internal/core/adt: clean up orphaned arcs

When a node is redirected to a disjunction,
for instance, or when a node becomes
erroneous, its arcs become irrelevant.
The evaluator clears the arc list in these
cases to avoid bugs resulting from
descening into the wrong set of arcs.

We now ensure these arcs are freed.

Issue #3334
Issue #2850

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: Ief2d59accc66cce28327b6ad31b347cbafce3d85
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1218190
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: mpvl

cue/testdata/basicrewrite/018_self-reference_cycles.txtar

@@ -137,8 +137,8 @@ c: [c[1], c[0]]
   }
 }
 -- out/evalalpha/stats --
-Leaks:  1
-Freed:  58
+Leaks:  0
+Freed:  59
 Reused: 38
 Allocs: 21
 Retain: 0
@@ -154,7 +154,7 @@ diff old new
 --- old
 +++ new
 @@ -1,9 +1,12 @@
- Leaks:  1
+-Leaks:  1
 -Freed:  57
 -Reused: 46
 -Allocs: 12
@@ -163,7 +163,8 @@ diff old new
 -Unifications: 48
 -Conjuncts:    285
 -Disjuncts:    88
-+Freed:  58
++Leaks:  0
++Freed:  59
 +Reused: 38
 +Allocs: 21
 +Retain: 0

cue/testdata/benchmarks/disjunctelim.txtar

@@ -40,8 +40,8 @@ issue3610: {
 }
 
 -- out/evalalpha/stats --
-Leaks:  1
-Freed:  798
+Leaks:  0
+Freed:  799
 Reused: 746
 Allocs: 53
 Retain: 0
@@ -57,12 +57,11 @@ diff old new
 --- old
 +++ new
 @@ -1,9 +1,12 @@
--Leaks:  0
+ Leaks:  0
 -Freed:  367
 -Reused: 356
 -Allocs: 11
-+Leaks:  1
-+Freed:  798
++Freed:  799
 +Reused: 746
 +Allocs: 53
  Retain: 0

cue/testdata/benchmarks/inlinedisjunction.txtar

@@ -14,8 +14,8 @@
 x: #def
 x: c: "foo"
 -- out/evalalpha/stats --
-Leaks:  1
-Freed:  111
+Leaks:  0
+Freed:  112
 Reused: 98
 Allocs: 14
 Retain: 0
@@ -49,12 +49,11 @@ diff old new
 --- old
 +++ new
 @@ -1,9 +1,12 @@
--Leaks:  0
+ Leaks:  0
 -Freed:  4674
 -Reused: 3903
 -Allocs: 771
-+Leaks:  1
-+Freed:  111
++Freed:  112
 +Reused: 98
 +Allocs: 14
  Retain: 0

cue/testdata/benchmarks/issue1684.txtar

@@ -62,10 +62,10 @@ nestedClosed: passing: {
 	D: {id: {}} | {[string]: D}
 }
 -- out/evalalpha/stats --
-Leaks:  13925
-Freed:  11152
-Reused: 11055
-Allocs: 14022
+Leaks:  13900
+Freed:  11177
+Reused: 11058
+Allocs: 14019
 Retain: 0
 
 Unifications: 3219
@@ -146,10 +146,10 @@ diff old new
 -Freed:  1064333
 -Reused: 1064282
 -Allocs: 51
-+Leaks:  13925
-+Freed:  11152
-+Reused: 11055
-+Allocs: 14022
++Leaks:  13900
++Freed:  11177
++Reused: 11058
++Allocs: 14019
  Retain: 0
 
 -Unifications: 792123

cue/testdata/benchmarks/issue3334.txtar

@@ -43,10 +43,10 @@ Schema: {
 	nullable?: bool
 }
 -- out/evalalpha/stats --
-Leaks:  11
-Freed:  773
-Reused: 33
-Allocs: 751
+Leaks:  0
+Freed:  784
+Reused: 44
+Allocs: 740
 Retain: 0
 
 Unifications: 452
@@ -60,7 +60,7 @@ diff old new
 --- old
 +++ new
 @@ -1,9 +1,12 @@
--Leaks:  0
+ Leaks:  0
 -Freed:  401
 -Reused: 388
 -Allocs: 13
@@ -69,10 +69,9 @@ diff old new
 -Unifications: 245
 -Conjuncts:    425
 -Disjuncts:    402
-+Leaks:  11
-+Freed:  773
-+Reused: 33
-+Allocs: 751
++Freed:  784
++Reused: 44
++Allocs: 740
 +Retain: 0
 +
 +Unifications: 452

cue/testdata/benchmarks/issue3514.txtar

@@ -36,8 +36,8 @@ _schema: {
     #timezone: or([for i in list.Range(0, 571, 1) {"\(i)"}])
 }
 -- out/evalalpha/stats --
-Leaks:  20
-Freed:  3582
+Leaks:  12
+Freed:  3590
 Reused: 2436
 Allocs: 1166
 Retain: 0
@@ -62,8 +62,8 @@ diff old new
 -Unifications: 189
 -Conjuncts:    92950
 -Disjuncts:    31139
-+Leaks:  20
-+Freed:  3582
++Leaks:  12
++Freed:  3590
 +Reused: 2436
 +Allocs: 1166
 +Retain: 0

cue/testdata/benchmarks/issue3633.txtar

@@ -1,7 +1,7 @@
 #Issue: 3633
 -- out/evalalpha/stats --
-Leaks:  1
-Freed:  2030
+Leaks:  0
+Freed:  2031
 Reused: 1798
 Allocs: 233
 Retain: 0
@@ -17,12 +17,11 @@ diff old new
 --- old
 +++ new
 @@ -1,9 +1,12 @@
--Leaks:  0
+ Leaks:  0
 -Freed:  3595
 -Reused: 3575
 -Allocs: 20
-+Leaks:  1
-+Freed:  2030
++Freed:  2031
 +Reused: 1798
 +Allocs: 233
  Retain: 0

cue/testdata/benchmarks/listdedup.txtar

@@ -33,10 +33,10 @@ C: #steps: #Script & {mount: [B]}
 
 #ref: {a: 1} | {b: 2}
 -- out/evalalpha/stats --
-Leaks:  2
-Freed:  87
-Reused: 50
-Allocs: 39
+Leaks:  0
+Freed:  89
+Reused: 51
+Allocs: 38
 Retain: 0
 
 Unifications: 33
@@ -467,7 +467,7 @@ diff old new
 --- old
 +++ new
 @@ -1,9 +1,12 @@
--Leaks:  0
+ Leaks:  0
 -Freed:  24096
 -Reused: 24051
 -Allocs: 45
@@ -476,10 +476,9 @@ diff old new
 -Unifications: 18724
 -Conjuncts:    100730
 -Disjuncts:    24097
-+Leaks:  2
-+Freed:  87
-+Reused: 50
-+Allocs: 39
++Freed:  89
++Reused: 51
++Allocs: 38
 +Retain: 0
 +
 +Unifications: 33

cue/testdata/builtins/closed.txtar

@@ -92,10 +92,10 @@ nestedWithSelfReference: t2: {
 	x: foo: disallowed: 5
 }
 -- out/evalalpha/stats --
-Leaks:  3
-Freed:  270
-Reused: 232
-Allocs: 41
+Leaks:  0
+Freed:  273
+Reused: 234
+Allocs: 39
 Retain: 0
 
 Unifications: 183
@@ -118,10 +118,10 @@ diff old new
 -Unifications: 261
 -Conjuncts:    504
 -Disjuncts:    266
-+Leaks:  3
-+Freed:  270
-+Reused: 232
-+Allocs: 41
++Leaks:  0
++Freed:  273
++Reused: 234
++Allocs: 39
 +Retain: 0
 +
 +Unifications: 183

cue/testdata/comprehensions/issue1732.txtar

@@ -122,10 +122,10 @@ foo: {
 	}
 }
 -- out/evalalpha/stats --
-Leaks:  7
-Freed:  89
-Reused: 54
-Allocs: 42
+Leaks:  3
+Freed:  93
+Reused: 56
+Allocs: 40
 Retain: 0
 
 Unifications: 82
@@ -139,7 +139,7 @@ diff old new
 --- old
 +++ new
 @@ -1,12 +1,12 @@
--Leaks:  3
+ Leaks:  3
 -Freed:  118
 -Reused: 103
 -Allocs: 18
@@ -151,10 +151,9 @@ diff old new
 -
 -CloseIDElems: 0
 -NumCloseIDs: 8
-+Leaks:  7
-+Freed:  89
-+Reused: 54
-+Allocs: 42
++Freed:  93
++Reused: 56
++Allocs: 40
 +Retain: 0
 +
 +Unifications: 82