Flow: Remove some of the 'existential type' usages

See: https://flow.org/en/docs/types/utilities/#toc-existential-type

src/execution/execute.js

@@ -293,8 +293,8 @@ export function buildExecutionContext(
   contextValue: mixed,
   rawVariableValues: ?{ +[variable: string]: mixed, ... },
   operationName: ?string,
-  fieldResolver: ?GraphQLFieldResolver<any, any>,
-  typeResolver?: ?GraphQLTypeResolver<any, any>,
+  fieldResolver: ?GraphQLFieldResolver<mixed, mixed>,
+  typeResolver?: ?GraphQLTypeResolver<mixed, mixed>,
 ): $ReadOnlyArray<GraphQLError> | ExecutionContext {
   const errors: Array<GraphQLError> = [];
   let operation: OperationDefinitionNode | void;
@@ -682,7 +682,7 @@ function resolveField(
 
 export function buildResolveInfo(
   exeContext: ExecutionContext,
-  fieldDef: GraphQLField<*, *>,
+  fieldDef: GraphQLField<mixed, mixed>,
   fieldNodes: $ReadOnlyArray<FieldNode>,
   parentType: GraphQLObjectType,
   path: ResponsePath,
@@ -705,12 +705,12 @@ export function buildResolveInfo(
 
 // Isolates the "ReturnOrAbrupt" behavior to not de-opt the `resolveField`
 // function. Returns the result of resolveFn or the abrupt-return Error object.
-export function resolveFieldValueOrError<TSource>(
+export function resolveFieldValueOrError(
   exeContext: ExecutionContext,
-  fieldDef: GraphQLField<TSource, *>,
+  fieldDef: GraphQLField<mixed, mixed>,
   fieldNodes: $ReadOnlyArray<FieldNode>,
-  resolveFn: GraphQLFieldResolver<TSource, *>,
-  source: TSource,
+  resolveFn: GraphQLFieldResolver<mixed, mixed>,
+  source: mixed,
   info: GraphQLResolveInfo,
 ): Error | mixed {
   try {
@@ -1165,7 +1165,7 @@ function _collectSubfields(
  * Otherwise, test each possible type for the abstract type by calling
  * isTypeOf for the object being coerced, returning the first type that matches.
  */
-export const defaultTypeResolver: GraphQLTypeResolver<any, *> = function(
+export const defaultTypeResolver: GraphQLTypeResolver<mixed, mixed> = function(
   value,
   contextValue,
   info,
@@ -1211,12 +1211,10 @@ export const defaultTypeResolver: GraphQLTypeResolver<any, *> = function(
  * and returns it as the result, or if it's a function, returns the result
  * of calling that function while passing along args and context value.
  */
-export const defaultFieldResolver: GraphQLFieldResolver<any, *> = function(
-  source,
-  args,
-  contextValue,
-  info,
-) {
+export const defaultFieldResolver: GraphQLFieldResolver<
+  mixed,
+  mixed,
+> = function(source: any, args, contextValue, info) {
   // ensure source is a value for which property access is acceptable.
   if (isObjectLike(source) || typeof source === 'function') {
     const property = source[info.fieldName];
@@ -1240,7 +1238,7 @@ export function getFieldDef(
   schema: GraphQLSchema,
   parentType: GraphQLObjectType,
   fieldName: string,
-): ?GraphQLField<*, *> {
+): ?GraphQLField<mixed, mixed> {
   if (
     fieldName === SchemaMetaFieldDef.name &&
     schema.getQueryType() === parentType

src/execution/values.js

@@ -119,7 +119,7 @@ export function getVariableValues(
  * Object prototype.
  */
 export function getArgumentValues(
-  def: GraphQLField<*, *> | GraphQLDirective,
+  def: GraphQLField<mixed, mixed> | GraphQLDirective,
   node: FieldNode | DirectiveNode,
   variableValues?: ?ObjMap<mixed>,
 ): { [argument: string]: mixed, ... } {

src/jsutils/defineToStringTag.js

@@ -13,7 +13,7 @@
  * typically one of your own creation through the class keyword; `class A {}`,
  * for example.
  */
-export default function defineToStringTag(classObject: Class<any>): void {
+export default function defineToStringTag(classObject: Class<mixed>): void {
   if (typeof Symbol === 'function' && Symbol.toStringTag) {
     Object.defineProperty(classObject.prototype, Symbol.toStringTag, {
       get() {

src/language/lexer.js

@@ -172,7 +172,7 @@ function printCharCode(code) {
  * punctuators immediately or calls the appropriate helper function for more
  * complicated tokens.
  */
-function readToken(lexer: Lexer<*>, prev: Token): Token {
+function readToken(lexer: Lexer<mixed>, prev: Token): Token {
   const source = lexer.source;
   const body = source.body;
   const bodyLength = body.length;
@@ -339,7 +339,7 @@ function unexpectedCharacterMessage(code) {
 function positionAfterWhitespace(
   body: string,
   startPosition: number,
-  lexer: Lexer<*>,
+  lexer: Lexer<mixed>,
 ): number {
   const bodyLength = body.length;
   let position = startPosition;

src/type/definition.js

@@ -727,7 +727,7 @@ defineToStringTag(GraphQLObjectType);
 defineToJSON(GraphQLObjectType);
 
 function defineInterfaces(
-  config: GraphQLObjectTypeConfig<*, *>,
+  config: GraphQLObjectTypeConfig<mixed, mixed>,
 ): Array<GraphQLInterfaceType> {
   const interfaces = resolveThunk(config.interfaces) || [];
   invariant(
@@ -1096,7 +1096,7 @@ defineToStringTag(GraphQLUnionType);
 defineToJSON(GraphQLUnionType);
 
 function defineTypes(
-  config: GraphQLUnionTypeConfig<*, *>,
+  config: GraphQLUnionTypeConfig<mixed, mixed>,
 ): Array<GraphQLObjectType> {
   const types = resolveThunk(config.types) || [];
   invariant(

src/utilities/TypeInfo.js

@@ -42,7 +42,7 @@ export class TypeInfo {
   _typeStack: Array<?GraphQLOutputType>;
   _parentTypeStack: Array<?GraphQLCompositeType>;
   _inputTypeStack: Array<?GraphQLInputType>;
-  _fieldDefStack: Array<?GraphQLField<*, *>>;
+  _fieldDefStack: Array<?GraphQLField<mixed, mixed>>;
   _defaultValueStack: Array<?mixed>;
   _directive: ?GraphQLDirective;
   _argument: ?GraphQLArgument;
@@ -106,7 +106,7 @@ export class TypeInfo {
     }
   }
 
-  getFieldDef(): ?GraphQLField<*, *> {
+  getFieldDef(): ?GraphQLField<mixed, mixed> {
     if (this._fieldDefStack.length > 0) {
       return this._fieldDefStack[this._fieldDefStack.length - 1];
     }
@@ -293,7 +293,7 @@ function getFieldDef(
   schema: GraphQLSchema,
   parentType: GraphQLType,
   fieldNode: FieldNode,
-): ?GraphQLField<*, *> {
+): ?GraphQLField<mixed, mixed> {
   const name = fieldNode.name.value;
   if (
     name === SchemaMetaFieldDef.name &&

src/utilities/findBreakingChanges.js

@@ -359,8 +359,8 @@ function findFieldChanges(
 
 function findArgChanges(
   oldType: GraphQLObjectType | GraphQLInterfaceType,
-  oldField: GraphQLField<*, *>,
-  newField: GraphQLField<*, *>,
+  oldField: GraphQLField<mixed, mixed>,
+  newField: GraphQLField<mixed, mixed>,
 ): Array<BreakingChange | DangerousChange> {
   const schemaChanges = [];
   const argsDiff = diff(oldField.args, newField.args);

src/validation/ValidationContext.js

@@ -227,7 +227,7 @@ export class ValidationContext extends ASTValidationContext {
     return this._typeInfo.getParentInputType();
   }
 
-  getFieldDef(): ?GraphQLField<*, *> {
+  getFieldDef(): ?GraphQLField<mixed, mixed> {
     return this._typeInfo.getFieldDef();
   }
 

src/validation/rules/OverlappingFieldsCanBeMerged.js

@@ -100,7 +100,11 @@ type ConflictReason = [string, ConflictReasonMessage];
 // Reason is a string, or a nested list of conflicts.
 type ConflictReasonMessage = string | Array<ConflictReason>;
 // Tuple defining a field node in a context.
-type NodeAndDef = [GraphQLCompositeType, FieldNode, ?GraphQLField<*, *>];
+type NodeAndDef = [
+  GraphQLCompositeType,
+  FieldNode,
+  ?GraphQLField<mixed, mixed>,
+];
 // Map of array of those.
 type NodeAndDefCollection = ObjMap<Array<NodeAndDef>>;