1 use clippy_utils::diagnostics::span_lint_and_help;
2 use rustc_ast::ast::{Expr, ExprKind};
3 use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
4 use rustc_middle::lint::in_external_macro;
5 use rustc_session::{declare_lint_pass, declare_tool_lint};
8 /// **What it does:** Checks for usage of `as` conversions.
10 /// Note that this lint is specialized in linting *every single* use of `as`
11 /// regardless of whether good alternatives exist or not.
12 /// If you want more precise lints for `as`, please consider using these separate lints:
13 /// `unnecessary_cast`, `cast_lossless/possible_truncation/possible_wrap/precision_loss/sign_loss`,
14 /// `fn_to_numeric_cast(_with_truncation)`, `char_lit_as_u8`, `ref_to_mut` and `ptr_as_ptr`.
15 /// There is a good explanation the reason why this lint should work in this way and how it is useful
16 /// [in this issue](https://github.com/rust-lang/rust-clippy/issues/5122).
18 /// **Why is this bad?** `as` conversions will perform many kinds of
19 /// conversions, including silently lossy conversions and dangerous coercions.
20 /// There are cases when it makes sense to use `as`, so the lint is
23 /// **Known problems:** None.
32 /// Usually better represents the semantics you expect:
38 /// f(a.try_into().expect("Unexpected u16 overflow in f"));
43 "using a potentially dangerous silent `as` conversion"
46 declare_lint_pass!(AsConversions => [AS_CONVERSIONS]);
48 impl EarlyLintPass for AsConversions {
49 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
50 if in_external_macro(cx.sess(), expr.span) {
54 if let ExprKind::Cast(_, _) = expr.kind {
59 "using a potentially dangerous silent `as` conversion",
61 "consider using a safe wrapper for this conversion",