use crate::utils::{get_parent_expr, higher, if_sequence, same_tys, snippet, span_lint_and_note, span_lint_and_then}; use crate::utils::{SpanlessEq, SpanlessHash}; use rustc::ty::Ty; use rustc_data_structures::fx::FxHashMap; use rustc_hir::*; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::symbol::Symbol; use std::collections::hash_map::Entry; use std::hash::BuildHasherDefault; declare_clippy_lint! { /// **What it does:** Checks for consecutive `if`s with the same condition. /// /// **Why is this bad?** This is probably a copy & paste error. /// /// **Known problems:** Hopefully none. /// /// **Example:** /// ```ignore /// if a == b { /// … /// } else if a == b { /// … /// } /// ``` /// /// Note that this lint ignores all conditions with a function call as it could /// have side effects: /// /// ```ignore /// if foo() { /// … /// } else if foo() { // not linted /// … /// } /// ``` pub IFS_SAME_COND, correctness, "consecutive `if`s with the same condition" } declare_clippy_lint! { /// **What it does:** Checks for consecutive `if`s with the same function call. /// /// **Why is this bad?** This is probably a copy & paste error. /// Despite the fact that function can have side effects and `if` works as /// intended, such an approach is implicit and can be considered a "code smell". /// /// **Known problems:** Hopefully none. /// /// **Example:** /// ```ignore /// if foo() == bar { /// … /// } else if foo() == bar { /// … /// } /// ``` /// /// This probably should be: /// ```ignore /// if foo() == bar { /// … /// } else if foo() == baz { /// … /// } /// ``` /// /// or if the original code was not a typo and called function mutates a state, /// consider move the mutation out of the `if` condition to avoid similarity to /// a copy & paste error: /// /// ```ignore /// let first = foo(); /// if first == bar { /// … /// } else { /// let second = foo(); /// if second == bar { /// … /// } /// } /// ``` pub SAME_FUNCTIONS_IN_IF_CONDITION, pedantic, "consecutive `if`s with the same function call" } declare_clippy_lint! { /// **What it does:** Checks for `if/else` with the same body as the *then* part /// and the *else* part. /// /// **Why is this bad?** This is probably a copy & paste error. /// /// **Known problems:** Hopefully none. /// /// **Example:** /// ```ignore /// let foo = if … { /// 42 /// } else { /// 42 /// }; /// ``` pub IF_SAME_THEN_ELSE, correctness, "`if` with the same `then` and `else` blocks" } declare_clippy_lint! { /// **What it does:** Checks for `match` with identical arm bodies. /// /// **Why is this bad?** This is probably a copy & paste error. If arm bodies /// are the same on purpose, you can factor them /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns). /// /// **Known problems:** False positive possible with order dependent `match` /// (see issue /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)). /// /// **Example:** /// ```rust,ignore /// match foo { /// Bar => bar(), /// Quz => quz(), /// Baz => bar(), // <= oops /// } /// ``` /// /// This should probably be /// ```rust,ignore /// match foo { /// Bar => bar(), /// Quz => quz(), /// Baz => baz(), // <= fixed /// } /// ``` /// /// or if the original code was not a typo: /// ```rust,ignore /// match foo { /// Bar | Baz => bar(), // <= shows the intent better /// Quz => quz(), /// } /// ``` pub MATCH_SAME_ARMS, pedantic, "`match` with identical arm bodies" } declare_lint_pass!(CopyAndPaste => [IFS_SAME_COND, SAME_FUNCTIONS_IN_IF_CONDITION, IF_SAME_THEN_ELSE, MATCH_SAME_ARMS]); impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CopyAndPaste { fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) { if !expr.span.from_expansion() { // skip ifs directly in else, it will be checked in the parent if if let Some(expr) = get_parent_expr(cx, expr) { if let Some((_, _, Some(ref else_expr))) = higher::if_block(&expr) { if else_expr.hir_id == expr.hir_id { return; } } } let (conds, blocks) = if_sequence(expr); lint_same_then_else(cx, &blocks); lint_same_cond(cx, &conds); lint_same_fns_in_if_cond(cx, &conds); lint_match_arms(cx, expr); } } } /// Implementation of `IF_SAME_THEN_ELSE`. fn lint_same_then_else(cx: &LateContext<'_, '_>, blocks: &[&Block<'_>]) { let eq: &dyn Fn(&&Block<'_>, &&Block<'_>) -> bool = &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).eq_block(lhs, rhs) }; if let Some((i, j)) = search_same_sequenced(blocks, eq) { span_lint_and_note( cx, IF_SAME_THEN_ELSE, j.span, "this `if` has identical blocks", i.span, "same as this", ); } } /// Implementation of `IFS_SAME_COND`. fn lint_same_cond(cx: &LateContext<'_, '_>, conds: &[&Expr<'_>]) { let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 { let mut h = SpanlessHash::new(cx, cx.tables); h.hash_expr(expr); h.finish() }; let eq: &dyn Fn(&&Expr<'_>, &&Expr<'_>) -> bool = &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, rhs) }; for (i, j) in search_same(conds, hash, eq) { span_lint_and_note( cx, IFS_SAME_COND, j.span, "this `if` has the same condition as a previous `if`", i.span, "same as this", ); } } /// Implementation of `SAME_FUNCTIONS_IN_IF_CONDITION`. fn lint_same_fns_in_if_cond(cx: &LateContext<'_, '_>, conds: &[&Expr<'_>]) { let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 { let mut h = SpanlessHash::new(cx, cx.tables); h.hash_expr(expr); h.finish() }; let eq: &dyn Fn(&&Expr<'_>, &&Expr<'_>) -> bool = &|&lhs, &rhs| -> bool { // Do not spawn warning if `IFS_SAME_COND` already produced it. if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, rhs) { return false; } SpanlessEq::new(cx).eq_expr(lhs, rhs) }; for (i, j) in search_same(conds, hash, eq) { span_lint_and_note( cx, SAME_FUNCTIONS_IN_IF_CONDITION, j.span, "this `if` has the same function call as a previous `if`", i.span, "same as this", ); } } /// Implementation of `MATCH_SAME_ARMS`. fn lint_match_arms<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr<'_>) { fn same_bindings<'tcx>( cx: &LateContext<'_, 'tcx>, lhs: &FxHashMap>, rhs: &FxHashMap>, ) -> bool { lhs.len() == rhs.len() && lhs .iter() .all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| same_tys(cx, l_ty, r_ty))) } if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.kind { let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 { let mut h = SpanlessHash::new(cx, cx.tables); h.hash_expr(&arm.body); h.finish() }; let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool { let min_index = usize::min(lindex, rindex); let max_index = usize::max(lindex, rindex); // Arms with a guard are ignored, those can’t always be merged together // This is also the case for arms in-between each there is an arm with a guard (min_index..=max_index).all(|index| arms[index].guard.is_none()) && SpanlessEq::new(cx).eq_expr(&lhs.body, &rhs.body) && // all patterns should have the same bindings same_bindings(cx, &bindings(cx, &lhs.pat), &bindings(cx, &rhs.pat)) }; let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect(); for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) { span_lint_and_then( cx, MATCH_SAME_ARMS, j.body.span, "this `match` has identical arm bodies", |db| { db.span_note(i.body.span, "same as this"); // Note: this does not use `span_suggestion` on purpose: // there is no clean way // to remove the other arm. Building a span and suggest to replace it to "" // makes an even more confusing error message. Also in order not to make up a // span for the whole pattern, the suggestion is only shown when there is only // one pattern. The user should know about `|` if they are already using it… let lhs = snippet(cx, i.pat.span, ""); let rhs = snippet(cx, j.pat.span, ""); if let PatKind::Wild = j.pat.kind { // if the last arm is _, then i could be integrated into _ // note that i.pat cannot be _, because that would mean that we're // hiding all the subsequent arms, and rust won't compile db.span_note( i.body.span, &format!( "`{}` has the same arm body as the `_` wildcard, consider removing it", lhs ), ); } else { db.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs)); } }, ); } } } /// Returns the list of bindings in a pattern. fn bindings<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat<'_>) -> FxHashMap> { fn bindings_impl<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat<'_>, map: &mut FxHashMap>) { match pat.kind { PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map), PatKind::TupleStruct(_, pats, _) => { for pat in pats { bindings_impl(cx, pat, map); } }, PatKind::Binding(.., ident, ref as_pat) => { if let Entry::Vacant(v) = map.entry(ident.name) { v.insert(cx.tables.pat_ty(pat)); } if let Some(ref as_pat) = *as_pat { bindings_impl(cx, as_pat, map); } }, PatKind::Or(fields) | PatKind::Tuple(fields, _) => { for pat in fields { bindings_impl(cx, pat, map); } }, PatKind::Struct(_, fields, _) => { for pat in fields { bindings_impl(cx, &pat.pat, map); } }, PatKind::Slice(lhs, ref mid, rhs) => { for pat in lhs { bindings_impl(cx, pat, map); } if let Some(ref mid) = *mid { bindings_impl(cx, mid, map); } for pat in rhs { bindings_impl(cx, pat, map); } }, PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild | PatKind::Path(..) => (), } } let mut result = FxHashMap::default(); bindings_impl(cx, pat, &mut result); result } fn search_same_sequenced(exprs: &[T], eq: Eq) -> Option<(&T, &T)> where Eq: Fn(&T, &T) -> bool, { for win in exprs.windows(2) { if eq(&win[0], &win[1]) { return Some((&win[0], &win[1])); } } None } fn search_common_cases<'a, T, Eq>(exprs: &'a [T], eq: &Eq) -> Option<(&'a T, &'a T)> where Eq: Fn(&T, &T) -> bool, { if exprs.len() == 2 && eq(&exprs[0], &exprs[1]) { Some((&exprs[0], &exprs[1])) } else { None } } fn search_same(exprs: &[T], hash: Hash, eq: Eq) -> Vec<(&T, &T)> where Hash: Fn(&T) -> u64, Eq: Fn(&T, &T) -> bool, { if let Some(expr) = search_common_cases(&exprs, &eq) { return vec![expr]; } let mut match_expr_list: Vec<(&T, &T)> = Vec::new(); let mut map: FxHashMap<_, Vec<&_>> = FxHashMap::with_capacity_and_hasher(exprs.len(), BuildHasherDefault::default()); for expr in exprs { match map.entry(hash(expr)) { Entry::Occupied(mut o) => { for o in o.get() { if eq(o, expr) { match_expr_list.push((o, expr)); } } o.get_mut().push(expr); }, Entry::Vacant(v) => { v.insert(vec![expr]); }, } } match_expr_list }