doc/faq: mention that copying discussion is semantics, not implementation

Fixes #17181.

Change-Id: If7cc4865e391acf76512f7ec7167d5a31377b598
Reviewed-on: https://go-review.googlesource.com/31574
Reviewed-by: Rob Pike <r@golang.org>

diff --git a/doc/go_faq.html b/doc/go_faq.html
index 6a955f6f3f7e6b4c842dd29895ac26b5a120207e..37a31ae289aaeeaa7fb9e058cd79669e259c47c5 100644 (file)
--- a/doc/go_faq.html
+++ b/doc/go_faq.html
@@ -1151,6 +1151,12 @@ struct.  If the interface value holds a pointer, copying the interface value
 makes a copy of the pointer, but again not the data it points to.
 </p>
 
+<p>
+Note that this discussion is about the semantics of the operations.
+Actual implementations may apply optimizations to avoid copying
+as long as the optimizations do not change the semantics.
+</p>
+
 <h3 id="pointer_to_interface">
 When should I use a pointer to an interface?</h3>