handle nested lists correctly

generate/testdata/queries/ListOfListsOfLists.graphql

@@ -0,0 +1,3 @@
+query ListOfListsOfLists {
+  listOfListsOfLists
+}

generate/testdata/queries/ListOfListsOfLists.graphql.go

@@ -0,0 +1,29 @@
+package test
+
+// Code generated by github.com/Khan/genqlient, DO NOT EDIT.
+
+import (
+	"github.com/Khan/genqlient/graphql"
+)
+
+type ListOfListsOfListsResponse struct {
+	ListOfListsOfLists [][][]string `json:"listOfListsOfLists"`
+}
+
+func ListOfListsOfLists(
+	client graphql.Client,
+) (*ListOfListsOfListsResponse, error) {
+	var retval ListOfListsOfListsResponse
+	err := client.MakeRequest(
+		nil,
+		"ListOfListsOfLists",
+		`
+query ListOfListsOfLists {
+	listOfListsOfLists
+}
+`,
+		&retval,
+		nil,
+	)
+	return &retval, err
+}

generate/testdata/queries/ListOfListsOfLists.graphql.json

@@ -0,0 +1,9 @@
+{
+  "operations": [
+    {
+      "operationName": "ListOfListsOfLists",
+      "query": "\nquery ListOfListsOfLists {\n\tlistOfListsOfLists\n}\n",
+      "sourceLocation": "testdata/queries/ListOfListsOfLists.graphql"
+    }
+  ]
+}

generate/testdata/queries/schema.graphql

@@ -67,6 +67,7 @@ type Query {
   convert(dt: DateTime!, tz: String): DateTime!
   maybeConvert(dt: DateTime, tz: String): DateTime
   getJunk: Junk
+  listOfListsOfLists: [[[String!]!]!]!
 }
 
 type Mutation {

generate/types.go

@@ -292,14 +292,15 @@ func (builder *typeBuilder) writeType(name, namePrefix string, typ *ast.Type, fi
 	// gqlgen does slightly different things here, but its implementation may
 	// be useful to crib from:
 	// https://github.com/99designs/gqlgen/blob/master/plugin/modelgen/models.go#L113
-	if typ.Elem != nil { // XXX: this should be for, not if
+	for typ.Elem != nil {
 		// Type is a list.
 		builder.WriteString("[]")
 		typ = typ.Elem
 	}
 	if options.GetPointer() {
 		// TODO: this does []*T, you might in principle want *[]T or
-		// *[]*T.  We could add a "sliceptr" option if it comes up.
+		// *[]*T.  We could add a "sliceptr" option if it comes up (that's
+		// still not correct if you wanted *[][]*[]T, but, like, tough luck).
 		builder.WriteString("*")
 	}