What could cause error "no concrete specializations"?

[zhwa]

Hi,

When trying to run the following code piece, I got some compilation errors saying call expansion failed - no concrete specializations:

@register_passable("trivial")
struct FP8:
    var value : __mlir_type.f8E4M3FN
    
    fn __init__(value : __mlir_type.f8E4M3FN) -> Self:
        return Self { value : value }
    
    fn __init__() -> Self:
        return Self { 
            value : __mlir_op.`llvm.mlir.constant`[
                value: __mlir_attr.`0.0 : f8E4M3FN`,
                _type: __mlir_type.f8E4M3FN
            ]()
        }

let x = FP8()

The detailed error information:

error: Expression [8]:6:1: no viable expansions found
fn __lldb_expr__(inout __mojo_repl_arg: __mojo_repl_context__):
^

Expression [8]:8:28:   call expansion failed - no concrete specializations
    __mojo_repl_expr_impl__(__mojo_repl_arg)
                           ^

Expression [8]:12:1:     no viable expansions found
def __mojo_repl_expr_impl__(inout __mojo_repl_arg: __mojo_repl_context__) -> None:
^

Expression [8]:19:26:       call expansion failed - no concrete specializations
  __mojo_repl_expr_body__()
                         ^

Expression [8]:14:3:         no viable expansions found
  def __mojo_repl_expr_body__() -> None:
  ^

Expression [8]:16:5:           could not simplify operator get_alignof(f8E4M3FN, #kgen.target<triple = "x86_64-unknown-linux-gnu", cpu = "icelake-server", features = "+64bit,+adx,+aes,+avx,+avx2,+avx512bitalg,+avx512bw,+avx512cd,+avx512dq,+avx512f,+avx512ifma,+avx512vbmi,+avx512vbmi2,+avx512vl,+avx512vnni,+avx512vpopcntdq,+bmi,+bmi2,+clflushopt,+clwb,+cmov,+crc32,+cx16,+cx8,+f16c,+fma,+fsgsbase,+fxsr,+gfni,+invpcid,+lzcnt,+mmx,+movbe,+pclmul,+pku,+popcnt,+prfchw,+rdpid,+rdrnd,+rdseed,+sahf,+sha,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+ssse3,+vaes,+vpclmulqdq,+wbnoinvd,+xsave,+xsavec,+xsaveopt,+xsaves", data_layout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128", simd_bit_width = 512>)
    let x = FP8()
    ^

Can someone help me understand what caused error, and how should I fix the it?

Thanks!