Fix #12940 Lambda type const wrongly suggested (#6605)

Author: chrchr-github

lib/symboldatabase.cpp

@@ -3066,7 +3066,7 @@ static bool checkReturns(const Function* function, bool unknown, bool emptyEnabl
 {
     if (!function)
         return false;
-    if (function->type != Function::eFunction && function->type != Function::eOperatorEqual)
+    if (function->type != Function::eFunction && function->type != Function::eOperatorEqual && function->type != Function::eLambda)
         return false;
     const Token* defStart = function->retDef;
     if (!defStart)

test/testother.cpp

@@ -3636,6 +3636,16 @@ class TestOther : public TestFixture {
               "    g(r[0] * 2);\n"
               "}\n");
         ASSERT_EQUALS("[test.cpp:6]: (style) Variable 'r' can be declared as reference to const\n", errout_str());
+
+        check("std::iostream& get();\n" // #12940
+              "std::iostream& Fun() {\n"
+              "    auto lam = []() -> std::iostream& {\n"
+              "        std::iostream& ios = get();\n"
+              "        return ios;\n"
+              "    };\n"
+              "    return lam();\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void constParameterCallback() {