1 files changed, 32 insertions, 0 deletions

diff --git a/docs/dev/style.md b/docs/dev/style.md
index 59067d234..20f1b6253 100644
--- a/docs/dev/style.md
+++ b/docs/dev/style.md
@@ -186,6 +186,31 @@ impl Person {
 }
 ```
 
+## Constructors
+
+Prefer `Default` to zero-argument `new` function
+
+```rust
+// Good
+#[derive(Default)]
+struct Foo {
+    bar: Option<Bar>
+}
+
+// Not as good
+struct Foo {
+    bar: Option<Bar>
+}
+
+impl Foo {
+    fn new() -> Foo {
+        Foo { bar: None }
+    }
+}
+```
+
+Prefer `Default` even it has to be implemented manually.
+
 ## Avoid Monomorphization
 
 Rust uses monomorphization to compile generic code, meaning that for each instantiation of a generic functions with concrete types, the function is compiled afresh, *per crate*.
@@ -223,6 +248,8 @@ fn frbonicate(f: impl AsRef<Path>) {
 
 # Premature Pessimization
 
+## Avoid Allocations
+
 Avoid writing code which is slower than it needs to be.
 Don't allocate a `Vec` where an iterator would do, don't allocate strings needlessly.
 
@@ -242,6 +269,8 @@ if words.len() != 2 {
 }
 ```
 
+## Push Allocations to the Call Site
+
 If allocation is inevitable, let the caller allocate the resource:
 
 ```rust
@@ -257,6 +286,9 @@ fn frobnicate(s: &str) {
 }
 ```
 
+This is better because it reveals the costs.
+It is also more efficient when the caller already owns the allocation.
+
 ## Collection types
 
 Prefer `rustc_hash::FxHashMap` and `rustc_hash::FxHashSet` instead of the ones in `std::collections`.