1 use clippy_utils::diagnostics::{span_lint_and_note, span_lint_and_then};
2 use clippy_utils::source::{first_line_of_span, indent_of, reindent_multiline, snippet, snippet_opt};
4 both, count_eq, eq_expr_value, get_enclosing_block, get_parent_expr, if_sequence, in_macro, is_else_clause,
5 is_lint_allowed, search_same, ContainsName, SpanlessEq, SpanlessHash,
7 use if_chain::if_chain;
8 use rustc_data_structures::fx::FxHashSet;
9 use rustc_errors::{Applicability, DiagnosticBuilder};
10 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
11 use rustc_hir::{Block, Expr, ExprKind, HirId};
12 use rustc_lint::{LateContext, LateLintPass};
13 use rustc_middle::hir::map::Map;
14 use rustc_session::{declare_lint_pass, declare_tool_lint};
15 use rustc_span::{source_map::Span, symbol::Symbol, BytePos};
18 declare_clippy_lint! {
19 /// **What it does:** Checks for consecutive `if`s with the same condition.
21 /// **Why is this bad?** This is probably a copy & paste error.
23 /// **Known problems:** Hopefully none.
29 /// } else if a == b {
34 /// Note that this lint ignores all conditions with a function call as it could
35 /// have side effects:
40 /// } else if foo() { // not linted
46 "consecutive `if`s with the same condition"
49 declare_clippy_lint! {
50 /// **What it does:** Checks for consecutive `if`s with the same function call.
52 /// **Why is this bad?** This is probably a copy & paste error.
53 /// Despite the fact that function can have side effects and `if` works as
54 /// intended, such an approach is implicit and can be considered a "code smell".
56 /// **Known problems:** Hopefully none.
62 /// } else if foo() == bar {
67 /// This probably should be:
71 /// } else if foo() == baz {
76 /// or if the original code was not a typo and called function mutates a state,
77 /// consider move the mutation out of the `if` condition to avoid similarity to
78 /// a copy & paste error:
81 /// let first = foo();
85 /// let second = foo();
86 /// if second == bar {
91 pub SAME_FUNCTIONS_IN_IF_CONDITION,
93 "consecutive `if`s with the same function call"
96 declare_clippy_lint! {
97 /// **What it does:** Checks for `if/else` with the same body as the *then* part
98 /// and the *else* part.
100 /// **Why is this bad?** This is probably a copy & paste error.
102 /// **Known problems:** Hopefully none.
112 pub IF_SAME_THEN_ELSE,
114 "`if` with the same `then` and `else` blocks"
117 declare_clippy_lint! {
118 /// **What it does:** Checks if the `if` and `else` block contain shared code that can be
119 /// moved out of the blocks.
121 /// **Why is this bad?** Duplicate code is less maintainable.
123 /// **Known problems:**
124 /// * The lint doesn't check if the moved expressions modify values that are beeing used in
125 /// the if condition. The suggestion can in that case modify the behavior of the program.
126 /// See [rust-clippy#7452](https://github.com/rust-lang/rust-clippy/issues/7452)
131 /// println!("Hello World");
134 /// println!("Hello World");
139 /// Could be written as:
141 /// println!("Hello World");
148 pub BRANCHES_SHARING_CODE,
150 "`if` statement with shared code in all blocks"
153 declare_lint_pass!(CopyAndPaste => [
155 SAME_FUNCTIONS_IN_IF_CONDITION,
157 BRANCHES_SHARING_CODE
160 impl<'tcx> LateLintPass<'tcx> for CopyAndPaste {
161 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
162 if !expr.span.from_expansion() {
163 if let ExprKind::If(_, _, _) = expr.kind {
164 // skip ifs directly in else, it will be checked in the parent if
166 kind: ExprKind::If(_, _, Some(else_expr)),
168 }) = get_parent_expr(cx, expr)
170 if else_expr.hir_id == expr.hir_id {
175 let (conds, blocks) = if_sequence(expr);
177 lint_same_cond(cx, &conds);
178 lint_same_fns_in_if_cond(cx, &conds);
180 lint_same_then_else(cx, &blocks, conds.len() == blocks.len(), expr);
186 /// Implementation of `BRANCHES_SHARING_CODE` and `IF_SAME_THEN_ELSE` if the blocks are equal.
187 fn lint_same_then_else<'tcx>(
188 cx: &LateContext<'tcx>,
189 blocks: &[&Block<'tcx>],
190 has_conditional_else: bool,
191 expr: &'tcx Expr<'_>,
193 // We only lint ifs with multiple blocks
194 if blocks.len() < 2 || is_else_clause(cx.tcx, expr) {
198 // Check if each block has shared code
199 let has_expr = blocks[0].expr.is_some();
201 let (start_eq, mut end_eq, expr_eq) = if let Some(block_eq) = scan_block_for_eq(cx, blocks) {
202 (block_eq.start_eq, block_eq.end_eq, block_eq.expr_eq)
207 // BRANCHES_SHARING_CODE prerequisites
208 if has_conditional_else || (start_eq == 0 && end_eq == 0 && (has_expr && !expr_eq)) {
212 // Only the start is the same
213 if start_eq != 0 && end_eq == 0 && (!has_expr || !expr_eq) {
214 let block = blocks[0];
215 let start_stmts = block.stmts.split_at(start_eq).0;
217 let mut start_walker = UsedValueFinderVisitor::new(cx);
218 for stmt in start_stmts {
219 intravisit::walk_stmt(&mut start_walker, stmt);
222 emit_branches_sharing_code_lint(
227 check_for_warn_of_moved_symbol(cx, &start_walker.def_symbols, expr),
231 } else if end_eq != 0 || (has_expr && expr_eq) {
232 let block = blocks[blocks.len() - 1];
233 let (start_stmts, block_stmts) = block.stmts.split_at(start_eq);
234 let (block_stmts, end_stmts) = block_stmts.split_at(block_stmts.len() - end_eq);
237 let mut start_walker = UsedValueFinderVisitor::new(cx);
238 for stmt in start_stmts {
239 intravisit::walk_stmt(&mut start_walker, stmt);
241 let mut moved_syms = start_walker.def_symbols;
244 let mut block_walker = UsedValueFinderVisitor::new(cx);
245 for stmt in block_stmts {
246 intravisit::walk_stmt(&mut block_walker, stmt);
248 let mut block_defs = block_walker.defs;
251 let mut moved_start: Option<usize> = None;
252 let mut end_walker = UsedValueFinderVisitor::new(cx);
253 for (index, stmt) in end_stmts.iter().enumerate() {
254 intravisit::walk_stmt(&mut end_walker, stmt);
256 for value in &end_walker.uses {
257 // Well we can't move this and all prev statements. So reset
258 if block_defs.contains(value) {
259 moved_start = Some(index + 1);
260 end_walker.defs.drain().for_each(|x| {
261 block_defs.insert(x);
264 end_walker.def_symbols.clear();
268 end_walker.uses.clear();
271 if let Some(moved_start) = moved_start {
272 end_eq -= moved_start;
275 let end_linable = block.expr.map_or_else(
278 intravisit::walk_expr(&mut end_walker, expr);
279 end_walker.uses.iter().any(|x| !block_defs.contains(x))
284 end_walker.def_symbols.drain().for_each(|x| {
285 moved_syms.insert(x);
289 emit_branches_sharing_code_lint(
294 check_for_warn_of_moved_symbol(cx, &moved_syms, expr),
302 /// The amount statements that are equal from the start
304 /// The amount statements that are equal from the end
306 /// An indication if the block expressions are the same. This will also be true if both are
311 /// This function can also trigger the `IF_SAME_THEN_ELSE` in which case it'll return `None` to
312 /// abort any further processing and avoid duplicate lint triggers.
313 fn scan_block_for_eq(cx: &LateContext<'tcx>, blocks: &[&Block<'tcx>]) -> Option<BlockEqual> {
314 let mut start_eq = usize::MAX;
315 let mut end_eq = usize::MAX;
316 let mut expr_eq = true;
317 for win in blocks.windows(2) {
318 let l_stmts = win[0].stmts;
319 let r_stmts = win[1].stmts;
321 // `SpanlessEq` now keeps track of the locals and is therefore context sensitive clippy#6752.
322 // The comparison therefore needs to be done in a way that builds the correct context.
323 let mut evaluator = SpanlessEq::new(cx);
324 let mut evaluator = evaluator.inter_expr();
326 let current_start_eq = count_eq(&mut l_stmts.iter(), &mut r_stmts.iter(), |l, r| evaluator.eq_stmt(l, r));
328 let current_end_eq = {
329 // We skip the middle statements which can't be equal
330 let end_comparison_count = l_stmts.len().min(r_stmts.len()) - current_start_eq;
331 let it1 = l_stmts.iter().skip(l_stmts.len() - end_comparison_count);
332 let it2 = r_stmts.iter().skip(r_stmts.len() - end_comparison_count);
334 .fold(0, |acc, (l, r)| if evaluator.eq_stmt(l, r) { acc + 1 } else { 0 })
336 let block_expr_eq = both(&win[0].expr, &win[1].expr, |l, r| evaluator.eq_expr(l, r));
341 if l_stmts.len() == r_stmts.len();
342 if l_stmts.len() == current_start_eq;
343 if !is_lint_allowed(cx, IF_SAME_THEN_ELSE, win[0].hir_id);
344 if !is_lint_allowed(cx, IF_SAME_THEN_ELSE, win[1].hir_id);
350 "this `if` has identical blocks",
359 start_eq = start_eq.min(current_start_eq);
360 end_eq = end_eq.min(current_end_eq);
361 expr_eq &= block_expr_eq;
368 // Check if the regions are overlapping. Set `end_eq` to prevent the overlap
369 let min_block_size = blocks.iter().map(|x| x.stmts.len()).min().unwrap();
370 if (start_eq + end_eq) > min_block_size {
371 end_eq = min_block_size - start_eq;
381 fn check_for_warn_of_moved_symbol(
382 cx: &LateContext<'tcx>,
383 symbols: &FxHashSet<Symbol>,
384 if_expr: &'tcx Expr<'_>,
386 get_enclosing_block(cx, if_expr.hir_id).map_or(false, |block| {
387 let ignore_span = block.span.shrink_to_lo().to(if_expr.span);
391 .filter(|sym| !sym.as_str().starts_with('_'))
393 let mut walker = ContainsName {
402 .filter(|stmt| !ignore_span.overlaps(stmt.span))
403 .for_each(|stmt| intravisit::walk_stmt(&mut walker, stmt));
405 if let Some(expr) = block.expr {
406 intravisit::walk_expr(&mut walker, expr);
414 fn emit_branches_sharing_code_lint(
415 cx: &LateContext<'tcx>,
419 warn_about_moved_symbol: bool,
420 blocks: &[&Block<'tcx>],
421 if_expr: &'tcx Expr<'_>,
423 if start_stmts == 0 && !lint_end {
427 // (help, span, suggestion)
428 let mut suggestions: Vec<(&str, Span, String)> = vec![];
429 let mut add_expr_note = false;
431 // Construct suggestions
433 let block = blocks[0];
434 let span_start = first_line_of_span(cx, if_expr.span).shrink_to_lo();
435 let span_end = block.stmts[start_stmts - 1].span.source_callsite();
437 let cond_span = first_line_of_span(cx, if_expr.span).until(block.span);
438 let cond_snippet = reindent_multiline(snippet(cx, cond_span, "_"), false, None);
439 let cond_indent = indent_of(cx, cond_span);
440 let moved_span = block.stmts[0].span.source_callsite().to(span_end);
441 let moved_snippet = reindent_multiline(snippet(cx, moved_span, "_"), true, None);
442 let suggestion = moved_snippet.to_string() + "\n" + &cond_snippet + "{";
443 let suggestion = reindent_multiline(Cow::Borrowed(&suggestion), true, cond_indent);
445 let span = span_start.to(span_end);
446 suggestions.push(("start", span, suggestion.to_string()));
450 let block = blocks[blocks.len() - 1];
451 let span_end = block.span.shrink_to_hi();
453 let moved_start = if end_stmts == 0 && block.expr.is_some() {
454 block.expr.unwrap().span
456 block.stmts[block.stmts.len() - end_stmts].span
459 let moved_end = block
461 .map_or_else(|| block.stmts[block.stmts.len() - 1].span, |expr| expr.span)
464 let moved_span = moved_start.to(moved_end);
465 let moved_snipped = reindent_multiline(snippet(cx, moved_span, "_"), true, None);
466 let indent = indent_of(cx, if_expr.span.shrink_to_hi());
467 let suggestion = "}\n".to_string() + &moved_snipped;
468 let suggestion = reindent_multiline(Cow::Borrowed(&suggestion), true, indent);
470 let mut span = moved_start.to(span_end);
471 // Improve formatting if the inner block has indention (i.e. normal Rust formatting)
472 let test_span = Span::new(span.lo() - BytePos(4), span.lo(), span.ctxt());
473 if snippet_opt(cx, test_span)
474 .map(|snip| snip == " ")
477 span = span.with_lo(test_span.lo());
480 suggestions.push(("end", span, suggestion.to_string()));
481 add_expr_note = !cx.typeck_results().expr_ty(if_expr).is_unit();
484 let add_optional_msgs = |diag: &mut DiagnosticBuilder<'_>| {
486 diag.note("The end suggestion probably needs some adjustments to use the expression result correctly");
489 if warn_about_moved_symbol {
490 diag.warn("Some moved values might need to be renamed to avoid wrong references");
495 if suggestions.len() == 1 {
496 let (place_str, span, sugg) = suggestions.pop().unwrap();
497 let msg = format!("all if blocks contain the same code at the {}", place_str);
498 let help = format!("consider moving the {} statements out like this", place_str);
499 span_lint_and_then(cx, BRANCHES_SHARING_CODE, span, msg.as_str(), |diag| {
500 diag.span_suggestion(span, help.as_str(), sugg, Applicability::Unspecified);
502 add_optional_msgs(diag);
504 } else if suggestions.len() == 2 {
505 let (_, end_span, end_sugg) = suggestions.pop().unwrap();
506 let (_, start_span, start_sugg) = suggestions.pop().unwrap();
509 BRANCHES_SHARING_CODE,
511 "all if blocks contain the same code at the start and the end. Here at the start",
513 diag.span_note(end_span, "and here at the end");
515 diag.span_suggestion(
517 "consider moving the start statements out like this",
519 Applicability::Unspecified,
522 diag.span_suggestion(
524 "and consider moving the end statements out like this",
526 Applicability::Unspecified,
529 add_optional_msgs(diag);
535 /// This visitor collects `HirId`s and Symbols of defined symbols and `HirId`s of used values.
536 struct UsedValueFinderVisitor<'a, 'tcx> {
537 cx: &'a LateContext<'tcx>,
539 /// The `HirId`s of defined values in the scanned statements
540 defs: FxHashSet<HirId>,
542 /// The Symbols of the defined symbols in the scanned statements
543 def_symbols: FxHashSet<Symbol>,
545 /// The `HirId`s of the used values
546 uses: FxHashSet<HirId>,
549 impl<'a, 'tcx> UsedValueFinderVisitor<'a, 'tcx> {
550 fn new(cx: &'a LateContext<'tcx>) -> Self {
551 UsedValueFinderVisitor {
553 defs: FxHashSet::default(),
554 def_symbols: FxHashSet::default(),
555 uses: FxHashSet::default(),
560 impl<'a, 'tcx> Visitor<'tcx> for UsedValueFinderVisitor<'a, 'tcx> {
561 type Map = Map<'tcx>;
563 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
564 NestedVisitorMap::All(self.cx.tcx.hir())
567 fn visit_local(&mut self, l: &'tcx rustc_hir::Local<'tcx>) {
568 let local_id = l.pat.hir_id;
569 self.defs.insert(local_id);
571 if let Some(sym) = l.pat.simple_ident() {
572 self.def_symbols.insert(sym.name);
575 if let Some(expr) = l.init {
576 intravisit::walk_expr(self, expr);
580 fn visit_qpath(&mut self, qpath: &'tcx rustc_hir::QPath<'tcx>, id: HirId, _span: rustc_span::Span) {
581 if let rustc_hir::QPath::Resolved(_, path) = *qpath {
582 if path.segments.len() == 1 {
583 if let rustc_hir::def::Res::Local(var) = self.cx.qpath_res(qpath, id) {
584 self.uses.insert(var);
591 /// Implementation of `IFS_SAME_COND`.
592 fn lint_same_cond(cx: &LateContext<'_>, conds: &[&Expr<'_>]) {
593 let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 {
594 let mut h = SpanlessHash::new(cx);
599 let eq: &dyn Fn(&&Expr<'_>, &&Expr<'_>) -> bool = &|&lhs, &rhs| -> bool { eq_expr_value(cx, lhs, rhs) };
601 for (i, j) in search_same(conds, hash, eq) {
606 "this `if` has the same condition as a previous `if`",
613 /// Implementation of `SAME_FUNCTIONS_IN_IF_CONDITION`.
614 fn lint_same_fns_in_if_cond(cx: &LateContext<'_>, conds: &[&Expr<'_>]) {
615 let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 {
616 let mut h = SpanlessHash::new(cx);
621 let eq: &dyn Fn(&&Expr<'_>, &&Expr<'_>) -> bool = &|&lhs, &rhs| -> bool {
622 // Do not lint if any expr originates from a macro
623 if in_macro(lhs.span) || in_macro(rhs.span) {
626 // Do not spawn warning if `IFS_SAME_COND` already produced it.
627 if eq_expr_value(cx, lhs, rhs) {
630 SpanlessEq::new(cx).eq_expr(lhs, rhs)
633 for (i, j) in search_same(conds, hash, eq) {
636 SAME_FUNCTIONS_IN_IF_CONDITION,
638 "this `if` has the same function call as a previous `if`",