Body Macro formatted despite formatMode disabled

That's correct. The leading trivia of statements is [newlines(1), spaces(8)]. The trivia is lost/changed after the return of expansion function.

I would expected the expansion to be:

{
let _ = { 
#sourceLocation(file: "/Users/mateusrodrigues/Desktop/TriviaMacro/Sources/TriviaMacroClient/main.swift", line: 8)
        let x: Int = 1
#sourceLocation() }()
}