Primitives

The data structures every other subsystem manipulates. Most of them are defined in src/compiler/types.ts (the largest single types file in the repo at 10,670 lines) and built by the parser, binder, or checker.

Primitive	Where it's created	Page
Node	parser	node
SourceFile	parser	source-file
Symbol	binder	symbol
Type	checker	type
Signature	checker	signature
Diagnostic	parser, binder, checker	diagnostic

These appear across nearly every API surface in the compiler — adding a new primitive is rare, but understanding the existing ones is essential.