96 lines
3.3 KiB
Rust
96 lines
3.3 KiB
Rust
use super::WHILE_LET_LOOP;
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::higher;
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use clippy_utils::source::snippet_with_applicability;
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use clippy_utils::ty::needs_ordered_drop;
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use clippy_utils::visitors::any_temporaries_need_ordered_drop;
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use rustc_errors::Applicability;
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use rustc_hir::{Block, Expr, ExprKind, Local, MatchSource, Pat, StmtKind};
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use rustc_lint::LateContext;
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pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, loop_block: &'tcx Block<'_>) {
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let (init, has_trailing_exprs) = match (loop_block.stmts, loop_block.expr) {
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([stmt, stmts @ ..], expr) => {
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if let StmtKind::Local(&Local { init: Some(e), .. }) | StmtKind::Semi(e) | StmtKind::Expr(e) = stmt.kind {
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(e, !stmts.is_empty() || expr.is_some())
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} else {
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return;
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}
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},
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([], Some(e)) => (e, false),
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_ => return,
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};
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if let Some(if_let) = higher::IfLet::hir(cx, init)
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&& let Some(else_expr) = if_let.if_else
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&& is_simple_break_expr(else_expr)
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{
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could_be_while_let(cx, expr, if_let.let_pat, if_let.let_expr, has_trailing_exprs);
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} else if let ExprKind::Match(scrutinee, [arm1, arm2], MatchSource::Normal) = init.kind
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&& arm1.guard.is_none()
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&& arm2.guard.is_none()
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&& is_simple_break_expr(arm2.body)
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{
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could_be_while_let(cx, expr, arm1.pat, scrutinee, has_trailing_exprs);
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}
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}
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/// Returns `true` if expr contains a single break expression without a label or eub-expression.
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fn is_simple_break_expr(e: &Expr<'_>) -> bool {
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matches!(peel_blocks(e).kind, ExprKind::Break(dest, None) if dest.label.is_none())
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}
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/// Removes any blocks containing only a single expression.
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fn peel_blocks<'tcx>(e: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> {
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if let ExprKind::Block(b, _) = e.kind {
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match (b.stmts, b.expr) {
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([s], None) => {
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if let StmtKind::Expr(e) | StmtKind::Semi(e) = s.kind {
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peel_blocks(e)
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} else {
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e
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}
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},
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([], Some(e)) => peel_blocks(e),
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_ => e,
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}
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} else {
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e
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}
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}
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fn could_be_while_let<'tcx>(
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cx: &LateContext<'tcx>,
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expr: &'tcx Expr<'_>,
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let_pat: &'tcx Pat<'_>,
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let_expr: &'tcx Expr<'_>,
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has_trailing_exprs: bool,
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) {
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if has_trailing_exprs
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&& (needs_ordered_drop(cx, cx.typeck_results().expr_ty(let_expr))
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|| any_temporaries_need_ordered_drop(cx, let_expr))
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{
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// Switching to a `while let` loop will extend the lifetime of some values.
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return;
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}
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// NOTE: we used to build a body here instead of using
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// ellipsis, this was removed because:
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// 1) it was ugly with big bodies;
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// 2) it was not indented properly;
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// 3) it wasn’t very smart (see #675).
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let mut applicability = Applicability::HasPlaceholders;
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span_lint_and_sugg(
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cx,
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WHILE_LET_LOOP,
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expr.span,
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"this loop could be written as a `while let` loop",
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"try",
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format!(
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"while let {} = {} {{ .. }}",
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snippet_with_applicability(cx, let_pat.span, "..", &mut applicability),
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snippet_with_applicability(cx, let_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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