internal/core/adt: split conjunct trees based on prefix

Before this change, any conjunct referred to was inserted
at the insertion point in full. Top-level conjuncts have
a tree representing the origin of their definition and
embedding. This caused the closedness rules to be repeated
when they should not, resulting in spurious "field not
allowed" errors.

The new algorithm splits a conjunct into branches with
roots that are shared with the insertion point removed.
This ensures that references that are in scope of a
definition do not get spuriously inserted.

Fixes #3330
Fixes #3331

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I7a573f9576d3c46374647045d8ec226a1cd543b3
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1199272
Reviewed-by: Matthew Sackman <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

cue/testdata/benchmarks/inlinedisjunction.txtar

@@ -21,7 +21,7 @@ Allocs: 147
 Retain: 0
 
 Unifications: 17
-Conjuncts:    199
+Conjuncts:    198
 Disjuncts:    76
 -- out/eval --
 (struct){
@@ -60,7 +60,7 @@ diff old new
 -Conjuncts:    13409
 -Disjuncts:    4674
 +Unifications: 17
-+Conjuncts:    199
++Conjuncts:    198
 +Disjuncts:    76
 -- out/eval/stats --
 Leaks:  0

cue/testdata/benchmarks/issue1684.txtar

@@ -69,7 +69,7 @@ Allocs: 2533
 Retain: 0
 
 Unifications: 707
-Conjuncts:    5878
+Conjuncts:    5373
 Disjuncts:    1102
 -- out/evalalpha --
 (struct){
@@ -159,7 +159,7 @@ diff old new
 -Conjuncts:    2480117
 -Disjuncts:    1064333
 +Unifications: 707
-+Conjuncts:    5878
++Conjuncts:    5373
 +Disjuncts:    1102
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new

cue/testdata/benchmarks/listdedup.txtar

@@ -40,7 +40,7 @@ Allocs: 163
 Retain: 0
 
 Unifications: 53
-Conjuncts:    431
+Conjuncts:    407
 Disjuncts:    40
 -- out/eval --
 (struct){
@@ -226,7 +226,7 @@ diff old new
 -Conjuncts:    100730
 -Disjuncts:    24097
 +Unifications: 53
-+Conjuncts:    431
++Conjuncts:    407
 +Disjuncts:    40
 -- out/eval/stats --
 Leaks:  0

cue/testdata/cycle/023_reentrance.txtar

@@ -70,7 +70,7 @@ Allocs: 70
 Retain: 0
 
 Unifications: 62
-Conjuncts:    227
+Conjuncts:    225
 Disjuncts:    0
 -- out/evalalpha --
 Errors:
@@ -133,7 +133,7 @@ diff old new
 -Conjuncts:    464
 -Disjuncts:    268
 +Unifications: 62
-+Conjuncts:    227
++Conjuncts:    225
 +Disjuncts:    0
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new

cue/testdata/cycle/chain.txtar

@@ -215,7 +215,7 @@ Allocs: 19986
 Retain: 0
 
 Unifications: 7496
-Conjuncts:    107561
+Conjuncts:    107414
 Disjuncts:    13651
 -- out/evalalpha --
 Errors:
@@ -735,7 +735,7 @@ diff old new
 -Conjuncts:    3175
 -Disjuncts:    1974
 +Unifications: 7496
-+Conjuncts:    107561
++Conjuncts:    107414
 +Disjuncts:    13651
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new

cue/testdata/cycle/inline_non_recursive.txtar

@@ -67,7 +67,7 @@ Allocs: 209
 Retain: 0
 
 Unifications: 194
-Conjuncts:    1097
+Conjuncts:    1034
 Disjuncts:    0
 -- out/evalalpha --
 Errors:
@@ -203,7 +203,7 @@ diff old new
 -Conjuncts:    2709
 -Disjuncts:    1414
 +Unifications: 194
-+Conjuncts:    1097
++Conjuncts:    1034
 +Disjuncts:    0
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new

cue/testdata/cycle/issue990.txtar

@@ -626,7 +626,7 @@ Allocs: 2198
 Retain: 0
 
 Unifications: 219
-Conjuncts:    8714
+Conjuncts:    6776
 Disjuncts:    462
 -- out/evalalpha --
 Errors:
@@ -816,7 +816,7 @@ diff old new
 -Conjuncts:    12056
 -Disjuncts:    3258
 +Unifications: 219
-+Conjuncts:    8714
++Conjuncts:    6776
 +Disjuncts:    462
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new