Array as parameter of function

There is what seems to me like a bug in support for non-dimension specific array passing to a function.
Consider this code:

float4 Func(float4 a[])
{
    return a[0];
}

float4 main() : SV_Target0
{
    float4 a[] = {float4(1,1,1,1), float4(1,1,1,1)};
    return Func(a);
}

fxc gives a nice

error X3072: 'a': array dimensions of function parameters must be explicit

but dxc does naught. no error no output, no code production no nothing.
If you put a dimension then you get a reasonable output of

;
; Input signature:
;
; Name Index Mask Register SysValue Format Used
; -------------------- ----- ------ -------- -------- ------- ------
; no parameters
;
; Output signature:
;
; Name Index Mask Register SysValue Format Used
; -------------------- ----- ------ -------- -------- ------- ------
; SV_Target 0 xyzw 0 TARGET float xyzw
;
;
; Pipeline Runtime Information:
;
; Pixel Shader
; DepthOutput=0
; SampleFrequency=0
;
;
; Output signature:
;
; Name Index InterpMode DynIdx
; -------------------- ----- ---------------------- ------
; SV_Target 0
;
; Buffer Definitions:
;
;
; Resource Bindings:
;
; Name Type Format Dim ID HLSL Bind Count
; ------------------------------ ---------- ------- ----------- ------- -------------- ------
;
;
; ViewId state:
;
; Number of inputs: 0, outputs: 4
; Outputs dependent on ViewId: { }
; Inputs contributing to computation of Outputs:
;
target datalayout = "e-m:e-p:32:32-i1:32-i8:32-i16:32-i32:32-i64:64-f16:32-f32:32-f64:64-n8:16:32:64"
target triple = "dxil-ms-dx"

define void @main() {
entry:
call void @dx.op.storeOutput.f32(i32 5, i32 0, i32 0, i8 0, float 1.000000e+00) ; StoreOutput(outputSigId,rowIndex,colIndex,value)
call void @dx.op.storeOutput.f32(i32 5, i32 0, i32 0, i8 1, float 1.000000e+00) ; StoreOutput(outputSigId,rowIndex,colIndex,value)
call void @dx.op.storeOutput.f32(i32 5, i32 0, i32 0, i8 2, float 1.000000e+00) ; StoreOutput(outputSigId,rowIndex,colIndex,value)
call void @dx.op.storeOutput.f32(i32 5, i32 0, i32 0, i8 3, float 1.000000e+00) ; StoreOutput(outputSigId,rowIndex,colIndex,value)
ret void
}

; Function Attrs: nounwind
declare void @dx.op.storeOutput.f32(i32, i32, i32, i8, float) #0

attributes #0 = { nounwind }

!llvm.ident = !{!0}
!dx.version = !{!1}
!dx.valver = !{!2}
!dx.shaderModel = !{!3}
!dx.typeAnnotations = !{!4}
!dx.viewIdState = !{!8}
!dx.entryPoints = !{!9}

!0 = !{!"clang version 3.7 (tags/RELEASE_370/final)"}
!1 = !{i32 1, i32 0}
!2 = !{i32 1, i32 3}
!3 = !{!"ps", i32 6, i32 0}
!4 = !{i32 1, void ()* @main, !5}
!5 = !{!6}
!6 = !{i32 0, !7, !7}
!7 = !{}
!8 = !{[2 x i32] [i32 0, i32 4]}
!9 = !{void ()* @main, !"main", !10, null, null}
!10 = !{null, !11, null}
!11 = !{!12}
!12 = !{i32 0, !"SV_Target", i8 9, i8 16, !13, i8 0, i32 1, i8 4, i32 0, i8 0, null}
!13 = !{i32 0}

even though that's much bloated comapred to fxc's nice 4 little lines with color, but it's orthogonal.