typeFromAST: use exhaustive switch and remove invariant (graphql#3396)

Author: IvanGoncharov

src/utilities/typeFromAST.ts

@@ -1,6 +1,3 @@
-import { inspect } from '../jsutils/inspect';
-import { invariant } from '../jsutils/invariant';
-
 import type {
   TypeNode,
   NamedTypeNode,
@@ -41,20 +38,16 @@ export function typeFromAST(
   schema: GraphQLSchema,
   typeNode: TypeNode,
 ): GraphQLType | undefined {
-  let innerType;
-  if (typeNode.kind === Kind.LIST_TYPE) {
-    innerType = typeFromAST(schema, typeNode.type);
-    return innerType && new GraphQLList(innerType);
-  }
-  if (typeNode.kind === Kind.NON_NULL_TYPE) {
-    innerType = typeFromAST(schema, typeNode.type);
-    return innerType && new GraphQLNonNull(innerType);
+  switch (typeNode.kind) {
+    case Kind.LIST_TYPE: {
+      const innerType = typeFromAST(schema, typeNode.type);
+      return innerType && new GraphQLList(innerType);
+    }
+    case Kind.NON_NULL_TYPE: {
+      const innerType = typeFromAST(schema, typeNode.type);
+      return innerType && new GraphQLNonNull(innerType);
+    }
+    case Kind.NAMED_TYPE:
+      return schema.getType(typeNode.name.value);
   }
-  // istanbul ignore else (See: 'https://github.com/graphql/graphql-js/issues/2618')
-  if (typeNode.kind === Kind.NAMED_TYPE) {
-    return schema.getType(typeNode.name.value);
-  }
-
-  // istanbul ignore next (Not reachable. All possible type nodes have been considered)
-  invariant(false, 'Unexpected type node: ' + inspect(typeNode));
 }