From 4fac6c5c40b1ff171db7ff6913534d307ac5a169 Mon Sep 17 00:00:00 2001
From: Retsam <Retsam@users.noreply.github.com>
Date: Thu, 14 Nov 2019 20:25:27 -0500
Subject: [PATCH] fix(eslint-plugin): [no-unnecessary-cond] fix naked type
 param (#1207)

---
 .../src/rules/no-unnecessary-condition.ts            | 12 ++++++++++--
 .../tests/rules/no-unnecessary-condition.test.ts     | 10 ++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts b/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
index 49c8f13401c..8e75f7adb3f 100644
--- a/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
+++ b/packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
@@ -110,8 +110,16 @@ export default createRule<Options, MessageId>({
     function checkNode(node: TSESTree.Node): void {
       const type = getNodeType(node);
 
-      // Conditional is always necessary if it involves `any` or `unknown`
-      if (isTypeFlagSet(type, TypeFlags.Any | TypeFlags.Unknown)) {
+      // Conditional is always necessary if it involves:
+      //    `any` or `unknown` or a naked type parameter
+      if (
+        unionTypeParts(type).some(part =>
+          isTypeFlagSet(
+            part,
+            TypeFlags.Any | TypeFlags.Unknown | ts.TypeFlags.TypeParameter,
+          ),
+        )
+      ) {
         return;
       }
       if (isTypeFlagSet(type, TypeFlags.Never)) {
diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
index f298495a26f..c5d90fd01ef 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
@@ -72,6 +72,16 @@ const t1 = (b1 && b2) ? 'yes' : 'no'`,
 function test<T extends string>(t: T) {
   return t ? 'yes' : 'no'
 }`,
+    `
+// Naked type param
+function test<T>(t: T) {
+  return t ? 'yes' : 'no'
+}`,
+    `
+// Naked type param in union
+function test<T>(t: T | []) {
+  return t ? 'yes' : 'no'
+}`,
 
     // Boolean expressions
     `