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use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_then};
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, TyKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// ### What it does
/// Check for the usage of `as _` conversion using inferred type.
///
/// ### Why is this bad?
/// The conversion might include lossy conversion and dangerous cast that might go
/// undetected du to the type being inferred.
///
/// The lint is allowed by default as using `_` is less wordy than always specifying the type.
///
/// ### Example
/// ```rust
/// fn foo(n: usize) {}
/// let n: u16 = 256;
/// foo(n as _);
/// ```
/// Use instead:
/// ```rust
/// fn foo(n: usize) {}
/// let n: u16 = 256;
/// foo(n as usize);
/// ```
#[clippy::version = "1.63.0"]
pub AS_UNDERSCORE,
restriction,
"detects `as _` conversion"
}
declare_lint_pass!(AsUnderscore => [AS_UNDERSCORE]);
impl<'tcx> LateLintPass<'tcx> for AsUnderscore {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
if in_external_macro(cx.sess(), expr.span) {
return;
}
if let ExprKind::Cast(_, ty) = expr.kind && let TyKind::Infer = ty.kind {
let ty_resolved = cx.typeck_results().expr_ty(expr);
if let ty::Error(_) = ty_resolved.kind() {
span_lint_and_help(
cx,
AS_UNDERSCORE,
expr.span,
"using `as _` conversion",
None,
"consider giving the type explicitly",
);
} else {
span_lint_and_then(
cx,
AS_UNDERSCORE,
expr.span,
"using `as _` conversion",
|diag| {
diag.span_suggestion(
ty.span,
"consider giving the type explicitly",
ty_resolved,
Applicability::MachineApplicable,
);
}
);
}
}
}
}
|
