1 use crate::utils::{get_parent_expr, higher, if_sequence, same_tys, snippet, span_lint_and_then, span_note_and_lint};
2 use crate::utils::{SpanlessEq, SpanlessHash};
3 use rustc::declare_lint_pass;
5 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
7 use rustc_data_structures::fx::FxHashMap;
8 use rustc_session::declare_tool_lint;
9 use rustc_span::symbol::Symbol;
10 use std::collections::hash_map::Entry;
11 use std::hash::BuildHasherDefault;
13 declare_clippy_lint! {
14 /// **What it does:** Checks for consecutive `if`s with the same condition.
16 /// **Why is this bad?** This is probably a copy & paste error.
18 /// **Known problems:** Hopefully none.
24 /// } else if a == b {
29 /// Note that this lint ignores all conditions with a function call as it could
30 /// have side effects:
35 /// } else if foo() { // not linted
41 "consecutive `ifs` with the same condition"
44 declare_clippy_lint! {
45 /// **What it does:** Checks for consecutive `if`s with the same function call.
47 /// **Why is this bad?** This is probably a copy & paste error.
48 /// Despite the fact that function can have side effects and `if` works as
49 /// intended, such an approach is implicit and can be considered a "code smell".
51 /// **Known problems:** Hopefully none.
57 /// } else if foo() == bar {
62 /// This probably should be:
66 /// } else if foo() == baz {
71 /// or if the original code was not a typo and called function mutates a state,
72 /// consider move the mutation out of the `if` condition to avoid similarity to
73 /// a copy & paste error:
76 /// let first = foo();
80 /// let second = foo();
81 /// if second == bar {
86 pub SAME_FUNCTIONS_IN_IF_CONDITION,
88 "consecutive `ifs` with the same function call"
91 declare_clippy_lint! {
92 /// **What it does:** Checks for `if/else` with the same body as the *then* part
93 /// and the *else* part.
95 /// **Why is this bad?** This is probably a copy & paste error.
97 /// **Known problems:** Hopefully none.
107 pub IF_SAME_THEN_ELSE,
109 "if with the same *then* and *else* blocks"
112 declare_clippy_lint! {
113 /// **What it does:** Checks for `match` with identical arm bodies.
115 /// **Why is this bad?** This is probably a copy & paste error. If arm bodies
116 /// are the same on purpose, you can factor them
117 /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
119 /// **Known problems:** False positive possible with order dependent `match`
121 /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
128 /// Baz => bar(), // <= oops
132 /// This should probably be
137 /// Baz => baz(), // <= fixed
141 /// or if the original code was not a typo:
144 /// Bar | Baz => bar(), // <= shows the intent better
150 "`match` with identical arm bodies"
153 declare_lint_pass!(CopyAndPaste => [IFS_SAME_COND, SAME_FUNCTIONS_IN_IF_CONDITION, IF_SAME_THEN_ELSE, MATCH_SAME_ARMS]);
155 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CopyAndPaste {
156 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
157 if !expr.span.from_expansion() {
158 // skip ifs directly in else, it will be checked in the parent if
159 if let Some(expr) = get_parent_expr(cx, expr) {
160 if let Some((_, _, Some(ref else_expr))) = higher::if_block(&expr) {
161 if else_expr.hir_id == expr.hir_id {
167 let (conds, blocks) = if_sequence(expr);
168 lint_same_then_else(cx, &blocks);
169 lint_same_cond(cx, &conds);
170 lint_same_fns_in_if_cond(cx, &conds);
171 lint_match_arms(cx, expr);
176 /// Implementation of `IF_SAME_THEN_ELSE`.
177 fn lint_same_then_else(cx: &LateContext<'_, '_>, blocks: &[&Block<'_>]) {
178 let eq: &dyn Fn(&&Block<'_>, &&Block<'_>) -> bool =
179 &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).eq_block(lhs, rhs) };
181 if let Some((i, j)) = search_same_sequenced(blocks, eq) {
186 "this `if` has identical blocks",
193 /// Implementation of `IFS_SAME_COND`.
194 fn lint_same_cond(cx: &LateContext<'_, '_>, conds: &[&Expr<'_>]) {
195 let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 {
196 let mut h = SpanlessHash::new(cx, cx.tables);
201 let eq: &dyn Fn(&&Expr<'_>, &&Expr<'_>) -> bool =
202 &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, rhs) };
204 for (i, j) in search_same(conds, hash, eq) {
209 "this `if` has the same condition as a previous if",
216 /// Implementation of `SAME_FUNCTIONS_IN_IF_CONDITION`.
217 fn lint_same_fns_in_if_cond(cx: &LateContext<'_, '_>, conds: &[&Expr<'_>]) {
218 let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 {
219 let mut h = SpanlessHash::new(cx, cx.tables);
224 let eq: &dyn Fn(&&Expr<'_>, &&Expr<'_>) -> bool = &|&lhs, &rhs| -> bool {
225 // Do not spawn warning if `IFS_SAME_COND` already produced it.
226 if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, rhs) {
229 SpanlessEq::new(cx).eq_expr(lhs, rhs)
232 for (i, j) in search_same(conds, hash, eq) {
235 SAME_FUNCTIONS_IN_IF_CONDITION,
237 "this `if` has the same function call as a previous if",
244 /// Implementation of `MATCH_SAME_ARMS`.
245 fn lint_match_arms<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr<'_>) {
246 fn same_bindings<'tcx>(
247 cx: &LateContext<'_, 'tcx>,
248 lhs: &FxHashMap<Symbol, Ty<'tcx>>,
249 rhs: &FxHashMap<Symbol, Ty<'tcx>>,
251 lhs.len() == rhs.len()
254 .all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| same_tys(cx, l_ty, r_ty)))
257 if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.kind {
258 let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
259 let mut h = SpanlessHash::new(cx, cx.tables);
260 h.hash_expr(&arm.body);
264 let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
265 let min_index = usize::min(lindex, rindex);
266 let max_index = usize::max(lindex, rindex);
268 // Arms with a guard are ignored, those can’t always be merged together
269 // This is also the case for arms in-between each there is an arm with a guard
270 (min_index..=max_index).all(|index| arms[index].guard.is_none()) &&
271 SpanlessEq::new(cx).eq_expr(&lhs.body, &rhs.body) &&
272 // all patterns should have the same bindings
273 same_bindings(cx, &bindings(cx, &lhs.pat), &bindings(cx, &rhs.pat))
276 let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
277 for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
282 "this `match` has identical arm bodies",
284 db.span_note(i.body.span, "same as this");
286 // Note: this does not use `span_suggestion` on purpose:
287 // there is no clean way
288 // to remove the other arm. Building a span and suggest to replace it to ""
289 // makes an even more confusing error message. Also in order not to make up a
290 // span for the whole pattern, the suggestion is only shown when there is only
291 // one pattern. The user should know about `|` if they are already using it…
293 let lhs = snippet(cx, i.pat.span, "<pat1>");
294 let rhs = snippet(cx, j.pat.span, "<pat2>");
296 if let PatKind::Wild = j.pat.kind {
297 // if the last arm is _, then i could be integrated into _
298 // note that i.pat cannot be _, because that would mean that we're
299 // hiding all the subsequent arms, and rust won't compile
303 "`{}` has the same arm body as the `_` wildcard, consider removing it`",
308 db.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs));
316 /// Returns the list of bindings in a pattern.
317 fn bindings<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat<'_>) -> FxHashMap<Symbol, Ty<'tcx>> {
318 fn bindings_impl<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat<'_>, map: &mut FxHashMap<Symbol, Ty<'tcx>>) {
320 PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
321 PatKind::TupleStruct(_, pats, _) => {
323 bindings_impl(cx, pat, map);
326 PatKind::Binding(.., ident, ref as_pat) => {
327 if let Entry::Vacant(v) = map.entry(ident.name) {
328 v.insert(cx.tables.pat_ty(pat));
330 if let Some(ref as_pat) = *as_pat {
331 bindings_impl(cx, as_pat, map);
334 PatKind::Or(fields) | PatKind::Tuple(fields, _) => {
336 bindings_impl(cx, pat, map);
339 PatKind::Struct(_, fields, _) => {
341 bindings_impl(cx, &pat.pat, map);
344 PatKind::Slice(lhs, ref mid, rhs) => {
346 bindings_impl(cx, pat, map);
348 if let Some(ref mid) = *mid {
349 bindings_impl(cx, mid, map);
352 bindings_impl(cx, pat, map);
355 PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild | PatKind::Path(..) => (),
359 let mut result = FxHashMap::default();
360 bindings_impl(cx, pat, &mut result);
364 fn search_same_sequenced<T, Eq>(exprs: &[T], eq: Eq) -> Option<(&T, &T)>
366 Eq: Fn(&T, &T) -> bool,
368 for win in exprs.windows(2) {
369 if eq(&win[0], &win[1]) {
370 return Some((&win[0], &win[1]));
376 fn search_common_cases<'a, T, Eq>(exprs: &'a [T], eq: &Eq) -> Option<(&'a T, &'a T)>
378 Eq: Fn(&T, &T) -> bool,
380 if exprs.len() == 2 && eq(&exprs[0], &exprs[1]) {
381 Some((&exprs[0], &exprs[1]))
387 fn search_same<T, Hash, Eq>(exprs: &[T], hash: Hash, eq: Eq) -> Vec<(&T, &T)>
390 Eq: Fn(&T, &T) -> bool,
392 if let Some(expr) = search_common_cases(&exprs, &eq) {
396 let mut match_expr_list: Vec<(&T, &T)> = Vec::new();
398 let mut map: FxHashMap<_, Vec<&_>> =
399 FxHashMap::with_capacity_and_hasher(exprs.len(), BuildHasherDefault::default());
402 match map.entry(hash(expr)) {
403 Entry::Occupied(mut o) => {
406 match_expr_list.push((o, expr));
409 o.get_mut().push(expr);
411 Entry::Vacant(v) => {
412 v.insert(vec![expr]);