e110231260
This commit makes `AdtDef` use `Interned`. Much the commit is tedious changes to introduce getter functions. The interesting changes are in `compiler/rustc_middle/src/ty/adt.rs`.
69 lines
2.2 KiB
Rust
69 lines
2.2 KiB
Rust
//! lint when there is an enum with no variants
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use clippy_utils::diagnostics::span_lint_and_help;
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use rustc_hir::{Item, ItemKind};
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use rustc_lint::{LateContext, LateLintPass};
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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
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/// Checks for `enum`s with no variants.
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///
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/// As of this writing, the `never_type` is still a
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/// nightly-only experimental API. Therefore, this lint is only triggered
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/// if the `never_type` is enabled.
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///
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/// ### Why is this bad?
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/// If you want to introduce a type which
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/// can't be instantiated, you should use `!` (the primitive type "never"),
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/// or a wrapper around it, because `!` has more extensive
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/// compiler support (type inference, etc...) and wrappers
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/// around it are the conventional way to define an uninhabited type.
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/// For further information visit [never type documentation](https://doc.rust-lang.org/std/primitive.never.html)
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///
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///
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/// ### Example
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/// Bad:
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/// ```rust
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/// enum Test {}
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/// ```
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///
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/// Good:
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/// ```rust
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/// #![feature(never_type)]
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///
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/// struct Test(!);
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/// ```
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#[clippy::version = "pre 1.29.0"]
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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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declare_lint_pass!(EmptyEnum => [EMPTY_ENUM]);
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impl<'tcx> LateLintPass<'tcx> for EmptyEnum {
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fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
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// Only suggest the `never_type` if the feature is enabled
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if !cx.tcx.features().never_type {
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return;
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}
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if let ItemKind::Enum(..) = item.kind {
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let ty = cx.tcx.type_of(item.def_id);
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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_help(
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cx,
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EMPTY_ENUM,
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item.span,
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"enum with no variants",
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None,
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"consider using the uninhabited type `!` (never type) or a wrapper \
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around it to introduce a type which can't be instantiated",
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);
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}
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}
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}
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}
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