Assignment to generic argument doesn't validate

[brson]

fn g<@T>(o: T) {
    o = o;
}

Instruction does not dominate all uses!
  %15 = call i8* @upcall_dynastack_alloc_2(%task* %1, i32 %14, %tydesc* %3)
  call void @llvm.memmove.p0i8.p0i8.i32(i8* %15, i8* %4, i32 %6, i32 1, i1 false)
Instruction does not dominate all uses!
  %15 = call i8* @upcall_dynastack_alloc_2(%task* %1, i32 %14, %tydesc* %3)
  call void %10(i1* null, %task* %1, i1* null, %tydesc** %8, i8* %15)
Broken module found, compilation aborted!
Stack dump:
0.      Running pass 'Function Pass Manager' on module 'rust_out'.
1.      Running pass 'Module Verifier' on function '@_ZN1g17_258c42cfc8628f4cE'