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That's a JIT. It uses the same compiler infrastructure but swaps out the AoT backend and replaces it with the JIT backend in LLVM. Notably, this blog post is targeting on-device usage which a custom JIT is not allowed. You can only interpret.

I suppose you could argue the repl is not a true interpreter (parsing and executing from an AST)

++ had the same reaction as you. When I was picking up Swift, the interpreter was invaluable to check my understanding (although I nearly always needed to begin with `import Foundation` to have my code actually work).