internal/core/adt: treat for loop values as non-cyclic

Issue #3903 had a spurious structural cycle. The
issue was that the #Schema value of the list
was recognized as a cyclic value, even though
it was a new introduction.

New introductions were marked by insertConjunct,
but some paths, like for comprehensions, would
use scheduleConjunct directly and thus
bypassing this mechanism. This would cause
a value to NOT be marked as noncyclic.

Fixes #3903

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: Ib739cf493faf22834b58e476a1328edd8688bf8c
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1215594
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: mpvl

cue/testdata/cycle/023_reentrance.txtar

@@ -76,7 +76,9 @@ NumCloseIDs: 41
 -- out/evalalpha --
 Errors:
 structural cycle:
-    ./in.cue:3:25
+    ./in.cue:8:9
+structural cycle:
+    ./in.cue:8:38
 
 Result:
 (_|_){
@@ -104,21 +106,24 @@ Result:
     n: (int){ int }
   }
   fib1: (int){ 1 }
-  fib2: (_|_){
-    // [structural cycle] structural cycle:
-    //     ./in.cue:3:25
-  }
+  fib2: (int){ 1 }
   fib3: (_|_){
     // [structural cycle] structural cycle:
-    //     ./in.cue:3:25
+    //     ./in.cue:8:9
+    // structural cycle:
+    //     ./in.cue:8:38
   }
   fib7: (_|_){
     // [structural cycle] structural cycle:
-    //     ./in.cue:3:25
+    //     ./in.cue:8:9
+    // structural cycle:
+    //     ./in.cue:8:38
   }
   fib12: (_|_){
     // [structural cycle] structural cycle:
-    //     ./in.cue:3:25
+    //     ./in.cue:8:9
+    // structural cycle:
+    //     ./in.cue:8:38
   }
 }
 -- diff/-out/evalalpha/stats<==>+out/eval/stats --
@@ -151,49 +156,39 @@ diff old new
 diff old new
 --- old
 +++ new
-@@ -1,10 +1,6 @@
+@@ -1,7 +1,5 @@
  Errors:
  structural cycle:
-     ./in.cue:3:25
--structural cycle:
--    ./in.cue:8:9
+-    ./in.cue:3:25
 -structural cycle:
--    ./in.cue:8:38
- 
- Result:
- (_|_){
-@@ -32,27 +28,20 @@
-     n: (int){ int }
-   }
-   fib1: (int){ 1 }
--  fib2: (int){ 1 }
-+  fib2: (_|_){
-+    // [structural cycle] structural cycle:
-+    //     ./in.cue:3:25
-+  }
+     ./in.cue:8:9
+ structural cycle:
+     ./in.cue:8:38
+@@ -35,14 +33,12 @@
+   fib2: (int){ 1 }
    fib3: (_|_){
      // [structural cycle] structural cycle:
-     //     ./in.cue:3:25
--    // structural cycle:
--    //     ./in.cue:8:38
+-    //     ./in.cue:3:25
++    //     ./in.cue:8:9
+     // structural cycle:
+     //     ./in.cue:8:38
    }
    fib7: (_|_){
      // [structural cycle] structural cycle:
-     //     ./in.cue:3:25
+-    //     ./in.cue:3:25
 -    // structural cycle:
--    //     ./in.cue:8:9
--    // structural cycle:
--    //     ./in.cue:8:38
+     //     ./in.cue:8:9
+     // structural cycle:
+     //     ./in.cue:8:38
+@@ -49,8 +45,6 @@
    }
    fib12: (_|_){
      // [structural cycle] structural cycle:
-     //     ./in.cue:3:25
--    // structural cycle:
--    //     ./in.cue:8:9
+-    //     ./in.cue:3:25
 -    // structural cycle:
--    //     ./in.cue:8:38
-   }
- }
+     //     ./in.cue:8:9
+     // structural cycle:
+     //     ./in.cue:8:38
 -- diff/todo/p3 --
 Note that it is okay for fib2 to fail.
 -- out/eval/stats --

cue/testdata/cycle/builtins.txtar

@@ -255,18 +255,18 @@ issue3634: reduced: {
 	out: len(#D & list.Repeat([#D & { a: b: 1 }], 1)[0])
 }
 -- out/evalalpha/stats --
-Leaks:  466
+Leaks:  478
 Freed:  0
 Reused: 0
-Allocs: 466
+Allocs: 478
 Retain: 0
 
-Unifications: 399
-Conjuncts:    731
-Disjuncts:    38
+Unifications: 407
+Conjuncts:    745
+Disjuncts:    42
 
-CloseIDElems: 116
-NumCloseIDs: 189
+CloseIDElems: 122
+NumCloseIDs: 191
 -- diff/-out/evalalpha/stats<==>+out/eval/stats --
 diff old new
 --- old
@@ -281,18 +281,18 @@ diff old new
 -Unifications: 441
 -Conjuncts:    821
 -Disjuncts:    537
-+Leaks:  466
++Leaks:  478
 +Freed:  0
 +Reused: 0
-+Allocs: 466
++Allocs: 478
 +Retain: 0
 +
-+Unifications: 399
-+Conjuncts:    731
-+Disjuncts:    38
++Unifications: 407
++Conjuncts:    745
++Disjuncts:    42
 +
-+CloseIDElems: 116
-+NumCloseIDs: 189
++CloseIDElems: 122
++NumCloseIDs: 191
 -- out/eval/stats --
 Leaks:  25
 Freed:  446