2015-09-29 06:11:19 -05:00
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use rustc::lint::*;
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2017-06-10 21:57:25 -05:00
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use rustc::ty::{self, Ty};
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2017-06-04 16:28:01 -05:00
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use rustc::ty::subst::Subst;
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2016-04-07 10:46:48 -05:00
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use rustc::hir::*;
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2016-02-24 10:38:57 -06:00
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use utils::span_lint;
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2015-09-29 06:11:19 -05:00
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2016-08-06 02:55:04 -05:00
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/// **What it does:** Detects giving a mutable reference to a function that only
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/// requires an immutable reference.
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2015-12-10 18:22:27 -06:00
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///
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2016-08-06 02:55:04 -05:00
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/// **Why is this bad?** The immutable reference rules out all other references
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/// to the value. Also the code misleads about the intent of the call site.
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2015-12-10 18:22:27 -06:00
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///
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2016-08-06 02:55:04 -05:00
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/// **Known problems:** None.
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2015-12-10 18:22:27 -06:00
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///
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2016-08-06 02:55:04 -05:00
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/// **Example:**
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2016-07-15 17:25:44 -05:00
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/// ```rust
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/// my_vec.push(&mut value)
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/// ```
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2018-03-28 08:24:26 -05:00
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declare_clippy_lint! {
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2015-09-29 06:11:19 -05:00
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pub UNNECESSARY_MUT_PASSED,
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2018-03-28 08:24:26 -05:00
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style,
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2016-08-06 03:18:36 -05:00
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"an argument passed as a mutable reference although the callee only demands an \
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2015-09-29 06:11:19 -05:00
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immutable reference"
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}
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2017-08-09 02:30:56 -05:00
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#[derive(Copy, Clone)]
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2015-09-29 06:11:19 -05:00
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pub struct UnnecessaryMutPassed;
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impl LintPass for UnnecessaryMutPassed {
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fn get_lints(&self) -> LintArray {
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lint_array!(UNNECESSARY_MUT_PASSED)
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}
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}
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2016-12-07 06:13:40 -06:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnecessaryMutPassed {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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2015-09-29 11:43:38 -05:00
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match e.node {
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2017-09-05 04:33:04 -05:00
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ExprCall(ref fn_expr, ref arguments) => if let ExprPath(ref path) = fn_expr.node {
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check_arguments(
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cx,
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arguments,
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cx.tables.expr_ty(fn_expr),
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&print::to_string(print::NO_ANN, |s| s.print_qpath(path, false)),
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);
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2016-12-20 11:21:30 -06:00
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},
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2017-07-10 03:17:40 -05:00
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ExprMethodCall(ref path, _, ref arguments) => {
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2017-08-15 04:10:49 -05:00
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let def_id = cx.tables.type_dependent_defs()[e.hir_id].def_id();
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let substs = cx.tables.node_substs(e.hir_id);
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2017-06-04 16:28:01 -05:00
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let method_type = cx.tcx.type_of(def_id).subst(cx.tcx, substs);
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2017-07-10 03:17:40 -05:00
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check_arguments(cx, arguments, method_type, &path.name.as_str())
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2016-12-20 11:21:30 -06:00
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},
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2016-04-14 13:14:03 -05:00
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_ => (),
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2015-09-29 06:11:19 -05:00
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}
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}
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}
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2015-09-30 06:08:29 -05:00
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2017-06-29 08:38:25 -05:00
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fn check_arguments<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, arguments: &[Expr], type_definition: Ty<'tcx>, name: &str) {
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2016-03-10 11:13:49 -06:00
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match type_definition.sty {
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2017-06-29 09:07:43 -05:00
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ty::TyFnDef(..) | ty::TyFnPtr(_) => {
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2017-06-29 08:38:25 -05:00
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let parameters = type_definition.fn_sig(cx.tcx).skip_binder().inputs();
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2016-03-10 11:13:49 -06:00
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for (argument, parameter) in arguments.iter().zip(parameters.iter()) {
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match parameter.sty {
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2017-09-05 04:33:04 -05:00
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ty::TyRef(
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_,
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2018-05-11 01:37:48 -05:00
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_,
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2018-05-11 02:50:29 -05:00
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MutImmutable,
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2017-09-05 04:33:04 -05:00
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) |
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ty::TyRawPtr(ty::TypeAndMut {
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mutbl: MutImmutable,
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..
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}) => if let ExprAddrOf(MutMutable, _) = argument.node {
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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 function/method `{}` doesn't need a mutable reference", name),
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);
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2016-12-20 11:21:30 -06:00
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},
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2016-04-14 13:14:03 -05:00
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_ => (),
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2015-11-16 22:39:42 -06:00
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}
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2015-09-30 06:08:29 -05:00
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}
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2016-12-20 11:21:30 -06:00
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},
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2016-03-10 11:13:49 -06:00
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_ => (),
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2015-09-30 06:08:29 -05:00
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}
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}
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