Using a runtime-length `SVector` within a closure allocates memory

General Usage Performance
4

It can do that, but since the call to make_test_Float16() is in the same compilation unit as the dynamic part, it doesn’t. You can make it do that by creating a function barrier though:

julia> function call_barrier(f::F, args...) where {F}
           f(args...)
       end;

julia> let
           make_test_Float16 = _make_test(Float16)
           call_barrier(make_test_Float16) do f
               @allocated f() 
           end
       end
0

Since call_barrier needs to specialize on the type of make_test_Float16, it forces its type to be resolved before it is called.

See also: this section of the performance tips

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