This trait includes all the tokens except braces plus the Bracket syntactic blocks. The Block in the name block member is either the top level statements in the file or the statements with in a bracket block. Conceptually the source file is considered a special case of bracket block where the beginning of substitutes for the opening bracket and the end of file substitutes for the closing bracket. BlockMember has only two sub traits StatementMember and SemiToken. So a sequence of TokenOrBlocks is simply a series of tokens which has been parsed into Blocks.