cl_ast/desugar/
while_else.rs

1//! Desugars `while {...} else` expressions
2//! into `loop if {...} else break` expressions
3
4use crate::{ast::*, ast_visitor::fold::Fold};
5use cl_structures::span::Span;
6
7/// Desugars while-else expressions
8/// into loop-if-else-break expressions
9pub struct WhileElseDesugar;
10
11impl Fold for WhileElseDesugar {
12    fn fold_expr(&mut self, e: Expr) -> Expr {
13        let Expr { span, kind } = e;
14        let kind = desugar_while(span, kind);
15        Expr { span: self.fold_span(span), kind: self.fold_expr_kind(kind) }
16    }
17}
18
19/// Desugars while(-else) expressions into loop-if-else-break expressions
20fn desugar_while(span: Span, kind: ExprKind) -> ExprKind {
21    match kind {
22        // work backwards: fail -> break -> if -> loop
23        ExprKind::While(While { cond, pass, fail: Else { body } }) => {
24            // Preserve the else-expression's span, if present, or use the parent's span
25            let fail_span = body.as_ref().map(|body| body.span).unwrap_or(span);
26            let break_expr = Expr { span: fail_span, kind: ExprKind::Break(Break { body }) };
27
28            let loop_body = If { cond, pass, fail: Else { body: Some(Box::new(break_expr)) } };
29            let loop_body = ExprKind::If(loop_body);
30            ExprKind::Unary(Unary {
31                kind: UnaryKind::Loop,
32                tail: Box::new(Expr { span, kind: loop_body }),
33            })
34        }
35        _ => kind,
36    }
37}
cl_ast/desugar/while_else.rs

cl_ast/desugar/
while_else.rs
