diff --git a/example/genqlient.yaml b/example/genqlient.yaml
index ad57911..7ef0bc7 100644
--- a/example/genqlient.yaml
+++ b/example/genqlient.yaml
@@ -5,7 +5,10 @@ operations:
 - genqlient.graphql
 generated: generated.go
 
-# We map github's DateTime type to Go's time.Time (which conveniently already
-# defines MarshalJSON and UnmarshalJSON).
-scalars:
-  DateTime: time.Time
+# We bind github's DateTime scalar type to Go's time.Time (which conveniently
+# already defines MarshalJSON and UnmarshalJSON).  This means genqlient will
+# use time.Time when a query requests a DateTime, and is required for custom
+# scalars.
+bindings:
+  DateTime:
+    type: time.Time
diff --git a/generate/config.go b/generate/config.go
index 4a07910..7ea3fcf 100644
--- a/generate/config.go
+++ b/generate/config.go
@@ -65,13 +65,25 @@ type Config struct {
 	// TODO(#5): This is a bit broken, fix it.
 	ClientGetter string `yaml:"client_getter"`
 
-	// A map from GraphQL scalar type name to Go fully-qualified type name for
-	// the types to use for any custom or builtin scalars.  By default, builtin
-	// scalars are mapped to the obvious Go types (String and ID to string, Int
-	// to int, Float to float64, and Boolean to bool), but this setting will
-	// extend or override those mappings.  These types must define MarshalJSON
-	// and UnmarshalJSON methods, or otherwise be convertible to JSON.
-	Scalars map[string]string `yaml:"scalars"`
+	// A map from GraphQL type name to Go fully-qualified type name to override
+	// the Go type genqlient will use for this GraphQL type.
+	//
+	// This is primarily used for custom scalars, or to map builtin scalars to
+	// a nonstandard type.  By default, builtin scalars are mapped to the
+	// obvious Go types (String and ID to string, Int to int, Float to float64,
+	// and Boolean to bool), but this setting will extend or override those
+	// mappings.
+	//
+	// genqlient does not validate these types in any way; they must define
+	// whatever logic is needed (MarshalJSON/UnmarshalJSON or JSON tags) to
+	// convert to/from JSON.  For this reason, it's not recommended to use this
+	// setting to map object, interface, or union types, because nothing
+	// guarantees that the fields requested in the query match those present in
+	// the Go type.
+	//
+	// To get equivalent behavior in just one query, use @genqlient(bind: ...);
+	// see GenqlientDirective.Bind for more details.
+	Bindings map[string]*TypeBinding `yaml:"bindings"`
 
 	// Set to true to use features that aren't fully ready to use.
 	//
@@ -84,6 +96,16 @@ type Config struct {
 	configFilename string
 }
 
+// A TypeBinding represents a Go type to which genqlient will bind a particular
+// GraphQL type.  See Config.Bind, above, for more details.
+type TypeBinding struct {
+	// The fully-qualified name of the Go type to which to bind.  For example:
+	//	time.Time
+	//  map[string]interface{}
+	//	github.com/you/yourpkg/subpkg.MyType
+	Type string `yaml:"type"`
+}
+
 // baseDir returns the directory of the config-file (relative to which
 // all the other paths are resolved).
 func (c *Config) baseDir() string {
diff --git a/generate/convert.go b/generate/convert.go
index ca3701d..d506615 100644
--- a/generate/convert.go
+++ b/generate/convert.go
@@ -53,7 +53,7 @@ func (g *generator) convertOperation(
 
 	goTyp, err := g.convertDefinition(
 		name, operation.Name, baseType, operation.Position,
-		operation.SelectionSet, queryOptions)
+		operation.SelectionSet, queryOptions, queryOptions)
 
 	if structType, ok := goTyp.(*goStructType); ok {
 		// Override the ordinary description; the GraphQL documentation for
@@ -140,6 +140,15 @@ func (g *generator) convertType(
 	selectionSet ast.SelectionSet,
 	options, queryOptions *GenqlientDirective,
 ) (goType, error) {
+	// We check for local bindings here, so that you can bind, say, a
+	// `[String!]` to a struct instead of a slice.  Global bindings can only
+	// bind GraphQL named types, at least for now.
+	localBinding := options.Bind
+	if localBinding != "" && localBinding != "-" {
+		goRef, err := g.addRef(localBinding)
+		return &goOpaqueType{goRef}, err
+	}
+
 	if typ.Elem != nil {
 		// Type is a list.
 		elem, err := g.convertType(
@@ -150,7 +159,7 @@ func (g *generator) convertType(
 	// If this is a builtin type or custom scalar, just refer to it.
 	def := g.schema.Types[typ.Name()]
 	goTyp, err := g.convertDefinition(
-		name, namePrefix, def, typ.Position, selectionSet, queryOptions)
+		name, namePrefix, def, typ.Position, selectionSet, options, queryOptions)
 
 	if options.GetPointer() {
 		// Whatever we get, wrap it in a pointer.  (Because of the way the
@@ -172,11 +181,16 @@ func (g *generator) convertDefinition(
 	def *ast.Definition,
 	pos *ast.Position,
 	selectionSet ast.SelectionSet,
-	queryOptions *GenqlientDirective,
+	options, queryOptions *GenqlientDirective,
 ) (goType, error) {
-	qualifiedGoName, ok := g.Config.Scalars[def.Name]
-	if ok {
-		goRef, err := g.addRef(qualifiedGoName)
+	// Check if we should use an existing type.  (This is usually true for
+	// GraphQL scalars, but we allow you to bind non-scalar types too, if you
+	// want, subject to the caveats described in Config.Bindings.)  Local
+	// bindings are checked in the caller (convertType) and never get here,
+	// unless the binding is "-" which means "ignore the global binding".
+	globalBinding, ok := g.Config.Bindings[def.Name]
+	if ok && options.Bind != "-" {
+		goRef, err := g.addRef(globalBinding.Type)
 		return &goOpaqueType{goRef}, err
 	}
 	goBuiltinName, ok := builtinTypes[def.Name]
@@ -306,7 +320,7 @@ func (g *generator) convertDefinition(
 			// preprocessQueryDocument).  But in practice it doesn't really
 			// hurt, and would be extra work to avoid, so we just leave it.
 			implTyp, err := g.convertDefinition(
-				implName, namePrefix, implDef, pos, selectionSet, queryOptions)
+				implName, namePrefix, implDef, pos, selectionSet, options, queryOptions)
 			if err != nil {
 				return nil, err
 			}
@@ -335,8 +349,9 @@ func (g *generator) convertDefinition(
 		return goType, nil
 
 	case ast.Scalar:
+		// (If you had an entry in bindings, we would have returned it above.)
 		return nil, errorf(
-			pos, "unknown scalar %v: please add it to genqlient.yaml", def.Name)
+			pos, `unknown scalar %v: please add it to "bindings" in genqlient.yaml`, def.Name)
 	default:
 		return nil, errorf(pos, "unexpected kind: %v", def.Kind)
 	}
diff --git a/generate/generate_test.go b/generate/generate_test.go
index f69f223..a909127 100644
--- a/generate/generate_test.go
+++ b/generate/generate_test.go
@@ -51,11 +51,13 @@ func TestGenerate(t *testing.T) {
 				Package:          "test",
 				Generated:        goFilename,
 				ExportOperations: queriesFilename,
-				Scalars: map[string]string{
-					"ID":          "github.com/Khan/genqlient/internal/testutil.ID",
-					"DateTime":    "time.Time",
-					"Junk":        "interface{}",
-					"ComplexJunk": "[]map[string]*[]*map[string]interface{}",
+				Bindings: map[string]*TypeBinding{
+					"ID":           {Type: "github.com/Khan/genqlient/internal/testutil.ID"},
+					"DateTime":     {Type: "time.Time"},
+					"Junk":         {Type: "interface{}"},
+					"ComplexJunk":  {Type: "[]map[string]*[]*map[string]interface{}"},
+					"Pokemon":      {Type: "github.com/Khan/genqlient/internal/testutil.Pokemon"},
+					"PokemonInput": {Type: "github.com/Khan/genqlient/internal/testutil.Pokemon"},
 				},
 				AllowBrokenFeatures: true,
 			})
@@ -138,9 +140,9 @@ func TestGenerateErrors(t *testing.T) {
 				Operations: []string{filepath.Join(errorsDir, sourceFilename)},
 				Package:    "test",
 				Generated:  os.DevNull,
-				Scalars: map[string]string{
-					"ValidScalar":   "string",
-					"InvalidScalar": "bogus",
+				Bindings: map[string]*TypeBinding{
+					"ValidScalar":   {Type: "string"},
+					"InvalidScalar": {Type: "bogus"},
 				},
 				AllowBrokenFeatures: true,
 			})
diff --git a/generate/genqlient_directive.go b/generate/genqlient_directive.go
index ab78029..5abf8b4 100644
--- a/generate/genqlient_directive.go
+++ b/generate/genqlient_directive.go
@@ -63,6 +63,27 @@ type GenqlientDirective struct {
 	// pointer to save copies) or if you wish to distinguish between the Go
 	// zero value and null (for nullable fields).
 	Pointer *bool
+
+	// If set, this argument or field will use the given Go type instead of a
+	// genqlient-generated type.
+	//
+	// The value should be the fully-qualified type name to use for the field,
+	// for example:
+	//	time.Time
+	//	map[string]interface{}
+	//	[]github.com/you/yourpkg/subpkg.MyType
+	// Note that the type is the type of the whole field, e.g. if your field in
+	// GraphQL has type `[DateTime]`, you'd do
+	//	# @genqlient(bind: "[]time.Time")
+	// (But you're not required to; if you want to map to some type DateList,
+	// you can do that, as long as its UnmarshalJSON method can accept a list
+	// of datetimes.)
+	//
+	// See Config.Bindings for more details; this is effectively to a local
+	// version of that global setting and should be used with similar care.
+	// If set to "-", overrides any such global setting and uses a
+	// genqlient-generated type.
+	Bind string
 }
 
 func (dir *GenqlientDirective) GetOmitempty() bool { return dir.Omitempty != nil && *dir.Omitempty }
@@ -70,7 +91,6 @@ func (dir *GenqlientDirective) GetPointer() bool   { return dir.Pointer != nil &
 
 func setBool(dst **bool, v *ast.Value) error {
 	ei, err := v.Value(nil) // no vars allowed
-	// TODO: here and below, put positions on these errors
 	if err != nil {
 		return errorf(v.Position, "invalid boolean value %v: %v", v, err)
 	}
@@ -81,6 +101,18 @@ func setBool(dst **bool, v *ast.Value) error {
 	return errorf(v.Position, "expected boolean, got non-boolean value %T(%v)", ei, ei)
 }
 
+func setString(dst *string, v *ast.Value) error {
+	ei, err := v.Value(nil) // no vars allowed
+	if err != nil {
+		return errorf(v.Position, "invalid string value %v: %v", v, err)
+	}
+	if b, ok := ei.(string); ok {
+		*dst = b
+		return nil
+	}
+	return errorf(v.Position, "expected string, got non-string value %T(%v)", ei, ei)
+}
+
 func fromGraphQL(dir *ast.Directive) (*GenqlientDirective, error) {
 	if dir.Name != "genqlient" {
 		// Actually we just won't get here; we only get here if the line starts
@@ -99,6 +131,8 @@ func fromGraphQL(dir *ast.Directive) (*GenqlientDirective, error) {
 			err = setBool(&retval.Omitempty, arg.Value)
 		case "pointer":
 			err = setBool(&retval.Pointer, arg.Value)
+		case "bind":
+			err = setString(&retval.Bind, arg.Value)
 		default:
 			return nil, errorf(arg.Position, "unknown argument %v for @genqlient", arg.Name)
 		}
@@ -112,8 +146,12 @@ func fromGraphQL(dir *ast.Directive) (*GenqlientDirective, error) {
 func (dir *GenqlientDirective) validate(node interface{}) error {
 	switch node := node.(type) {
 	case *ast.OperationDefinition:
-		// Anything is valid on the entire operation; it will just apply to
-		// whatever it is relevant to.
+		if dir.Bind != "" {
+			return errorf(dir.pos, "bind may not be applied to the entire operation")
+		}
+
+		// Anything else is valid on the entire operation; it will just apply
+		// to whatever it is relevant to.
 		return nil
 	case *ast.VariableDefinition:
 		if dir.Omitempty != nil && node.Type.NonNull {
@@ -122,7 +160,7 @@ func (dir *GenqlientDirective) validate(node interface{}) error {
 		return nil
 	case *ast.Field:
 		if dir.Omitempty != nil {
-			return errorf(dir.pos, "omitempty is not appilcable to fields")
+			return errorf(dir.pos, "omitempty is not applicable to fields")
 		}
 		return nil
 	default:
@@ -138,6 +176,9 @@ func (dir *GenqlientDirective) merge(other *GenqlientDirective) *GenqlientDirect
 	if other.Pointer != nil {
 		retval.Pointer = other.Pointer
 	}
+	if other.Bind != "" {
+		retval.Bind = other.Bind
+	}
 	return &retval
 }
 
diff --git a/generate/testdata/queries/Pokemon.graphql b/generate/testdata/queries/Pokemon.graphql
new file mode 100644
index 0000000..5b40414
--- /dev/null
+++ b/generate/testdata/queries/Pokemon.graphql
@@ -0,0 +1,16 @@
+query GetPokemonSiblings($input: PokemonInput!) {
+  user(query: {hasPokemon: $input}) {
+    # this will override the default mapping to internal/testutil.ID:
+    # @genqlient(bind: "string")
+    id
+    # this is normally an enum, but here we make it a (list of) string:
+    # @genqlient(bind: "[]string")
+    roles
+    name
+    # this is mapped globally to internal/testutil.Pokemon:
+    pokemon { species level }
+    # this overrides said mapping:
+    # @genqlient(bind: "-")
+    genqlientPokemon: pokemon { species level }
+  }
+}
diff --git a/generate/testdata/queries/schema.graphql b/generate/testdata/queries/schema.graphql
index dc872c8..feaf9b2 100644
--- a/generate/testdata/queries/schema.graphql
+++ b/generate/testdata/queries/schema.graphql
@@ -20,6 +20,16 @@ enum Role {
   TEACHER
 }
 
+input PokemonInput {
+  species: String!
+  level: Int!
+}
+
+type Pokemon {
+  species: String!
+  level: Int!
+}
+
 """UserQueryInput is the argument to Query.users.
 
 Ideally this would support anything and everything!
@@ -33,6 +43,7 @@ input UserQueryInput {
   id: ID
   role: Role
   names: [String]
+  hasPokemon: PokemonInput
 }
 
 type AuthMethod {
@@ -53,6 +64,7 @@ type User {
   emailsWithNulls: [String]!
   emailsWithNullsOrNull: [String]
   authMethods: [AuthMethod!]!
+  pokemon: [Pokemon!]
 }
 
 """Content is implemented by various types like Article, Video, and Topic."""
diff --git a/generate/testdata/snapshots/TestGenerate-InputObject.graphql-InputObject.graphql.go b/generate/testdata/snapshots/TestGenerate-InputObject.graphql-InputObject.graphql.go
index 2f844be..288650c 100644
--- a/generate/testdata/snapshots/TestGenerate-InputObject.graphql-InputObject.graphql.go
+++ b/generate/testdata/snapshots/TestGenerate-InputObject.graphql-InputObject.graphql.go
@@ -50,9 +50,10 @@ type UserQueryInput struct {
 	Email string `json:"email"`
 	Name  string `json:"name"`
 	// id looks the user up by ID.  It's a great way to look up users.
-	Id    testutil.ID `json:"id"`
-	Role  Role        `json:"role"`
-	Names []string    `json:"names"`
+	Id         testutil.ID      `json:"id"`
+	Role       Role             `json:"role"`
+	Names      []string         `json:"names"`
+	HasPokemon testutil.Pokemon `json:"hasPokemon"`
 }
 
 func InputObjectQuery(
diff --git a/generate/testdata/snapshots/TestGenerate-Omitempty.graphql-Omitempty.graphql.go b/generate/testdata/snapshots/TestGenerate-Omitempty.graphql-Omitempty.graphql.go
index 77c2d58..4d750cd 100644
--- a/generate/testdata/snapshots/TestGenerate-Omitempty.graphql-Omitempty.graphql.go
+++ b/generate/testdata/snapshots/TestGenerate-Omitempty.graphql-Omitempty.graphql.go
@@ -66,9 +66,10 @@ type UserQueryInput struct {
 	Email string `json:"email"`
 	Name  string `json:"name"`
 	// id looks the user up by ID.  It's a great way to look up users.
-	Id    testutil.ID `json:"id"`
-	Role  Role        `json:"role"`
-	Names []string    `json:"names"`
+	Id         testutil.ID      `json:"id"`
+	Role       Role             `json:"role"`
+	Names      []string         `json:"names"`
+	HasPokemon testutil.Pokemon `json:"hasPokemon"`
 }
 
 func OmitEmptyQuery(
diff --git a/generate/testdata/snapshots/TestGenerate-Pointers.graphql-Pointers.graphql.go b/generate/testdata/snapshots/TestGenerate-Pointers.graphql-Pointers.graphql.go
index 8862ff9..0a17884 100644
--- a/generate/testdata/snapshots/TestGenerate-Pointers.graphql-Pointers.graphql.go
+++ b/generate/testdata/snapshots/TestGenerate-Pointers.graphql-Pointers.graphql.go
@@ -73,9 +73,10 @@ type UserQueryInput struct {
 	Email *string `json:"email"`
 	Name  *string `json:"name"`
 	// id looks the user up by ID.  It's a great way to look up users.
-	Id    *testutil.ID `json:"id"`
-	Role  *Role        `json:"role"`
-	Names []*string    `json:"names"`
+	Id         *testutil.ID      `json:"id"`
+	Role       *Role             `json:"role"`
+	Names      []*string         `json:"names"`
+	HasPokemon *testutil.Pokemon `json:"hasPokemon"`
 }
 
 func PointersQuery(
diff --git a/generate/testdata/snapshots/TestGenerate-PointersInline.graphql-PointersInline.graphql.go b/generate/testdata/snapshots/TestGenerate-PointersInline.graphql-PointersInline.graphql.go
index 8ab0598..d3ada1e 100644
--- a/generate/testdata/snapshots/TestGenerate-PointersInline.graphql-PointersInline.graphql.go
+++ b/generate/testdata/snapshots/TestGenerate-PointersInline.graphql-PointersInline.graphql.go
@@ -73,9 +73,10 @@ type UserQueryInput struct {
 	Email string `json:"email"`
 	Name  string `json:"name"`
 	// id looks the user up by ID.  It's a great way to look up users.
-	Id    testutil.ID `json:"id"`
-	Role  Role        `json:"role"`
-	Names []string    `json:"names"`
+	Id         testutil.ID      `json:"id"`
+	Role       Role             `json:"role"`
+	Names      []string         `json:"names"`
+	HasPokemon testutil.Pokemon `json:"hasPokemon"`
 }
 
 func PointersQuery(
diff --git a/generate/testdata/snapshots/TestGenerate-Pokemon.graphql-Pokemon.graphql.go b/generate/testdata/snapshots/TestGenerate-Pokemon.graphql-Pokemon.graphql.go
new file mode 100644
index 0000000..4a4796b
--- /dev/null
+++ b/generate/testdata/snapshots/TestGenerate-Pokemon.graphql-Pokemon.graphql.go
@@ -0,0 +1,74 @@
+package test
+
+// Code generated by github.com/Khan/genqlient, DO NOT EDIT.
+
+import (
+	"github.com/Khan/genqlient/graphql"
+	"github.com/Khan/genqlient/internal/testutil"
+)
+
+// GetPokemonSiblingsResponse is returned by GetPokemonSiblings on success.
+type GetPokemonSiblingsResponse struct {
+	// user looks up a user by some stuff.
+	//
+	// See UserQueryInput for what stuff is supported.
+	// If query is null, returns the current user.
+	User GetPokemonSiblingsUser `json:"user"`
+}
+
+// GetPokemonSiblingsUser includes the requested fields of the GraphQL type User.
+// The GraphQL type's documentation follows.
+//
+// A User is a user!
+type GetPokemonSiblingsUser struct {
+	// id is the user's ID.
+	//
+	// It is stable, unique, and opaque, like all good IDs.
+	Id               string                                   `json:"id"`
+	Roles            []string                                 `json:"roles"`
+	Name             string                                   `json:"name"`
+	Pokemon          []testutil.Pokemon                       `json:"pokemon"`
+	GenqlientPokemon []GetPokemonSiblingsUserGenqlientPokemon `json:"genqlientPokemon"`
+}
+
+// GetPokemonSiblingsUserGenqlientPokemon includes the requested fields of the GraphQL type Pokemon.
+type GetPokemonSiblingsUserGenqlientPokemon struct {
+	Species string `json:"species"`
+	Level   int    `json:"level"`
+}
+
+func GetPokemonSiblings(
+	client graphql.Client,
+	input testutil.Pokemon,
+) (*GetPokemonSiblingsResponse, error) {
+	variables := map[string]interface{}{
+		"input": input,
+	}
+
+	var retval GetPokemonSiblingsResponse
+	err := client.MakeRequest(
+		nil,
+		"GetPokemonSiblings",
+		`
+query GetPokemonSiblings ($input: PokemonInput!) {
+	user(query: {hasPokemon:$input}) {
+		id
+		roles
+		name
+		pokemon {
+			species
+			level
+		}
+		genqlientPokemon: pokemon {
+			species
+			level
+		}
+	}
+}
+`,
+		&retval,
+		variables,
+	)
+	return &retval, err
+}
+
diff --git a/generate/testdata/snapshots/TestGenerate-Pokemon.graphql-Pokemon.graphql.json b/generate/testdata/snapshots/TestGenerate-Pokemon.graphql-Pokemon.graphql.json
new file mode 100644
index 0000000..046d226
--- /dev/null
+++ b/generate/testdata/snapshots/TestGenerate-Pokemon.graphql-Pokemon.graphql.json
@@ -0,0 +1,9 @@
+{
+  "operations": [
+    {
+      "operationName": "GetPokemonSiblings",
+      "query": "\nquery GetPokemonSiblings ($input: PokemonInput!) {\n\tuser(query: {hasPokemon:$input}) {\n\t\tid\n\t\troles\n\t\tname\n\t\tpokemon {\n\t\t\tspecies\n\t\t\tlevel\n\t\t}\n\t\tgenqlientPokemon: pokemon {\n\t\t\tspecies\n\t\t\tlevel\n\t\t}\n\t}\n}\n",
+      "sourceLocation": "testdata/queries/Pokemon.graphql"
+    }
+  ]
+}
diff --git a/generate/testdata/snapshots/TestGenerate-unexported.graphql-unexported.graphql.go b/generate/testdata/snapshots/TestGenerate-unexported.graphql-unexported.graphql.go
index c07b814..f5c5b39 100644
--- a/generate/testdata/snapshots/TestGenerate-unexported.graphql-unexported.graphql.go
+++ b/generate/testdata/snapshots/TestGenerate-unexported.graphql-unexported.graphql.go
@@ -50,9 +50,10 @@ type userQueryInput struct {
 	Email string `json:"email"`
 	Name  string `json:"name"`
 	// id looks the user up by ID.  It's a great way to look up users.
-	Id    testutil.ID `json:"id"`
-	Role  Role        `json:"role"`
-	Names []string    `json:"names"`
+	Id         testutil.ID      `json:"id"`
+	Role       Role             `json:"role"`
+	Names      []string         `json:"names"`
+	HasPokemon testutil.Pokemon `json:"hasPokemon"`
 }
 
 func unexported(
diff --git a/generate/testdata/snapshots/TestGenerateErrors-UnknownScalar.go b/generate/testdata/snapshots/TestGenerateErrors-UnknownScalar.go
index c3d339b..3c698d2 100644
--- a/generate/testdata/snapshots/TestGenerateErrors-UnknownScalar.go
+++ b/generate/testdata/snapshots/TestGenerateErrors-UnknownScalar.go
@@ -1 +1 @@
-testdata/errors/UnknownScalar.schema.graphql:3: unknown scalar UnknownScalar: please add it to genqlient.yaml
+testdata/errors/UnknownScalar.schema.graphql:3: unknown scalar UnknownScalar: please add it to "bindings" in genqlient.yaml
diff --git a/generate/testdata/snapshots/TestGenerateErrors-UnknownScalar.graphql b/generate/testdata/snapshots/TestGenerateErrors-UnknownScalar.graphql
index c3d339b..3c698d2 100644
--- a/generate/testdata/snapshots/TestGenerateErrors-UnknownScalar.graphql
+++ b/generate/testdata/snapshots/TestGenerateErrors-UnknownScalar.graphql
@@ -1 +1 @@
-testdata/errors/UnknownScalar.schema.graphql:3: unknown scalar UnknownScalar: please add it to genqlient.yaml
+testdata/errors/UnknownScalar.schema.graphql:3: unknown scalar UnknownScalar: please add it to "bindings" in genqlient.yaml
diff --git a/generate/types.go b/generate/types.go
index a5433da..f978385 100644
--- a/generate/types.go
+++ b/generate/types.go
@@ -46,8 +46,8 @@ var (
 )
 
 type (
-	// goOpaqueType represents a user-defined or builtin type, used to
-	// represent a GraphQL scalar.
+	// goOpaqueType represents a user-defined or builtin type, often used to
+	// represent a GraphQL scalar.  (See Config.Bindings for more context.)
 	goOpaqueType struct{ GoRef string }
 	// goSliceType represents the Go type []Elem, used to represent GraphQL
 	// list types.
diff --git a/internal/testutil/types.go b/internal/testutil/types.go
index b61b4e0..d5d5446 100644
--- a/internal/testutil/types.go
+++ b/internal/testutil/types.go
@@ -1,3 +1,12 @@
 package testutil
 
 type ID string
+
+type Pokemon struct {
+	Species string `json:"species"`
+	Level   int    `json:"level"`
+}
+
+func (p Pokemon) Battle(q Pokemon) bool {
+	return p.Level > q.Level
+}