fix #13770: Variadic lambda parameters treated as a fold expression (cppcheck-opensource#7607)

Author: ludviggunne

lib/templatesimplifier.cpp

@@ -4061,7 +4061,7 @@ void TemplateSimplifier::simplifyTemplates(const std::time_t maxtime)
             if (Token::Match(tok, "( ... %op%")) {
                 op = tok->tokAt(2);
                 args = tok->link()->previous();
-            } else if (Token::Match(tok, "( %name% %op% ...")) {
+            } else if (Token::Match(tok, "( %name% %op% ...") && !Token::simpleMatch(tok->previous(), "] (")) {
                 op = tok->tokAt(2);
                 args = tok->link()->previous()->isName() ? nullptr : tok->next();
             } else if (Token::Match(tok->link()->tokAt(-3), "%op% ... )")) {

test/testsimplifytemplate.cpp

@@ -220,6 +220,7 @@ class TestSimplifyTemplate : public TestFixture {
         TEST_CASE(template179);
         TEST_CASE(template180);
         TEST_CASE(template181);
+        TEST_CASE(template182); // #13770
         TEST_CASE(template_specialization_1);  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         TEST_CASE(template_specialization_2);  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         TEST_CASE(template_specialization_3);
@@ -4636,6 +4637,15 @@ class TestSimplifyTemplate : public TestFixture {
         ASSERT_EQUALS(exp2, tok(code2));
     }
 
+    void template182() {
+        const char code[] = "template <class...>\n"
+                            "auto f() {\n"
+                            "    return [](auto&&...) {};\n"
+                            "}\n";
+        const char exp[] = "template < class ... > auto f ( ) { return [ ] ( auto && ... ) { } ; }";
+        ASSERT_EQUALS(exp, tok(code));
+    }
+
     void template_specialization_1() {  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         const char code[] = "template <typename T> struct C {};\n"
                             "template <typename T> struct S {a};\n"