Locating source of plus(Iterable<FileCollection>) deprecation log

When running my build I observe the following log statement:

The plus(Iterable) method and using the ‘+’ operator in conjunction with an Iterable object have been deprecated and are scheduled to be removed in 3.0. Please use the plus(FileCollection) method or the ‘+’ operator with a FileCollection object instead.

Which seems to be coming from here: https://github.com/gradle/gradle/blob/master/subprojects/core/src/main/groovy/org/gradle/api/internal/file/AbstractFileCollection.java#L81

Unfortunately, there’s no file/line number indication of where this is coming from. I think it’s likely coming from a plugin as a grep through my build files doesn’t show any use of this method.

How can I track down the source of the log line so I can fix it locally or submit a fix to the problematic plugin?

The line before that warning should have a location.

You can also run with -Dorg.gradle.deprecation.trace=true, which will produce a stacktrace.