| use crate::utils::span_lint; |
| use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_middle::ty::subst::Subst; |
| use rustc_middle::ty::{self, Ty}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Detects passing a mutable reference to a function that only |
| /// requires an immutable reference. |
| /// |
| /// **Why is this bad?** The immutable reference rules out all other references |
| /// to the value. Also the code misleads about the intent of the call site. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```ignore |
| /// // Bad |
| /// my_vec.push(&mut value) |
| /// |
| /// // Good |
| /// my_vec.push(&value) |
| /// ``` |
| pub UNNECESSARY_MUT_PASSED, |
| style, |
| "an argument passed as a mutable reference although the callee only demands an immutable reference" |
| } |
| |
| declare_lint_pass!(UnnecessaryMutPassed => [UNNECESSARY_MUT_PASSED]); |
| |
| impl<'tcx> LateLintPass<'tcx> for UnnecessaryMutPassed { |
| fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) { |
| match e.kind { |
| ExprKind::Call(ref fn_expr, ref arguments) => { |
| if let ExprKind::Path(ref path) = fn_expr.kind { |
| check_arguments( |
| cx, |
| arguments, |
| cx.tables().expr_ty(fn_expr), |
| &rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false)), |
| ); |
| } |
| }, |
| ExprKind::MethodCall(ref path, _, ref arguments, _) => { |
| let def_id = cx.tables().type_dependent_def_id(e.hir_id).unwrap(); |
| let substs = cx.tables().node_substs(e.hir_id); |
| let method_type = cx.tcx.type_of(def_id).subst(cx.tcx, substs); |
| check_arguments(cx, arguments, method_type, &path.ident.as_str()) |
| }, |
| _ => (), |
| } |
| } |
| } |
| |
| fn check_arguments<'tcx>(cx: &LateContext<'tcx>, arguments: &[Expr<'_>], type_definition: Ty<'tcx>, name: &str) { |
| match type_definition.kind { |
| ty::FnDef(..) | ty::FnPtr(_) => { |
| let parameters = type_definition.fn_sig(cx.tcx).skip_binder().inputs(); |
| for (argument, parameter) in arguments.iter().zip(parameters.iter()) { |
| match parameter.kind { |
| ty::Ref(_, _, Mutability::Not) |
| | ty::RawPtr(ty::TypeAndMut { |
| mutbl: Mutability::Not, .. |
| }) => { |
| if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Mut, _) = argument.kind { |
| span_lint( |
| cx, |
| UNNECESSARY_MUT_PASSED, |
| argument.span, |
| &format!("The function/method `{}` doesn't need a mutable reference", name), |
| ); |
| } |
| }, |
| _ => (), |
| } |
| } |
| }, |
| _ => (), |
| } |
| } |