internal/core/adt: allow self-referential comprehensions

Analogous to reference cycles, we allow comprehensions to use the struct in which they are defined as source, as long as they do not introduce new fields, which would alter the source on which they iterate. Fixes cuelang#779 Fixes #1934 Fixes #1881 Signed-off-by: Marcel van Lohuizen <[email protected]> Change-Id: Id349de7738567d86bda3cbb137d5ad84aef5b551 Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/544129 Reviewed-by: Roger Peppe <[email protected]> Unity-Result: CUEcueckoo <[email protected]> TryBot-Result: CUEcueckoo <[email protected]>
rogpeppe-contrib · Nov 1, 2022 · f1daf4b · f1daf4b
1 parent e4f4900
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diff --git a/cue/testdata/builtins/all.txtar b/cue/testdata/builtins/all.txtar
@@ -21,7 +21,7 @@ Errors:
 fatalArg.x: invalid operands "eee" and 'eee' to '+' (type string and bytes):
     ./in.cue:2:9
     ./in.cue:2:17
-fatalChild.0.a: undefined field: c:
+fatalChild.x.a: undefined field: c:
     ./in.cue:8:17
 
 Result:
@@ -40,8 +40,11 @@ Result:
     #b: (#struct){
     }
     x: (_|_){
-      // [eval] fatalChild.0.a: undefined field: c:
-      //     ./in.cue:8:17
+      // [eval]
+      a: (_|_){
+        // [eval] fatalChild.x.a: undefined field: c:
+        //     ./in.cue:8:17
+      }
     }
   }
   okIncompleteChild: (struct){