Update discussion of AST safety check in README (#2159)

[etc/vim.git] / README.md

diff --git a/README.md b/README.md
index 8d6adb0567ef487611c6cb91ab4269d96c64932b..c7577fbbd041eaf2a8d4c1230ffaf9b74c7f62d7 100644 (file)
--- a/README.md
+++ b/README.md
@@ -238,8 +238,10 @@ change in the future**. That being said, no drastic stylistic changes are planne
 mostly responses to bug reports.
 
 Also, as a temporary safety measure, _Black_ will check that the reformatted code still
-produces a valid AST that is equivalent to the original. This slows it down. If you're
-feeling confident, use `--fast`.
+produces a valid AST that is mostly equivalent to the original. This slows it down. If
+you're feeling confident, use `--fast`. In a few contexts, Black does make changes to
+the AST: it cleans up whitespace in docstrings, adds or removes parentheses in some
+`del` statements, and may move around type comments.
 
 ## The _Black_ code style