go/ast: document that ast.FilterFile always filters imports
Fixes #9248.
Change-Id: Id1c50af5eb35d7720b8f0a4d4881414baf061d56
Reviewed-on: https://go-review.googlesource.com/3241
Reviewed-by: Alan Donovan <adonovan@google.com>
diff --git a/src/go/ast/filter.go b/src/go/ast/filter.go
index fc3eeb4..50e576e 100644
--- a/src/go/ast/filter.go
+++ b/src/go/ast/filter.go
@@ -221,8 +221,8 @@
// names from top-level declarations (including struct field and
// interface method names, but not from parameter lists) that don't
// pass through the filter f. If the declaration is empty afterwards,
-// the declaration is removed from the AST. The File.Comments list
-// is not changed.
+// the declaration is removed from the AST. Import declarations are
+// always removed. The File.Comments list is not changed.
//
// FilterFile returns true if there are any top-level declarations
// left after filtering; it returns false otherwise.
