Module syn::fold [−][src]
This is supported on crate feature
fold only.Expand description
Syntax tree traversal to transform the nodes of an owned syntax tree.
Each method of the Fold trait is a hook that can be overridden to
customize the behavior when transforming the corresponding type of node.
By default, every method recursively visits the substructure of the
input by invoking the right visitor method of each of its fields.
pub trait Fold {
/* ... */
fn fold_expr_binary(&mut self, node: ExprBinary) -> ExprBinary {
fold_expr_binary(self, node)
}
/* ... */
}
pub fn fold_expr_binary<V>(v: &mut V, node: ExprBinary) -> ExprBinary
where
V: Fold + ?Sized,
{
ExprBinary {
attrs: node
.attrs
.into_iter()
.map(|attr| v.fold_attribute(attr))
.collect(),
left: Box::new(v.fold_expr(*node.left)),
op: v.fold_bin_op(node.op),
right: Box::new(v.fold_expr(*node.right)),
}
}
/* ... */This module is available only if Syn is built with the "fold" feature.
Example
This fold inserts parentheses to fully parenthesizes any expression.
// [dependencies]
// quote = "1.0"
// syn = { version = "1.0", features = ["fold", "full"] }
use quote::quote;
use syn::fold::{fold_expr, Fold};
use syn::{token, Expr, ExprParen};
struct ParenthesizeEveryExpr;
impl Fold for ParenthesizeEveryExpr {
fn fold_expr(&mut self, expr: Expr) -> Expr {
Expr::Paren(ExprParen {
attrs: Vec::new(),
expr: Box::new(fold_expr(self, expr)),
paren_token: token::Paren::default(),
})
}
}
fn main() {
let code = quote! { a() + b(1) * c.d };
let expr: Expr = syn::parse2(code).unwrap();
let parenthesized = ParenthesizeEveryExpr.fold_expr(expr);
println!("{}", quote!(#parenthesized));
// Output: (((a)()) + (((b)((1))) * ((c).d)))
}Traits
Syntax tree traversal to transform the nodes of an owned syntax tree.
Functions
fold_abi
derive or fullfold_angle_bracketed_generic_arguments
derive or fullfold_arm
fullfold_attr_style
derive or fullfold_attribute
derive or fullfold_bare_fn_arg
derive or fullfold_bin_op
derive or fullfold_binding
derive or fullfold_block
fullfold_bound_lifetimes
derive or fullfold_const_param
derive or fullfold_constraint
derive or fullfold_data
derivefold_data_enum
derivefold_data_struct
derivefold_data_union
derivefold_derive_input
derivefold_expr
derive or fullfold_expr_array
fullfold_expr_assign
fullfold_expr_async
fullfold_expr_await
fullfold_expr_binary
derive or fullfold_expr_block
fullfold_expr_box
fullfold_expr_break
fullfold_expr_call
derive or fullfold_expr_cast
derive or fullfold_expr_field
derive or fullfold_expr_group
fullfold_expr_if
fullfold_expr_index
derive or fullfold_expr_let
fullfold_expr_lit
derive or fullfold_expr_loop
fullfold_expr_macro
fullfold_expr_match
fullfold_expr_paren
derive or fullfold_expr_path
derive or fullfold_expr_range
fullfold_expr_repeat
fullfold_expr_return
fullfold_expr_struct
fullfold_expr_try
fullfold_expr_tuple
fullfold_expr_type
fullfold_expr_unary
derive or fullfold_expr_unsafe
fullfold_expr_while
fullfold_expr_yield
fullfold_field
derive or fullfold_field_pat
fullfold_field_value
fullfold_fields
derive or fullfold_fields_named
derive or fullfold_fields_unnamed
derive or fullfold_file
fullfold_fn_arg
fullfold_generic_argument
derive or fullfold_generic_param
derive or fullfold_generics
derive or fullfold_impl_item
fullfold_index
derive or fullfold_item
fullfold_item_const
fullfold_item_enum
fullfold_item_fn
fullfold_item_impl
fullfold_item_macro
fullfold_item_macro2
fullfold_item_mod
fullfold_item_static
fullfold_item_struct
fullfold_item_trait
fullfold_item_type
fullfold_item_union
fullfold_item_use
fullfold_label
fullfold_lifetime_def
derive or fullfold_local
fullfold_macro
derive or fullfold_macro_delimiter
derive or fullfold_member
derive or fullfold_meta
derive or fullfold_meta_list
derive or fullfold_meta_name_value
derive or fullfold_nested_meta
derive or fullfold_parenthesized_generic_arguments
derive or fullfold_pat
fullfold_pat_box
fullfold_pat_ident
fullfold_pat_lit
fullfold_pat_macro
fullfold_pat_or
fullfold_pat_path
fullfold_pat_range
fullfold_pat_rest
fullfold_pat_slice
fullfold_pat_struct
fullfold_pat_tuple
fullfold_pat_type
fullfold_pat_wild
fullfold_path
derive or fullfold_path_arguments
derive or fullfold_path_segment
derive or fullfold_predicate_eq
derive or fullfold_predicate_lifetime
derive or fullfold_predicate_type
derive or fullfold_qself
derive or fullfold_receiver
fullfold_return_type
derive or fullfold_signature
fullfold_stmt
fullfold_trait_bound
derive or fullfold_trait_bound_modifier
derive or fullfold_trait_item
fullfold_type
derive or fullfold_type_array
derive or fullfold_type_bare_fn
derive or fullfold_type_group
derive or fullfold_type_impl_trait
derive or fullfold_type_infer
derive or fullfold_type_macro
derive or fullfold_type_never
derive or fullfold_type_param
derive or fullfold_type_param_bound
derive or fullfold_type_paren
derive or fullfold_type_path
derive or fullfold_type_ptr
derive or fullfold_type_reference
derive or fullfold_type_slice
derive or fullfold_type_trait_object
derive or fullfold_type_tuple
derive or fullfold_un_op
derive or fullfold_use_glob
fullfold_use_group
fullfold_use_name
fullfold_use_path
fullfold_use_rename
fullfold_use_tree
fullfold_variadic
derive or fullfold_variant
derive or fullfold_vis_crate
derive or fullfold_vis_public
derive or fullfold_vis_restricted
derive or fullfold_visibility
derive or fullfold_where_clause
derive or fullfold_where_predicate
derive or full