[emcfarlane]

An empty ; is allowed at the top level and in message, enum, service, method and group bodies, but not in a oneof or extend block. The experimental compiler accepted it everywhere. Now reports it in those two blocks.

message M {
  oneof o {
    int32 a = 1;
    ;          // was: accepted
  }
}
extend M {
  ;            // was: accepted
}
option (foo) = {
  strs []      // was: warning only (strs is repeated string)
  foos []      // still accepted (foos is a message field)
};

In a message literal, the text format grammar lets a field leave out the : only if the field is message-typed:

MessageField = FieldName, [ ":" ], ( MessageValue | MessageList ) ...
ScalarField  = FieldName, ":", ( ScalarValue | ScalarList ) ...

So foos [] and foos [{}] are valid for a message field, but strs [] and strs ["x"] are not valid for a scalar one. The parser already rejected strs ["x"] by looking at the list's elements. An empty list has no elements to look at, so strs [] was accepted. The check needs the field's type. It now also runs during option evaluation so the type is known.