diff options
| -rw-r--r-- | CHANGELOG.md | 1 | ||||
| -rw-r--r-- | clippy_lints/src/lib.rs | 3 | ||||
| -rw-r--r-- | clippy_lints/src/loops.rs | 265 | ||||
| -rw-r--r-- | src/lintlist/mod.rs | 7 | ||||
| -rw-r--r-- | tests/ui/same_item_push.rs | 77 | ||||
| -rw-r--r-- | tests/ui/same_item_push.stderr | 35 |
6 files changed, 388 insertions, 0 deletions
diff --git a/CHANGELOG.md b/CHANGELOG.md index 43d83d978b8..fbc783f1c2c 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -1687,6 +1687,7 @@ Released 2018-09-13 [`result_map_unit_fn`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_map_unit_fn [`reversed_empty_ranges`]: https://rust-lang.github.io/rust-clippy/master/index.html#reversed_empty_ranges [`same_functions_in_if_condition`]: https://rust-lang.github.io/rust-clippy/master/index.html#same_functions_in_if_condition +[`same_item_push`]: https://rust-lang.github.io/rust-clippy/master/index.html#same_item_push [`search_is_some`]: https://rust-lang.github.io/rust-clippy/master/index.html#search_is_some [`serde_api_misuse`]: https://rust-lang.github.io/rust-clippy/master/index.html#serde_api_misuse [`shadow_reuse`]: https://rust-lang.github.io/rust-clippy/master/index.html#shadow_reuse diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 26aff6af8cd..2bd5ae0ed98 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -610,6 +610,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: &loops::WHILE_IMMUTABLE_CONDITION, &loops::WHILE_LET_LOOP, &loops::WHILE_LET_ON_ITERATOR, + &loops::SAME_ITEM_PUSH, ¯o_use::MACRO_USE_IMPORTS, &main_recursion::MAIN_RECURSION, &manual_async_fn::MANUAL_ASYNC_FN, @@ -1405,6 +1406,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&repeat_once::REPEAT_ONCE), LintId::of(&returns::NEEDLESS_RETURN), LintId::of(&returns::UNUSED_UNIT), + LintId::of(&loops::SAME_ITEM_PUSH), LintId::of(&serde_api::SERDE_API_MISUSE), LintId::of(&single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS), LintId::of(&slow_vector_initialization::SLOW_VECTOR_INITIALIZATION), @@ -1543,6 +1545,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(®ex::TRIVIAL_REGEX), LintId::of(&returns::NEEDLESS_RETURN), LintId::of(&returns::UNUSED_UNIT), + LintId::of(&loops::SAME_ITEM_PUSH), LintId::of(&single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS), LintId::of(&strings::STRING_LIT_AS_BYTES), LintId::of(&tabs_in_doc_comments::TABS_IN_DOC_COMMENTS), diff --git a/clippy_lints/src/loops.rs b/clippy_lints/src/loops.rs index 6359c20040c..48891a59c00 100644 --- a/clippy_lints/src/loops.rs +++ b/clippy_lints/src/loops.rs @@ -419,6 +419,39 @@ declare_clippy_lint! { "variables used within while expression are not mutated in the body" } +declare_clippy_lint! { + /// **What it does:** Checks whether a for loop is being used to push a constant + /// value into a Vec. + /// + /// **Why is this bad?** This kind of operation can be expressed more succinctly with + /// `vec![item;SIZE]` or `vec.resize(NEW_SIZE, item)` and using these alternatives may also + /// have better performance. + /// **Known problems:** None + /// + /// **Example:** + /// ```rust + /// let item1 = 2; + /// let item2 = 3; + /// let mut vec: Vec<u8> = Vec::new(); + /// for _ in 0..20 { + /// vec.push(item1); + /// } + /// for _ in 0..30 { + /// vec.push(item2); + /// } + /// ``` + /// could be written as + /// ```rust + /// let item1 = 2; + /// let item2 = 3; + /// let mut vec: Vec<u8> = vec![item1; 20]; + /// vec.resize(20 + 30, item2); + /// ``` + pub SAME_ITEM_PUSH, + style, + "the same item is pushed inside of a for loop" +} + declare_lint_pass!(Loops => [ MANUAL_MEMCPY, NEEDLESS_RANGE_LOOP, @@ -435,6 +468,7 @@ declare_lint_pass!(Loops => [ NEVER_LOOP, MUT_RANGE_BOUND, WHILE_IMMUTABLE_CONDITION, + SAME_ITEM_PUSH, ]); impl<'tcx> LateLintPass<'tcx> for Loops { @@ -740,6 +774,7 @@ fn check_for_loop<'tcx>( check_for_loop_over_map_kv(cx, pat, arg, body, expr); check_for_mut_range_bound(cx, arg, body); detect_manual_memcpy(cx, pat, arg, body, expr); + detect_same_item_push(cx, pat, arg, body, expr); } fn same_var<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, var: HirId) -> bool { @@ -1016,6 +1051,236 @@ fn detect_manual_memcpy<'tcx>( } } +// Delegate that traverses expression and detects mutable variables being used +struct UsesMutableDelegate { + found_mutable: bool, +} + +impl<'tcx> Delegate<'tcx> for UsesMutableDelegate { + fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: ConsumeMode) {} + + fn borrow(&mut self, _: &PlaceWithHirId<'tcx>, bk: ty::BorrowKind) { + // Mutable variable is found + if let ty::BorrowKind::MutBorrow = bk { + self.found_mutable = true; + } + } + + fn mutate(&mut self, _: &PlaceWithHirId<'tcx>) {} +} + +// Uses UsesMutableDelegate to find mutable variables in an expression expr +fn has_mutable_variables<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool { + let mut delegate = UsesMutableDelegate { found_mutable: false }; + let def_id = expr.hir_id.owner.to_def_id(); + cx.tcx.infer_ctxt().enter(|infcx| { + ExprUseVisitor::new( + &mut delegate, + &infcx, + def_id.expect_local(), + cx.param_env, + cx.tables(), + ).walk_expr(expr); + }); + + delegate.found_mutable +} + +// Scans for the usage of the for loop pattern +struct ForPatternVisitor<'a, 'tcx> { + found_pattern: bool, + // Pattern that we are searching for + for_pattern: &'a Pat<'tcx>, + cx: &'a LateContext<'tcx>, +} + +impl<'a, 'tcx> Visitor<'tcx> for ForPatternVisitor<'a, 'tcx> { + type Map = Map<'tcx>; + + fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { + // Recursively explore an expression until a ExprKind::Path is found + match &expr.kind { + ExprKind::Array(expr_list) | ExprKind::MethodCall(_, _, expr_list, _) | ExprKind::Tup(expr_list) => { + for expr in *expr_list { + self.visit_expr(expr) + } + }, + ExprKind::Binary(_, lhs_expr, rhs_expr) => { + self.visit_expr(lhs_expr); + self.visit_expr(rhs_expr); + }, + ExprKind::Box(expr) + | ExprKind::Unary(_, expr) + | ExprKind::Cast(expr, _) + | ExprKind::Type(expr, _) + | ExprKind::AddrOf(_, _, expr) + | ExprKind::Struct(_, _, Some(expr)) => self.visit_expr(expr), + _ => { + // Exploration cannot continue ... calculate the hir_id of the current + // expr assuming it is a Path + if let Some(hir_id) = var_def_id(self.cx, &expr) { + // Pattern is found + if hir_id == self.for_pattern.hir_id { + self.found_pattern = true; + } + // If the for loop pattern is a tuple, determine whether the current + // expr is inside that tuple pattern + if let PatKind::Tuple(pat_list, _) = &self.for_pattern.kind { + let hir_id_list: Vec<HirId> = pat_list.iter().map(|p| p.hir_id).collect(); + if hir_id_list.contains(&hir_id) { + self.found_pattern = true; + } + } + } + }, + } + } + + // This is triggered by walk_expr() for the case of vec.push(pat) + fn visit_qpath(&mut self, qpath: &'tcx QPath<'_>, _: HirId, _: Span) { + if_chain! { + if let QPath::Resolved(_, path) = qpath; + if let Res::Local(hir_id) = &path.res; + then { + if *hir_id == self.for_pattern.hir_id{ + self.found_pattern = true; + } + + if let PatKind::Tuple(pat_list, _) = &self.for_pattern.kind { + let hir_id_list: Vec<HirId> = pat_list.iter().map(|p| p.hir_id).collect(); + if hir_id_list.contains(&hir_id) { + self.found_pattern = true; + } + } + } + } + } + + fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { + NestedVisitorMap::None + } +} + +// Scans the body of the for loop and determines whether lint should be given +struct SameItemPushVisitor<'a, 'tcx> { + should_lint: bool, + // this field holds the last vec push operation visited, which should be the only push seen + vec_push: Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)>, + cx: &'a LateContext<'tcx>, +} + +impl<'a, 'tcx> Visitor<'tcx> for SameItemPushVisitor<'a, 'tcx> { + type Map = Map<'tcx>; + + fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { + match &expr.kind { + // Non-determinism may occur ... don't give a lint + ExprKind::Loop(_, _, _) | ExprKind::Match(_, _, _) => self.should_lint = false, + ExprKind::Block(block, _) => self.visit_block(block), + _ => {}, + } + } + + fn visit_block(&mut self, b: &'tcx Block<'_>) { + for stmt in b.stmts.iter() { + self.visit_stmt(stmt); + } + } + + fn visit_stmt(&mut self, s: &'tcx Stmt<'_>) { + let vec_push_option = get_vec_push(self.cx, s); + if vec_push_option.is_none() { + // Current statement is not a push so visit inside + match &s.kind { + StmtKind::Expr(expr) | StmtKind::Semi(expr) => self.visit_expr(&expr), + _ => {}, + } + } else { + // Current statement is a push ...check whether another + // push had been previously done + if self.vec_push.is_none() { + self.vec_push = vec_push_option; + } else { + // There are multiple pushes ... don't lint + self.should_lint = false; + } + } + } + + fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { + NestedVisitorMap::None + } +} + +// Given some statement, determine if that statement is a push on a Vec. If it is, return +// the Vec being pushed into and the item being pushed +fn get_vec_push<'tcx>(cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> { + if_chain! { + // Extract method being called + if let StmtKind::Semi(semi_stmt) = &stmt.kind; + if let ExprKind::MethodCall(path, _, args, _) = &semi_stmt.kind; + // Figure out the parameters for the method call + if let Some(self_expr) = args.get(0); + if let Some(pushed_item) = args.get(1); + // Check that the method being called is push() on a Vec + if match_type(cx, cx.tables().expr_ty(self_expr), &paths::VEC); + if path.ident.name.as_str() == "push"; + then { + return Some((self_expr, pushed_item)) + } + } + None +} + +/// Detects for loop pushing the same item into a Vec +fn detect_same_item_push<'tcx>( + cx: &LateContext<'tcx>, + pat: &'tcx Pat<'_>, + _: &'tcx Expr<'_>, + body: &'tcx Expr<'_>, + _: &'tcx Expr<'_>, +) { + // Determine whether it is safe to lint the body + let mut same_item_push_visitor = SameItemPushVisitor { + should_lint: true, + vec_push: None, + cx, + }; + walk_expr(&mut same_item_push_visitor, body); + if same_item_push_visitor.should_lint { + if let Some((vec, pushed_item)) = same_item_push_visitor.vec_push { + // Make sure that the push does not involve possibly mutating values + if !has_mutable_variables(cx, pushed_item) { + // Walk through the expression being pushed and make sure that it + // does not contain the for loop pattern + let mut for_pat_visitor = ForPatternVisitor { + found_pattern: false, + for_pattern: pat, + cx, + }; + walk_expr(&mut for_pat_visitor, pushed_item); + + if !for_pat_visitor.found_pattern { + let vec_str = snippet(cx, vec.span, ""); + let item_str = snippet(cx, pushed_item.span, ""); + + span_lint_and_help( + cx, + SAME_ITEM_PUSH, + vec.span, + "it looks like the same item is being pushed into this Vec", + None, + &format!( + "try using vec![{};SIZE] or {}.resize(NEW_SIZE, {})", + item_str, vec_str, item_str + ), + ) + } + } + } + } +} + /// Checks for looping over a range and then indexing a sequence with it. /// The iteratee must be a range literal. #[allow(clippy::too_many_lines)] diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index a08d7da6dcb..1b10226c930 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -1936,6 +1936,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![ module: "copies", }, Lint { + name: "same_item_push", + group: "style", + desc: "default lint description", + deprecation: None, + module: "same_item_push", + }, + Lint { name: "search_is_some", group: "complexity", desc: "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`", diff --git a/tests/ui/same_item_push.rs b/tests/ui/same_item_push.rs new file mode 100644 index 00000000000..e3a5a647f76 --- /dev/null +++ b/tests/ui/same_item_push.rs @@ -0,0 +1,77 @@ +#![warn(clippy::same_item_push)] + +fn mutate_increment(x: &mut u8) -> u8 { + *x += 1; + *x +} + +fn increment(x: u8) -> u8 { + x + 1 +} + +fn main() { + // Test for basic case + let mut spaces = Vec::with_capacity(10); + for _ in 0..10 { + spaces.push(vec![b' ']); + } + + let mut vec2: Vec<u8> = Vec::new(); + let item = 2; + for _ in 5..=20 { + vec2.push(item); + } + + let mut vec3: Vec<u8> = Vec::new(); + for _ in 0..15 { + let item = 2; + vec3.push(item); + } + + let mut vec4: Vec<u8> = Vec::new(); + for _ in 0..15 { + vec4.push(13); + } + + // Suggestion should not be given as pushed variable can mutate + let mut vec5: Vec<u8> = Vec::new(); + let mut item: u8 = 2; + for _ in 0..30 { + vec5.push(mutate_increment(&mut item)); + } + + let mut vec6: Vec<u8> = Vec::new(); + let mut item: u8 = 2; + let mut item2 = &mut mutate_increment(&mut item); + for _ in 0..30 { + vec6.push(mutate_increment(item2)); + } + + let mut vec7: Vec<usize> = Vec::new(); + for (a, b) in [0, 1, 4, 9, 16].iter().enumerate() { + vec7.push(a); + } + + let mut vec8: Vec<u8> = Vec::new(); + for i in 0..30 { + vec8.push(increment(i)); + } + + let mut vec9: Vec<u8> = Vec::new(); + for i in 0..30 { + vec9.push(i + i * i); + } + + // Suggestion should not be given as there are multiple pushes that are not the same + let mut vec10: Vec<u8> = Vec::new(); + let item: u8 = 2; + for _ in 0..30 { + vec10.push(item); + vec10.push(item * 2); + } + + // Suggestion should not be given as Vec is not involved + for _ in 0..5 { + println!("Same Item Push"); + } +} diff --git a/tests/ui/same_item_push.stderr b/tests/ui/same_item_push.stderr new file mode 100644 index 00000000000..559cc450b9d --- /dev/null +++ b/tests/ui/same_item_push.stderr @@ -0,0 +1,35 @@ +error: it looks like the same item is being pushed into this Vec + --> $DIR/same_item_push.rs:16:9 + | +LL | spaces.push(vec![b' ']); + | ^^^^^^ + | + = note: `-D clippy::same-item-push` implied by `-D warnings` + = help: try using vec![<[_]>::into_vec(box [$($x),+]);SIZE] or spaces.resize(NEW_SIZE, <[_]>::into_vec(box [$($x),+])) + +error: it looks like the same item is being pushed into this Vec + --> $DIR/same_item_push.rs:22:9 + | +LL | vec2.push(item); + | ^^^^ + | + = help: try using vec![item;SIZE] or vec2.resize(NEW_SIZE, item) + +error: it looks like the same item is being pushed into this Vec + --> $DIR/same_item_push.rs:28:9 + | +LL | vec3.push(item); + | ^^^^ + | + = help: try using vec![item;SIZE] or vec3.resize(NEW_SIZE, item) + +error: it looks like the same item is being pushed into this Vec + --> $DIR/same_item_push.rs:33:9 + | +LL | vec4.push(13); + | ^^^^ + | + = help: try using vec![13;SIZE] or vec4.resize(NEW_SIZE, 13) + +error: aborting due to 4 previous errors + |