Simplify for loop desugar
This commit is contained in:
Cameron Steffen
parent
3bfde2f1f4
commit
9c83f8c4d1
26 changed files with 181 additions and 256 deletions
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@ -13,7 +13,7 @@ use rustc_session::parse::feature_err;
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use rustc_span::hygiene::ExpnId;
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use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned};
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use rustc_span::symbol::{sym, Ident, Symbol};
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use rustc_span::{hygiene::ForLoopLoc, DUMMY_SP};
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use rustc_span::DUMMY_SP;
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impl<'hir> LoweringContext<'_, 'hir> {
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fn lower_exprs(&mut self, exprs: &[AstP<Expr>]) -> &'hir [hir::Expr<'hir>] {
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@ -1308,16 +1308,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
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/// Desugar `ExprForLoop` from: `[opt_ident]: for <pat> in <head> <body>` into:
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/// ```rust
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/// {
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/// let result = match ::std::iter::IntoIterator::into_iter(<head>) {
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/// let result = match IntoIterator::into_iter(<head>) {
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/// mut iter => {
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/// [opt_ident]: loop {
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/// let mut __next;
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/// match ::std::iter::Iterator::next(&mut iter) {
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/// ::std::option::Option::Some(val) => __next = val,
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/// ::std::option::Option::None => break
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/// match Iterator::next(&mut iter) {
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/// None => break,
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/// Some(<pat>) => <body>,
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/// };
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/// let <pat> = __next;
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/// StmtKind::Expr(<body>);
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/// }
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/// }
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/// };
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@ -1332,133 +1329,75 @@ impl<'hir> LoweringContext<'_, 'hir> {
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body: &Block,
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opt_label: Option<Label>,
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) -> hir::Expr<'hir> {
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// expand <head>
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let head = self.lower_expr_mut(head);
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let desugared_span =
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self.mark_span_with_reason(DesugaringKind::ForLoop(ForLoopLoc::Head), head.span, None);
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let e_span = self.lower_span(e.span);
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let pat = self.lower_pat(pat);
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let for_span =
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self.mark_span_with_reason(DesugaringKind::ForLoop, self.lower_span(e.span), None);
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let head_span = self.mark_span_with_reason(DesugaringKind::ForLoop, head.span, None);
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let pat_span = self.mark_span_with_reason(DesugaringKind::ForLoop, pat.span, None);
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let iter = Ident::with_dummy_span(sym::iter);
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let next_ident = Ident::with_dummy_span(sym::__next);
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let (next_pat, next_pat_hid) = self.pat_ident_binding_mode(
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desugared_span,
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next_ident,
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hir::BindingAnnotation::Mutable,
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);
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// `::std::option::Option::Some(val) => __next = val`
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let pat_arm = {
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let val_ident = Ident::with_dummy_span(sym::val);
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let pat_span = self.lower_span(pat.span);
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let (val_pat, val_pat_hid) = self.pat_ident(pat_span, val_ident);
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let val_expr = self.expr_ident(pat_span, val_ident, val_pat_hid);
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let next_expr = self.expr_ident(pat_span, next_ident, next_pat_hid);
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let assign = self.arena.alloc(self.expr(
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pat_span,
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hir::ExprKind::Assign(next_expr, val_expr, self.lower_span(pat_span)),
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ThinVec::new(),
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));
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let some_pat = self.pat_some(pat_span, val_pat);
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self.arm(some_pat, assign)
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};
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// `::std::option::Option::None => break`
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let break_arm = {
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// `None => break`
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let none_arm = {
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let break_expr =
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self.with_loop_scope(e.id, |this| this.expr_break_alloc(e_span, ThinVec::new()));
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let pat = self.pat_none(e_span);
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self.with_loop_scope(e.id, |this| this.expr_break_alloc(for_span, ThinVec::new()));
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let pat = self.pat_none(for_span);
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self.arm(pat, break_expr)
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};
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// `mut iter`
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let (iter_pat, iter_pat_nid) =
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self.pat_ident_binding_mode(desugared_span, iter, hir::BindingAnnotation::Mutable);
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// Some(<pat>) => <body>,
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let some_arm = {
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let some_pat = self.pat_some(pat_span, pat);
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let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
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let body_expr = self.arena.alloc(self.expr_block(body_block, ThinVec::new()));
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self.arm(some_pat, body_expr)
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};
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// `match ::std::iter::Iterator::next(&mut iter) { ... }`
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// `mut iter`
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let iter = Ident::with_dummy_span(sym::iter);
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let (iter_pat, iter_pat_nid) =
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self.pat_ident_binding_mode(head_span, iter, hir::BindingAnnotation::Mutable);
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// `match Iterator::next(&mut iter) { ... }`
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let match_expr = {
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let iter = self.expr_ident(desugared_span, iter, iter_pat_nid);
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let ref_mut_iter = self.expr_mut_addr_of(desugared_span, iter);
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let iter = self.expr_ident(head_span, iter, iter_pat_nid);
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let ref_mut_iter = self.expr_mut_addr_of(head_span, iter);
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let next_expr = self.expr_call_lang_item_fn(
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desugared_span,
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head_span,
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hir::LangItem::IteratorNext,
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arena_vec![self; ref_mut_iter],
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);
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let arms = arena_vec![self; pat_arm, break_arm];
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let arms = arena_vec![self; none_arm, some_arm];
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self.expr_match(desugared_span, next_expr, arms, hir::MatchSource::ForLoopDesugar)
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self.expr_match(head_span, next_expr, arms, hir::MatchSource::ForLoopDesugar)
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};
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let match_stmt = self.stmt_expr(desugared_span, match_expr);
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let match_stmt = self.stmt_expr(for_span, match_expr);
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let next_expr = self.expr_ident(desugared_span, next_ident, next_pat_hid);
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// `let mut __next`
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let next_let = self.stmt_let_pat(
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None,
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desugared_span,
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None,
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next_pat,
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hir::LocalSource::ForLoopDesugar,
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);
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// `let <pat> = __next`
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let pat = self.lower_pat(pat);
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let pat_let = self.stmt_let_pat(
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None,
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desugared_span,
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Some(next_expr),
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pat,
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hir::LocalSource::ForLoopDesugar,
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);
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let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
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let body_expr = self.expr_block(body_block, ThinVec::new());
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let body_stmt = self.stmt_expr(body_block.span, body_expr);
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let loop_block = self.block_all(
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e_span,
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arena_vec![self; next_let, match_stmt, pat_let, body_stmt],
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None,
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);
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let loop_block = self.block_all(for_span, arena_vec![self; match_stmt], None);
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// `[opt_ident]: loop { ... }`
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let kind = hir::ExprKind::Loop(
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loop_block,
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self.lower_label(opt_label),
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hir::LoopSource::ForLoop,
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self.lower_span(e_span.with_hi(head.span.hi())),
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self.lower_span(for_span.with_hi(head.span.hi())),
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);
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let loop_expr = self.arena.alloc(hir::Expr {
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hir_id: self.lower_node_id(e.id),
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kind,
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span: self.lower_span(e.span),
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});
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let loop_expr =
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self.arena.alloc(hir::Expr { hir_id: self.lower_node_id(e.id), kind, span: for_span });
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// `mut iter => { ... }`
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let iter_arm = self.arm(iter_pat, loop_expr);
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let into_iter_span = self.mark_span_with_reason(
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DesugaringKind::ForLoop(ForLoopLoc::IntoIter),
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head.span,
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None,
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);
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// `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
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let into_iter_expr = {
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self.expr_call_lang_item_fn(
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into_iter_span,
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head_span,
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hir::LangItem::IntoIterIntoIter,
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arena_vec![self; head],
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)
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};
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// #82462: to correctly diagnose borrow errors, the block that contains
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// the iter expr needs to have a span that covers the loop body.
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let desugared_full_span =
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self.mark_span_with_reason(DesugaringKind::ForLoop(ForLoopLoc::Head), e_span, None);
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let match_expr = self.arena.alloc(self.expr_match(
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desugared_full_span,
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for_span,
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into_iter_expr,
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arena_vec![self; iter_arm],
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hir::MatchSource::ForLoopDesugar,
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@ -1472,7 +1411,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
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// surrounding scope of the `match` since the `match` is not a terminating scope.
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//
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// Also, add the attributes to the outer returned expr node.
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self.expr_drop_temps_mut(desugared_full_span, match_expr, attrs.into())
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self.expr_drop_temps_mut(for_span, match_expr, attrs.into())
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}
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/// Desugar `ExprKind::Try` from: `<expr>?` into:
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