Fix type parser for types with keyword prefix

E.g. a type `constant` would become `const ant`.

test/code_generator.cpp

@@ -19,6 +19,10 @@ template<template<typename>class... T>
 struct templated{
 };
 
+using struct_=int;
+
+struct_ var2;
+
 struct foo{
   int a;
 
@@ -56,6 +60,10 @@ struct templated
 {
 };
 
+using struct_ = int;
+
+struct_ var2;
+
 struct foo
 {
   int a;