syntax: Add #[deriving(FromPrimitive)] syntax extension

Right now this only works for c-style enums.

1 files changed, 27 insertions, 0 deletions

diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 5111682f6d0..8e4f553cb83 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -113,6 +113,7 @@ pub trait AstBuilder {
                         expr: @ast::Expr, ident: ast::Ident,
                         args: ~[@ast::Expr]) -> @ast::Expr;
     fn expr_block(&self, b: ast::Block) -> @ast::Expr;
+    fn expr_cast(&self, sp: Span, expr: @ast::Expr, ty: ast::Ty) -> @ast::Expr;
 
     fn field_imm(&self, span: Span, name: Ident, e: @ast::Expr) -> ast::Field;
     fn expr_struct(&self, span: Span, path: ast::Path, fields: ~[ast::Field]) -> @ast::Expr;
@@ -132,6 +133,9 @@ pub trait AstBuilder {
     fn expr_str(&self, sp: Span, s: @str) -> @ast::Expr;
     fn expr_str_uniq(&self, sp: Span, s: @str) -> @ast::Expr;
 
+    fn expr_some(&self, sp: Span, expr: @ast::Expr) -> @ast::Expr;
+    fn expr_none(&self, sp: Span) -> @ast::Expr;
+
     fn expr_unreachable(&self, span: Span) -> @ast::Expr;
 
     fn pat(&self, span: Span, pat: ast::Pat_) -> @ast::Pat;
@@ -564,6 +568,29 @@ impl AstBuilder for @ExtCtxt {
     }
 
 
+    fn expr_cast(&self, sp: Span, expr: @ast::Expr, ty: ast::Ty) -> @ast::Expr {
+        self.expr(sp, ast::ExprCast(expr, ty))
+    }
+
+
+    fn expr_some(&self, sp: Span, expr: @ast::Expr) -> @ast::Expr {
+        let some = ~[
+            self.ident_of("std"),
+            self.ident_of("option"),
+            self.ident_of("Some"),
+        ];
+        self.expr_call_global(sp, some, ~[expr])
+    }
+
+    fn expr_none(&self, sp: Span) -> @ast::Expr {
+        let none = self.path_global(sp, ~[
+            self.ident_of("std"),
+            self.ident_of("option"),
+            self.ident_of("None"),
+        ]);
+        self.expr_path(none)
+    }
+
     fn expr_unreachable(&self, span: Span) -> @ast::Expr {
         let loc = self.codemap().lookup_char_pos(span.lo);
         self.expr_call_global(