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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,161 @@ | ||
| use std::ops::ControlFlow; | ||
|
|
||
| use clippy_utils::diagnostics::span_lint_and_then; | ||
| use clippy_utils::eq_expr_value; | ||
| use clippy_utils::source::snippet; | ||
| use clippy_utils::ty::is_type_diagnostic_item; | ||
| use clippy_utils::visitors::for_each_expr; | ||
| use rustc_ast::LitKind; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::{Expr, ExprKind, Local, Node, UnOp}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::declare_lint_pass; | ||
| use rustc_span::sym; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Checks for the use of `seq.is_empty()` in an if-conditional where `seq` is a slice, array, or Vec, | ||
| /// and in which the first element of the sequence is indexed. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// This code is unnecessarily complicated and can instead be simplified to the use of an | ||
| /// if..let expression which accessed the first element of the sequence. | ||
| /// | ||
| /// ### Example | ||
| /// ```no_run | ||
| /// let a: &[i32] = &[1]; | ||
| /// if !a.is_empty() { | ||
| /// let b = a[0]; | ||
| /// } | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```no_run | ||
| /// let a: &[i32] = &[1]; | ||
| /// if let Some(b) = a.first() { | ||
| /// | ||
| /// } | ||
| /// ``` | ||
| #[clippy::version = "1.78.0"] | ||
| pub UNNECESSARY_INDEXING, | ||
| complexity, | ||
| "unnecessary use of `seq.is_empty()` in a conditional when if..let is more appropriate" | ||
| } | ||
|
|
||
| declare_lint_pass!(UnnecessaryIndexing => [UNNECESSARY_INDEXING]); | ||
|
|
||
| impl LateLintPass<'_> for UnnecessaryIndexing { | ||
| fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'_ rustc_hir::Expr<'_>) { | ||
| if let Some(if_expr) = clippy_utils::higher::If::hir(expr) | ||
| // check for negation | ||
| && let ExprKind::Unary(op, unary_inner) = if_expr.cond.kind | ||
| && UnOp::Not == op | ||
| // check for call of is_empty | ||
| && let ExprKind::MethodCall(method, conditional_receiver, _, _) = unary_inner.kind | ||
| && method.ident.as_str() == "is_empty" | ||
| && let expr_ty = cx.typeck_results().expr_ty(conditional_receiver).peel_refs() | ||
| && (expr_ty.is_array_slice() || expr_ty.is_array() || is_type_diagnostic_item(cx, expr_ty, sym::Vec)) | ||
| && let ExprKind::Block(block, _) = if_expr.then.kind | ||
| { | ||
| // the receiver for the index operation | ||
| let mut index_receiver: Option<&Expr<'_>> = None; | ||
| // first local in the block - used as pattern for `Some(pat)` | ||
| let mut first_local: Option<&Local<'_>> = None; | ||
| // any other locals to be aware of, these are set to the value of `pat` | ||
| let mut extra_locals: Vec<&Local<'_>> = vec![]; | ||
| // any other index expressions to replace with `pat` (or "element" if no local exists) | ||
| let mut extra_exprs: Vec<&Expr<'_>> = vec![]; | ||
|
|
||
| for_each_expr(block.stmts, |x| { | ||
| if let ExprKind::Index(receiver, index, _) = x.kind | ||
| && let ExprKind::Lit(lit) = index.kind | ||
| && let LitKind::Int(val, _) = lit.node | ||
| && eq_expr_value(cx, receiver, conditional_receiver) | ||
| && val.0 == 0 | ||
| { | ||
| index_receiver = Some(receiver); | ||
| if let Node::Local(local) = cx.tcx.parent_hir_node(x.hir_id) { | ||
| if first_local.is_none() { | ||
| first_local = Some(local); | ||
| } else { | ||
| extra_locals.push(local); | ||
| }; | ||
| } else { | ||
| extra_exprs.push(x); | ||
| }; | ||
| }; | ||
|
|
||
| ControlFlow::Continue::<()>(()) | ||
| }); | ||
|
|
||
| if let Some(receiver) = index_receiver { | ||
| span_lint_and_then( | ||
| cx, | ||
| UNNECESSARY_INDEXING, | ||
| expr.span, | ||
| "condition can be simplified with if..let syntax", | ||
| |x| { | ||
| if let Some(first_local) = first_local { | ||
| x.span_suggestion( | ||
| if_expr.cond.span, | ||
| "consider using if..let syntax (variable may need to be dereferenced)", | ||
| format!( | ||
| "let Some({}) = {}.first()", | ||
| snippet(cx, first_local.pat.span, ".."), | ||
| snippet(cx, receiver.span, "..") | ||
| ), | ||
| Applicability::Unspecified, | ||
| ); | ||
| x.span_suggestion( | ||
| first_local.span, | ||
| "remove this line", | ||
| "", | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| if !extra_locals.is_empty() { | ||
| let extra_local_suggestions = extra_locals | ||
| .iter() | ||
| .map(|x| { | ||
| ( | ||
| x.init.unwrap().span, | ||
| snippet(cx, first_local.pat.span, "..").to_string(), | ||
| ) | ||
| }) | ||
| .collect::<Vec<_>>(); | ||
|
|
||
| x.multipart_suggestion( | ||
| "initialize this variable to be the `Some` variant (may need dereferencing)", | ||
| extra_local_suggestions, | ||
| Applicability::Unspecified, | ||
| ); | ||
| } | ||
| if !extra_exprs.is_empty() { | ||
| let index_accesses = extra_exprs | ||
| .iter() | ||
| .map(|x| (x.span, snippet(cx, first_local.pat.span, "..").to_string())) | ||
| .collect::<Vec<_>>(); | ||
|
|
||
| x.multipart_suggestion( | ||
| "set this index to be the `Some` variant (may need dereferencing)", | ||
| index_accesses, | ||
| Applicability::Unspecified, | ||
| ); | ||
| } | ||
| } else { | ||
| let mut index_accesses = vec![( | ||
| if_expr.cond.span, | ||
| format!("let Some(element) = {}.first()", snippet(cx, receiver.span, "..")), | ||
| )]; | ||
| index_accesses.extend(extra_exprs.iter().map(|x| (x.span, "element".to_owned()))); | ||
|
|
||
| x.multipart_suggestion( | ||
| "consider using if..let syntax (variable may need to be dereferenced)", | ||
| index_accesses, | ||
| Applicability::Unspecified, | ||
| ); | ||
| } | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } |
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