From 714378d1e9c081e24b085044a5f57b0e455625fd Mon Sep 17 00:00:00 2001
From: Lee Danilek <lee@convex.dev>
Date: Thu, 19 Dec 2024 13:46:29 -0500
Subject: [PATCH] `IndexedFields::by_id()` can be const (#32430)

make it clear that `IndexedFields::by_id()` does no allocations by making it const. this is nice when figuring out the memory footprint of readsets

GitOrigin-RevId: d83b2bfe4e3ff96962a72bd46d3dac5041d2acfa
---
 .../index/database_index/indexed_fields.rs               | 4 ++--
 crates/value/src/heap_size.rs                            | 9 +++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/crates/common/src/bootstrap_model/index/database_index/indexed_fields.rs b/crates/common/src/bootstrap_model/index/database_index/indexed_fields.rs
index e1e27dd4..6695f906 100644
--- a/crates/common/src/bootstrap_model/index/database_index/indexed_fields.rs
+++ b/crates/common/src/bootstrap_model/index/database_index/indexed_fields.rs
@@ -35,8 +35,8 @@ use crate::{
 pub struct IndexedFields(WithHeapSize<Vec<FieldPath>>);
 
 impl IndexedFields {
-    pub fn by_id() -> Self {
-        IndexedFields(vec![].into())
+    pub const fn by_id() -> Self {
+        IndexedFields(WithHeapSize::new_vec())
     }
 
     pub fn creation_time() -> Self {
diff --git a/crates/value/src/heap_size.rs b/crates/value/src/heap_size.rs
index 8d8aa68d..f6fef7ef 100644
--- a/crates/value/src/heap_size.rs
+++ b/crates/value/src/heap_size.rs
@@ -238,6 +238,15 @@ impl<T: HeapSize> From<Vec<T>> for WithHeapSize<Vec<T>> {
     }
 }
 
+impl<T: HeapSize> WithHeapSize<Vec<T>> {
+    pub const fn new_vec() -> Self {
+        Self {
+            inner: Vec::new(),
+            elements_heap_size: 0,
+        }
+    }
+}
+
 impl<T: HeapSize> From<WithHeapSize<Vec<T>>> for Vec<T> {
     fn from(value: WithHeapSize<Vec<T>>) -> Self {
         value.inner