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Lint only if array length is a literal zero.

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This commit is contained in:
Lzu Tao 2024-07-18 12:22:08 +07:00
parent 5540060d5d
commit 3c50e7af5a
4 changed files with 33 additions and 67 deletions
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52
clippy_lints/src/zero_repeat_side_effects.rs
View file

@ -3,11 +3,11 @@ use clippy_utils::higher::VecArgs;
use clippy_utils::source::snippet;
use clippy_utils::visitors::for_each_expr_without_closures;
use rustc_ast::LitKind;
use rustc_data_structures::packed::Pu128;
use rustc_errors::Applicability;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::{ArrayLen, ExprKind, ItemKind, Node, QPath};
use rustc_hir::{ArrayLen, ExprKind, Node};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::{self, ConstKind, Ty};
use rustc_middle::ty::Ty;
use rustc_session::declare_lint_pass;
use rustc_span::Span;
@ -51,39 +51,23 @@ impl LateLintPass<'_> for ZeroRepeatSideEffects {
if let Some(args) = VecArgs::hir(cx, expr)
&& let VecArgs::Repeat(inner_expr, len) = args
&& let ExprKind::Lit(l) = len.kind
&& let LitKind::Int(i, _) = l.node
&& i.0 == 0
&& let LitKind::Int(Pu128(0), _) = l.node
{
inner_check(cx, expr, inner_expr, true);
} else {
let ExprKind::Repeat(inner_expr, length) = expr.kind else {
return;
};
// Skip if the length is from a macro.
if let ArrayLen::Body(anon_const) = length {
let length_expr = hir_map.body(anon_const.body).value;
if !length_expr.span.eq_ctxt(expr.span) {
return;
}
// Get the initialization span of a const item and compare it with the span at use-site.
if let ExprKind::Path(QPath::Resolved(None, path)) = length_expr.kind
&& let Res::Def(DefKind::Const, def_id) = path.res
&& let Some(def_id) = def_id.as_local()
&& let Node::Item(item) = cx.tcx.hir_node_by_def_id(def_id)
&& let ItemKind::Const(_ty, _, body_id) = item.kind
&& let init_span = hir_map.span_with_body(body_id.hir_id)
&& !init_span.eq_ctxt(length_expr.span)
{
return;
}
}
if let ty::Array(_, cst) = cx.typeck_results().expr_ty(expr).kind()
&& let ConstKind::Value(_, ty::ValTree::Leaf(element_count)) = cst.kind()
&& element_count.to_target_usize(cx.tcx) == 0
{
inner_check(cx, expr, inner_expr, false);
}
}
// Lint only if the length is a literal zero, and not a path to any constants.
// NOTE(@y21): When reading `[f(); LEN]`, I intuitively expect that the function is called and it
// doesn't seem as confusing as `[f(); 0]`. It would also have false positives when eg.
// the const item depends on `#[cfg]s` and has different values in different compilation
// sessions).
else if let ExprKind::Repeat(inner_expr, length) = expr.kind
&& let ArrayLen::Body(anon_const) = length
&& let length_expr = hir_map.body(anon_const.body).value
&& !length_expr.span.from_expansion()
&& let ExprKind::Lit(literal) = length_expr.kind
&& let LitKind::Int(Pu128(0), _) = literal.node
{
inner_check(cx, expr, inner_expr, false);
}
}
}

6
tests/ui/zero_repeat_side_effects.fixed
View file

@ -16,10 +16,8 @@ fn main() {
// on arrays
f(); let a: [i32; 0] = [];
f(); let a: [i32; 0] = [];
let mut b;
f(); b = [] as [i32; 0];
f(); b = [] as [i32; 0];
// on vecs
// vecs dont support infering value of consts
@ -39,9 +37,11 @@ fn main() {
// when singled out/not part of assignment/local
{ f(); vec![] as std::vec::Vec<i32> };
{ f(); [] as [i32; 0] };
{ f(); [] as [i32; 0] };
// should not trigger
let a = [f(); N];
b = [f(); N];
[f(); N];
// on arrays with > 0 repeat
let a = [f(); 1];

6
tests/ui/zero_repeat_side_effects.rs
View file

@ -16,10 +16,8 @@ fn main() {
// on arrays
let a = [f(); 0];
let a = [f(); N];
let mut b;
b = [f(); 0];
b = [f(); N];
// on vecs
// vecs dont support infering value of consts
@ -39,9 +37,11 @@ fn main() {
// when singled out/not part of assignment/local
vec![f(); 0];
[f(); 0];
[f(); N];
// should not trigger
let a = [f(); N];
b = [f(); N];
[f(); N];
// on arrays with > 0 repeat
let a = [f(); 1];

36
tests/ui/zero_repeat_side_effects.stderr
View file

@ -8,70 +8,52 @@ LL | let a = [f(); 0];
= help: to override `-D warnings` add `#[allow(clippy::zero_repeat_side_effects)]`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:19:5
|
LL | let a = [f(); N];
| ^^^^^^^^^^^^^^^^^ help: consider using: `f(); let a: [i32; 0] = [];`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:21:5
--> tests/ui/zero_repeat_side_effects.rs:20:5
|
LL | b = [f(); 0];
| ^^^^^^^^^^^^ help: consider using: `f(); b = [] as [i32; 0]`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:22:5
|
LL | b = [f(); N];
| ^^^^^^^^^^^^ help: consider using: `f(); b = [] as [i32; 0]`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:26:5
--> tests/ui/zero_repeat_side_effects.rs:24:5
|
LL | let c = vec![f(); 0];
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f(); let c: std::vec::Vec<i32> = vec![];`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:28:5
--> tests/ui/zero_repeat_side_effects.rs:26:5
|
LL | d = vec![f(); 0];
| ^^^^^^^^^^^^^^^^ help: consider using: `f(); d = vec![] as std::vec::Vec<i32>`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:31:5
--> tests/ui/zero_repeat_side_effects.rs:29:5
|
LL | let e = [println!("side effect"); 0];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `println!("side effect"); let e: [(); 0] = [];`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:34:5
--> tests/ui/zero_repeat_side_effects.rs:32:5
|
LL | let g = [{ f() }; 0];
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using: `{ f() }; let g: [i32; 0] = [];`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:37:10
--> tests/ui/zero_repeat_side_effects.rs:35:10
|
LL | drop(vec![f(); 0]);
| ^^^^^^^^^^^^ help: consider using: `{ f(); vec![] as std::vec::Vec<i32> }`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:40:5
--> tests/ui/zero_repeat_side_effects.rs:38:5
|
LL | vec![f(); 0];
| ^^^^^^^^^^^^ help: consider using: `{ f(); vec![] as std::vec::Vec<i32> }`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:41:5
--> tests/ui/zero_repeat_side_effects.rs:39:5
|
LL | [f(); 0];
| ^^^^^^^^ help: consider using: `{ f(); [] as [i32; 0] }`
error: function or method calls as the initial value in zero-sized array initializers may cause side effects
--> tests/ui/zero_repeat_side_effects.rs:42:5
|
LL | [f(); N];
| ^^^^^^^^ help: consider using: `{ f(); [] as [i32; 0] }`
error: aborting due to 12 previous errors
error: aborting due to 9 previous errors