CmdRedirect constructor throwing TypeError

[giordano]

BinaryBuilderBase.jl tests are failing on 532125d. A smaller reproducer cooked up with the help of https://github.com/maleadt/creduce_julia is:

function a(b; stdout )
    c = setenv(b, b.env)
    if true
        c = pipeline(c, stdout)
    end
    c
end
a(``; stdout)

The output is

ERROR: LoadError: TypeError: in new, expected Base.AbstractCmd, got a value of type Nothing
Stacktrace:
 [1] CmdRedirect
   @ ./cmd.jl:186 [inlined]
 [2] CmdRedirect
   @ ./cmd.jl:191 [inlined]
 [3] redir_out
   @ ./cmd.jl:355 [inlined]
 [4] #pipeline#761
   @ ./cmd.jl:389 [inlined]
 [5] pipeline
   @ ./cmd.jl:397 [inlined]
 [6] #a#3
   @ /tmp/foo.jl:4 [inlined]
 [7] top-level scope
   @ /tmp/foo.jl:8
in expression starting at /tmp/foo.jl:8

I don't see how you can enter

julia/base/cmd.jl

Line 355 in d89b96b

redir_out(src::AbstractCmd, dest::Redirectable) = CmdRedirect(src, dest, STDOUT_NO)

where src::AbstractCmd and then the CmdRedirect constructor complains src isn't AbstractCmd.

Last time tests passed was on 7f507e6.

[giordano]

git bisect blames 0620361 (from #47080). CC: @Keno

To reproduce the bisect run:

$ cat ./script.sh
#!/bin/bash

make cleanall || true
make -j40 USECCACHE=1 JULIA_PRECOMPILE=0 || exit 125

./usr/bin/julia -t1 --startup-file=no -e '
function a(b; stdout )
    c = setenv(b, b.env)
    if true
        c = pipeline(c, stdout)
    end
    c
end
a(``; stdout)
'
$ git bisect start
$ git bisect bad 532125d51d23f22c3fd117fe8a37c158fe16ac62
$ git bisect good 7f507e64aa14dbbd7e0c9b51a0ee72e7ea97bb19
$ git bisect run ./script.sh

[Keno]

That commit itself is probably not bad, but if there's another unrelated bug that commit would have stopped hiding it. I'll turn on the oracle check and take a look.