Skip references to functions in checkConstVariable

A reference to a function returning a reference was no longer skipped
because isRValueReference() is now false for it. A function reference
can't be const-qualified, so it is never reported.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: autoantwort

lib/checkother.cpp

@@ -1768,6 +1768,8 @@ void CheckOtherImpl::checkConstVariable()
             continue;
         if (var->isConst())
             continue;
+        if (Token::Match(var->nameToken(), "%name% ) (")) // reference to function
+            continue;
         const Scope* scope = var->scope();
         if (!scope)
             continue;

test/testother.cpp

@@ -4213,6 +4213,17 @@ class TestOther : public TestFixture {
               "    }\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("int& g();\n" // reference to function
+              "int k();\n"
+              "int f1() { int& (&r)() = g; return r(); }\n"
+              "int f2() { int (&r)() = k; return r(); }\n"
+              "int& f3(int& (&f)()) { return f(); }\n"
+              "int f4(int&& (&f)()) { return f(); }\n"
+              "int f5(int (&f)()) { return f(); }\n"
+              "using FR = int&(&)();\n"
+              "void f6(FR f) { f(); }\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void constParameterCallback() {

test/testsymboldatabase.cpp

@@ -1653,6 +1653,18 @@ class TestSymbolDatabase : public TestFixture {
             ASSERT(p->valueType());
             ASSERT(p->valueType()->reference == Reference::LValue);
         }
+        { // reference to function returning a reference
+            GET_SYMBOL_DB("void foo(int& (&f)()) {}\n");
+            const Variable* const p = db->getVariableFromVarId(1);
+            ASSERT(p->isReference());
+            ASSERT(!p->isRValueReference());
+        }
+        {
+            GET_SYMBOL_DB("void foo(int&& (&f)()) {}\n");
+            const Variable* const p = db->getVariableFromVarId(1);
+            ASSERT(p->isReference());
+            ASSERT(!p->isRValueReference());
+        }
     }
 
     void VariableValueTypeTemplate() {
@@ -2461,6 +2473,11 @@ class TestSymbolDatabase : public TestFixture {
             ASSERT(db && ctor && ctor->type == FunctionType::eMoveConstructor);
             ASSERT(ctor && ctor->retDef == nullptr);
         }
+        {
+            GET_SYMBOL_DB("class Foo { Foo(Foo&& (*f)()); };\n");
+            const Function* ctor = tokenizer.tokens()->tokAt(3)->function();
+            ASSERT(db && ctor && ctor->type == FunctionType::eConstructor);
+        }
         {
             GET_SYMBOL_DB("void f() { extern void f(); }\n");
             ASSERT(db && db->scopeList.size() == 2);