Incomplete type error when using typename of a template struct in Constant or StructuredBuffer

Description
Using a typename of a template struct inside a Constant or Structured buffer throws an error: error: variable has incomplete type.

This is an example where it fails:

typedef Foo<float> FooFloat;
ConstantBuffer<FooFloat> x;

It appears to be a workaround if the template itself is being used:

ConstantBuffer<Foo<float> > x;

I assume the error is an omission.

Steps to Reproduce
This is an example compute shader:

template<typename T>
struct TFoo
{
    T x;
};

#if 1
typedef TFoo<float> Foo; // ERROR
#else
#define Foo TFoo<float> // Workaround
#endif

ConstantBuffer<Foo> g_f;

[numthreads(1, 1, 1)]
void main()
{   
}

Compiled using: -T cs_6_8 -E main

Actual Behavior
It works without error.

Environment

• DXC version: trunk (40e27eb4)
• Host Operating System: Any

Start by compiling the provided compute shader with DXC using -T cs_6_8 -E main and reproduce the incomplete-type error. Trace how typedefs of template structs are handled when used as ConstantBuffer or StructuredBuffer element types, then add coverage showing the typedef form behaves like the direct template form.