[Solved] decltype in static_assert

Question

static_assert works fine, is your code that never assert.
The template struct X defines low and high as of type IntT. They are both the same type, whatever values they have.
When you instantiate the struct (X<char,1,'a'> x) you are telling the compiler that the type of IntT is char and are giving to low the value 1 and to high the value 'a' (i.e. 97). However, the type of low and high is always char so the static_assert will never assert.

Accepted Answer

static_assert works fine, is your code that never assert.
The template struct X defines low and high as of type IntT. They are both the same type, whatever values they have.
When you instantiate the struct (X<char,1,'a'> x) you are telling the compiler that the type of IntT is char and are giving to low the value 1 and to high the value 'a' (i.e. 97). However, the type of low and high is always char so the static_assert will never assert.