Fix #11420 FN returnDanglingLifetime with auto (regression) (danmar#7228)

Author: chrchr-github

lib/valueflow.cpp

@@ -1792,11 +1792,12 @@ static bool isDifferentType(const Token* src, const Token* dst)
     } else {
         std::pair<const Token*, const Token*> decl = Token::typeDecl(src);
         std::pair<const Token*, const Token*> parentdecl = Token::typeDecl(dst);
-        if (isNotEqual(decl, parentdecl))
+        const bool isCpp = (src && src->isCpp()) || (dst && dst->isCpp());
+        if (isNotEqual(decl, parentdecl) && !(isCpp && (Token::simpleMatch(decl.first, "auto") || Token::simpleMatch(parentdecl.first, "auto"))))
             return true;
-        if (isNotEqual(decl, dst->valueType(), dst->isCpp()))
+        if (isNotEqual(decl, dst->valueType(), isCpp))
             return true;
-        if (isNotEqual(parentdecl, src->valueType(), src->isCpp()))
+        if (isNotEqual(parentdecl, src->valueType(), isCpp))
             return true;
     }
     return false;

test/testautovariables.cpp

@@ -2864,6 +2864,13 @@ class TestAutoVariables : public TestFixture {
               "    std::cerr << str;\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("auto f() {\n" // #11420
+              "    std::vector<int> x;\n"
+              "    std::vector<int>::iterator it = x.begin();\n"
+              "    return it;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:3] -> [test.cpp:2] -> [test.cpp:4]: (error) Returning iterator to local container 'x' that will be invalid when returning.\n", errout_str());
     }
 
     void danglingLifetimeContainerView()
@@ -3083,6 +3090,14 @@ class TestAutoVariables : public TestFixture {
         ASSERT_EQUALS(
             "[test.cpp:3] -> [test.cpp:2] -> [test.cpp:3]: (error) Returning pointer to local variable 'a' that will be invalid when returning.\n",
             errout_str());
+
+        check("std::string_view f() {\n" // #10995
+              "    char a[10]{};\n"
+              "    return a;\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:3] -> [test.cpp:2] -> [test.cpp:3]: (error) Returning pointer to local variable 'a' that will be invalid when returning.\n",
+            errout_str());
     }
 
     void danglingLifetimeUniquePtr()