field: i32,
last: [usize; 0],
}
#[must_use]
struct OnlyAnotherAttributeMustUse {
// NOTE: Unfortunately the attribute isn't included in the lint output. I'm not sure how to make it
// show up.
#[derive(Debug)]
struct OnlyAnotherAttributeDerive {
field: i32,
last: [usize; 0],
}
@ -82,6 +83,12 @@ struct NonZeroSizedArray {
last: [usize; 1],
}
struct NotLastField {
f1: u32,
zero_sized: [usize; 0],
last: i32,
}
const ONE: usize = 1;
struct NonZeroSizedWithConst {
field: i32,
@ -133,21 +140,4 @@ enum DontLintAnonymousStructsFromDesuraging {
C { x: u32, y: [u64; 0] },
}
// NOTE: including these (along with the required feature) triggers an ICE. Not sure why. Should
// make sure the const generics people are aware of that if they weren't already.
// #[repr(C)]
// struct ConstParamOk<const N: usize = 0> {
// field: i32,
// last: [usize; N]
// }
// struct ConstParamLint<const N: usize = 0> {
// field: i32,
// last: [usize; N]
// }
fn main() {
let _ = OnlyAnotherAttributeMustUse { field: 0, last: [] };
let _ = OtherAttributesMustUse { field: 0, last: [] };
}
fn main() {}

97
tests/ui/trailing_zero_sized_array_without_repr_c.stderr
View File

@ -1,5 +1,5 @@
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:4:1
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:5:1
|
LL | / struct RarelyUseful {
LL | | field: i32,
@ -8,33 +8,20 @@ LL | | }
| |_^
|
= note: `-D clippy::trailing-zero-sized-array-without-repr-c` implied by `-D warnings`
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct RarelyUseful {
LL + field: i32,
LL + last: [usize; 0],
LL + }
|
= help: consider annotating the struct definition with `#[repr(C)]` (or another `repr` attribute)
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:15:1
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:10:1
|
LL | / struct OnlyFieldIsZeroSizeArray {
LL | / struct OnlyField {
LL | | first_and_last: [usize; 0],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct OnlyFieldIsZeroSizeArray {
LL + first_and_last: [usize; 0],
LL + }
|
= help: consider annotating the struct definition with `#[repr(C)]` (or another `repr` attribute)
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:19:1
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:14:1
|
LL | / struct GenericArrayType<T> {
LL | | field: i32,
@ -42,53 +29,55 @@ LL | | last: [T; 0],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct GenericArrayType<T> {
LL + field: i32,
LL + last: [T; 0],
LL + }
|
= help: consider annotating the struct definition with `#[repr(C)]` (or another `repr` attribute)
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:30:1
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:19:1
|
LL | / struct ZeroSizedFromExternalConst {
LL | / #[must_use]
LL | | struct OnlyAnotherAttributeMustUse {
LL | | field: i32,
LL | | last: [usize; 0],
LL | | }
| |_^
|
= help: consider annotating the struct definition with `#[repr(C)]` (or another `repr` attribute)
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:28:1
|
LL | / struct OnlyAnotherAttributeDerive {
LL | | field: i32,
LL | | last: [usize; 0],
LL | | }
| |_^
|
= help: consider annotating the struct definition with `#[repr(C)]` (or another `repr` attribute)
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:34:1
|
LL | / struct ZeroSizedWithConst {
LL | | field: i32,
LL | | last: [usize; ZERO],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct ZeroSizedFromExternalConst {
LL + field: i32,
LL + last: [usize; ZERO],
LL + }
|
= help: consider annotating the struct definition with `#[repr(C)]` (or another `repr` attribute)
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:45:1
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:43:1
|
LL | / struct UsingFunction {
LL | / struct ZeroSizedWithConstFunction {
LL | | field: i32,
LL | | last: [usize; compute_zero()],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct UsingFunction {
LL + field: i32,
LL + last: [usize; compute_zero()],
LL + }
|
= help: consider annotating the struct definition with `#[repr(C)]` (or another `repr` attribute)
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:94:1
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:48:1
|
LL | / struct LotsOfFields {
LL | | f1: u32,
@ -99,15 +88,7 @@ LL | | last: [usize; 0],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct LotsOfFields {
LL + f1: u32,
LL + f2: u32,
LL + f3: u32,
LL + f4: u32,
...
= help: consider annotating the struct definition with `#[repr(C)]` (or another `repr` attribute)
error: aborting due to 6 previous errors
error: aborting due to 8 previous errors