paulk-asert commented on code in PR #2489:
URL: https://github.com/apache/groovy/pull/2489#discussion_r3142430989
##########
src/test/groovy/gls/statements/MultipleAssignmentDeclarationTest.groovy:
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@@ -226,4 +226,1326 @@ final class MultipleAssignmentDeclarationTest {
assert baz == 'baz'
'''
}
+
+ // GEP-20 tail-rest tests
+
+ @Test
+ void testTailRestFromList() {
+ assertScript '''
+ def (h, *t) = [1, 2, 3, 4]
+ assert h == 1
+ assert t == [2, 3, 4]
+ '''
+ }
+
+ @Test
+ void testTailRestWithMultipleHeads() {
+ assertScript '''
+ def (a, b, *rest) = [10, 20, 30, 40, 50]
+ assert a == 10
+ assert b == 20
+ assert rest == [30, 40, 50]
+ '''
+ }
+
+ @Test
+ void testTailRestWithTypedHead() {
+ assertScript '''
+ def (int h, *t) = [1, 2, 3]
+ assert h == 1
+ assert h instanceof Integer
+ assert t == [2, 3]
+ '''
+ }
+
+ @Test
+ void testTailRestFromEmptyList() {
+ assertScript '''
+ def (h, *t) = []
+ assert h == null
+ assert t == []
+ '''
+ }
+
+ @Test
+ void testTailRestFromString() {
+ assertScript '''
+ def (c, *cs) = "hello"
+ assert c == 'h'
+ assert cs == "ello"
+ '''
+ }
+
+ @Test
+ void testTailRestFromIterator() {
+ assertScript '''
+ def (h, t) = [1, 2, 3].iterator() // baseline: same iterator
semantics as existing
+ assert h == 1
+ assert t == 2
+
+ // tail-rest binds the advanced iterator (Path B)
+ def it = [10, 20, 30].iterator()
+ def (head, *tail) = it
+ assert head == 10
+ assert tail instanceof Iterator
+ assert tail.next() == 20
+ assert tail.next() == 30
+ assert !tail.hasNext()
+ '''
+ }
+
+ @Test
+ void testTailRestFromSet() {
+ assertScript '''
+ def s = new LinkedHashSet<>([7, 8, 9])
+ def (sh, *st) = s
+ assert sh == 7
+ def remaining = []
+ while (st.hasNext()) remaining << st.next()
+ assert remaining == [8, 9]
+ '''
+ }
+
+ @Test
+ void testTailRestFromStream() {
+ assertScript '''import java.util.stream.Stream
+ def (first, *rest) = Stream.of('a', 'b', 'c')
+ assert first == 'a'
+ assert rest instanceof Iterator
Review Comment:
I was going for a simple mental model: RHS supports `getAt(IntRange)` or
fallback to `iterator()`, and a `Stream` is only a `.stream()` call away.
But I agree, `Stream` is important, maybe it is worth have a third
alternative in the model. I'll see if any complications arise.
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