67 lines
2.3 KiB
Rust
67 lines
2.3 KiB
Rust
use rustc_ast::ast::{Expr, ExprKind};
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use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use crate::utils::span_lint_and_help;
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declare_clippy_lint! {
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/// **What it does:** 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/possible_truncation/possible_wrap/precision_loss/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 is this bad?** `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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/// **Known problems:** None.
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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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/// Usually better represents the semantics you expect:
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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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/// ```rust,ignore
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/// f(a.try_into().expect("Unexpected u16 overflow in f"));
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/// ```
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///
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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 EarlyLintPass for AsConversions {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
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if in_external_macro(cx.sess(), expr.span) {
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return;
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}
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if let ExprKind::Cast(_, _) = expr.kind {
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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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