Add meta-definitions for AST types

- The big change here is that all the definitions for syntax-node classes have been macro-ized, to that we can do light metaprogramming over them
  - The use of macros for this has big down-sides, but I'm not quite ready to do anything more heavy-weight right now
  - The macro-ized definitions can be included multiple times, to generate different declarations/code as needed

- The first example of using this meta-programming facility is a new visitor system
  - The actual visitor base classes and the dispatch logic are all generated from the meta-files

- There was only one visitor left in the code: the semantics checker, so that was ported to the new system.

- All current test cases pass, so *of course* that means all is well.

1 files changed, 36 insertions, 0 deletions

diff --git a/source/slang/object-meta-begin.h b/source/slang/object-meta-begin.h
new file mode 100644
index 000000000..e4187a600
--- /dev/null
+++ b/source/slang/object-meta-begin.h
@@ -0,0 +1,36 @@
+// object-meta-begin.h
+
+#ifndef SYNTAX_CLASS
+#error The 'SYNTAX_CLASS' macro should be defined before including 'object-meta-begin.h'
+#endif
+
+#ifndef ABSTRACT_SYNTAX_CLASS
+#define ABSTRACT_SYNTAX_CLASS(NAME, BASE) SYNTAX_CLASS(NAME, BASE)
+#endif
+
+#ifndef END_SYNTAX_CLASS
+#define END_SYNTAX_CLASS() /* empty */
+#endif
+
+#ifndef DECL_FIELD
+#define DECL_FIELD(TYPE, NAME) SYNTAX_FIELD(TYPE, NAME)
+#endif
+
+#ifndef SYNTAX_FIELD
+#define SYNTAX_FIELD(TYPE, NAME) FIELD(TYPE, NAME)
+#endif
+
+#ifndef FIELD_INIT
+#define FIELD_INIT(TYPE, NAME, INIT) FIELD(TYPE, NAME)
+#endif
+
+#ifndef FIELD
+#define FIELD(...) /* empty */
+#endif
+
+#ifndef RAW
+#define RAW(...) /* empty */
+#endif
+
+#define SIMPLE_SYNTAX_CLASS(NAME, BASE) SYNTAX_CLASS(NAME, BASE) END_SYNTAX_CLASS()
+