Reword description of promotability

ecstatic-morse · ecstatic-morse · commit 49e161bbe71e · 2019-10-21T11:47:25.000-07:00
diff --git a/promotion.md b/promotion.md
@@ -87,7 +87,8 @@ contexts are treated as explicit.
 
 We have described the circumstances where promotion is desirable, but what
 expressions are actually eligible for promotion? We refer to eligible
-expressions as "promotable".
+expressions as "promotable" and describe the restrictions on such expressions
+below.
 
 ### Named locals
 
