rustdoc-search: sort typ-based inverted indexes by length

This gives us incremental search results back for types, so
type-based search feels faster even for queries with lots of matches.

Author: notriddle

src/librustdoc/html/render/mod.rs

@@ -151,6 +151,19 @@ struct RenderType {
 }
 
 impl RenderType {
+    fn size(&self) -> usize {
+        let mut size = 1;
+        if let Some(generics) = &self.generics {
+            size += generics.iter().map(RenderType::size).sum::<usize>();
+        }
+        if let Some(bindings) = &self.bindings {
+            for (_, constraints) in bindings.iter() {
+                size += 1;
+                size += constraints.iter().map(RenderType::size).sum::<usize>();
+            }
+        }
+        size
+    }
     // Types are rendered as lists of lists, because that's pretty compact.
     // The contents of the lists are always integers in self-terminating hex
     // form, handled by `RenderTypeId::write_to_string`, so no commas are
@@ -296,6 +309,15 @@ pub(crate) struct IndexItemFunctionType {
 }
 
 impl IndexItemFunctionType {
+    fn size(&self) -> usize {
+        self.inputs.iter().map(RenderType::size).sum::<usize>()
+            + self.output.iter().map(RenderType::size).sum::<usize>()
+            + self
+                .where_clause
+                .iter()
+                .map(|constraints| constraints.iter().map(RenderType::size).sum::<usize>())
+                .sum::<usize>()
+    }
     fn read_from_string_without_param_names(string: &[u8]) -> (IndexItemFunctionType, usize) {
         let mut i = 0;
         if string[i] == b'`' {