[vidarh]

Yes, it is. It also doesn't really make much difference per se, as e.g. Wirth-style compilers still maintain careful separation of the code generation and parsing.

And if you want to/need to later, you can trivially introduce an AST in those compilers by replacing the calls to the code-generator with calls to a tree builder, and then write a visitor-style driver for the code generation.

[mcejp]

"trivially"?

[vidarh]

Yes, it's work of course, but it's quite mechanical work that requires little thought.

Instead of calling the code emitter, you call an AST builder.

Then you build a tree walker that call the code emitter.

At least the Wirth Oberon compiler was retrofitted with an AST by at least one student in Wirth's group as part of experiments with optimization passes.