default initialisers in parametric parent types that refer to the type parameter lead to error in constructor call

[mhinsch]

MWE:

@kwdef struct Foo{T}
    x :: Int = sizeof(T)
end

@composite @kwdef struct Bar
    Foo{Int}...
end

Calling Bar() errors with "UndefVarError: T not defined".

The problem seems to be that the keyword constructor @composite generates calls Foo(...) instead of Foo{Int}(...).