[bug/user's fault?] shader_feature will not include in build if used UsePass

I created a material using the following shader, put that material on a cube in a scene.While in Editor, shader_feature(both on & off) is working correctly.
But when I build it to mobile(android), the shader_feature code are always turned off.

if I switch shader_feature to multi_compile instead, it works in mobile.
if I copy the whole pass's code and use it to replace the UsePass"" line, it works in mobile.

Code (CSharp):

1. Shader "UsePassWithShaderFeature"
2. {
3.     Properties
4.     {
5.         _MainTex ("Texture", 2D) = "white" {}
6.         [Toggle(INVERT_ON)]_invert("invert?",float) = 0
7.     }
8.  
9.     SubShader
10.     {
11.         //UsePass will lose all shader_feature code when build
12.         UsePass "Hidden/PassWithShaderFeature/COLOR"
13.     }
14. }
15.  

Code (CSharp):

1. Shader "Hidden/PassWithShaderFeature"
2. {
3.     SubShader
4.     {
5.         //We only need the Pass itself
6.         Pass
7.         {
8.             Name "COLOR"
9.             CGPROGRAM
10.             #pragma vertex vert
11.             #pragma fragment frag
12.  
13.             #pragma shader_feature _ INVERT_ON
14.             #include "UnityCG.cginc"
15.  
16.             struct appdata
17.             {
18.                 float4 vertex : POSITION;
19.                 float2 uv : TEXCOORD0;
20.             };
21.  
22.             struct v2f
23.             {
24.                 float2 uv : TEXCOORD0;
25.                 float4 vertex : SV_POSITION;
26.             };
27.  
28.             sampler2D _MainTex;
29.             float4 _MainTex_ST;
30.          
31.             v2f vert (appdata v)
32.             {
33.                 v2f o;
34.                 o.vertex = UnityObjectToClipPos(v.vertex);
35.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
36.                 return o;
37.             }
38.          
39.             fixed4 frag (v2f i) : SV_Target
40.             {
41.                 // sample the texture
42.                 fixed4 col = tex2D(_MainTex, i.uv);
43. #if INVERT_ON
44.             col = 1 - col;
45. #endif
46.                 return col;
47.             }
48.             ENDCG
49.         }
50.     }
51. }
52.  

so question is:
can I use UsePass while the pass contains shader_feature?
if not, any better workaround?
(can not replace shader_feature with multi_compile, as there are lots of variants - 2^n)
(can not copy the pass as it makes maintenance very difficult)
-------
using Unity5.5.0f3

 

submitted bug report

(Case 892777) shader feature will always NOT toggled ON in mobile build, only when UsePass is used

 

bump

 

confirmed is a bug(received email from UnityQA), is there any workaround currently?

because the email said

 

Bug still not fixed in 2018.1.8f1 ...