Shader compiler: internal error compiling shader snippet type=0 platform=0:

Cant find any information about this error. I'm writing a basic flat color shader as part of a tutorial and I'm pretty sure I wrote it out correctly. Any ideas on what I'm doing wrong? I'm on a 2014 macbook pro. TIA!

Here are the errors I get:

 Shader compiler: internal error compiling shader snippet type=0 platform=0: 
 Shader error in 'Custom/Tutorial/FlatColor - 1': Internal error communicating with the shader compiler process

Here's my simple flat color shader:

 Shader "Custom/Tutorial/FlatColor - 1" {
     Properties {
         _Color ("Color", Color) = (1.0,1.0,1.0,1.0)
     }
     
     SubShader {
         Pass {
             CGPROGRAM
             //pragmas
             #pragma vertex vert
             #pragma fragment frag
             
             //user defined vars
             uniform float4 _Color;
             
             //structs
             struct vertexInput{
                 float4 vertex : POSITION;
             }
             
             struct vertexOutput{
                 float4 pos : SV_POSITON;
             }
 //            
             //vert prog
             vertexOutput vert(vertexInput v){
                 vertexOutput o;
                 o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                 return o;
             }    
             
             //frag program        
             float4 frag(vertexOutput i) : COLOR
             {
                 return _Color;
             }
 //            
             ENDCG
         }
     }
     
     
     //fallback "Diffuse"
 }