obelix 0.2.0

Obélix is a tool to reduce Rust source files to produce MVEs
Documentation 
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use syn::spanned::Spanned;

#[derive(Default)]
pub struct RemoveReturnValueVisitor {
    done: bool,
    visited: std::collections::BTreeSet<(proc_macro2::LineColumn, proc_macro2::LineColumn)>,
}

impl super::Visiter for RemoveReturnValueVisitor {
    fn reset(&mut self) {
        self.done = false;
    }

    fn visited_count(&self) -> usize {
        self.visited.len()
    }
}

impl syn::fold::Fold for RemoveReturnValueVisitor {
    fn fold_expr(&mut self, expr: syn::Expr) -> syn::Expr {
        if self.done {
            return expr;
        }

        let span = expr.span();
        let span = (span.start(), span.end());

        if self.visited.insert(span) {
            if let syn::Expr::Return(mut ret) = expr {
                ret.expr = Some(syn::parse_quote! { loop { } });
                self.done = true;
                return syn::Expr::Return(ret);
            }
        } 

        syn::fold::fold_expr(self, expr)
    }

    fn fold_block(&mut self, mut block: syn::Block) -> syn::Block {
        if self.done {
            return block;
        }

        let span = block.span();
        let span = (span.start(), span.end());

        if self.visited.insert(span) {
            if let Some(syn::Stmt::Expr(expr)) = block.stmts.last_mut() {
                *expr = syn::parse_quote! { loop { } };
                self.done = true;
                return block;
            }
        }

        syn::fold::fold_block(self, block)
    }
}