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