Print parens for nullable union/intersection types (benjamn#293)

* print parens for nullable union/intersection types * switched to use FastPath#needsParens instead
fkling · Jul 7, 2016 · dc79e98 · dc79e98
1 parent 1c9725d
commit dc79e98
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Showing 2 changed files with 24 additions and 2 deletions.
diff --git a/lib/fast-path.js b/lib/fast-path.js
@@ -192,8 +192,8 @@ FPp.needsParens = function(assumeExpressionContext) {
         return false;
     }
 
-    // Only expressions need parentheses.
-    if (!n.Expression.check(node)) {
+    // Only statements don't need parentheses.
+    if (n.Statement.check(node)) {
         return false;
     }
 
@@ -289,6 +289,10 @@ FPp.needsParens = function(assumeExpressionContext) {
             return false;
         }
 
+    case "IntersectionTypeAnnotation":
+    case "UnionTypeAnnotation":
+        return parent.type === "NullableTypeAnnotation";
+
     case "Literal":
         return parent.type === "MemberExpression"
             && isNumber.check(node.value)

diff --git a/test/printer.js b/test/printer.js
@@ -1454,4 +1454,22 @@ describe("printer", function() {
         var pretty = printer.printGenerically(ast).code;
         assert.strictEqual(pretty, code);
     });
+
+    it("prints parens for nullable union/intersection types", function() {
+        var code = "type MyType = ?(string | number);";
+
+        var ast = b.typeAlias(
+            b.identifier("MyType"),
+            null,
+            b.nullableTypeAnnotation(
+                b.unionTypeAnnotation(
+                    [b.stringTypeAnnotation(), b.numberTypeAnnotation()]
+                )
+            )
+        );
+
+        var printer = new Printer({});
+        var pretty = printer.printGenerically(ast).code;
+        assert.strictEqual(pretty, code);
+    });
 });