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Add rustc comment into while desugaring

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This commit is contained in:
hkalbasi 2023-08-04 16:35:13 +03:30
parent 3115d6988f
commit cc5664c5a2
1 changed files with 27 additions and 14 deletions
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41
crates/hir-def/src/body/lower.rs
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@ -313,20 +313,7 @@ impl ExprCollector<'_> {
let body = self.collect_labelled_block_opt(label, e.loop_body()); let body = self.collect_labelled_block_opt(label, e.loop_body());
self.alloc_expr(Expr::Loop { body, label }, syntax_ptr) self.alloc_expr(Expr::Loop { body, label }, syntax_ptr)
} }
ast::Expr::WhileExpr(e) => { ast::Expr::WhileExpr(e) => self.collect_while_loop(syntax_ptr, e),
// Desugar `while <cond> { <body> }` to
// `loop { if <cond> { <body> } else { break } }`
let label = e.label().map(|label| self.collect_label(label));
let body = self.collect_labelled_block_opt(label, e.loop_body());
let condition = self.collect_expr_opt(e.condition());
let break_expr =
self.alloc_expr(Expr::Break { expr: None, label: None }, syntax_ptr.clone());
let if_expr = self.alloc_expr(
Expr::If { condition, then_branch: body, else_branch: Some(break_expr) },
syntax_ptr.clone(),
);
self.alloc_expr(Expr::Loop { body: if_expr, label }, syntax_ptr)
}
ast::Expr::ForExpr(e) => self.collect_for_loop(syntax_ptr, e), ast::Expr::ForExpr(e) => self.collect_for_loop(syntax_ptr, e),
ast::Expr::CallExpr(e) => { ast::Expr::CallExpr(e) => {
let is_rustc_box = { let is_rustc_box = {
@ -738,6 +725,32 @@ impl ExprCollector<'_> {
expr_id expr_id
} }
/// Desugar `ast::WhileExpr` from: `[opt_ident]: while <cond> <body>` into:
/// ```ignore (pseudo-rust)
/// [opt_ident]: loop {
/// if <cond> {
/// <body>
/// }
/// else {
/// break;
/// }
/// }
/// ```
/// FIXME: Rustc wraps the condition in a construct equivalent to `{ let _t = <cond>; _t }`
/// to preserve drop semantics. We should probably do the same in future.
fn collect_while_loop(&mut self, syntax_ptr: AstPtr<ast::Expr>, e: ast::WhileExpr) -> ExprId {
let label = e.label().map(|label| self.collect_label(label));
let body = self.collect_labelled_block_opt(label, e.loop_body());
let condition = self.collect_expr_opt(e.condition());
let break_expr =
self.alloc_expr(Expr::Break { expr: None, label: None }, syntax_ptr.clone());
let if_expr = self.alloc_expr(
Expr::If { condition, then_branch: body, else_branch: Some(break_expr) },
syntax_ptr.clone(),
);
self.alloc_expr(Expr::Loop { body: if_expr, label }, syntax_ptr)
}
/// Desugar `ast::ForExpr` from: `[opt_ident]: for <pat> in <head> <body>` into: /// Desugar `ast::ForExpr` from: `[opt_ident]: for <pat> in <head> <body>` into:
/// ```ignore (pseudo-rust) /// ```ignore (pseudo-rust)
/// match IntoIterator::into_iter(<head>) { /// match IntoIterator::into_iter(<head>) {