Allows top-level variable to be used in its own initial value #70380
Description
Description
In Swift 5.4 and later, a variable can in some cases be used in the initial value of its own declaration. Doing so produces a crash at runtime rather than a compiler error.
Reproduction
let x: Any = xRun in a Swift Playground in Xcode 15.0.1. Crashes at runtime with error:
error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0xfffffffffffffff8).
Expected behavior
Compiler error such as use of variable 'x' before its declaration or variable used within its own initial value.
The former is the compiler error given for do { let x: Any = x }.
The latter is the error given by Swift 5.3.
Environment
The runtime error was produced in a Swift Playground in Xcode 15.0.1.
The lack of compiler error was reproduced in swiftc 5.9 and 5.4, but not in 5.3, using swift.godbolt.org.
Additional information
No response