Merge pull request #1666 from dtolnay/foldhelper

Generate fewer monomorphizations in Fold
dtolnay · May 19, 2024 · 7273aa7 · 7273aa7
2 parents b2ee932 + 8124c0e
commit 7273aa7
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Showing 3 changed files with 163 additions and 159 deletions.
diff --git a/codegen/src/fold.rs b/codegen/src/fold.rs
@@ -7,12 +7,14 @@ use syn_codegen::{Data, Definitions, Features, Node, Type};
 
 const FOLD_SRC: &str = "src/gen/fold.rs";
 
-fn simple_visit(item: &str, name: &TokenStream) -> TokenStream {
+fn method_name(item: &str) -> Ident {
     let ident = gen::under_name(item);
-    let method = format_ident!("fold_{}", ident);
-    quote! {
-        f.#method(#name)
-    }
+    format_ident!("fold_{}", ident)
+}
+
+fn simple_fold(item: &str, name: &TokenStream) -> TokenStream {
+    let method = method_name(item);
+    quote! { f.#method(#name) }
 }
 
 fn visit(
@@ -29,17 +31,18 @@ fn visit(
             })
         }
         Type::Vec(t) => {
-            let operand = quote!(it);
-            let val = visit(t, features, defs, &operand)?;
+            let Type::Syn(t) = &**t else { unimplemented!() };
+            let method = method_name(t);
             Some(quote! {
-                FoldHelper::lift(#name, |it| #val)
+                FoldHelper::lift(#name, f, F::#method)
             })
         }
         Type::Punctuated(p) => {
-            let operand = quote!(it);
-            let val = visit(&p.element, features, defs, &operand)?;
+            let t = &*p.element;
+            let Type::Syn(t) = t else { unimplemented!() };
+            let method = method_name(t);
             Some(quote! {
-                FoldHelper::lift(#name, |it| #val)
+                FoldHelper::lift(#name, f, F::#method)
             })
         }
         Type::Option(t) => {
@@ -66,14 +69,14 @@ fn visit(
             fn requires_full(features: &Features) -> bool {
                 features.any.contains("full") && features.any.len() == 1
             }
-            let mut res = simple_visit(t, name);
+            let mut res = simple_fold(t, name);
             let target = defs.types.iter().find(|ty| ty.ident == *t).unwrap();
             if requires_full(&target.features) && !requires_full(features) {
                 res = quote!(full!(#res));
             }
             Some(res)
         }
-        Type::Ext(t) if gen::TERMINAL_TYPES.contains(&&t[..]) => Some(simple_visit(t, name)),
+        Type::Ext(t) if gen::TERMINAL_TYPES.contains(&&t[..]) => Some(simple_fold(t, name)),
         Type::Ext(_) | Type::Std(_) | Type::Token(_) | Type::Group(_) => None,
     }
 }