1 use crate::utils::span_lint;
3 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
4 use rustc::ty::subst::Subst;
5 use rustc::ty::{self, Ty};
6 use rustc::{declare_tool_lint, lint_array};
9 /// **What it does:** Detects giving a mutable reference to a function that only
10 /// requires an immutable reference.
12 /// **Why is this bad?** The immutable reference rules out all other references
13 /// to the value. Also the code misleads about the intent of the call site.
15 /// **Known problems:** None.
19 /// my_vec.push(&mut value)
21 pub UNNECESSARY_MUT_PASSED,
23 "an argument passed as a mutable reference although the callee only demands an immutable reference"
26 #[derive(Copy, Clone)]
27 pub struct UnnecessaryMutPassed;
29 impl LintPass for UnnecessaryMutPassed {
30 fn get_lints(&self) -> LintArray {
31 lint_array!(UNNECESSARY_MUT_PASSED)
34 fn name(&self) -> &'static str {
35 "UnneccessaryMutPassed"
39 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnecessaryMutPassed {
40 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
42 ExprKind::Call(ref fn_expr, ref arguments) => {
43 if let ExprKind::Path(ref path) = fn_expr.node {
47 cx.tables.expr_ty(fn_expr),
48 &print::to_string(print::NO_ANN, |s| s.print_qpath(path, false)),
52 ExprKind::MethodCall(ref path, _, ref arguments) => {
53 let def_id = cx.tables.type_dependent_def_id(e.hir_id).unwrap();
54 let substs = cx.tables.node_substs(e.hir_id);
55 let method_type = cx.tcx.type_of(def_id).subst(cx.tcx, substs);
56 check_arguments(cx, arguments, method_type, &path.ident.as_str())
63 fn check_arguments<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, arguments: &[Expr], type_definition: Ty<'tcx>, name: &str) {
64 match type_definition.sty {
65 ty::FnDef(..) | ty::FnPtr(_) => {
66 let parameters = type_definition.fn_sig(cx.tcx).skip_binder().inputs();
67 for (argument, parameter) in arguments.iter().zip(parameters.iter()) {
69 ty::Ref(_, _, MutImmutable)
70 | ty::RawPtr(ty::TypeAndMut {
71 mutbl: MutImmutable, ..
73 if let ExprKind::AddrOf(MutMutable, _) = argument.node {
76 UNNECESSARY_MUT_PASSED,
78 &format!("The function/method `{}` doesn't need a mutable reference", name),