clippy_lints/src/methods/filter_map.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::source::{indent_of, reindent_multiline, snippet};
   3 use clippy_utils::ty::is_type_diagnostic_item;
   4 use clippy_utils::{is_trait_method, path_to_local_id, peel_blocks, SpanlessEq};
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir as hir;
   8 use rustc_hir::def::Res;
   9 use rustc_hir::{Closure, Expr, ExprKind, PatKind, PathSegment, QPath, UnOp};
  10 use rustc_lint::LateContext;
  11 use rustc_span::source_map::Span;
  12 use rustc_span::symbol::{sym, Symbol};
  13 use std::borrow::Cow;
  14
  15 use super::MANUAL_FILTER_MAP;
  16 use super::MANUAL_FIND_MAP;
  17 use super::OPTION_FILTER_MAP;
  18
  19 fn is_method<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, method_name: Symbol) -> bool {
  20     match &expr.kind {
  21         hir::ExprKind::Path(QPath::TypeRelative(_, mname)) => mname.ident.name == method_name,
  22         hir::ExprKind::Path(QPath::Resolved(_, segments)) => {
  23             segments.segments.last().unwrap().ident.name == method_name
  24         },
  25         hir::ExprKind::Closure(&hir::Closure { body, .. }) => {
  26             let body = cx.tcx.hir().body(body);
  27             let closure_expr = peel_blocks(&body.value);
  28             let arg_id = body.params[0].pat.hir_id;
  29             match closure_expr.kind {
  30                 hir::ExprKind::MethodCall(hir::PathSegment { ident, .. }, args, _) => {
  31                     if_chain! {
  32                     if ident.name == method_name;
  33                     if let hir::ExprKind::Path(path) = &args[0].kind;
  34                     if let Res::Local(ref local) = cx.qpath_res(path, args[0].hir_id);
  35                     then {
  36                         return arg_id == *local
  37                     }
  38                     }
  39                     false
  40                 },
  41                 _ => false,
  42             }
  43         },
  44         _ => false,
  45     }
  46 }
  47
  48 fn is_option_filter_map<'tcx>(cx: &LateContext<'tcx>, filter_arg: &hir::Expr<'_>, map_arg: &hir::Expr<'_>) -> bool {
  49     is_method(cx, map_arg, sym::unwrap) && is_method(cx, filter_arg, sym!(is_some))
  50 }
  51
  52 /// lint use of `filter().map()` for `Iterators`
  53 fn lint_filter_some_map_unwrap(
  54     cx: &LateContext<'_>,
  55     expr: &hir::Expr<'_>,
  56     filter_recv: &hir::Expr<'_>,
  57     filter_arg: &hir::Expr<'_>,
  58     map_arg: &hir::Expr<'_>,
  59     target_span: Span,
  60     methods_span: Span,
  61 ) {
  62     let iterator = is_trait_method(cx, expr, sym::Iterator);
  63     let option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(filter_recv), sym::Option);
  64     if (iterator || option) && is_option_filter_map(cx, filter_arg, map_arg) {
  65         let msg = "`filter` for `Some` followed by `unwrap`";
  66         let help = "consider using `flatten` instead";
  67         let sugg = format!(
  68             "{}",
  69             reindent_multiline(Cow::Borrowed("flatten()"), true, indent_of(cx, target_span),)
  70         );
  71         span_lint_and_sugg(
  72             cx,
  73             OPTION_FILTER_MAP,
  74             methods_span,
  75             msg,
  76             help,
  77             sugg,
  78             Applicability::MachineApplicable,
  79         );
  80     }
  81 }
  82
  83 /// lint use of `filter().map()` or `find().map()` for `Iterators`
  84 #[allow(clippy::too_many_arguments)]
  85 pub(super) fn check<'tcx>(
  86     cx: &LateContext<'tcx>,
  87     expr: &hir::Expr<'_>,
  88     filter_recv: &hir::Expr<'_>,
  89     filter_arg: &hir::Expr<'_>,
  90     filter_span: Span,
  91     map_recv: &hir::Expr<'_>,
  92     map_arg: &hir::Expr<'_>,
  93     map_span: Span,
  94     is_find: bool,
  95 ) {
  96     lint_filter_some_map_unwrap(
  97         cx,
  98         expr,
  99         filter_recv,
 100         filter_arg,
 101         map_arg,
 102         map_span,
 103         filter_span.with_hi(expr.span.hi()),
 104     );
 105     if_chain! {
 106             if is_trait_method(cx, map_recv, sym::Iterator);
 107
 108             // filter(|x| ...is_some())...
 109             if let ExprKind::Closure(&Closure { body: filter_body_id, .. }) = filter_arg.kind;
 110             let filter_body = cx.tcx.hir().body(filter_body_id);
 111             if let [filter_param] = filter_body.params;
 112             // optional ref pattern: `filter(|&x| ..)`
 113             let (filter_pat, is_filter_param_ref) = if let PatKind::Ref(ref_pat, _) = filter_param.pat.kind {
 114                 (ref_pat, true)
 115             } else {
 116                 (filter_param.pat, false)
 117             };
 118             // closure ends with is_some() or is_ok()
 119             if let PatKind::Binding(_, filter_param_id, _, None) = filter_pat.kind;
 120             if let ExprKind::MethodCall(path, [filter_arg], _) = filter_body.value.kind;
 121             if let Some(opt_ty) = cx.typeck_results().expr_ty(filter_arg).ty_adt_def();
 122             if let Some(is_result) = if cx.tcx.is_diagnostic_item(sym::Option, opt_ty.did()) {
 123                 Some(false)
 124             } else if cx.tcx.is_diagnostic_item(sym::Result, opt_ty.did()) {
 125                 Some(true)
 126             } else {
 127                 None
 128             };
 129             if path.ident.name.as_str() == if is_result { "is_ok" } else { "is_some" };
 130
 131             // ...map(|x| ...unwrap())
 132             if let ExprKind::Closure(&Closure { body: map_body_id, .. }) = map_arg.kind;
 133             let map_body = cx.tcx.hir().body(map_body_id);
 134             if let [map_param] = map_body.params;
 135             if let PatKind::Binding(_, map_param_id, map_param_ident, None) = map_param.pat.kind;
 136             // closure ends with expect() or unwrap()
 137             if let ExprKind::MethodCall(seg, [map_arg, ..], _) = map_body.value.kind;
 138             if matches!(seg.ident.name, sym::expect | sym::unwrap | sym::unwrap_or);
 139
 140             let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| {
 141                 // in `filter(|x| ..)`, replace `*x` with `x`
 142                 let a_path = if_chain! {
 143                     if !is_filter_param_ref;
 144                     if let ExprKind::Unary(UnOp::Deref, expr_path) = a.kind;
 145                     then { expr_path } else { a }
 146                 };
 147                 // let the filter closure arg and the map closure arg be equal
 148                 if_chain! {
 149                     if path_to_local_id(a_path, filter_param_id);
 150                     if path_to_local_id(b, map_param_id);
 151                     if cx.typeck_results().expr_ty_adjusted(a) == cx.typeck_results().expr_ty_adjusted(b);
 152                     then {
 153                         return true;
 154                     }
 155                 }
 156                 false
 157             };
 158
 159             if match map_arg.kind {
 160                 ExprKind::MethodCall(method, [original_arg], _) => {
 161                     acceptable_methods(method)
 162                         && SpanlessEq::new(cx).expr_fallback(eq_fallback).eq_expr(filter_arg, original_arg)
 163                 },
 164                 _ => SpanlessEq::new(cx).expr_fallback(eq_fallback).eq_expr(filter_arg, map_arg)
 165             };
 166
 167             then {
 168                 let span = filter_span.with_hi(expr.span.hi());
 169                 let (filter_name, lint) = if is_find {
 170                     ("find", MANUAL_FIND_MAP)
 171                 } else {
 172                     ("filter", MANUAL_FILTER_MAP)
 173                 };
 174                 let msg = format!("`{}(..).map(..)` can be simplified as `{0}_map(..)`", filter_name);
 175                 let to_opt = if is_result { ".ok()" } else { "" };
 176                 let sugg = format!("{}_map(|{}| {}{})", filter_name, map_param_ident,
 177                     snippet(cx, map_arg.span, ".."), to_opt);
 178                 span_lint_and_sugg(cx, lint, span, &msg, "try", sugg, Applicability::MachineApplicable);
 179             }
 180     }
 181 }
 182
 183 fn acceptable_methods(method: &PathSegment<'_>) -> bool {
 184     let methods: [Symbol; 8] = [
 185         sym::clone,
 186         sym::as_ref,
 187         sym!(copied),
 188         sym!(cloned),
 189         sym!(as_deref),
 190         sym!(as_mut),
 191         sym!(as_deref_mut),
 192         sym!(to_owned),
 193     ];
 194
 195     methods.contains(&method.ident.name)
 196 }