...if (ret) return ret;
		}

		// Now recurse child nodes
		if (lhs) {
			auto ret = lhs.opApply(dg...

...here is that depth would be too restrictive as it would prevent reasonable insertions nodes.

...graphs? How do you prove that none of the nodes in the graph are shared?

...provides methods for building detailed syntactical AST nodes, but actually builds the existing AST, then...

...actually the only way to dyncast cast nodes as DMD AST is extern(C++)... But...

...IRs that point back to the language nodes if needed. Then run the algorithm on...

...better if its API was not AST nodes, but just values. Let the caller construct...

...imports, or...
2. Moving type definitions of AST nodes into modules that _only_ contain definitions.

...do semantic analysis? Which files declare AST nodes? Which files interface with the backend (and...

...target abstraction need to know about AST nodes? At least half of these imports shouldn...