hir::ExprKind::Match(P(scrutinee), vec![then_arm, else_arm].into(), desugar)
}
- // FIXME(#53667): handle lowering of && and parens.
ExprKind::While(ref cond, ref body, opt_label) => self.with_loop_scope(e.id, |this| {
- // Note that the block AND the condition are evaluated in the loop scope.
- // This is done to allow `break` from inside the condition of the loop.
-
- // `_ => break`:
- let else_arm = {
- let else_pat = this.pat_wild(e.span);
- let else_expr = this.expr_break(e.span, ThinVec::new());
- this.arm(hir_vec![else_pat], else_expr)
- };
-
- // Handle then + scrutinee:
- let then_blk = this.lower_block(body, false);
- let then_expr = this.expr_block(then_blk, ThinVec::new());
- let (then_pats, scrutinee, desugar, source) = match cond.node {
- ExprKind::Let(ref pats, ref scrutinee) => {
- // to:
- //
- // [opt_ident]: loop {
- // match <sub_expr> {
- // <pat> => <body>,
- // _ => break
- // }
- // }
- let scrutinee = this.with_loop_condition_scope(|t| t.lower_expr(scrutinee));
- let pats = pats.iter().map(|pat| this.lower_pat(pat)).collect();
- let desugar = hir::MatchSource::WhileLetDesugar;
- (pats, scrutinee, desugar, hir::LoopSource::WhileLet)
- }
- _ => {
- // We desugar: `'label: while $cond $body` into:
- //
- // ```
- // 'label: loop {
- // match DropTemps($cond) {
- // true => $body,
- // _ => break,
- // }
- // }
- // ```
-
- // Lower condition:
- let cond = this.with_loop_condition_scope(|this| this.lower_expr(cond));
- let span_block = this.mark_span_with_reason(
- DesugaringKind::CondTemporary, cond.span, None
- );
- // Wrap in a construct equivalent to `{ let _t = $cond; _t }`
- // to preserve drop semantics since `while cond { ... }` does not
- // let temporaries live outside of `cond`.
- let cond = this.expr_drop_temps(span_block, P(cond), ThinVec::new());
-
- let desugar = hir::MatchSource::WhileDesugar;
- // `true => <then>`:
- let pats = hir_vec![this.pat_bool(e.span, true)];
- (pats, cond, desugar, hir::LoopSource::While)
- }
- };
- let then_arm = this.arm(then_pats, P(then_expr));
-
- // `match <scrutinee> { ... }`
- let match_expr = this.expr_match(
- scrutinee.span,
- P(scrutinee),
- hir_vec![then_arm, else_arm],
- desugar,
- );
-
- // `[opt_ident]: loop { ... }`
- hir::ExprKind::Loop(
- P(this.block_expr(P(match_expr))),
- this.lower_label(opt_label),
- source
- )
+ this.lower_expr_while_in_loop_scope(e.span, cond, body, opt_label)
}),
ExprKind::Loop(ref body, opt_label) => self.with_loop_scope(e.id, |this| {
hir::ExprKind::Loop(
}
}
+ fn lower_expr_while_in_loop_scope(
+ &mut self,
+ span: Span,
+ cond: &Expr,
+ body: &Block,
+ opt_label: Option<Label>
+ ) -> hir::ExprKind {
+ // FIXME(#53667): handle lowering of && and parens.
+
+ // Note that the block AND the condition are evaluated in the loop scope.
+ // This is done to allow `break` from inside the condition of the loop.
+
+ // `_ => break`:
+ let else_arm = {
+ let else_pat = self.pat_wild(span);
+ let else_expr = self.expr_break(span, ThinVec::new());
+ self.arm(hir_vec![else_pat], else_expr)
+ };
+
+ // Handle then + scrutinee:
+ let then_blk = self.lower_block(body, false);
+ let then_expr = self.expr_block(then_blk, ThinVec::new());
+ let (then_pats, scrutinee, desugar, source) = match cond.node {
+ ExprKind::Let(ref pats, ref scrutinee) => {
+ // to:
+ //
+ // [opt_ident]: loop {
+ // match <sub_expr> {
+ // <pat> => <body>,
+ // _ => break
+ // }
+ // }
+ let scrutinee = self.with_loop_condition_scope(|t| t.lower_expr(scrutinee));
+ let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
+ let desugar = hir::MatchSource::WhileLetDesugar;
+ (pats, scrutinee, desugar, hir::LoopSource::WhileLet)
+ }
+ _ => {
+ // We desugar: `'label: while $cond $body` into:
+ //
+ // ```
+ // 'label: loop {
+ // match DropTemps($cond) {
+ // true => $body,
+ // _ => break,
+ // }
+ // }
+ // ```
+
+ // Lower condition:
+ let cond = self.with_loop_condition_scope(|this| this.lower_expr(cond));
+ let span_block = self.mark_span_with_reason(
+ DesugaringKind::CondTemporary,
+ cond.span,
+ None,
+ );
+ // Wrap in a construct equivalent to `{ let _t = $cond; _t }`
+ // to preserve drop semantics since `while cond { ... }` does not
+ // let temporaries live outside of `cond`.
+ let cond = self.expr_drop_temps(span_block, P(cond), ThinVec::new());
+
+ let desugar = hir::MatchSource::WhileDesugar;
+ // `true => <then>`:
+ let pats = hir_vec![self.pat_bool(span, true)];
+ (pats, cond, desugar, hir::LoopSource::While)
+ }
+ };
+ let then_arm = self.arm(then_pats, P(then_expr));
+
+ // `match <scrutinee> { ... }`
+ let match_expr = self.expr_match(
+ scrutinee.span,
+ P(scrutinee),
+ hir_vec![then_arm, else_arm],
+ desugar,
+ );
+
+ // `[opt_ident]: loop { ... }`
+ hir::ExprKind::Loop(
+ P(self.block_expr(P(match_expr))),
+ self.lower_label(opt_label),
+ source
+ )
+ }
+
fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind {
self.with_catch_scope(body.id, |this| {
let unstable_span = this.mark_span_with_reason(
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