Today I noticed something, I think for the first time.

When used inside Compile variable values within Module (and Block) are sequentially shared:

Compile[n, Module[{a = 7, b = a}, b + 1]] @ 1

8

Compare the behavior outside of Compile:

Module[{a = 7, b = a}, b + 1]

1 + a

• Is this documented behavior or just a happy accident?

• Can it be relied upon or should this "trick" be avoided?