Consider the following:

import spock.lang.*
final class SpockTests extends Specification {
  @Unroll
  void 'test #a equals #b'() {
   expect:
    a == b
   where:
    a | b
    1 | 1
    2 | a
  }
}

The spock transform adds parameters "a" and "b" to the test method. This is throwing off the type inference engine and so occurrences of "a" and "b" are showing as unknown (underlined).

See also: https://stackoverflow.com/questions/54597908/spock-test-eclipse-doesnt-seem-to-recoganize-the-data-variables-in-where-claus