Simplify template keyword bracket (#3399)

lib/token.h

@@ -641,6 +641,13 @@ public:
         setFlag(fIsInline, b);
     }
 
+    bool isTemplate() const {
+        return getFlag(fIsTemplate);
+    }
+    void isTemplate(bool b) {
+        setFlag(fIsTemplate, b);
+    }
+
     bool isBitfield() const {
         return mImpl->mBits > 0;
     }
@@ -1239,7 +1246,8 @@ private:
         fIsSplitVarDeclComma    = (1 << 29), // set to true when variable declarations are split up ('int a,b;' => 'int a; int b;')
         fIsSplitVarDeclEq       = (1 << 30), // set to true when variable declaration with initialization is split up ('int a=5;' => 'int a; a=5;')
         fIsImplicitInt          = (1U << 31),   // Is "int" token implicitly added?
-        fIsInline               = (1ULL << 32)  // Is this a inline type
+        fIsInline               = (1ULL << 32), // Is this a inline type
+        fIsTemplate             = (1ULL << 33)
     };
 
     Token::Type mTokType;

lib/tokenize.cpp

@@ -4509,7 +4509,8 @@ void Tokenizer::createLinks2()
                 type.pop();
             }
         } else if (token->str() == "<" &&
-                   ((token->previous() && token->previous()->isName() && !token->previous()->varId()) ||
+                   ((token->previous() && (token->previous()->isTemplate() ||
+                                           (token->previous()->isName() && !token->previous()->varId()))) ||
                     Token::Match(token->next(), ">|>>"))) {
             type.push(token);
             if (!templateToken && (token->previous()->str() == "template"))
@@ -5634,8 +5635,19 @@ void Tokenizer::removeExtraTemplateKeywords()
 {
     if (isCPP()) {
         for (Token *tok = list.front(); tok; tok = tok->next()) {
-            if (Token::Match(tok, "%name%|> .|:: template %name%"))
+            if (Token::Match(tok, "%name%|>|) .|:: template %name%")) {
                 tok->next()->deleteNext();
+                Token* templateName = tok->tokAt(2);
+                while (Token::Match(templateName, "%name%|::")) {
+                    templateName->isTemplate(true);
+                    templateName = templateName->next();
+                }
+                if (Token::Match(templateName->previous(), "operator %op%|(")) {
+                    templateName->isTemplate(true);
+                    if (templateName->str() == "(" && templateName->link())
+                        templateName->link()->isTemplate(true);
+                }
+            }
         }
     }
 }

test/testtokenize.cpp

@@ -6632,6 +6632,12 @@ private:
                                              "  for (size_t e = 0; e < d; e++)\n"
                                              "    ;\n"
                                              "}\n"));
+
+        ASSERT_NO_THROW(tokenizeAndStringify(
+                            "template <std::size_t First, std::size_t... Indices, typename Functor>\n"
+                            "constexpr void constexpr_for_fold_impl([[maybe_unused]] Functor&& f, std::index_sequence<Indices...>) noexcept {\n"
+                            "    (std::forward<Functor>(f).template operator() < First + Indices > (), ...);\n"
+                            "}\n"));
     }
 
     void checkNamespaces() {