rust-clippy/clippy_lints/src/mem_forget.rs

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use crate::utils::{match_def_path, paths, span_lint};
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
/// **What it does:** Checks for usage of `std::mem::forget(t)` where `t` is
/// `Drop`.
///
/// **Why is this bad?** `std::mem::forget(t)` prevents `t` from running its
/// destructor, possibly causing leaks.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # use std::mem;
/// # use std::rc::Rc;
/// mem::forget(Rc::new(55))
/// ```
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pub MEM_FORGET,
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restriction,
"`mem::forget` usage on `Drop` types, likely to cause memory leaks"
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}
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declare_lint_pass!(MemForget => [MEM_FORGET]);
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impl<'tcx> LateLintPass<'tcx> for MemForget {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
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if let ExprKind::Call(ref path_expr, ref args) = e.kind {
if let ExprKind::Path(ref qpath) = path_expr.kind {
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if let Some(def_id) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id() {
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if match_def_path(cx, def_id, &paths::MEM_FORGET) {
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let forgot_ty = cx.typeck_results().expr_ty(&args[0]);
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if forgot_ty.ty_adt_def().map_or(false, |def| def.has_dtor(cx.tcx)) {
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span_lint(cx, MEM_FORGET, e.span, "usage of `mem::forget` on `Drop` type");
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}
}
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}
}
}
}
}