regexp/syntax: document the upper limit of n in x{n}
Fixes #7252.
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/77990044
diff --git a/src/pkg/regexp/syntax/doc.go b/src/pkg/regexp/syntax/doc.go
index e52632e..8e72c90 100644
--- a/src/pkg/regexp/syntax/doc.go
+++ b/src/pkg/regexp/syntax/doc.go
@@ -46,6 +46,10 @@
x{n,}? n or more x, prefer fewer
x{n}? exactly n x
+Implementation restriction: The counting forms x{n} etc. (but not the other
+forms x* etc.) have an upper limit of n=1000. Negative or higher explicit
+counts yield the parse error ErrInvalidRepeatSize.
+
Grouping:
(re) numbered capturing group (submatch)
(?P<name>re) named & numbered capturing group (submatch)
