Fix #12757 FP knownEmptyContainer with template specialization (regression) (#6434)

Author: chrchr-github

lib/valueflow.cpp

@@ -2205,6 +2205,8 @@ static Analyzer::Result valueFlowForward(Token* startToken,
     const Function* f = Scope::nestedInFunction(startToken->scope());
     if (f && f->functionScope)
         endToken = f->functionScope->bodyEnd;
+    if (!endToken && exprTok && exprTok->variable() && !exprTok->variable()->isLocal())
+        endToken = startToken->scope()->bodyEnd;
     return valueFlowForward(startToken, endToken, exprTok, std::move(v), tokenlist, errorLogger, settings, loc);
 }
 

test/teststl.cpp

@@ -6738,6 +6738,21 @@ class TestStl : public TestFixture {
               "}\n",
               true);
         ASSERT_EQUALS("", errout_str());
+
+        check("struct S {\n" // #12757
+              "    template<class T = int>\n"
+              "    void clear() {}\n"
+              "    template<class T = int>\n"
+              "    std::vector<T> get() const { return {}; }\n"
+              "    std::vector<int> m;\n"
+              "};\n"
+              "template<> void S::clear() { m.clear(); }\n"
+              "template<> std::vector<int> S::get() const {\n"
+              "    for (const auto& i : m) {}\n"
+              "    return {};\n"
+              "}\n",
+              true);
+        ASSERT_EQUALS("", errout_str());
     }
 
     void checkMutexes() {