prefer-default-export: don't warn on TypeAlias & TSTypeAliasDeclaration

Fixes #1332.

src/rules/prefer-default-export.js

@@ -47,9 +47,16 @@ module.exports = {
         // if there are specifiers, node.declaration should be null
         if (!node.declaration) return
 
-        // don't count flow types exports
+        // don't warn on single type aliases or declarations
         if (node.exportKind === 'type') return
 
+        if (
+          node.declaration.type === 'TSTypeAliasDeclaration' ||
+          node.declaration.type === 'TypeAlias'
+        ) {
+          return
+        }
+
         if (node.declaration.declarations) {
           node.declaration.declarations.forEach(function(declaration) {
             captureDeclaration(declaration.id)

tests/src/rules/prefer-default-export.js

@@ -84,6 +84,27 @@ ruleTester.run('prefer-default-export', rule, {
       parser: 'babel-eslint',
     }),
 
+    // Exporting types
+    test({
+      code: `
+        export type foo = string;
+        export type bar = number;`,
+      parser: 'typescript-eslint-parser',
+    }),
+    test({
+      code: `
+        export type foo = string;
+        export type bar = number;`,
+      parser: 'babel-eslint',
+    }),
+    test({
+      code: 'export type foo = string',
+      parser: 'typescript-eslint-parser',
+    }),
+    test({
+      code: 'export type foo = string',
+      parser: 'babel-eslint',
+    }),
     // ...SYNTAX_CASES,
   ],
   invalid: [