feat: add basic support for non static lifetimes

src/expand.rs

@@ -1,3 +1,4 @@
+use crate::utils::type_lifetimes_to_static;
 use proc_macro2::{Ident, Span, TokenStream};
 use quote::quote;
 use syn::{parse_quote, ItemStruct};
@@ -23,7 +24,10 @@ pub(crate) fn expand_struct(mut item: ItemStruct) -> proc_macro::TokenStream {
             } else {
                 let fn_name_lit = format!("__serde_inline_default_{}_{}", item.ident, i);
                 let fn_name_ident = Ident::new(&fn_name_lit, Span::call_site());
-                let return_type = &field.ty;
+                let mut return_type = field.ty.clone();
+
+                // replaces most lifetimes with 'static
+                type_lifetimes_to_static(&mut return_type);
 
                 let inline_fn = quote! {
                     #[doc(hidden)]

src/lib.rs

@@ -4,6 +4,7 @@ use proc_macro::TokenStream;
 use syn::{parse_macro_input, Item};
 
 mod expand;
+mod utils;
 
 /// The main macro of this crate.
 /// Use it to define default values of fields in structs you [`Serialize`] or [`Deserialize`].

src/utils.rs

@@ -0,0 +1,41 @@
+use syn::{parse_quote, GenericArgument, PathArguments, Type};
+
+pub(crate) fn type_lifetimes_to_static(ty: &mut Type) {
+    match ty {
+        Type::Array(array) => type_lifetimes_to_static(array.elem.as_mut()),
+        Type::Group(group) => type_lifetimes_to_static(&mut group.elem),
+        Type::ImplTrait(_) => {}
+        Type::Path(path) => {
+            for segment in &mut path.path.segments {
+                match &mut segment.arguments {
+                    PathArguments::None => (),
+                    PathArguments::AngleBracketed(angle_bracketed) => {
+                        for arg in &mut angle_bracketed.args {
+                            match arg {
+                                GenericArgument::Lifetime(lifetime) => {
+                                    *lifetime = parse_quote!('static);
+                                }
+                                GenericArgument::Type(ty) => type_lifetimes_to_static(ty),
+                                _ => (),
+                            }
+                        }
+                    }
+                    PathArguments::Parenthesized(parenthesized) => {
+                        for input in &mut parenthesized.inputs {
+                            type_lifetimes_to_static(input)
+                        }
+                    }
+                }
+            }
+        }
+        Type::Ptr(ptr) => type_lifetimes_to_static(&mut ptr.elem),
+        Type::Reference(reference) => reference.lifetime = Some(parse_quote!('static)),
+        Type::Slice(slice) => type_lifetimes_to_static(&mut slice.elem),
+        Type::Tuple(tuple) => {
+            for elem in &mut tuple.elems {
+                type_lifetimes_to_static(elem)
+            }
+        }
+        _ => (),
+    }
+}

tests/test_serde_inline_default.rs

@@ -1,6 +1,7 @@
 use serde::Deserialize;
 use serde_inline_default::serde_inline_default;
 use serde_json::json;
+use std::borrow::Cow;
 
 #[test]
 fn test_serde_inline_default() {
@@ -28,3 +29,17 @@ fn test_serde_inline_default() {
     assert_eq!(test.inline_negative, -1337);
     assert_eq!(test.string, "string".to_string());
 }
+
+#[test]
+fn test_lifetime() {
+    #[serde_inline_default]
+    #[derive(Deserialize)]
+    struct LifetimeTest<'a> {
+        #[serde_inline_default("test".into())]
+        test_str: Cow<'a, str>,
+    }
+
+    let lifetime_test: LifetimeTest = serde_json::from_value(json!({})).unwrap();
+
+    assert_eq!(lifetime_test.test_str, "test");
+}