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Refactor ZS array detection again and this one seems great 👍

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This commit is contained in:
Nathaniel Hamovitz 2021-10-18 00:51:30 -07:00
parent c5d3167a23
commit 2a5a4f07cf
1 changed files with 9 additions and 17 deletions
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26
clippy_lints/src/trailing_zero_sized_array_without_repr_c.rs
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@ -1,4 +1,4 @@
use clippy_utils::consts::{miri_to_const, Constant};
use clippy_utils::consts::{constant, miri_to_const, ConstEvalLateContext, Constant};
use clippy_utils::diagnostics::span_lint_and_help;
use rustc_ast::Attribute;
use rustc_hir::{Item, ItemKind, VariantData};
@ -38,9 +38,11 @@ declare_lint_pass!(TrailingZeroSizedArrayWithoutReprC => [TRAILING_ZERO_SIZED_AR
impl<'tcx> LateLintPass<'tcx> for TrailingZeroSizedArrayWithoutReprC {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
dbg!(item.ident);
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.
// is to not do that with struct definitions (I'm not sure), then this isn't necessary. (note: if
// you don't get rid of this, change `has_repr_attr` to `includes_repr_attr`).
let attrs = cx.tcx.get_attrs(item.def_id.to_def_id());
let first_attr = attrs.iter().min_by_key(|attr| attr.span.lo());
let lint_span = if let Some(first_attr) = first_attr {
@ -70,21 +72,11 @@ fn is_struct_with_trailing_zero_sized_array(cx: &LateContext<'tcx>, item: &'tcx
if let Some(last_field) = field_defs.last() {
if let rustc_hir::TyKind::Array(_, length) = last_field.ty.kind {
// 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 {
let length_ldid = cx.tcx.hir().local_def_id(length.hir_id);
let length = Const::from_anon_const(cx.tcx, length_ldid);
let length = length.try_eval_usize(cx.tcx, cx.param_env);
// if let Some((Constant::Int(length), _)) = length {
if let Some(length) = length {
length == 0
} else {
false