[clang-tidy] make several member functions const

Found with readability-make-member-function-const

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Author: neheb

src/scanner.h

@@ -141,8 +141,8 @@ class Scanner {
   struct SimpleKey {
     SimpleKey(const Mark &mark_, std::size_t flowLevel_);
 
-    void Validate();
-    void Invalidate();
+    void Validate() const;
+    void Invalidate() const;
 
     Mark mark;
     std::size_t flowLevel;

src/simplekey.cpp

@@ -11,7 +11,7 @@ Scanner::SimpleKey::SimpleKey(const Mark& mark_, std::size_t flowLevel_)
       pMapStart(nullptr),
       pKey(nullptr) {}
 
-void Scanner::SimpleKey::Validate() {
+void Scanner::SimpleKey::Validate() const {
   // Note: pIndent will *not* be garbage here;
   //       we "garbage collect" them so we can
   //       always refer to them
@@ -23,7 +23,7 @@ void Scanner::SimpleKey::Validate() {
     pKey->status = Token::VALID;
 }
 
-void Scanner::SimpleKey::Invalidate() {
+void Scanner::SimpleKey::Invalidate() const {
   if (pIndent)
     pIndent->status = IndentMarker::INVALID;
   if (pMapStart)

src/tag.cpp

@@ -29,7 +29,7 @@ Tag::Tag(const Token& token)
   }
 }
 
-std::string Tag::Translate(const Directives& directives) {
+std::string Tag::Translate(const Directives& directives) const {
   switch (type) {
     case VERBATIM:
       return value;

src/tag.h

@@ -23,7 +23,7 @@ struct Tag {
   };
 
   Tag(const Token& token);
-  std::string Translate(const Directives& directives);
+  std::string Translate(const Directives& directives) const;
 
   TYPE type;
   std::string handle, value;