rust-clippy/clippy_lints/src/as_conversions.rs
Mikhail Babenko 9ec8888b91 implemented as_conversions lint
actuall add files

add better example and change pedantic to restriction
2019-11-25 18:12:52 +03:00

56 lines
1.6 KiB
Rust

use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
use rustc::{declare_lint_pass, declare_tool_lint};
use syntax::ast::*;
use crate::utils::span_help_and_lint;
declare_clippy_lint! {
/// **What it does:** Checks for usage of `as` conversions.
///
/// **Why is this bad?** `as` conversions will perform many kinds of
/// conversions, including silently lossy conversions and dangerous coercions.
/// There are cases when it makes sense to use `as`, so the lint is
/// Allow by default.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust,ignore
/// let a: u32;
/// ...
/// f(a as u16);
/// ```
///
/// Usually better represents the semantics you expect:
/// ```rust,ignore
/// f(a.try_into()?);
/// ```
/// or
/// ```rust,ignore
/// f(a.try_into().expect("Unexpected u16 overflow in f"));
/// ```
///
pub AS_CONVERSIONS,
restriction,
"using a potentially dangerous silent `as` conversion"
}
declare_lint_pass!(AsConversions => [AS_CONVERSIONS]);
impl EarlyLintPass for AsConversions {
fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
if in_external_macro(cx.sess(), expr.span) {
return;
}
if let ExprKind::Cast(_, _) = expr.kind {
span_help_and_lint(
cx,
AS_CONVERSIONS,
expr.span,
"using a potentially dangerous silent `as` conversion",
"consider using a safe wrapper for this conversion",
);
}
}
}