0f5338cd90
The `restriction` group contains many lints which are not about necessarily “bad” things, but style choices — perhaps even style choices which contradict conventional Rust style — or are otherwise very situational. This results in silly wording like “Why is this bad? It isn't, but ...”, which I’ve seen confuse a newcomer at least once. To improve this situation, this commit replaces the “Why is this bad?” section heading with “Why restrict this?”, for most, but not all, restriction lints. I left alone the ones whose placement in the restriction group is more incidental. In order to make this make sense, I had to remove the “It isn't, but” texts from the contents of the sections. Sometimes further changes were needed, or there were obvious fixes to make, and I went ahead and made those changes without attempting to split them into another commit, even though many of them are not strictly necessary for the “Why restrict this?” project.
65 lines
2.3 KiB
Rust
65 lines
2.3 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::is_from_proc_macro;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::declare_lint_pass;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for usage of `as` conversions.
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///
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/// Note that this lint is specialized in linting *every single* use of `as`
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/// regardless of whether good alternatives exist or not.
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/// If you want more precise lints for `as`, please consider using these separate lints:
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/// `unnecessary_cast`, `cast_lossless/cast_possible_truncation/cast_possible_wrap/cast_precision_loss/cast_sign_loss`,
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/// `fn_to_numeric_cast(_with_truncation)`, `char_lit_as_u8`, `ref_to_mut` and `ptr_as_ptr`.
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/// There is a good explanation the reason why this lint should work in this way and how it is useful
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/// [in this issue](https://github.com/rust-lang/rust-clippy/issues/5122).
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///
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/// ### Why restrict this?
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/// `as` conversions will perform many kinds of
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/// conversions, including silently lossy conversions and dangerous coercions.
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/// There are cases when it makes sense to use `as`, so the lint is
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/// Allow by default.
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///
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/// ### Example
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/// ```rust,ignore
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/// let a: u32;
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/// ...
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/// f(a as u16);
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/// ```
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///
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/// Use instead:
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/// ```rust,ignore
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/// f(a.try_into()?);
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///
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/// // or
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///
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/// f(a.try_into().expect("Unexpected u16 overflow in f"));
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/// ```
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#[clippy::version = "1.41.0"]
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pub AS_CONVERSIONS,
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restriction,
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"using a potentially dangerous silent `as` conversion"
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}
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declare_lint_pass!(AsConversions => [AS_CONVERSIONS]);
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impl<'tcx> LateLintPass<'tcx> for AsConversions {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
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if let ExprKind::Cast(_, _) = expr.kind
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&& !in_external_macro(cx.sess(), expr.span)
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&& !is_from_proc_macro(cx, expr)
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{
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span_lint_and_help(
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cx,
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AS_CONVERSIONS,
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expr.span,
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"using a potentially dangerous silent `as` conversion",
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None,
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"consider using a safe wrapper for this conversion",
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);
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}
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}
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}
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