52 lines
1.4 KiB
Rust
52 lines
1.4 KiB
Rust
//! lint when there is an enum with no variants
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use crate::utils::span_lint_and_then;
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::{declare_tool_lint, lint_array};
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/// **What it does:** Checks for `enum`s with no variants.
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///
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/// **Why is this bad?** Enum's with no variants should be replaced with `!`,
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/// the uninhabited type,
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/// or a wrapper around it.
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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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/// enum Test {}
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/// ```
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declare_clippy_lint! {
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pub EMPTY_ENUM,
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pedantic,
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"enum with no variants"
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}
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#[derive(Copy, Clone)]
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pub struct EmptyEnum;
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impl LintPass for EmptyEnum {
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fn get_lints(&self) -> LintArray {
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lint_array!(EMPTY_ENUM)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EmptyEnum {
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fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &Item) {
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let did = cx.tcx.hir().local_def_id(item.id);
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if let ItemKind::Enum(..) = item.node {
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let ty = cx.tcx.type_of(did);
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let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
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if adt.variants.is_empty() {
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span_lint_and_then(cx, EMPTY_ENUM, item.span, "enum with no variants", |db| {
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db.span_help(
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item.span,
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"consider using the uninhabited type `!` or a wrapper around it",
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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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