Arguments passed via the ScalarPair abi cannot be correctly inspected via WinDbg or VS debuggers. This occurs because the platform debuggers expect the type to passed via a pointer (as the abi says they should) and the debuggers are hardcoded to expect that.

Example:

fn foo(r: Range<usize>) {
    zzz(); // #break
}

Debuggers:

> dx r
r               : 0x14 [Type: core::ops::range::Range<usize> *]

(Notice the * in the type indicating the debugger expects to be looking at a pointer to the actual value, not it passed by value)

This is a more general version of #81894 which #81898 fixed for &str and slices.