move most of front to libsyntax

1 files changed, 253 insertions, 0 deletions

diff --git a/src/libsyntax/config.rs b/src/libsyntax/config.rs
new file mode 100644
index 00000000000..cb96cd911b5
--- /dev/null
+++ b/src/libsyntax/config.rs
@@ -0,0 +1,253 @@
+// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use fold::Folder;
+use {ast, fold, attr};
+use codemap::Spanned;
+use ptr::P;
+
+/// A folder that strips out items that do not belong in the current
+/// configuration.
+struct Context<'a> {
+    in_cfg: |attrs: &[ast::Attribute]|: 'a -> bool,
+}
+
+// Support conditional compilation by transforming the AST, stripping out
+// any items that do not belong in the current configuration
+pub fn strip_unconfigured_items(krate: ast::Crate) -> ast::Crate {
+    let config = krate.config.clone();
+    strip_items(krate, |attrs| in_cfg(config.as_slice(), attrs))
+}
+
+impl<'a> fold::Folder for Context<'a> {
+    fn fold_mod(&mut self, module: ast::Mod) -> ast::Mod {
+        fold_mod(self, module)
+    }
+    fn fold_block(&mut self, block: P<ast::Block>) -> P<ast::Block> {
+        fold_block(self, block)
+    }
+    fn fold_foreign_mod(&mut self, foreign_mod: ast::ForeignMod) -> ast::ForeignMod {
+        fold_foreign_mod(self, foreign_mod)
+    }
+    fn fold_item_underscore(&mut self, item: ast::Item_) -> ast::Item_ {
+        fold_item_underscore(self, item)
+    }
+    fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
+        fold_expr(self, expr)
+    }
+    fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
+        fold::noop_fold_mac(mac, self)
+    }
+}
+
+pub fn strip_items(krate: ast::Crate,
+                   in_cfg: |attrs: &[ast::Attribute]| -> bool)
+                   -> ast::Crate {
+    let mut ctxt = Context {
+        in_cfg: in_cfg,
+    };
+    ctxt.fold_crate(krate)
+}
+
+fn filter_view_item(cx: &mut Context, view_item: ast::ViewItem) -> Option<ast::ViewItem> {
+    if view_item_in_cfg(cx, &view_item) {
+        Some(view_item)
+    } else {
+        None
+    }
+}
+
+fn fold_mod(cx: &mut Context, ast::Mod {inner, view_items, items}: ast::Mod) -> ast::Mod {
+    ast::Mod {
+        inner: inner,
+        view_items: view_items.into_iter().filter_map(|a| {
+            filter_view_item(cx, a).map(|x| cx.fold_view_item(x))
+        }).collect(),
+        items: items.into_iter().filter_map(|a| {
+            if item_in_cfg(cx, &*a) {
+                Some(cx.fold_item(a))
+            } else {
+                None
+            }
+        }).flat_map(|x| x.into_iter()).collect()
+    }
+}
+
+fn filter_foreign_item(cx: &mut Context, item: P<ast::ForeignItem>)
+                       -> Option<P<ast::ForeignItem>> {
+    if foreign_item_in_cfg(cx, &*item) {
+        Some(item)
+    } else {
+        None
+    }
+}
+
+fn fold_foreign_mod(cx: &mut Context, ast::ForeignMod {abi, view_items, items}: ast::ForeignMod)
+                    -> ast::ForeignMod {
+    ast::ForeignMod {
+        abi: abi,
+        view_items: view_items.into_iter().filter_map(|a| {
+            filter_view_item(cx, a).map(|x| cx.fold_view_item(x))
+        }).collect(),
+        items: items.into_iter()
+                    .filter_map(|a| filter_foreign_item(cx, a))
+                    .collect()
+    }
+}
+
+fn fold_item_underscore(cx: &mut Context, item: ast::Item_) -> ast::Item_ {
+    let item = match item {
+        ast::ItemImpl(a, b, c, impl_items) => {
+            let impl_items = impl_items.into_iter()
+                                       .filter(|ii| impl_item_in_cfg(cx, ii))
+                                       .collect();
+            ast::ItemImpl(a, b, c, impl_items)
+        }
+        ast::ItemTrait(a, b, c, methods) => {
+            let methods = methods.into_iter()
+                                 .filter(|m| trait_method_in_cfg(cx, m))
+                                 .collect();
+            ast::ItemTrait(a, b, c, methods)
+        }
+        ast::ItemStruct(def, generics) => {
+            ast::ItemStruct(fold_struct(cx, def), generics)
+        }
+        ast::ItemEnum(def, generics) => {
+            let mut variants = def.variants.into_iter().filter_map(|v| {
+                if !(cx.in_cfg)(v.node.attrs.as_slice()) {
+                    None
+                } else {
+                    Some(v.map(|Spanned {node: ast::Variant_ {id, name, attrs, kind,
+                                                              disr_expr, vis}, span}| {
+                        Spanned {
+                            node: ast::Variant_ {
+                                id: id,
+                                name: name,
+                                attrs: attrs,
+                                kind: match kind {
+                                    ast::TupleVariantKind(..) => kind,
+                                    ast::StructVariantKind(def) => {
+                                        ast::StructVariantKind(fold_struct(cx, def))
+                                    }
+                                },
+                                disr_expr: disr_expr,
+                                vis: vis
+                            },
+                            span: span
+                        }
+                    }))
+                }
+            });
+            ast::ItemEnum(ast::EnumDef {
+                variants: variants.collect(),
+            }, generics)
+        }
+        item => item,
+    };
+
+    fold::noop_fold_item_underscore(item, cx)
+}
+
+fn fold_struct(cx: &mut Context, def: P<ast::StructDef>) -> P<ast::StructDef> {
+    def.map(|ast::StructDef {fields, ctor_id, super_struct, is_virtual}| {
+        ast::StructDef {
+            fields: fields.into_iter().filter(|m| {
+                (cx.in_cfg)(m.node.attrs.as_slice())
+            }).collect(),
+            ctor_id: ctor_id,
+            super_struct: super_struct,
+            is_virtual: is_virtual,
+        }
+    })
+}
+
+fn retain_stmt(cx: &mut Context, stmt: &ast::Stmt) -> bool {
+    match stmt.node {
+        ast::StmtDecl(ref decl, _) => {
+            match decl.node {
+                ast::DeclItem(ref item) => {
+                    item_in_cfg(cx, &**item)
+                }
+                _ => true
+            }
+        }
+        _ => true
+    }
+}
+
+fn fold_block(cx: &mut Context, b: P<ast::Block>) -> P<ast::Block> {
+    b.map(|ast::Block {id, view_items, stmts, expr, rules, span}| {
+        let resulting_stmts: Vec<P<ast::Stmt>> =
+            stmts.into_iter().filter(|a| retain_stmt(cx, &**a)).collect();
+        let resulting_stmts = resulting_stmts.into_iter()
+            .flat_map(|stmt| cx.fold_stmt(stmt).into_iter())
+            .collect();
+        let filtered_view_items = view_items.into_iter().filter_map(|a| {
+            filter_view_item(cx, a).map(|x| cx.fold_view_item(x))
+        }).collect();
+        ast::Block {
+            id: id,
+            view_items: filtered_view_items,
+            stmts: resulting_stmts,
+            expr: expr.map(|x| cx.fold_expr(x)),
+            rules: rules,
+            span: span,
+        }
+    })
+}
+
+fn fold_expr(cx: &mut Context, expr: P<ast::Expr>) -> P<ast::Expr> {
+    expr.map(|ast::Expr {id, span, node}| {
+        fold::noop_fold_expr(ast::Expr {
+            id: id,
+            node: match node {
+                ast::ExprMatch(m, arms) => {
+                    ast::ExprMatch(m, arms.into_iter()
+                                        .filter(|a| (cx.in_cfg)(a.attrs.as_slice()))
+                                        .collect())
+                }
+                _ => node
+            },
+            span: span
+        }, cx)
+    })
+}
+
+fn item_in_cfg(cx: &mut Context, item: &ast::Item) -> bool {
+    return (cx.in_cfg)(item.attrs.as_slice());
+}
+
+fn foreign_item_in_cfg(cx: &mut Context, item: &ast::ForeignItem) -> bool {
+    return (cx.in_cfg)(item.attrs.as_slice());
+}
+
+fn view_item_in_cfg(cx: &mut Context, item: &ast::ViewItem) -> bool {
+    return (cx.in_cfg)(item.attrs.as_slice());
+}
+
+fn trait_method_in_cfg(cx: &mut Context, meth: &ast::TraitItem) -> bool {
+    match *meth {
+        ast::RequiredMethod(ref meth) => (cx.in_cfg)(meth.attrs.as_slice()),
+        ast::ProvidedMethod(ref meth) => (cx.in_cfg)(meth.attrs.as_slice())
+    }
+}
+
+fn impl_item_in_cfg(cx: &mut Context, impl_item: &ast::ImplItem) -> bool {
+    match *impl_item {
+        ast::MethodImplItem(ref meth) => (cx.in_cfg)(meth.attrs.as_slice()),
+    }
+}
+
+// Determine if an item should be translated in the current crate
+// configuration based on the item's attributes
+fn in_cfg(cfg: &[P<ast::MetaItem>], attrs: &[ast::Attribute]) -> bool {
+    attr::test_cfg(cfg, attrs.iter())
+}
+