64 lines
1.8 KiB
Rust
64 lines
1.8 KiB
Rust
use crate::utils::span_lint;
|
|
use rustc_hir::{Expr, ExprKind};
|
|
use rustc_lint::{LateContext, LateLintPass};
|
|
use rustc_middle::ty;
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
|
|
|
declare_clippy_lint! {
|
|
/// **What it does:** Checks for needlessly including a base struct on update
|
|
/// when all fields are changed anyway.
|
|
///
|
|
/// **Why is this bad?** This will cost resources (because the base has to be
|
|
/// somewhere), and make the code less readable.
|
|
///
|
|
/// **Known problems:** None.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust
|
|
/// # struct Point {
|
|
/// # x: i32,
|
|
/// # y: i32,
|
|
/// # z: i32,
|
|
/// # }
|
|
/// # let zero_point = Point { x: 0, y: 0, z: 0 };
|
|
///
|
|
/// // Bad
|
|
/// Point {
|
|
/// x: 1,
|
|
/// y: 1,
|
|
/// z: 1,
|
|
/// ..zero_point
|
|
/// };
|
|
///
|
|
/// // Ok
|
|
/// Point {
|
|
/// x: 1,
|
|
/// y: 1,
|
|
/// ..zero_point
|
|
/// };
|
|
/// ```
|
|
pub NEEDLESS_UPDATE,
|
|
complexity,
|
|
"using `Foo { ..base }` when there are no missing fields"
|
|
}
|
|
|
|
declare_lint_pass!(NeedlessUpdate => [NEEDLESS_UPDATE]);
|
|
|
|
impl<'tcx> LateLintPass<'tcx> for NeedlessUpdate {
|
|
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
|
|
if let ExprKind::Struct(_, ref fields, Some(ref base)) = expr.kind {
|
|
let ty = cx.typeck_results().expr_ty(expr);
|
|
if let ty::Adt(def, _) = ty.kind() {
|
|
if fields.len() == def.non_enum_variant().fields.len() {
|
|
span_lint(
|
|
cx,
|
|
NEEDLESS_UPDATE,
|
|
base.span,
|
|
"struct update has no effect, all the fields in the struct have already been specified",
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|