UndefVarError not caught in if/else statement

[nantiamak]

I ran JET.report_file("UndefVarError_branching_test.jl"; mode=:typo) on the following code:

function foo(a)
    if a == 1
        output_string = "a is 1"
        return output_string
    else
        return "$output_string is not true"
    end
end

foo(2)

Variable output_string is defined only inside if, but JET didn't report an UndefVarError for return "$output_string is not true". Is this expected?