run tests on node 15

fix test case

azure-pipelines.yml

@@ -8,7 +8,7 @@ jobs:
     steps:
       - task: NodeTool@0
         inputs:
-          versionSpec: "^12.4.0"
+          versionSpec: "^14.0.0"
         displayName: "Install Node.js"
       - script: |
           curl -o- -L https://yarnpkg.com/install.sh | bash
@@ -58,7 +58,7 @@ jobs:
     steps:
       - task: NodeTool@0
         inputs:
-          versionSpec: "^12.4.0"
+          versionSpec: "^14.0.0"
         displayName: "Install Node.js"
       - script: |
           curl -o- -L https://yarnpkg.com/install.sh | bash
@@ -153,7 +153,7 @@ jobs:
     pool:
       vmImage: ubuntu-latest
     strategy:
-      maxParallel: 3
+      maxParallel: 4
       matrix:
         node-10:
           node_version: ^10.13.0
@@ -161,6 +161,8 @@ jobs:
           node_version: ^12.4.0
         node-14:
           node_version: ^14.0.0
+        node-15:
+          node_version: ^15.0.0
     steps:
       - task: NodeTool@0
         inputs:

test/cases/parsing/logical-assignment/module.js

@@ -1,6 +1,7 @@
-export default function() {
+export default function () {
 	var x = null;
 	x ??= true;
 	x &&= true;
 	x ||= false;
+	return x;
 }