Ensure only static lifetimes appear in derived types

derive/Cargo.toml

@@ -16,5 +16,5 @@ proc-macro = true
 
 [dependencies]
 quote = "1.0"
-syn = { version = "1.0", features = ["derive"] }
+syn = { version = "1.0", features = ["derive", "visit-mut"] }
 proc-macro2 = "1.0"

derive/src/lib.rs

@@ -35,8 +35,10 @@ use syn::{
         Error,
         Result,
     },
+    parse_quote,
     punctuated::Punctuated,
     token::Comma,
+    visit_mut::VisitMut,
     Data,
     DataEnum,
     DataStruct,
@@ -45,6 +47,7 @@ use syn::{
     ExprLit,
     Field,
     Fields,
+    Lifetime,
     Lit,
     Variant,
 };
@@ -69,7 +72,11 @@ fn generate_type(input: TokenStream2) -> Result<TokenStream2> {
     let ident = &ast.ident;
     trait_bounds::add(ident, &mut ast.generics, &ast.data)?;
 
-    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
+    ast.generics
+        .lifetimes_mut()
+        .for_each(|l| *l = parse_quote!('static));
+
+    let (_, ty_generics, where_clause) = ast.generics.split_for_impl();
     let generic_type_ids = ast.generics.type_params().map(|ty| {
         let ty_ident = &ty.ident;
         quote! {
@@ -83,9 +90,9 @@ fn generate_type(input: TokenStream2) -> Result<TokenStream2> {
         Data::Enum(ref e) => generate_variant_type(e),
         Data::Union(_) => return Err(Error::new_spanned(input, "Unions not supported")),
     };
-
+    let generic_types = ast.generics.type_params();
     let type_info_impl = quote! {
-        impl #impl_generics ::scale_info::TypeInfo for #ident #ty_generics #where_clause {
+        impl <#( #generic_types ),*> ::scale_info::TypeInfo for #ident #ty_generics #where_clause {
             type Identity = Self;
             fn type_info() -> ::scale_info::Type {
                 ::scale_info::Type::builder()
@@ -107,6 +114,17 @@ fn generate_fields(fields: &FieldsList) -> Vec<TokenStream2> {
         .iter()
         .map(|f| {
             let (ty, ident) = (&f.ty, &f.ident);
+            // Replace any field lifetime params with `static to prevent "unnecessary lifetime parameter"
+            // warning. Any lifetime parameters are specified as 'static in the type of the impl.
+            struct StaticLifetimesReplace;
+            impl VisitMut for StaticLifetimesReplace {
+                fn visit_lifetime_mut(&mut self, lifetime: &mut Lifetime) {
+                    *lifetime = parse_quote!('static)
+                }
+            }
+            let mut ty = ty.clone();
+            StaticLifetimesReplace.visit_type_mut(&mut ty);
+
             let type_name = clean_type_string(&quote!(#ty).to_string());
 
             if let Some(i) = ident {
@@ -139,6 +157,7 @@ fn clean_type_string(input: &str) -> String {
         .replace(" <", "<")
         .replace("< ", "<")
         .replace(" >", ">")
+        .replace("& \'", "&'")
 }
 
 fn generate_composite_type(data_struct: &DataStruct) -> TokenStream2 {

derive/src/trait_bounds.rs

@@ -28,29 +28,34 @@ use syn::{
 /// associated types (e.g. `T::A: TypeInfo`), correctly dealing with
 /// self-referential types.
 pub fn add(input_ident: &Ident, generics: &mut Generics, data: &syn::Data) -> Result<()> {
-    let ty_params = generics.type_params_mut().fold(Vec::new(), |mut acc, p| {
-        p.bounds.push(parse_quote!(::scale_info::TypeInfo));
-        p.bounds.push(parse_quote!('static));
-        acc.push(p.ident.clone());
-        acc
-    });
+    let ty_params_ids = generics
+        .type_params()
+        .map(|type_param| type_param.ident.clone())
+        .collect::<Vec<Ident>>();
 
-    if ty_params.is_empty() {
+    if ty_params_ids.is_empty() {
         return Ok(())
     }
 
-    let types = collect_types_to_bind(input_ident, data, &ty_params)?;
-
-    if !types.is_empty() {
-        let where_clause = generics.make_where_clause();
+    let types = collect_types_to_bind(input_ident, data, &ty_params_ids)?;
+    let type_params = generics.type_params().cloned().collect::<Vec<_>>();
+    let where_clause = generics.make_where_clause();
 
-        types.into_iter().for_each(|ty| {
-            where_clause
-                .predicates
-                .push(parse_quote!(#ty : ::scale_info::TypeInfo + 'static))
-        });
-    }
+    types.into_iter().for_each(|ty| {
+        where_clause
+            .predicates
+            .push(parse_quote!(#ty : ::scale_info::TypeInfo + 'static))
+    });
 
+    type_params.into_iter().for_each(|type_param| {
+        let ident = type_param.ident;
+        let mut bounds = type_param.bounds;
+        bounds.push(parse_quote!(::scale_info::TypeInfo));
+        bounds.push(parse_quote!('static));
+        where_clause
+            .predicates
+            .push(parse_quote!( #ident : #bounds));
+    });
     Ok(())
 }
 

test_suite/tests/derive.rs

@@ -186,8 +186,9 @@ fn associated_types_derive_without_bounds() {
     }
     #[allow(unused)]
     #[derive(TypeInfo)]
-    struct Assoc<T: Types> {
+    struct Assoc<'bar, T: Types> {
         a: T::A,
+        b: &'bar u64,
     }
 
     #[derive(TypeInfo)]
@@ -199,7 +200,11 @@ fn associated_types_derive_without_bounds() {
     let struct_type = Type::builder()
         .path(Path::new("Assoc", "derive"))
         .type_params(tuple_meta_type!(ConcreteTypes))
-        .composite(Fields::named().field_of::<bool>("a", "T::A"));
+        .composite(
+            Fields::named()
+                .field_of::<bool>("a", "T::A")
+                .field_of::<u64>("b", "&'static u64"),
+        );
 
     assert_type!(Assoc<ConcreteTypes>, struct_type);
 }
@@ -224,8 +229,8 @@ fn whitespace_scrubbing_works() {
 fn ui_tests() {
     let t = trybuild::TestCases::new();
     t.compile_fail("tests/ui/fail_missing_derive.rs");
-    t.compile_fail("tests/ui/fail_non_static_lifetime.rs");
     t.compile_fail("tests/ui/fail_unions.rs");
+    t.pass("tests/ui/pass_non_static_lifetime.rs");
     t.pass("tests/ui/pass_self_referential.rs");
     t.pass("tests/ui/pass_basic_generic_type.rs");
     t.pass("tests/ui/pass_complex_generic_self_referential_type.rs");

test_suite/tests/ui/pass_non_static_lifetime.rs

@@ -0,0 +1,12 @@
+use scale_info::TypeInfo;
+
+#[derive(TypeInfo)]
+struct Me<'a> {
+    _me: &'a Me<'a>,
+}
+
+fn assert_type_info<T: TypeInfo + 'static>() {}
+
+fn main() {
+    assert_type_info::<Me>();
+}