101 lines
3.5 KiB
Rust
101 lines
3.5 KiB
Rust
use clippy_utils::diagnostics::span_lint;
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use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::{self, Ty};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use std::iter;
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declare_clippy_lint! {
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/// ### What it does
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/// Detects passing a mutable reference to a function that only
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/// requires an immutable reference.
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///
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/// ### Why is this bad?
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/// The mutable reference rules out all other references to
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/// the value. Also the code misleads about the intent of the call site.
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///
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/// ### Example
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/// ```rust
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/// # let mut vec = Vec::new();
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/// # let mut value = 5;
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/// vec.push(&mut value);
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// # let mut vec = Vec::new();
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/// # let value = 5;
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/// vec.push(&value);
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub UNNECESSARY_MUT_PASSED,
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style,
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"an argument passed as a mutable reference although the callee only demands an immutable reference"
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}
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declare_lint_pass!(UnnecessaryMutPassed => [UNNECESSARY_MUT_PASSED]);
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impl<'tcx> LateLintPass<'tcx> for UnnecessaryMutPassed {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
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match e.kind {
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ExprKind::Call(fn_expr, arguments) => {
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if let ExprKind::Path(ref path) = fn_expr.kind {
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check_arguments(
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cx,
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arguments.iter().collect(),
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cx.typeck_results().expr_ty(fn_expr),
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&rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false)),
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"function",
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);
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}
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},
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ExprKind::MethodCall(path, receiver, arguments, _) => {
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let def_id = cx.typeck_results().type_dependent_def_id(e.hir_id).unwrap();
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let substs = cx.typeck_results().node_substs(e.hir_id);
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let method_type = cx.tcx.bound_type_of(def_id).subst(cx.tcx, substs);
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check_arguments(
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cx,
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std::iter::once(receiver).chain(arguments.iter()).collect(),
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method_type,
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path.ident.as_str(),
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"method",
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);
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},
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_ => (),
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}
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}
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}
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fn check_arguments<'tcx>(
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cx: &LateContext<'tcx>,
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arguments: Vec<&Expr<'_>>,
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type_definition: Ty<'tcx>,
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name: &str,
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fn_kind: &str,
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) {
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match type_definition.kind() {
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ty::FnDef(..) | ty::FnPtr(_) => {
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let parameters = type_definition.fn_sig(cx.tcx).skip_binder().inputs();
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for (argument, parameter) in iter::zip(arguments, parameters) {
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match parameter.kind() {
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ty::Ref(_, _, Mutability::Not)
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| ty::RawPtr(ty::TypeAndMut {
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mutbl: Mutability::Not, ..
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}) => {
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if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Mut, _) = argument.kind {
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span_lint(
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cx,
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UNNECESSARY_MUT_PASSED,
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argument.span,
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&format!("the {fn_kind} `{name}` doesn't need a mutable reference"),
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);
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}
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},
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_ => (),
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}
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}
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},
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_ => (),
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}
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}
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