fix: fix double map

Merged in check (pull request #2)

Approved-by: Ian He <ian-he@outlook.com>

packages/types/src/Metadata/v0/Modules.ts

@@ -151,7 +151,7 @@ export class DoubleMapType extends Struct {
   get key1 (): Text {
     return this.get('key1') as Text;
   }
-  
+
   /**
    * @description The mapped key as [[Text]]
    */
@@ -213,14 +213,22 @@ export class MapType extends Struct {
 class PlainType extends Type {
 }
 
-export class StorageFunctionType extends EnumType<PlainType | MapType> {
+export class StorageFunctionType extends EnumType<PlainType | MapType | DoubleMapType> {
   constructor (value?: any, index?: number) {
     super({
       PlainType,
-      MapType
+      MapType,
+      DoubleMapType
     }, value, index);
   }
 
+  /**
+   * @description `true` if the storage entry is a doublemap
+   */
+  get isDoubleMap (): boolean {
+    return this.toNumber() === 2;
+  }
+
   /**
    * @description `true` if the storage entry is a map
    */
@@ -228,6 +236,13 @@ export class StorageFunctionType extends EnumType<PlainType | MapType> {
     return this.toNumber() === 1;
   }
 
+  /**
+   * @description The value as a mapped value
+   */
+  get asDoubleMap (): DoubleMapType {
+    return this.value as DoubleMapType;
+  }
+
   /**
    * @description The value as a mapped value
    */
@@ -246,6 +261,10 @@ export class StorageFunctionType extends EnumType<PlainType | MapType> {
    * @description Returns the string representation of the value
    */
   toString (): string {
+    if (this.isDoubleMap) {
+      return this.asDoubleMap.value.toString();
+    }
+
     if (this.isMap) {
       if (this.asMap.isLinked) {
         return `(${this.asMap.value.toString()}, Linkage<${this.asMap.key.toString()}>)`;