| use clippy_utils::consts::{constant, Constant}; |
| use clippy_utils::diagnostics::span_lint; |
| use clippy_utils::{is_integer_literal, is_path_diagnostic_item}; |
| use rustc_hir::{Expr, ExprKind}; |
| use rustc_lint::LateContext; |
| use rustc_middle::ty::Ty; |
| use rustc_span::symbol::sym; |
| |
| use super::TRANSMUTING_NULL; |
| |
| const LINT_MSG: &str = "transmuting a known null pointer into a reference"; |
| |
| pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, arg: &'tcx Expr<'_>, to_ty: Ty<'tcx>) -> bool { |
| if !to_ty.is_ref() { |
| return false; |
| } |
| |
| // Catching transmute over constants that resolve to `null`. |
| if let ExprKind::Path(ref _qpath) = arg.kind |
| && let Some(Constant::RawPtr(0)) = constant(cx, cx.typeck_results(), arg) |
| { |
| span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG); |
| return true; |
| } |
| |
| // Catching: |
| // `std::mem::transmute(0 as *const i32)` |
| if let ExprKind::Cast(inner_expr, _cast_ty) = arg.kind |
| && is_integer_literal(inner_expr, 0) |
| { |
| span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG); |
| return true; |
| } |
| |
| // Catching: |
| // `std::mem::transmute(std::ptr::null::<i32>())` |
| if let ExprKind::Call(func1, []) = arg.kind |
| && is_path_diagnostic_item(cx, func1, sym::ptr_null) |
| { |
| span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG); |
| return true; |
| } |
| |
| // FIXME: |
| // Also catch transmutations of variables which are known nulls. |
| // To do this, MIR const propagation seems to be the better tool. |
| // Whenever MIR const prop routines are more developed, this will |
| // become available. As of this writing (25/03/19) it is not yet. |
| false |
| } |