diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index 64c5a74a3c6..e28993f76e7 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -2579,8 +2579,8 @@ bool isVariableChanged(const Token *tok, int indirect, const Settings *settings,
         if (indirect == 0 && astIsPointer(tok))
             return false;
 
-        const Token *ftok = tok->tokAt(2);
-        if (astIsContainer(tok) && vt && vt->container) {
+        const Token *ftok = tok2->astParent()->astOperand2();
+        if (astIsContainer(tok2->astParent()->astOperand1()) && vt && vt->container) {
             const Library::Container* c = vt->container;
             const Library::Container::Action action = c->getAction(ftok->str());
             if (contains({Library::Container::Action::INSERT,
diff --git a/lib/checkclass.cpp b/lib/checkclass.cpp
index b69010bd9b4..676d69733b4 100644
--- a/lib/checkclass.cpp
+++ b/lib/checkclass.cpp
@@ -659,12 +659,11 @@ std::vector<CheckClass::Usage> CheckClass::createUsageList(const Scope *scope)
 
 void CheckClass::assignVar(std::vector<Usage> &usageList, nonneg int varid)
 {
-    for (Usage& usage: usageList) {
-        if (usage.var->declarationId() == varid) {
-            usage.assign = true;
-            return;
-        }
-    }
+    auto it = std::find_if(usageList.begin(), usageList.end(), [varid](const Usage& usage) {
+        return usage.var->declarationId() == varid;
+    });
+    if (it != usageList.end())
+        it->assign = true;
 }
 
 void CheckClass::assignVar(std::vector<Usage> &usageList, const Token* vartok)
@@ -673,23 +672,21 @@ void CheckClass::assignVar(std::vector<Usage> &usageList, const Token* vartok)
         assignVar(usageList, vartok->varId());
         return;
     }
-    for (Usage& usage: usageList) {
+    auto it = std::find_if(usageList.begin(), usageList.end(), [vartok](const Usage& usage) {
         // FIXME: This is a workaround when varid is not set for a derived member
-        if (usage.var->name() == vartok->str()) {
-            usage.assign = true;
-            return;
-        }
-    }
+        return usage.var->name() == vartok->str();
+    });
+    if (it != usageList.end())
+        it->assign = true;
 }
 
 void CheckClass::initVar(std::vector<Usage> &usageList, nonneg int varid)
 {
-    for (Usage& usage: usageList) {
-        if (usage.var->declarationId() == varid) {
-            usage.init = true;
-            return;
-        }
-    }
+    auto it = std::find_if(usageList.begin(), usageList.end(), [varid](const Usage& usage) {
+        return usage.var->declarationId() == varid;
+    });
+    if (it != usageList.end())
+        it->init = true;
 }
 
 void CheckClass::assignAllVar(std::vector<Usage> &usageList)
diff --git a/test/testother.cpp b/test/testother.cpp
index d3bb8e4d91b..0615492fbdb 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -2191,6 +2191,25 @@ class TestOther : public TestFixture {
               "}\n");
         ASSERT_EQUALS("", errout.str());
 
+        check("struct S { std::list<int> l; };\n" // #12147
+              "class C { public: std::list<int> l; };\n"
+              "bool f(S s) {\n"
+              "    return s.l.empty();\n"
+              "}\n"
+              "bool f(C c) {\n"
+              "    return c.l.empty();\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:3]: (performance) Function parameter 's' should be passed by const reference.\n"
+                      "[test.cpp:6]: (performance) Function parameter 'c' should be passed by const reference.\n",
+                      errout.str());
+
+        check("struct S { std::list<int> a[1][1]; };\n"
+              "bool f(S s) {\n"
+              "    return s.a[0][0].empty();\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:2]: (performance) Function parameter 's' should be passed by const reference.\n",
+                      errout.str());
+
         Settings settings1 = settingsBuilder().platform(Platform::Type::Win64).build();
         check("using ui64 = unsigned __int64;\n"
               "ui64 Test(ui64 one, ui64 two) { return one + two; }\n",