1 use super::WHILE_LET_LOOP;
2 use clippy_utils::diagnostics::span_lint_and_sugg;
3 use clippy_utils::higher;
4 use clippy_utils::source::snippet_with_applicability;
5 use clippy_utils::ty::needs_ordered_drop;
6 use clippy_utils::visitors::any_temporaries_need_ordered_drop;
7 use rustc_errors::Applicability;
8 use rustc_hir::{Block, Expr, ExprKind, Local, MatchSource, Pat, StmtKind};
9 use rustc_lint::LateContext;
11 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, loop_block: &'tcx Block<'_>) {
12 let (init, has_trailing_exprs) = match (loop_block.stmts, loop_block.expr) {
13 ([stmt, stmts @ ..], expr) => {
14 if let StmtKind::Local(&Local {
20 | StmtKind::Expr(e) = stmt.kind
22 (e, !stmts.is_empty() || expr.is_some())
27 ([], Some(e)) => (e, false),
31 if let Some(if_let) = higher::IfLet::hir(cx, init)
32 && let Some(else_expr) = if_let.if_else
33 && is_simple_break_expr(else_expr)
35 could_be_while_let(cx, expr, if_let.let_pat, if_let.let_expr, has_trailing_exprs);
36 } else if let ExprKind::Match(scrutinee, [arm1, arm2], MatchSource::Normal) = init.kind
37 && arm1.guard.is_none()
38 && arm2.guard.is_none()
39 && is_simple_break_expr(arm2.body)
41 could_be_while_let(cx, expr, arm1.pat, scrutinee, has_trailing_exprs);
45 /// Returns `true` if expr contains a single break expression without a label or eub-expression.
46 fn is_simple_break_expr(e: &Expr<'_>) -> bool {
47 matches!(peel_blocks(e).kind, ExprKind::Break(dest, None) if dest.label.is_none())
50 /// Removes any blocks containing only a single expression.
51 fn peel_blocks<'tcx>(e: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> {
52 if let ExprKind::Block(b, _) = e.kind {
53 match (b.stmts, b.expr) {
55 if let StmtKind::Expr(e) | StmtKind::Semi(e) = s.kind {
61 ([], Some(e)) => peel_blocks(e),
69 fn could_be_while_let<'tcx>(
70 cx: &LateContext<'tcx>,
72 let_pat: &'tcx Pat<'_>,
73 let_expr: &'tcx Expr<'_>,
74 has_trailing_exprs: bool,
77 && (needs_ordered_drop(cx, cx.typeck_results().expr_ty(let_expr))
78 || any_temporaries_need_ordered_drop(cx, let_expr))
80 // Switching to a `while let` loop will extend the lifetime of some values.
84 // NOTE: we used to build a body here instead of using
85 // ellipsis, this was removed because:
86 // 1) it was ugly with big bodies;
87 // 2) it was not indented properly;
88 // 3) it wasn’t very smart (see #675).
89 let mut applicability = Applicability::HasPlaceholders;
94 "this loop could be written as a `while let` loop",
97 "while let {} = {} {{ .. }}",
98 snippet_with_applicability(cx, let_pat.span, "..", &mut applicability),
99 snippet_with_applicability(cx, let_expr.span, "..", &mut applicability),