Add support for the TAU constant. Fixes #12094.

modules/gdscript/gd_editor.cpp

@@ -337,6 +337,11 @@ void GDScriptLanguage::get_public_constants(List<Pair<String, Variant> > *p_cons
 	pi.second = Math_PI;
 	p_constants->push_back(pi);
 
+	Pair<String, Variant> tau;
+	tau.first = "TAU";
+	tau.second = Math_TAU;
+	p_constants->push_back(tau);
+
 	Pair<String, Variant> infinity;
 	infinity.first = "INF";
 	infinity.second = Math_INF;

modules/gdscript/gd_parser.cpp

@@ -362,6 +362,13 @@ GDParser::Node *GDParser::_parse_expression(Node *p_parent, bool p_static, bool
 			constant->value = Math_PI;
 			tokenizer->advance();
 			expr = constant;
+		} else if (tokenizer->get_token() == GDTokenizer::TK_CONST_TAU) {
+
+			//constant defined by tokenizer
+			ConstantNode *constant = alloc_node<ConstantNode>();
+			constant->value = Math_TAU;
+			tokenizer->advance();
+			expr = constant;
 		} else if (tokenizer->get_token() == GDTokenizer::TK_CONST_INF) {
 
 			//constant defined by tokenizer

modules/gdscript/gd_script.cpp

@@ -1324,6 +1324,7 @@ void GDScriptLanguage::init() {
 	}
 
 	_add_global(StaticCString::create("PI"), Math_PI);
+	_add_global(StaticCString::create("TAU"), Math_TAU);
 	_add_global(StaticCString::create("INF"), Math_INF);
 	_add_global(StaticCString::create("NAN"), Math_NAN);
 
@@ -1700,6 +1701,7 @@ void GDScriptLanguage::get_reserved_words(List<String> *p_words) const {
 		"bool",
 		"null",
 		"PI",
+		"TAU",
 		"INF",
 		"NAN",
 		"self",

modules/gdscript/gd_tokenizer.cpp

@@ -123,6 +123,7 @@ const char *GDTokenizer::token_names[TK_MAX] = {
 	"'$'",
 	"'\\n'",
 	"PI",
+	"TAU",
 	"_",
 	"INF",
 	"NAN",
@@ -217,6 +218,7 @@ static const _kws _keyword_list[] = {
 	{ GDTokenizer::TK_CF_PASS, "pass" },
 	{ GDTokenizer::TK_SELF, "self" },
 	{ GDTokenizer::TK_CONST_PI, "PI" },
+	{ GDTokenizer::TK_CONST_TAU, "TAU" },
 	{ GDTokenizer::TK_WILDCARD, "_" },
 	{ GDTokenizer::TK_CONST_INF, "INF" },
 	{ GDTokenizer::TK_CONST_NAN, "NAN" },
@@ -280,6 +282,7 @@ bool GDTokenizer::is_token_literal(int p_offset, bool variable_safe) const {
 		case TK_CF_PASS:
 		case TK_SELF:
 		case TK_CONST_PI:
+		case TK_CONST_TAU:
 		case TK_WILDCARD:
 		case TK_CONST_INF:
 		case TK_CONST_NAN:

modules/gdscript/gd_tokenizer.h

@@ -128,6 +128,7 @@ public:
 		TK_DOLLAR,
 		TK_NEWLINE,
 		TK_CONST_PI,
+		TK_CONST_TAU,
 		TK_WILDCARD,
 		TK_CONST_INF,
 		TK_CONST_NAN,