repro.sh

#!/usr/bin/env bash

set -e

cd /tmp
rm -rf /tmp/mock
mkdir /tmp/mock
cd /tmp/mock

git clone https://github.com/golang/mock mock-before
git clone https://github.com/golang/mock mock-after
(cd mock-before &&
     git checkout bfa1e97ed7a159b123865559eabdec69b78fe1d5 &&
     go build -o ../mockgen-before ./mockgen)
(cd mock-after &&
     git checkout 837231f7bb377b365da147e5ff6c031b12f0dfaa &&
     go build -o ../mockgen-after ./mockgen)

cat <<EOF >interface.go
package foo

type Interface interface {
	Bar()
}
EOF

# works
./mockgen-before -package foo -destination interface_mock.go -source interface.go Interface

# doesn't work
./mockgen-after -package foo -destination interface_mock.go -source interface.go Interface