.

wcfs/δbtail.go

@@ -686,6 +686,9 @@ func diffT(ctx context.Context, a, b *Tree, δZTC SetOid, trackIdx map[zodb.Oid]
 	tracef("  diffT %s %s\n", xidOf(a), xidOf(b))
 	defer xerr.Contextf(&err, "diffT %s %s", xidOf(a), xidOf(b))
 
+	if a == nil { panic("a is nil") }
+	if b == nil { panic("b is nil") }
+
 	δ = map[Key]ΔValue{}
 	defer tracef("  -> δ: %v\n", δ)
 
@@ -696,15 +699,12 @@ func diffT(ctx context.Context, a, b *Tree, δZTC SetOid, trackIdx map[zodb.Oid]
 	Adone  := SetKey{} // "processed" keys on A
 	Bdone  := SetKey{} // "processed" keys on B
 
-	if b != nil { // XXX kill (always !nil) ?
 	// XXX precise range as for a ^^^ ?
 	btop := &nodeInRange{lo: KeyMin, hi_: KeyMax, node: b} // [-∞, ∞)
 	bv   = rangeSplit{btop}
-	}
 
 	// initial phase: expand changed nodes in a till buckets;
 	// XXX changed buckets -> δ-
-	if a != nil {	// XXX kill (always !nil) ?
 	// XXX maybe walk till a from root to get more precise initial range?
 	atop := &nodeInRange{lo: KeyMin, hi_: KeyMax, node: a} // [-∞, ∞)
 	av  = rangeSplit{atop}
@@ -789,7 +789,6 @@ func diffT(ctx context.Context, a, b *Tree, δZTC SetOid, trackIdx map[zodb.Oid]
 			}
 		}
 	}
-	}
 
 	tracef("  av: %s\n", av)
 	tracef("  bv: %s\n", bv)