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Evaluate constant expressions in suspicious_splitn

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This commit is contained in:
Jason Newcomb 2021-05-30 13:25:24 -04:00
parent 898b6a0e07
commit 5fa08eaf53
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GPG key ID: DA59E8643A37ED06
4 changed files with 34 additions and 9 deletions
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5
clippy_lints/src/methods/mod.rs
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@ -1635,8 +1635,9 @@ declare_clippy_lint! {
}
declare_clippy_lint! {
/// **What it does:** Checks for calls to `splitn` and related functions with
/// either zero or one splits.
/// **What it does:** Checks for calls to [`splitn`]
/// (https://doc.rust-lang.org/std/primitive.str.html#method.splitn) and
/// related functions with either zero or one splits.
///
/// **Why is this bad?** These calls don't actually split the value and are
/// likely to be intended as a different number.

16
clippy_lints/src/methods/suspicious_splitn.rs
View file

@ -1,3 +1,4 @@
use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_and_note;
use if_chain::if_chain;
use rustc_ast::LitKind;
@ -15,18 +16,21 @@ pub(super) fn check(
count_arg: &Expr<'_>,
) {
if_chain! {
// Ignore empty slice literal
if !matches!(self_arg.kind, ExprKind::Array([]));
// Ignore empty string literal
if !matches!(self_arg.kind, ExprKind::Lit(Spanned { node: LitKind::Str(s, _), .. }) if s.is_empty());
if let ExprKind::Lit(count_lit) = &count_arg.kind;
if let LitKind::Int(count, _) = count_lit.node;
if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg);
if count <= 1;
if let Some(call_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
if let Some(impl_id) = cx.tcx.impl_of_method(call_id);
let lang_items = cx.tcx.lang_items();
if lang_items.slice_impl() == Some(impl_id) || lang_items.str_impl() == Some(impl_id);
then {
// Ignore empty slice and string literals when used with a literal count.
if (matches!(self_arg.kind, ExprKind::Array([]))
|| matches!(self_arg.kind, ExprKind::Lit(Spanned { node: LitKind::Str(s, _), .. }) if s.is_empty())
) && matches!(count_arg.kind, ExprKind::Lit(_))
{
return;
}
let (msg, note_msg) = if count == 0 {
(format!("`{}` called with `0` splits", method_name),
"the resulting iterator will always return `None`")