Module visit_mut

Syntax tree traversal to mutate an exclusive borrow of a syntax tree in place.

Each method of the VisitMut trait is a hook that can be overridden to customize the behavior when mutating 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 VisitMut {
    /* ... */

    fn visit_expr_binary_mut(&mut self, node: &mut ExprBinary) {
        visit_expr_binary_mut(self, node);
    }

    /* ... */
}

pub fn visit_expr_binary_mut<V>(v: &mut V, node: &mut ExprBinary)
where
    V: VisitMut + ?Sized,
{
    for attr in &mut node.attrs {
        v.visit_attribute_mut(attr);
    }
    v.visit_expr_mut(&mut *node.left);
    v.visit_bin_op_mut(&mut node.op);
    v.visit_expr_mut(&mut *node.right);
}

/* ... */

Example

This mut visitor replace occurrences of u256 suffixed integer literals like 999u256 with a macro invocation bigint::u256!(999).

// [dependencies]
// quote = "1.0"
// syn = { version = "2.0", features = ["full", "visit-mut"] }

use quote::quote;
use syn::visit_mut::{self, VisitMut};
use syn::{parse_quote, Expr, File, Lit, LitInt};

struct BigintReplace;

impl VisitMut for BigintReplace {
    fn visit_expr_mut(&mut self, node: &mut Expr) {
        if let Expr::Lit(expr) = &node {
            if let Lit::Int(int) = &expr.lit {
                if int.suffix() == "u256" {
                    let digits = int.base10_digits();
                    let unsuffixed: LitInt = syn::parse_str(digits).unwrap();
                    *node = parse_quote!(bigint::u256!(#unsuffixed));
                    return;
                }
            }
        }

        // Delegate to the default impl to visit nested expressions.
        visit_mut::visit_expr_mut(self, node);
    }
}

fn main() {
    let code = quote! {
        fn main() {
            let _ = 999u256;
        }
    };

    let mut syntax_tree: File = syn::parse2(code).unwrap();
    BigintReplace.visit_file_mut(&mut syntax_tree);
    println!("{}", quote!(#syntax_tree));
}

Traits

VisitMut

Syntax tree traversal to mutate an exclusive borrow of a syntax tree in place.

Functions

visit_abi_mut

visit_angle_bracketed_generic_arguments_mut

visit_arm_mut

visit_assoc_const_mut

visit_assoc_type_mut

visit_attr_style_mut

visit_attribute_mut

visit_bare_fn_arg_mut

visit_bare_variadic_mut

visit_bin_op_mut

visit_block_mut

visit_bound_lifetimes_mut

visit_captured_param_mut

visit_const_param_mut

visit_constraint_mut

visit_data_enum_mut

visit_data_mut

visit_data_struct_mut

visit_data_union_mut

visit_derive_input_mut

visit_expr_array_mut

visit_expr_assign_mut

visit_expr_async_mut

visit_expr_await_mut

visit_expr_binary_mut

visit_expr_block_mut

visit_expr_break_mut

visit_expr_call_mut

visit_expr_cast_mut

visit_expr_closure_mut

visit_expr_const_mut

visit_expr_continue_mut

visit_expr_field_mut

visit_expr_for_loop_mut

visit_expr_group_mut

visit_expr_if_mut

visit_expr_index_mut

visit_expr_infer_mut

visit_expr_let_mut

visit_expr_lit_mut

visit_expr_loop_mut

visit_expr_macro_mut

visit_expr_match_mut

visit_expr_method_call_mut

visit_expr_mut

visit_expr_paren_mut

visit_expr_path_mut

visit_expr_range_mut

visit_expr_raw_addr_mut

visit_expr_reference_mut

visit_expr_repeat_mut

visit_expr_return_mut

visit_expr_struct_mut

visit_expr_try_block_mut

visit_expr_try_mut

visit_expr_tuple_mut

visit_expr_unary_mut

visit_expr_unsafe_mut

visit_expr_while_mut

visit_expr_yield_mut

visit_field_mut

visit_field_mutability_mut

visit_field_pat_mut

visit_field_value_mut

visit_fields_mut

visit_fields_named_mut

visit_fields_unnamed_mut

visit_file_mut

visit_fn_arg_mut

visit_foreign_item_fn_mut

visit_foreign_item_macro_mut

visit_foreign_item_mut

visit_foreign_item_static_mut

visit_foreign_item_type_mut

visit_generic_argument_mut

visit_generic_param_mut

visit_generics_mut

visit_ident_mut

visit_impl_item_const_mut

visit_impl_item_fn_mut

visit_impl_item_macro_mut

visit_impl_item_mut

visit_impl_item_type_mut

visit_impl_restriction_mut

visit_index_mut

visit_item_const_mut

visit_item_enum_mut

visit_item_extern_crate_mut

visit_item_fn_mut

visit_item_foreign_mod_mut

visit_item_impl_mut

visit_item_macro_mut

visit_item_mod_mut

visit_item_mut

visit_item_static_mut

visit_item_struct_mut

visit_item_trait_alias_mut

visit_item_trait_mut

visit_item_type_mut

visit_item_union_mut

visit_item_use_mut

visit_label_mut

visit_lifetime_mut

visit_lifetime_param_mut

visit_lit_bool_mut

visit_lit_byte_mut

visit_lit_byte_str_mut

visit_lit_char_mut

visit_lit_cstr_mut

visit_lit_float_mut

visit_lit_int_mut

visit_lit_mut

visit_lit_str_mut

visit_local_init_mut

visit_local_mut

visit_macro_delimiter_mut

visit_macro_mut

visit_member_mut

visit_meta_list_mut

visit_meta_mut

visit_meta_name_value_mut

visit_parenthesized_generic_arguments_mut

visit_pat_ident_mut

visit_pat_mut

visit_pat_or_mut

visit_pat_paren_mut

visit_pat_reference_mut

visit_pat_rest_mut

visit_pat_slice_mut

visit_pat_struct_mut

visit_pat_tuple_mut

visit_pat_tuple_struct_mut

visit_pat_type_mut

visit_pat_wild_mut

visit_path_arguments_mut

visit_path_mut

visit_path_segment_mut

visit_pointer_mutability_mut

visit_precise_capture_mut

visit_predicate_lifetime_mut

visit_predicate_type_mut

visit_qself_mut

visit_range_limits_mut

visit_receiver_mut

visit_return_type_mut

visit_signature_mut

visit_span_mut

visit_static_mutability_mut

visit_stmt_macro_mut

visit_stmt_mut

visit_trait_bound_modifier_mut

visit_trait_bound_mut

visit_trait_item_const_mut

visit_trait_item_fn_mut

visit_trait_item_macro_mut

visit_trait_item_mut

visit_trait_item_type_mut

visit_type_array_mut

visit_type_bare_fn_mut

visit_type_group_mut

visit_type_impl_trait_mut

visit_type_infer_mut

visit_type_macro_mut

visit_type_mut

visit_type_never_mut

visit_type_param_bound_mut

visit_type_param_mut

visit_type_paren_mut

visit_type_path_mut

visit_type_ptr_mut

visit_type_reference_mut

visit_type_slice_mut

visit_type_trait_object_mut

visit_type_tuple_mut

visit_un_op_mut

visit_use_glob_mut

visit_use_group_mut

visit_use_name_mut

visit_use_path_mut

visit_use_rename_mut

visit_use_tree_mut

visit_variadic_mut

visit_variant_mut

visit_vis_restricted_mut

visit_visibility_mut

visit_where_clause_mut

visit_where_predicate_mut