I believe parser is now passing my small corpus

TODO.md

@@ -6,6 +6,8 @@
  - [ ] need canonical form making it easy to run all these validation 
        passes
  - [ ] are recursive slices inclusive?
+ - [ ] you can apparently have empty SigConCats - but what does this
+       even mean?
  - [ ] what are the semantics of connection `<conn-stmt>`?
  - [ ] Validate that `123456789[0:9][0:8]` is valid RTLIL
  - [ ] add validation section to README

src/RTLILParser/Parser.hs

@@ -246,7 +246,7 @@ pSigSpecConcat = p <?> name where
     name = "SigSpecConcat"
     p =
         do
-        char '{' <* pWs
+        char '{' <* pMaybeWs
         sigspecs    <- many $ pSigSpec <* pWs
         char '}'
         return $ SigSpecConcat sigspecs