#[hook]: clippy::multiple_bound_locations lint no longer triggered

This is achieved by reworking the logic for rewriting the function signature of the hook.

Author: its-the-shrimp

packages/yew-macro/src/hook/lifetime.rs

@@ -10,7 +10,6 @@ use syn::{
 // borrowed from the awesome async-trait crate.
 pub struct CollectLifetimes {
     pub elided: Vec<Lifetime>,
-    pub explicit: Vec<Lifetime>,
     pub name: &'static str,
     pub default_span: Span,
 
@@ -23,7 +22,6 @@ impl CollectLifetimes {
     pub fn new(name: &'static str, default_span: Span) -> Self {
         CollectLifetimes {
             elided: Vec::new(),
-            explicit: Vec::new(),
             name,
             default_span,
 
@@ -55,8 +53,6 @@ impl CollectLifetimes {
     fn visit_lifetime(&mut self, lifetime: &mut Lifetime) {
         if lifetime.ident == "_" {
             *lifetime = self.next_lifetime(lifetime.span());
-        } else {
-            self.explicit.push(lifetime.clone());
         }
     }
 

packages/yew-macro/src/hook/mod.rs

@@ -3,7 +3,7 @@ use proc_macro_error::emit_error;
 use quote::quote;
 use syn::parse::{Parse, ParseStream};
 use syn::{
-    parse_file, parse_quote, visit_mut, Attribute, Ident, ItemFn, LitStr, ReturnType, Signature,
+    parse_quote, visit_mut, Attribute, File, Ident, Item, ItemFn, LitStr, ReturnType, Signature,
     Type,
 };
 
@@ -51,16 +51,14 @@ impl Parse for HookFn {
 
 impl HookFn {
     fn doc_attr(&self) -> Attribute {
-        let vis = &self.inner.vis;
-        let sig = &self.inner.sig;
-
-        let sig_s = quote! { #vis #sig {
-            __yew_macro_dummy_function_body__
-        } }
-        .to_string();
-
-        let sig_file = parse_file(&sig_s).unwrap();
-        let sig_formatted = prettyplease::unparse(&sig_file);
+        let sig_formatted = prettyplease::unparse(&File {
+            shebang: None,
+            attrs: vec![],
+            items: vec![Item::Fn(ItemFn {
+                block: parse_quote!({ __yew_macro_dummy_function_body__ }),
+                ..self.inner.clone()
+            })],
+        });
 
         let literal = LitStr::new(
             &format!(

packages/yew-macro/src/hook/signature.rs

@@ -1,15 +1,27 @@
+use std::iter::once;
+use std::mem::take;
+
 use proc_macro2::{Span, TokenStream};
 use proc_macro_error::emit_error;
 use quote::{quote, ToTokens};
+use syn::punctuated::{Pair, Punctuated};
 use syn::spanned::Spanned;
 use syn::visit_mut::VisitMut;
 use syn::{
-    parse_quote, parse_quote_spanned, token, visit_mut, FnArg, GenericParam, Ident, Lifetime, Pat,
-    Receiver, ReturnType, Signature, Type, TypeImplTrait, TypeReference, WhereClause,
+    parse_quote, parse_quote_spanned, visit_mut, FnArg, GenericParam, Ident, Lifetime,
+    LifetimeParam, Pat, Receiver, ReturnType, Signature, Type, TypeImplTrait, TypeParam,
+    TypeParamBound, TypeReference, WherePredicate,
 };
 
 use super::lifetime;
 
+fn type_is_generic(ty: &Type, param: &TypeParam) -> bool {
+    match ty {
+        Type::Path(path) => path.path.is_ident(&param.ident),
+        _ => false,
+    }
+}
+
 #[derive(Default)]
 pub struct CollectArgs {
     needs_boxing: bool,
@@ -99,48 +111,68 @@ impl HookSignature {
             ..
         } = sig;
 
-        let hook_lifetime = {
-            let hook_lifetime = Lifetime::new("'hook", Span::mixed_site());
-            generics.params = {
-                let elided_lifetimes = &lifetimes.elided;
-                let params = &generics.params;
-
-                parse_quote!(#hook_lifetime, #(#elided_lifetimes,)* #params)
-            };
-
-            let mut where_clause = generics
-                .where_clause
-                .clone()
-                .unwrap_or_else(|| WhereClause {
-                    where_token: token::Where {
-                        span: Span::mixed_site(),
-                    },
-                    predicates: Default::default(),
-                });
+        let hook_lifetime = Lifetime::new("'hook", Span::mixed_site());
+        let mut params: Punctuated<_, _> = once(hook_lifetime.clone())
+            .chain(lifetimes.elided)
+            .map(|lifetime| {
+                GenericParam::Lifetime(LifetimeParam {
+                    attrs: vec![],
+                    lifetime,
+                    colon_token: None,
+                    bounds: Default::default(),
+                })
+            })
+            .map(|param| Pair::new(param, Some(Default::default())))
+            .chain(take(&mut generics.params).into_pairs())
+            .collect();
 
-            for elided in lifetimes.elided.iter() {
-                where_clause
-                    .predicates
-                    .push(parse_quote!(#elided: #hook_lifetime));
-            }
+        for type_param in params.iter_mut().skip(1) {
+            match type_param {
+                GenericParam::Lifetime(param) => {
+                    if let Some(predicate) = generics
+                        .where_clause
+                        .iter_mut()
+                        .flat_map(|c| &mut c.predicates)
+                        .find_map(|predicate| match predicate {
+                            WherePredicate::Lifetime(p) if p.lifetime == param.lifetime => Some(p),
+                            _ => None,
+                        })
+                    {
+                        predicate.bounds.push(hook_lifetime.clone());
+                    } else {
+                        param.colon_token = Some(param.colon_token.unwrap_or_default());
+                        param.bounds.push(hook_lifetime.clone());
+                    }
+                }
 
-            for explicit in lifetimes.explicit.iter() {
-                where_clause
-                    .predicates
-                    .push(parse_quote!(#explicit: #hook_lifetime));
-            }
+                GenericParam::Type(param) => {
+                    if let Some(predicate) = generics
+                        .where_clause
+                        .iter_mut()
+                        .flat_map(|c| &mut c.predicates)
+                        .find_map(|predicate| match predicate {
+                            WherePredicate::Type(p) if type_is_generic(&p.bounded_ty, param) => {
+                                Some(p)
+                            }
+                            _ => None,
+                        })
+                    {
+                        predicate
+                            .bounds
+                            .push(TypeParamBound::Lifetime(hook_lifetime.clone()));
+                    } else {
+                        param.colon_token = Some(param.colon_token.unwrap_or_default());
+                        param
+                            .bounds
+                            .push(TypeParamBound::Lifetime(hook_lifetime.clone()));
+                    }
+                }
 
-            for type_param in generics.type_params() {
-                let type_param_ident = &type_param.ident;
-                where_clause
-                    .predicates
-                    .push(parse_quote!(#type_param_ident: #hook_lifetime));
+                GenericParam::Const(_) => {}
             }
+        }
 
-            generics.where_clause = Some(where_clause);
-
-            hook_lifetime
-        };
+        generics.params = params;
 
         let (output, output_type) = Self::rewrite_return_type(&hook_lifetime, return_type);
         sig.output = output;
@@ -165,7 +197,15 @@ impl HookSignature {
         self.sig
             .generics
             .lifetimes()
-            .map(|life| parse_quote! { &#life () })
+            .map(|life| TypeReference {
+                and_token: Default::default(),
+                lifetime: Some(life.lifetime.clone()),
+                mutability: None,
+                elem: Box::new(Type::Tuple(syn::TypeTuple {
+                    paren_token: Default::default(),
+                    elems: Default::default(),
+                })),
+            })
             .collect()
     }
 

packages/yew-macro/src/lib.rs

@@ -140,7 +140,7 @@ pub fn classes(input: TokenStream) -> TokenStream {
 
 #[proc_macro_error::proc_macro_error]
 #[proc_macro_attribute]
-pub fn function_component(attr: TokenStream, item: TokenStream) -> proc_macro::TokenStream {
+pub fn function_component(attr: TokenStream, item: TokenStream) -> TokenStream {
     let item = parse_macro_input!(item as FunctionComponent);
     let attr = parse_macro_input!(attr as FunctionComponentName);
 
@@ -151,7 +151,7 @@ pub fn function_component(attr: TokenStream, item: TokenStream) -> proc_macro::T
 
 #[proc_macro_error::proc_macro_error]
 #[proc_macro_attribute]
-pub fn hook(attr: TokenStream, item: TokenStream) -> proc_macro::TokenStream {
+pub fn hook(attr: TokenStream, item: TokenStream) -> TokenStream {
     let item = parse_macro_input!(item as HookFn);
 
     if let Some(m) = proc_macro2::TokenStream::from(attr).into_iter().next() {