Function macro_tools::exposed::generic_args::merge

source · 
pub fn merge(
    a: &AngleBracketedGenericArguments,
    b: &AngleBracketedGenericArguments,
) -> AngleBracketedGenericArguments
Expand description

Merges two syn::AngleBracketedGenericArguments instances into a new one, prioritizing lifetime parameters before other types of generic arguments.

This function takes two references to syn::AngleBracketedGenericArguments and categorizes their arguments into lifetimes and other types. It then combines them such that all lifetimes from both instances precede any other arguments in the resulting syn::AngleBracketedGenericArguments instance. This is particularly useful for ensuring that the merged generics conform to typical Rust syntax requirements where lifetimes are declared before other generic parameters.

§Arguments

  • a - A reference to the first syn::AngleBracketedGenericArguments instance, containing one or more generic arguments.
  • b - A reference to the second syn::AngleBracketedGenericArguments instance, containing one or more generic arguments.

§Returns

Returns a new syn::AngleBracketedGenericArguments instance containing the merged arguments from both a and b, with lifetimes appearing first.

§Examples

use macro_tools::{
  generic_args,
  syn::{parse_quote, AngleBracketedGenericArguments},
};

let a : AngleBracketedGenericArguments = parse_quote! { <'a, T: Clone, U: Default> };
let b : AngleBracketedGenericArguments = parse_quote! { <'b, V: core::fmt::Debug> };
let merged = generic_args::merge(&a, &b);

let expected: AngleBracketedGenericArguments = parse_quote! { <'a, 'b, T: Clone, U: Default, V: core::fmt::Debug> };
assert_eq!(merged, expected);

This example demonstrates how lifetimes 'a and 'b are placed before other generic parameters like T, U, and V in the merged result, adhering to the expected syntax order in Rust generics.