Introduce a config property to the crate AST node

This represents the compilation environment, defined as AST meta_items, Used
for driving conditional compilation and will eventually replace the
environment used by the parser for the current conditional compilation scheme.

Issue #489

src/comp/front/ast.rs

@@ -76,11 +76,16 @@ fn def_id_of_def(def d) -> def_id {
     fail;
 }
 
+// The set of meta_items that define the compilation environment of the crate,
+// used to drive conditional compilation
+type crate_cfg = vec[@meta_item];
+
 type crate = spanned[crate_];
 
 type crate_ = rec(vec[@crate_directive] directives,
                   _mod module,
-                  vec[attribute] attrs);
+                  vec[attribute] attrs,
+                  crate_cfg config);
 
 tag crate_directive_ {
     cdir_expr(@expr);

src/comp/front/fold.rs

@@ -131,7 +131,8 @@ fn noop_fold_crate(&crate_ c, ast_fold fld) -> crate_ {
     auto fold_attribute = bind fold_attribute_(_,fold_meta_item);
 
     ret rec(directives=map(fld.fold_crate_directive, c.directives),
-            module=c.module, attrs=map(fold_attribute, c.attrs));
+            module=c.module, attrs=map(fold_attribute, c.attrs),
+            config=map(fold_meta_item, c.config));
 }
 
 fn noop_fold_crate_directive(&crate_directive_ cd, ast_fold fld) 

src/comp/front/parser.rs

@@ -2318,7 +2318,8 @@ fn parse_crate_from_source_file(&parser p) -> @ast::crate {
     let vec[@ast::crate_directive] cdirs = [];
     ret @spanned(lo, p.get_lo_pos(), rec(directives=cdirs,
                                          module=m,
-                                         attrs=crate_attrs._0));
+                                         attrs=crate_attrs._0,
+                                         config=[]));
 }
 
 fn parse_str(&parser p) -> ast::ident {
@@ -2450,7 +2451,8 @@ fn parse_crate_from_crate_file(&parser p) -> @ast::crate {
     expect(p, token::EOF);
     ret @spanned(lo, hi, rec(directives=cdirs,
                              module=m,
-                             attrs=crate_attrs));
+                             attrs=crate_attrs,
+                             config=[]));
 }
 //
 // Local Variables: