Lower coverage in Julia v1.11

In Julia v1.10.6, the code below gets 100% coverage. In Julia v1.11.1, foo is not marked as covered.

src/Example.jl:

module Example

export foo, bar

function foo(x) end       # covered in v1.10 but not covered in v1.11
function bar(x; o=1) end  # covered in both versions

end

test/runtests.jl:

using Example, Test

@test isnothing(foo(1))
@test isnothing(bar(1))

I understand that this package uses a workaround to mark lines as code that then may not be marked as covered. Indeed, with DISABLE_AMEND_COVERAGE_FROM_SRC=yes, I get full coverage in v1.11.

Based on that, I presume the explanation here is that the compiler optimizes foo out, while bar has a default parameter and somehow gets tracked anyway.

But I am surprised to see this change when switching between Julia versions. My questions are:

• Is this intended behavior?
• Is there a way to get full coverage back in v1.11 without setting the environment variable?

Reproduce the example from src/Example.jl and test/runtests.jl on Julia 1.10.6 and 1.11.1, including a run with DISABLE_AMEND_COVERAGE_FROM_SRC=yes. Read the Coverage.jl workaround documentation and the coverage-amendment path to determine whether the change is expected. Done means documenting the behavior and an evidence-backed supported way to restore full coverage, if one exists.