From f5d71ae5da91c34152efe2fa0d6a5917de849961 Mon Sep 17 00:00:00 2001
From: cxtom <chxtom2015@163.com>
Date: Tue, 4 Jun 2019 19:46:51 +0800
Subject: [PATCH] feat: support x === undefined & x !== undefined

---
 src/features/global.ts    | 23 ++++++++++++++++++++++-
 src/utilities/nodeTest.ts |  2 +-
 test/features/isset.php   |  9 +++++++++
 test/features/isset.ts    |  9 +++++++++
 typescript.d.ts           |  1 +
 5 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 test/features/isset.php
 create mode 100644 test/features/isset.ts

diff --git a/src/features/global.ts b/src/features/global.ts
index 3c1ebd6..a94c4e4 100644
--- a/src/features/global.ts
+++ b/src/features/global.ts
@@ -7,7 +7,11 @@ import {
     EmitHint,
     isCallExpression,
     isPropertyAccessExpression,
-    isIdentifier
+    isIdentifier,
+    isBinaryExpression,
+    SyntaxKind,
+    createCall,
+    createIdentifier
 } from 'typescript';
 
 import method from '../utilities/method';
@@ -59,6 +63,23 @@ export default {
             }
         }
 
+        if (
+            isBinaryExpression(node)
+            && node.operatorToken.kind === SyntaxKind.EqualsEqualsEqualsToken
+            && node.right.originalKeywordKind === SyntaxKind.UndefinedKeyword
+        ) {
+            helpers.writePunctuation('!');
+            return helpers.emitExpression(createCall(createIdentifier('isset'), [], [node.left]));
+        }
+
+        if (
+            isBinaryExpression(node)
+            && node.operatorToken.kind === SyntaxKind.ExclamationEqualsEqualsToken
+            && node.right.originalKeywordKind === SyntaxKind.UndefinedKeyword
+        ) {
+            return helpers.emitExpression(createCall(createIdentifier('isset'), [], [node.left]));
+        }
+
         return false;
     }
 };
diff --git a/src/utilities/nodeTest.ts b/src/utilities/nodeTest.ts
index c5865c4..863b8c7 100644
--- a/src/utilities/nodeTest.ts
+++ b/src/utilities/nodeTest.ts
@@ -184,4 +184,4 @@ export function isVisibilityModifier(node: ts.Modifier) {
 
 export function isSupportedPropertyModifier(node: ts.Modifier) {
     return isVisibilityModifier(node) || node.kind === SyntaxKind.StaticKeyword;
-}
+}
\ No newline at end of file
diff --git a/test/features/isset.php b/test/features/isset.php
new file mode 100644
index 0000000..f8f4b67
--- /dev/null
+++ b/test/features/isset.php
@@ -0,0 +1,9 @@
+<?php
+namespace test\case_isset;
+$a = 1;
+if (!isset($a)) {
+    echo "a";
+}
+if (isset($a)) {
+    echo "a";
+}
diff --git a/test/features/isset.ts b/test/features/isset.ts
new file mode 100644
index 0000000..11bb773
--- /dev/null
+++ b/test/features/isset.ts
@@ -0,0 +1,9 @@
+const a = 1;
+
+if (a === undefined) {
+    console.log('a');
+}
+
+if (a !== undefined) {
+    console.log('a');
+}
diff --git a/typescript.d.ts b/typescript.d.ts
index 7e99c99..2204537 100644
--- a/typescript.d.ts
+++ b/typescript.d.ts
@@ -1148,6 +1148,7 @@ declare namespace ts {
     type StringLiteralLike = StringLiteral | NoSubstitutionTemplateLiteral;
     interface Expression extends Node {
         _expressionBrand: any;
+        originalKeywordKind?: SyntaxKind
     }
     interface OmittedExpression extends Expression {
         kind: SyntaxKind.OmittedExpression;