| use clippy_utils::diagnostics::span_lint; |
| use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_middle::ty::{self, Ty}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use std::iter; |
| |
| 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 mutable reference rules out all other references to |
| /// the value. Also the code misleads about the intent of the call site. |
| /// |
| /// ### Example |
| /// ```rust |
| /// # let mut vec = Vec::new(); |
| /// # let mut value = 5; |
| /// vec.push(&mut value); |
| /// ``` |
| /// |
| /// Use instead: |
| /// ```rust |
| /// # let mut vec = Vec::new(); |
| /// # let value = 5; |
| /// vec.push(&value); |
| /// ``` |
| #[clippy::version = "pre 1.29.0"] |
| 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<'_>) { |
| if e.span.from_expansion() { |
| // Issue #11268 |
| return; |
| } |
| |
| match e.kind { |
| ExprKind::Call(fn_expr, arguments) => { |
| if let ExprKind::Path(ref path) = fn_expr.kind { |
| check_arguments( |
| cx, |
| arguments.iter().collect(), |
| cx.typeck_results().expr_ty(fn_expr), |
| &rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false)), |
| "function", |
| ); |
| } |
| }, |
| ExprKind::MethodCall(path, receiver, arguments, _) => { |
| let def_id = cx.typeck_results().type_dependent_def_id(e.hir_id).unwrap(); |
| let args = cx.typeck_results().node_args(e.hir_id); |
| let method_type = cx.tcx.type_of(def_id).instantiate(cx.tcx, args); |
| check_arguments( |
| cx, |
| std::iter::once(receiver).chain(arguments.iter()).collect(), |
| method_type, |
| path.ident.as_str(), |
| "method", |
| ); |
| }, |
| _ => (), |
| } |
| } |
| } |
| |
| fn check_arguments<'tcx>( |
| cx: &LateContext<'tcx>, |
| arguments: Vec<&Expr<'_>>, |
| type_definition: Ty<'tcx>, |
| name: &str, |
| fn_kind: &str, |
| ) { |
| match type_definition.kind() { |
| ty::FnDef(..) | ty::FnPtr(_) => { |
| let parameters = type_definition.fn_sig(cx.tcx).skip_binder().inputs(); |
| for (argument, parameter) in iter::zip(arguments, parameters) { |
| 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 {fn_kind} `{name}` doesn't need a mutable reference"), |
| ); |
| } |
| }, |
| _ => (), |
| } |
| } |
| }, |
| _ => (), |
| } |
| } |