[bendmorris]

That is correct. I think there are tradeoffs in making the language too extensible; in this case it's changing some of the details but not the high-level semantics of how the language works. If every library looked completely different lexically, it would be a nightmare to reuse code. Users of Rust macros may already start to feel this; many libraries are implemented as essentially DSLs.

With that said, down the line I plan to add procedural macros, and those will likely be lexical (they take a series of tokens as input, which doesn't need to parse into valid AST.) If I do go that route, such macros would have to be invoked explicitly.