doc: Mention Span in developer-notes.md

sipa · furszy · commit da207d405b0e · 2021-07-06T20:59:21.000-03:00
diff --git a/doc/developer-notes.md b/doc/developer-notes.md
@@ -500,6 +500,12 @@ class A
   - *Rationale*: Easier to understand what is happening, thus easier to spot mistakes, even for those
   that are not language lawyers
 
+- Use `Span` as function argument when it can operate on any range-like container.
+
+  - *Rationale*: Compared to `Foo(const vector<int>&)` this avoids the need for a (potentially expensive)
+    conversion to vector if the caller happens to have the input stored in another type of container.
+    However, be aware of the pitfalls documented in [span.h](../src/span.h).
+
 Strings and formatting
 ------------------------
 
