Add tests for empty IntSeq iteration (#1739)

pkl-core/src/test/files/LanguageSnippetTests/input/generators/elementGenerators.pkl

@@ -30,6 +30,20 @@ res1d = new Dynamic {
   }
 }
 
+// noinspection ReplaceForGeneratorWithSpread
+res1e = new Dynamic {
+  for (n in IntSeq(0, -1)) {
+    n
+  }
+}
+
+// noinspection ReplaceForGeneratorWithSpread
+res1f = new Dynamic {
+  for (n in IntSeq(0, 1).step(-1)) {
+    n
+  }
+}
+
 res2 = new Listing {
   for (n in List(1, 2, 3, 4, 5)) {
     when (n.isOdd) {

pkl-core/src/test/files/LanguageSnippetTests/input/generators/elementGeneratorsTyped.pkl

@@ -32,6 +32,20 @@ res1d = test.catch(() -> new Listing {
   }
 })
 
+// noinspection ReplaceForGeneratorWithSpread
+res1e = new Dynamic {
+  for (n: Int in IntSeq(0, -1)) {
+    n
+  }
+}
+
+// noinspection ReplaceForGeneratorWithSpread
+res1f = new Dynamic {
+  for (n: Int in IntSeq(0, 1).step(-1)) {
+    n
+  }
+}
+
 res2 = new Dynamic {
   for (n: Number in List(1, 2, 3, 4, 5)) {
     when (n.isOdd) {

pkl-core/src/test/files/LanguageSnippetTests/input/generators/spreadSyntaxListing.pkl

@@ -85,3 +85,11 @@ res19 = new Listing {
   0
   0
 }
+
+res20 = new Listing {
+  ...IntSeq(0, -1)
+}
+
+res21 = new Listing {
+  ...IntSeq(0, 1).step(-1)
+}

pkl-core/src/test/files/LanguageSnippetTests/output/generators/elementGenerators.pcf

@@ -18,6 +18,8 @@ res1d {
   6
   20
 }
+res1e {}
+res1f {}
 res2 {
   2
   6

pkl-core/src/test/files/LanguageSnippetTests/output/generators/elementGeneratorsTyped.pcf

@@ -10,6 +10,8 @@ res1c {
   20
 }
 res1d = "Expected value of type `String`, but got type `Int`. Value: 0"
+res1e {}
+res1f {}
 res2 {
   2
   6

pkl-core/src/test/files/LanguageSnippetTests/output/generators/spreadSyntaxListing.pcf

@@ -119,3 +119,5 @@ res19 {
   0
   0
 }
+res20 {}
+res21 {}