Add a comment to util/unbrace.

With a regexp to match things that need braces.  Unfortunately, there are
some false positives, and we can't tell where the braces are supposed to go.

1 files changed, 21 insertions, 0 deletions

diff --git a/crawl-ref/source/util/unbrace b/crawl-ref/source/util/unbrace
index ac73a24fa2..9febd6dc62 100755
--- a/crawl-ref/source/util/unbrace
+++ b/crawl-ref/source/util/unbrace
@@ -26,6 +26,27 @@ for $f (@files)
     # Eliminate braces around one-line blocks.
     s&^( +(?:if|while|for|do|else)\b[^\n]*)\n +{\n( *[^/ }][^\n]*)\n +}$&$1\n$2&msg;
 
+    # Something like the following should match multi-line flow-control statements
+    # with missing braces, but:
+    #  1. it's slow (for example, on beam.cc);
+    #  2. it has false positives at the end of do-while loops; and
+    #  3. it's not clear how to determine where to put the braces.
+    #
+    # /( # Save multi-line statement with missing braces in \1.
+    #    # Save indent of first line in \2
+    #    ^(\s+)     (?:if|while|for|do|else)\b           .*\n
+    #
+    #     # Second line: not flow-control, greater indent.
+    #     \2 \s+    (?! \s | (?:if|while|for|do|else)\b) .*\n
+    #
+    #     # One or more lines of greater indent than the first.
+    #     (?: \2 \s+ .*\n)+
+    #  )
+    #  # Next line falls outside the indentation of the first line: it has
+    #  # either a smaller indent, or the same indent then a non-brace.
+    #  (?! \2 [\s{])
+    # /mgx; # No /s !
+
     # return is not a function, eliminate totally enclosing parentheses.
     # This part handles parenthese-less payloads.
     while (/^( *)return \(([^()]+)\);/sm)