69 lines
2.6 KiB
Rust
69 lines
2.6 KiB
Rust
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use crate::methods::derefs_to_slice;
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use crate::utils::{get_parent_expr, higher, is_type_diagnostic_item, snippet_with_applicability, span_lint_and_sugg};
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use if_chain::if_chain;
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use rustc_ast::ast;
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use rustc_errors::Applicability;
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use rustc_hir as hir;
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use rustc_lint::LateContext;
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use rustc_middle::ty;
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use rustc_span::symbol::sym;
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use super::ITER_NEXT_SLICE;
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pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, iter_args: &'tcx [hir::Expr<'_>]) {
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let caller_expr = &iter_args[0];
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// Skip lint if the `iter().next()` expression is a for loop argument,
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// since it is already covered by `&loops::ITER_NEXT_LOOP`
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let mut parent_expr_opt = get_parent_expr(cx, expr);
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while let Some(parent_expr) = parent_expr_opt {
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if higher::for_loop(parent_expr).is_some() {
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return;
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}
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parent_expr_opt = get_parent_expr(cx, parent_expr);
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}
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if derefs_to_slice(cx, caller_expr, cx.typeck_results().expr_ty(caller_expr)).is_some() {
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// caller is a Slice
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if_chain! {
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if let hir::ExprKind::Index(ref caller_var, ref index_expr) = &caller_expr.kind;
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if let Some(higher::Range { start: Some(start_expr), end: None, limits: ast::RangeLimits::HalfOpen })
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= higher::range(index_expr);
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if let hir::ExprKind::Lit(ref start_lit) = &start_expr.kind;
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if let ast::LitKind::Int(start_idx, _) = start_lit.node;
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then {
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let mut applicability = Applicability::MachineApplicable;
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span_lint_and_sugg(
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cx,
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ITER_NEXT_SLICE,
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expr.span,
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"using `.iter().next()` on a Slice without end index",
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"try calling",
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format!("{}.get({})", snippet_with_applicability(cx, caller_var.span, "..", &mut applicability), start_idx),
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applicability,
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);
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}
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}
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} else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(caller_expr), sym::vec_type)
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|| matches!(
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&cx.typeck_results().expr_ty(caller_expr).peel_refs().kind(),
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ty::Array(_, _)
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)
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{
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// caller is a Vec or an Array
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let mut applicability = Applicability::MachineApplicable;
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span_lint_and_sugg(
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cx,
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ITER_NEXT_SLICE,
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expr.span,
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"using `.iter().next()` on an array",
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"try calling",
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format!(
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"{}.get(0)",
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snippet_with_applicability(cx, caller_expr.span, "..", &mut applicability)
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),
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applicability,
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);
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}
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}
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