rust/clippy_lints/src/large_const_arrays.rs
xFrednet d647696c1f
Added clippy::version attribute to all normal lints
So, some context for this, well, more a story. I'm not used to scripting, I've never really scripted anything, even if it's a valuable skill. I just never really needed it. Now, `@flip1995` correctly suggested using a script for this in `rust-clippy#7813`...

And I decided to write a script using nushell because why not? This was a mistake... I spend way more time on this than I would like to admit. It has definitely been more than 4 hours. It shouldn't take that long, but me being new to scripting and nushell just wasn't a good mixture... Anyway, here is the script that creates another script which adds the versions. Fun...

Just execute this on the `gh-pages` branch and the resulting `replacer.sh` in `clippy_lints` and it should all work.

```nu
mv v0.0.212 rust-1.00.0;
mv beta rust-1.57.0;
mv master rust-1.58.0;

let paths = (open ./rust-1.58.0/lints.json | select id id_span | flatten | select id path);
let versions = (
    ls | where name =~ "rust-" | select name | format {name}/lints.json |
    each { open $it | select id | insert version $it | str substring "5,11" version} |
    group-by id | rotate counter-clockwise id version |
    update version {get version | first 1} | flatten | select id version);
$paths | each { |row|
    let version = ($versions | where id == ($row.id) | format {version})
    let idu = ($row.id | str upcase)
    $"sed -i '0,/($idu),/{s/pub ($idu),/#[clippy::version = "($version)"]\n    pub ($idu),/}' ($row.path)"
} | str collect ";" | str find-replace --all '1.00.0' 'pre 1.29.0' | save "replacer.sh";
```

And this still has some problems, but at this point I just want to be done -.-
2021-11-10 19:48:31 +01:00

87 lines
2.9 KiB
Rust

use clippy_utils::diagnostics::span_lint_and_then;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Item, ItemKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::mir::interpret::ConstValue;
use rustc_middle::ty::layout::LayoutOf;
use rustc_middle::ty::{self, ConstKind};
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::{BytePos, Pos, Span};
use rustc_typeck::hir_ty_to_ty;
declare_clippy_lint! {
/// ### What it does
/// Checks for large `const` arrays that should
/// be defined as `static` instead.
///
/// ### Why is this bad?
/// Performance: const variables are inlined upon use.
/// Static items result in only one instance and has a fixed location in memory.
///
/// ### Example
/// ```rust,ignore
/// // Bad
/// pub const a = [0u32; 1_000_000];
///
/// // Good
/// pub static a = [0u32; 1_000_000];
/// ```
#[clippy::version = "1.44.0"]
pub LARGE_CONST_ARRAYS,
perf,
"large non-scalar const array may cause performance overhead"
}
pub struct LargeConstArrays {
maximum_allowed_size: u64,
}
impl LargeConstArrays {
#[must_use]
pub fn new(maximum_allowed_size: u64) -> Self {
Self { maximum_allowed_size }
}
}
impl_lint_pass!(LargeConstArrays => [LARGE_CONST_ARRAYS]);
impl<'tcx> LateLintPass<'tcx> for LargeConstArrays {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
if_chain! {
if !item.span.from_expansion();
if let ItemKind::Const(hir_ty, _) = &item.kind;
let ty = hir_ty_to_ty(cx.tcx, hir_ty);
if let ty::Array(element_type, cst) = ty.kind();
if let ConstKind::Value(ConstValue::Scalar(element_count)) = cst.val;
if let Ok(element_count) = element_count.to_machine_usize(&cx.tcx);
if let Ok(element_size) = cx.layout_of(element_type).map(|l| l.size.bytes());
if self.maximum_allowed_size < element_count * element_size;
then {
let hi_pos = item.ident.span.lo() - BytePos::from_usize(1);
let sugg_span = Span::new(
hi_pos - BytePos::from_usize("const".len()),
hi_pos,
item.span.ctxt(),
item.span.parent(),
);
span_lint_and_then(
cx,
LARGE_CONST_ARRAYS,
item.span,
"large array defined as const",
|diag| {
diag.span_suggestion(
sugg_span,
"make this a static item",
"static".to_string(),
Applicability::MachineApplicable,
);
}
);
}
}
}
}