Remove flow option experimental.const_params

.flowconfig

@@ -9,7 +9,6 @@
 [libs]
 
 [options]
-experimental.const_params=true
 
 [version]
 ^0.61.0

src/error/GraphQLError.js

@@ -125,7 +125,8 @@ export function GraphQLError( // eslint-disable-line no-redeclare
 
   let _locations;
   if (positions && source) {
-    _locations = positions.map(pos => getLocation(source, pos));
+    const providedSource = source;
+    _locations = positions.map(pos => getLocation(providedSource, pos));
   } else if (_nodes) {
     _locations = _nodes.reduce((list, node) => {
       if (node.loc) {

src/type/introspection.js

@@ -27,7 +27,7 @@ import {
 import { GraphQLList, GraphQLNonNull } from '../type/wrappers';
 import { GraphQLString, GraphQLBoolean } from './scalars';
 import { DirectiveLocation } from '../language/directiveLocation';
-import type { GraphQLField, GraphQLType } from './definition';
+import type { GraphQLField } from './definition';
 
 export const __Schema = new GraphQLObjectType({
   name: '__Schema',
@@ -465,11 +465,18 @@ export const introspectionTypes: $ReadOnlyArray<*> = [
   __TypeKind,
 ];
 
-export function isIntrospectionType(type: ?GraphQLType): boolean %checks {
+export function isIntrospectionType(type: mixed): boolean %checks {
   return (
     isNamedType(type) &&
-    introspectionTypes.some(
-      introspectionType => introspectionType.name === type.name,
-    )
+    // Would prefer to use introspectionTypes.some(), however %checks needs
+    // a simple expression.
+    (type.name === __Schema.name ||
+      type.name === __Directive.name ||
+      type.name === __DirectiveLocation.name ||
+      type.name === __Type.name ||
+      type.name === __Field.name ||
+      type.name === __InputValue.name ||
+      type.name === __EnumValue.name ||
+      type.name === __TypeKind.name)
   );
 }

src/type/scalars.js

@@ -9,7 +9,6 @@
 
 import { GraphQLScalarType, isNamedType } from './definition';
 import * as Kind from '../language/kinds';
-import type { GraphQLType } from './definition';
 
 // As per the GraphQL Spec, Integers are only treated as valid when a valid
 // 32-bit signed integer, providing the broadest support across platforms.
@@ -145,11 +144,15 @@ export const specifiedScalarTypes: $ReadOnlyArray<*> = [
   GraphQLID,
 ];
 
-export function isSpecifiedScalarType(type: ?GraphQLType): boolean %checks {
+export function isSpecifiedScalarType(type: mixed): boolean %checks {
   return (
     isNamedType(type) &&
-    specifiedScalarTypes.some(
-      specifiedScalarType => specifiedScalarType.name === type.name,
-    )
+    // Would prefer to use specifiedScalarTypes.some(), however %checks needs
+    // a simple expression.
+    (type.name === GraphQLString.name ||
+      type.name === GraphQLInt.name ||
+      type.name === GraphQLFloat.name ||
+      type.name === GraphQLBoolean.name ||
+      type.name === GraphQLID.name)
   );
 }