cue: implementation of marked defaults

Change-Id: I7b0ed2b1e372a71410cbd05253ca819f08509a2a
diff --git a/doc/tutorial/basics/coalesce.md b/doc/tutorial/basics/coalesce.md
index 082708a..dde8c77 100644
--- a/doc/tutorial/basics/coalesce.md
+++ b/doc/tutorial/basics/coalesce.md
@@ -29,11 +29,11 @@
 ```
 list: [ "Cat", "Mouse", "Dog" ]
 
-a: list[0] | "None"
-b: list[5] | "None"
+a: *list[0] | "None"
+b: *list[5] | "None"
 
 n: [null]
-v: n[0] & string | "default"
+v: *n[0] & string | "default"
 ```
 
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