Auto merge of rust-lang#98475 - notriddle:notriddle/index-fn-signatures, r=GuillaumeGomez

rustdoc: reference function signature types from the `p` array

This reduces the size of the function signature index, because it's common to have many functions that operate on the same types.

    $ wc -c search-index-old.js search-index-new.js
    5224374 search-index-old.js
    3932314 search-index-new.js

By my math, this reduces the uncompressed size of the search index by 32%.
On compressed signatures, the wins are less drastic, a mere 8%:

    $ wc -c search-index-old.js.gz search-index-new.js.gz
    404532 search-index-old.js.gz
    371635 search-index-new.js.gz

Author: bors

src/librustdoc/clean/types.rs

@@ -1671,10 +1671,6 @@ impl Type {
         matches!(self, Type::ImplTrait(_))
     }
 
-    pub(crate) fn is_primitive(&self) -> bool {
-        self.primitive_type().is_some()
-    }
-
     pub(crate) fn projection(&self) -> Option<(&Type, DefId, PathSegment)> {
         if let QPath { self_type, trait_, assoc, .. } = self {
             Some((self_type, trait_.def_id(), *assoc.clone()))

src/librustdoc/formats/item_type.rs

@@ -48,7 +48,6 @@ pub(crate) enum ItemType {
     ProcAttribute = 23,
     ProcDerive = 24,
     TraitAlias = 25,
-    Generic = 26,
 }
 
 impl Serialize for ItemType {
@@ -175,7 +174,6 @@ impl ItemType {
             ItemType::ProcAttribute => "attr",
             ItemType::ProcDerive => "derive",
             ItemType::TraitAlias => "traitalias",
-            ItemType::Generic => "generic",
         }
     }
 }

src/librustdoc/html/render/mod.rs

@@ -110,63 +110,72 @@ pub(crate) struct IndexItem {
 /// A type used for the search index.
 #[derive(Debug)]
 pub(crate) struct RenderType {
-    name: Option<String>,
-    generics: Option<Vec<TypeWithKind>>,
+    id: Option<RenderTypeId>,
+    generics: Option<Vec<RenderType>>,
 }
 
-/// Full type of functions/methods in the search index.
-#[derive(Debug)]
-pub(crate) struct IndexItemFunctionType {
-    inputs: Vec<TypeWithKind>,
-    output: Vec<TypeWithKind>,
-}
-
-impl Serialize for IndexItemFunctionType {
+impl Serialize for RenderType {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
         S: Serializer,
     {
-        // If we couldn't figure out a type, just write `null`.
-        let has_missing = self.inputs.iter().chain(self.output.iter()).any(|i| i.ty.name.is_none());
-        if has_missing {
-            serializer.serialize_none()
-        } else {
+        let id = match &self.id {
+            // 0 is a sentinel, everything else is one-indexed
+            None => 0,
+            Some(RenderTypeId::Index(idx)) => idx + 1,
+            _ => panic!("must convert render types to indexes before serializing"),
+        };
+        if let Some(generics) = &self.generics {
             let mut seq = serializer.serialize_seq(None)?;
-            seq.serialize_element(&self.inputs)?;
-            match self.output.as_slice() {
-                [] => {}
-                [one] => seq.serialize_element(one)?,
-                all => seq.serialize_element(all)?,
-            }
+            seq.serialize_element(&id)?;
+            seq.serialize_element(generics)?;
             seq.end()
+        } else {
+            id.serialize(serializer)
         }
     }
 }
 
-#[derive(Debug)]
-pub(crate) struct TypeWithKind {
-    ty: RenderType,
-    kind: ItemType,
+#[derive(Clone, Debug)]
+pub(crate) enum RenderTypeId {
+    DefId(DefId),
+    Primitive(clean::PrimitiveType),
+    Index(usize),
 }
 
-impl From<(RenderType, ItemType)> for TypeWithKind {
-    fn from(x: (RenderType, ItemType)) -> TypeWithKind {
-        TypeWithKind { ty: x.0, kind: x.1 }
-    }
+/// Full type of functions/methods in the search index.
+#[derive(Debug)]
+pub(crate) struct IndexItemFunctionType {
+    inputs: Vec<RenderType>,
+    output: Vec<RenderType>,
 }
 
-impl Serialize for TypeWithKind {
+impl Serialize for IndexItemFunctionType {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
         S: Serializer,
     {
-        let mut seq = serializer.serialize_seq(None)?;
-        seq.serialize_element(&self.ty.name)?;
-        seq.serialize_element(&self.kind)?;
-        if let Some(generics) = &self.ty.generics {
-            seq.serialize_element(generics)?;
+        // If we couldn't figure out a type, just write `0`.
+        let has_missing = self
+            .inputs
+            .iter()
+            .chain(self.output.iter())
+            .any(|i| i.id.is_none() && i.generics.is_none());
+        if has_missing {
+            0.serialize(serializer)
+        } else {
+            let mut seq = serializer.serialize_seq(None)?;
+            match &self.inputs[..] {
+                [one] if one.generics.is_none() => seq.serialize_element(one)?,
+                _ => seq.serialize_element(&self.inputs)?,
+            }
+            match &self.output[..] {
+                [] => {}
+                [one] if one.generics.is_none() => seq.serialize_element(one)?,
+                _ => seq.serialize_element(&self.output)?,
+            }
+            seq.end()
         }
-        seq.end()
     }
 }
 
@@ -2517,7 +2526,6 @@ fn item_ty_to_section(ty: ItemType) -> ItemSection {
         ItemType::ProcAttribute => ItemSection::AttributeMacros,
         ItemType::ProcDerive => ItemSection::DeriveMacros,
         ItemType::TraitAlias => ItemSection::TraitAliases,
-        ItemType::Generic => unreachable!(),
     }
 }