Add static type assertions

Assert that various iterators satisfy the graph.Nexter interface

graph/bolt/all_iterator.go

@@ -204,3 +204,5 @@ func (it *AllIterator) Stats() graph.IteratorStats {
 		Size:         s,
 	}
 }
+
+var _ graph.Nexter = &AllIterator{}

graph/bolt/iterator.go

@@ -316,3 +316,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         s,
 	}
 }
+
+var _ graph.Nexter = &Iterator{}

graph/gaedatastore/iterator.go

@@ -323,3 +323,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         size,
 	}
 }
+
+var _ graph.Nexter = &Iterator{}

graph/iterator/all_iterator.go

@@ -160,3 +160,5 @@ func (it *Int64) Stats() graph.IteratorStats {
 		Contains:     it.runstats.Contains,
 	}
 }
+
+var _ graph.Nexter = &Int64{}

graph/iterator/and_iterator.go

@@ -265,3 +265,5 @@ func (it *And) Close() {
 
 // Register this as an "and" iterator.
 func (it *And) Type() graph.Type { return graph.And }
+
+var _ graph.Nexter = &And{}

graph/iterator/fixed_iterator.go

@@ -186,3 +186,5 @@ func (it *Fixed) Stats() graph.IteratorStats {
 		Size:         int64(len(it.values)),
 	}
 }
+
+var _ graph.Nexter = &Fixed{}

graph/iterator/hasa_iterator.go

@@ -252,3 +252,5 @@ func (it *HasA) Type() graph.Type { return graph.HasA }
 func (it *HasA) Size() (int64, bool) {
 	return it.Stats().Size, false
 }
+
+var _ graph.Nexter = &HasA{}

graph/iterator/iterator.go

@@ -116,3 +116,5 @@ func (it *Null) Close() {}
 func (it *Null) Stats() graph.IteratorStats {
 	return graph.IteratorStats{}
 }
+
+var _ graph.Nexter = &Null{}

graph/iterator/linksto_iterator.go

@@ -214,3 +214,5 @@ func (it *LinksTo) Stats() graph.IteratorStats {
 func (it *LinksTo) Size() (int64, bool) {
 	return it.Stats().Size, false
 }
+
+var _ graph.Nexter = &LinksTo{}

graph/iterator/materialize_iterator.go

@@ -293,3 +293,5 @@ func (it *Materialize) materializeSet() {
 	}
 	it.hasRun = true
 }
+
+var _ graph.Nexter = &Materialize{}

graph/iterator/not_iterator.go

@@ -161,3 +161,5 @@ func (it *Not) Describe() graph.Description {
 		Iterators: subIts,
 	}
 }
+
+var _ graph.Nexter = &Not{}

graph/iterator/or_iterator.go

@@ -289,3 +289,5 @@ func (it *Or) Stats() graph.IteratorStats {
 
 // Register this as an "or" graph.iterator.
 func (it *Or) Type() graph.Type { return graph.Or }
+
+var _ graph.Nexter = &Or{}

graph/iterator/value_comparison_iterator.go

@@ -218,3 +218,5 @@ func (it *Comparison) Stats() graph.IteratorStats {
 func (it *Comparison) Size() (int64, bool) {
 	return 0, true
 }
+
+var _ graph.Nexter = &Comparison{}

graph/leveldb/all_iterator.go

@@ -183,3 +183,5 @@ func (it *AllIterator) Stats() graph.IteratorStats {
 		Size:         s,
 	}
 }
+
+var _ graph.Nexter = &AllIterator{}

graph/leveldb/iterator.go

@@ -283,3 +283,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         s,
 	}
 }
+
+var _ graph.Nexter = &Iterator{}

graph/memstore/all_iterator.go

@@ -69,3 +69,6 @@ func (it *quadsAllIterator) Next() bool {
 	}
 	return out
 }
+
+var _ graph.Nexter = &nodesAllIterator{}
+var _ graph.Nexter = &quadsAllIterator{}

graph/memstore/iterator.go

@@ -191,3 +191,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         int64(it.tree.Len()),
 	}
 }
+
+var _ graph.Nexter = &Iterator{}

graph/mongo/iterator.go

@@ -230,3 +230,5 @@ func (it *Iterator) Stats() graph.IteratorStats {
 		Size:         size,
 	}
 }
+
+var _ graph.Nexter = &Iterator{}