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use proc_macro2::{Delimiter, Group, TokenStream, TokenTree};
use std::mem;
use syn::visit_mut::{self, VisitMut};
use syn::{Expr, File, Generics, LifetimeParam, MacroDelimiter, Stmt, StmtMacro, TypeParam};
pub struct FlattenParens;
impl FlattenParens {
pub fn visit_token_stream_mut(tokens: &mut TokenStream) {
*tokens = mem::take(tokens)
.into_iter()
.flat_map(|tt| {
if let TokenTree::Group(group) = tt {
let delimiter = group.delimiter();
let mut content = group.stream();
Self::visit_token_stream_mut(&mut content);
if let Delimiter::Parenthesis = delimiter {
content
} else {
TokenStream::from(TokenTree::Group(Group::new(delimiter, content)))
}
} else {
TokenStream::from(tt)
}
})
.collect();
}
}
impl VisitMut for FlattenParens {
fn visit_expr_mut(&mut self, e: &mut Expr) {
while let Expr::Paren(paren) = e {
*e = mem::replace(&mut *paren.expr, Expr::PLACEHOLDER);
}
visit_mut::visit_expr_mut(self, e);
}
}
pub struct AsIfPrinted;
impl VisitMut for AsIfPrinted {
fn visit_file_mut(&mut self, file: &mut File) {
file.shebang = None;
visit_mut::visit_file_mut(self, file);
}
fn visit_generics_mut(&mut self, generics: &mut Generics) {
if generics.params.is_empty() {
generics.lt_token = None;
generics.gt_token = None;
}
if let Some(where_clause) = &generics.where_clause {
if where_clause.predicates.is_empty() {
generics.where_clause = None;
}
}
visit_mut::visit_generics_mut(self, generics);
}
fn visit_lifetime_param_mut(&mut self, param: &mut LifetimeParam) {
if param.bounds.is_empty() {
param.colon_token = None;
}
visit_mut::visit_lifetime_param_mut(self, param);
}
fn visit_stmt_mut(&mut self, stmt: &mut Stmt) {
if let Stmt::Expr(expr, semi) = stmt {
if let Expr::Macro(e) = expr {
if match e.mac.delimiter {
MacroDelimiter::Brace(_) => true,
MacroDelimiter::Paren(_) | MacroDelimiter::Bracket(_) => semi.is_some(),
} {
let Expr::Macro(expr) = mem::replace(expr, Expr::PLACEHOLDER) else {
unreachable!();
};
*stmt = Stmt::Macro(StmtMacro {
attrs: expr.attrs,
mac: expr.mac,
semi_token: *semi,
});
}
}
}
visit_mut::visit_stmt_mut(self, stmt);
}
fn visit_type_param_mut(&mut self, param: &mut TypeParam) {
if param.bounds.is_empty() {
param.colon_token = None;
}
visit_mut::visit_type_param_mut(self, param);
}
}
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