cue: exempt aliases and embeddings from recursive closing
See comments in spec.
Issue #40.
Change-Id: I7e17864c649ef3576d6992eb5a2b530c76f5496e
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/3043
Reviewed-by: Jonathan Amsterdam <jba@google.com>
diff --git a/doc/ref/spec.md b/doc/ref/spec.md
index ca04260..6b694f1 100644
--- a/doc/ref/spec.md
+++ b/doc/ref/spec.md
@@ -1198,9 +1198,32 @@
It is illegal to have a regular field and a definition with the same name
within the same struct.
Literal structs that are part of a definition's value are implicitly closed.
+This excludes literals structs in embeddings and aliases.
An ellipsis `...` in such literal structs keeps them open,
as it defines `_` for all labels.
+<!--
+Excluding embeddings from recursive closing allows comprehensions to be
+interpreted as embeddings without some exception. For instance,
+ if x > 2 {
+ foo: string
+ }
+should not cause any failure. It is also consistent with embeddings being
+opened when included in a closed struct.
+Finally, excluding embeddings from recursive closing allows for
+a mechanism to not recursively close, without needing an additional language
+construct, such as a triple colon or something else:
+foo :: {
+ {
+ // not recursively closed
+ }
+ ... // include this to not close outer struct
+}
+
+Including aliases from this exclusion, which are more a separate definition
+than embedding seems sensible, and allows for an easy mechanism to avoid
+closing, aside from embedding.
+-->
```
// MyStruct is closed and as there is no expression label or `...`, we know
