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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:03:36 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:03:36 +0000 |
commit | 17d40c6057c88f4c432b0d7bac88e1b84cb7e67f (patch) | |
tree | 3f66c4a5918660bb8a758ab6cda5ff8ee4f6cdcd /src/tools/clippy/clippy_lints/src/unused_peekable.rs | |
parent | Adding upstream version 1.64.0+dfsg1. (diff) | |
download | rustc-f7f0cc2a5d72e2c61c1f6900e70eec992bea4273.tar.xz rustc-f7f0cc2a5d72e2c61c1f6900e70eec992bea4273.zip |
Adding upstream version 1.65.0+dfsg1.upstream/1.65.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/unused_peekable.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/unused_peekable.rs | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/unused_peekable.rs b/src/tools/clippy/clippy_lints/src/unused_peekable.rs new file mode 100644 index 000000000..cc8656435 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/unused_peekable.rs @@ -0,0 +1,226 @@ +use clippy_utils::diagnostics::span_lint_and_help; +use clippy_utils::ty::{match_type, peel_mid_ty_refs_is_mutable}; +use clippy_utils::{fn_def_id, is_trait_method, path_to_local_id, paths, peel_ref_operators}; +use rustc_ast::Mutability; +use rustc_hir::intravisit::{walk_expr, Visitor}; +use rustc_hir::lang_items::LangItem; +use rustc_hir::{Block, Expr, ExprKind, HirId, Local, Node, PatKind, PathSegment, StmtKind}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::sym; + +declare_clippy_lint! { + /// ### What it does + /// Checks for the creation of a `peekable` iterator that is never `.peek()`ed + /// + /// ### Why is this bad? + /// Creating a peekable iterator without using any of its methods is likely a mistake, + /// or just a leftover after a refactor. + /// + /// ### Example + /// ```rust + /// let collection = vec![1, 2, 3]; + /// let iter = collection.iter().peekable(); + /// + /// for item in iter { + /// // ... + /// } + /// ``` + /// + /// Use instead: + /// ```rust + /// let collection = vec![1, 2, 3]; + /// let iter = collection.iter(); + /// + /// for item in iter { + /// // ... + /// } + /// ``` + #[clippy::version = "1.64.0"] + pub UNUSED_PEEKABLE, + nursery, + "creating a peekable iterator without using any of its methods" +} + +declare_lint_pass!(UnusedPeekable => [UNUSED_PEEKABLE]); + +impl<'tcx> LateLintPass<'tcx> for UnusedPeekable { + fn check_block(&mut self, cx: &LateContext<'tcx>, block: &Block<'tcx>) { + // Don't lint `Peekable`s returned from a block + if let Some(expr) = block.expr + && let Some(ty) = cx.typeck_results().expr_ty_opt(peel_ref_operators(cx, expr)) + && match_type(cx, ty, &paths::PEEKABLE) + { + return; + } + + for (idx, stmt) in block.stmts.iter().enumerate() { + if !stmt.span.from_expansion() + && let StmtKind::Local(local) = stmt.kind + && let PatKind::Binding(_, binding, ident, _) = local.pat.kind + && let Some(init) = local.init + && !init.span.from_expansion() + && let Some(ty) = cx.typeck_results().expr_ty_opt(init) + && let (ty, _, Mutability::Mut) = peel_mid_ty_refs_is_mutable(ty) + && match_type(cx, ty, &paths::PEEKABLE) + { + let mut vis = PeekableVisitor::new(cx, binding); + + if idx + 1 == block.stmts.len() && block.expr.is_none() { + return; + } + + for stmt in &block.stmts[idx..] { + vis.visit_stmt(stmt); + } + + if let Some(expr) = block.expr { + vis.visit_expr(expr); + } + + if !vis.found_peek_call { + span_lint_and_help( + cx, + UNUSED_PEEKABLE, + ident.span, + "`peek` never called on `Peekable` iterator", + None, + "consider removing the call to `peekable`" + ); + } + } + } + } +} + +struct PeekableVisitor<'a, 'tcx> { + cx: &'a LateContext<'tcx>, + expected_hir_id: HirId, + found_peek_call: bool, +} + +impl<'a, 'tcx> PeekableVisitor<'a, 'tcx> { + fn new(cx: &'a LateContext<'tcx>, expected_hir_id: HirId) -> Self { + Self { + cx, + expected_hir_id, + found_peek_call: false, + } + } +} + +impl<'tcx> Visitor<'_> for PeekableVisitor<'_, 'tcx> { + fn visit_expr(&mut self, ex: &'_ Expr<'_>) { + if self.found_peek_call { + return; + } + + if path_to_local_id(ex, self.expected_hir_id) { + for (_, node) in self.cx.tcx.hir().parent_iter(ex.hir_id) { + match node { + Node::Expr(expr) => { + match expr.kind { + // some_function(peekable) + // + // If the Peekable is passed to a function, stop + ExprKind::Call(_, args) => { + if let Some(func_did) = fn_def_id(self.cx, expr) + && let Ok(into_iter_did) = self + .cx + .tcx + .lang_items() + .require(LangItem::IntoIterIntoIter) + && func_did == into_iter_did + { + // Probably a for loop desugar, stop searching + return; + } + + if args.iter().any(|arg| { + matches!(arg.kind, ExprKind::Path(_)) && arg_is_mut_peekable(self.cx, arg) + }) { + self.found_peek_call = true; + return; + } + }, + // Catch anything taking a Peekable mutably + ExprKind::MethodCall( + PathSegment { + ident: method_name_ident, + .. + }, + self_arg, + remaining_args, + _, + ) => { + let method_name = method_name_ident.name.as_str(); + + // `Peekable` methods + if matches!(method_name, "peek" | "peek_mut" | "next_if" | "next_if_eq") + && arg_is_mut_peekable(self.cx, self_arg) + { + self.found_peek_call = true; + return; + } + + // foo.some_method() excluding Iterator methods + if remaining_args.iter().any(|arg| arg_is_mut_peekable(self.cx, arg)) + && !is_trait_method(self.cx, expr, sym::Iterator) + { + self.found_peek_call = true; + return; + } + + // foo.by_ref(), keep checking for `peek` + if method_name == "by_ref" { + continue; + } + + return; + }, + ExprKind::AddrOf(_, Mutability::Mut, _) | ExprKind::Unary(..) | ExprKind::DropTemps(_) => { + }, + ExprKind::AddrOf(_, Mutability::Not, _) => return, + _ => { + self.found_peek_call = true; + return; + }, + } + }, + Node::Local(Local { init: Some(init), .. }) => { + if arg_is_mut_peekable(self.cx, init) { + self.found_peek_call = true; + return; + } + + break; + }, + Node::Stmt(stmt) => match stmt.kind { + StmtKind::Expr(_) | StmtKind::Semi(_) => {}, + _ => { + self.found_peek_call = true; + return; + }, + }, + Node::Block(_) | Node::ExprField(_) => {}, + _ => { + break; + }, + } + } + } + + walk_expr(self, ex); + } +} + +fn arg_is_mut_peekable(cx: &LateContext<'_>, arg: &Expr<'_>) -> bool { + if let Some(ty) = cx.typeck_results().expr_ty_opt(arg) + && let (ty, _, Mutability::Mut) = peel_mid_ty_refs_is_mutable(ty) + && match_type(cx, ty, &paths::PEEKABLE) + { + true + } else { + false + } +} |