Fix 13760: false negative: danglingTemporaryLifetime with temporary lambda (danmar#7460)

Author: pfultz2

lib/astutils.cpp

@@ -440,6 +440,8 @@ bool isTemporary(const Token* tok, const Library* library, bool unknown)
         return isTemporary(tok->astOperand2(), library);
     if (tok->isCast() || (tok->isCpp() && isCPPCast(tok)))
         return isTemporary(tok->astOperand2(), library);
+    if (findLambdaEndToken(tok) != nullptr)
+        return true;
     if (Token::Match(tok, ".|[|++|--|%name%|%assign%"))
         return false;
     if (tok->isUnaryOp("*"))

test/testautovariables.cpp

@@ -4209,6 +4209,21 @@ class TestAutoVariables : public TestFixture {
               "	if (!p) {}\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        // #13760
+        check("template<class T>\n"
+              "auto f(T&& x) {\n"
+              "    return [&] {\n"
+              "        return x();\n"
+              "    };\n"
+              "}\n"
+              "auto g() {\n"
+              "    auto y = f([](auto x) { return 1; });\n"
+              "    return y();\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:3:12] -> [test.cpp:2:13] -> [test.cpp:4:16] -> [test.cpp:8:16] -> [test.cpp:8:16] -> [test.cpp:9:12]: (error) Using object that is a temporary. [danglingTemporaryLifetime]\n",
+            errout_str());
     }
 
     void danglingLifetimeBorrowedMembers()