Fix #14477 internalAstError with fold expression in template (#8203)

Co-authored-by: Daniel Marjamäki <daniel.marjamaki@gmail.com>

Author: chrchr-github

lib/templatesimplifier.cpp

@@ -2104,8 +2104,6 @@ void TemplateSimplifier::expandTemplate(
                     Token * const beforeTypeToken = mTokenList.back();
                     bool pointerType = false;
                     const bool isVariadicTemplateArg = templateDeclaration.isVariadic() && itype + 1 == typeParametersInDeclaration.size();
-                    if (isVariadicTemplateArg && mTypesUsedInTemplateInstantiation.size() > 1 && !Token::Match(tok3->next(), "...|<"))
-                        continue;
                     if (isVariadicTemplateArg && Token::Match(tok3, "%name% ... %name%"))
                         tok3 = tok3->tokAt(2);
                     if (!isVariadicTemplateArg && copy && Token::Match(mTypesUsedInTemplateInstantiation[itype].token(), "%num% ,|>|>>") &&
@@ -2130,6 +2128,7 @@ void TemplateSimplifier::expandTemplate(
                         }
                     }
                     const std::string endStr(isVariadicTemplateArg ? ">" : ",>");
+                    Token* begPar = nullptr;
                     for (Token *typetok = mTypesUsedInTemplateInstantiation[itype].token();
                          typetok && (typeindentlevel > 0 || endStr.find(typetok->str()[0]) == std::string::npos);
                          typetok = typetok->next()) {
@@ -2153,6 +2152,10 @@ void TemplateSimplifier::expandTemplate(
                             --typeindentlevel;
                         Token *back;
                         if (copy) {
+                            if (isVariadicTemplateArg && typetok == mTypesUsedInTemplateInstantiation[itype].token() && typetok->isLiteral()) {
+                                mTokenList.addtoken("(", mTokenList.back());
+                                begPar = mTokenList.back();
+                            }
                             mTokenList.addtoken(typetok, tok3);
                             back = mTokenList.back();
                         } else
@@ -2181,6 +2184,10 @@ void TemplateSimplifier::expandTemplate(
                         if (copy)
                             back->templateArgFrom(typetok);
                     }
+                    if (begPar) {
+                        mTokenList.addtoken(")", mTokenList.back());
+                        Token::createMutualLinks(begPar, mTokenList.back());
+                    }
                     if (pointerType && Token::simpleMatch(beforeTypeToken, "const")) {
                         mTokenList.addtoken(beforeTypeToken);
                         beforeTypeToken->deleteThis();

test/testsimplifytemplate.cpp

@@ -6372,7 +6372,7 @@ class TestSimplifyTemplate : public TestFixture {
                                 "class E<1,3> { "
                                 "template < int ... I > "
                                 "int f ( int n , std :: integer_sequence < int , I ... > ) { "
-                                "return ( ( ( I == n ) ? : 0 ) + ... ) ; "
+                                "return ( ( ( I == n ) ? ( 1 , 3 ) : 0 ) + ... ) ; "  // TODO the simplification is not quite correct
                                 "} "
                                 "} ;";
         ASSERT_EQUALS(expected, tok(code));
@@ -6390,6 +6390,18 @@ class TestSimplifyTemplate : public TestFixture {
                                  "A<int,S> a ; "
                                  "struct A<int,S> { } ;";
         ASSERT_EQUALS(expected2, tok(code2));
+
+        const char code3[] = "template <int... N>\n" // #14477
+                             "    int f() {\n"
+                             "    return (0 | ... | (1, 2, 4));\n"
+                             "}\n"
+                             "int main() {\n"
+                             "    return f<1, 2, 4>();\n"
+                             "}\n";
+        const char expected3[] = "int f<1,2,4> ( ) ; "
+                                 "int main ( ) { return f<1,2,4> ( ) ; } "
+                                 "int f<1,2,4> ( ) { return ( 0 | ... | ( 1 , 2 , 4 ) ) ; }";
+        ASSERT_EQUALS(expected3, tok(code3));
     }
 
     void template_variable_1() {