Update index-signatures.md

basarat · web-flow · commit e0b67badfaf5 · 2018-05-07T14:40:01.000+10:00
diff --git a/docs/types/index-signatures.md b/docs/types/index-signatures.md
@@ -280,5 +280,5 @@ type FieldState = {
 
 type FormState =
   { isValid: boolean }
-  & { [fieldName: number]: FieldState } 
+  & { [fieldName: string]: FieldState } 
 ```
