47 lines
1.2 KiB
Rust
47 lines
1.2 KiB
Rust
//! lint when there is an enum with no variants
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use rustc::lint::*;
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use rustc::hir::*;
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use utils::span_lint_and_then;
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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 `!`, 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_lint! {
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pub EMPTY_ENUM,
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Allow,
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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 ItemEnum(..) = 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(item.span, "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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