src/libsyntax/config.rs - third_party/rust - Git at Google

 // 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 attr::{AttrMetaMethods, HasAttrs};
 use feature_gate::{emit_feature_err, EXPLAIN_STMT_ATTR_SYNTAX, Features, get_features, GateIssue};
 use fold::Folder;
 use {fold, attr};
 use ast;
 use codemap::{Spanned, respan};
 use parse::{ParseSess, token};
 use ptr::P;

 use util::small_vector::SmallVector;

 /// A folder that strips out items that do not belong in the current configuration.
 pub struct StripUnconfigured<'a> {
     pub config: &'a ast::CrateConfig,
     pub should_test: bool,
     pub sess: &'a ParseSess,
     pub features: Option<&'a Features>,
 }

 impl<'a> StripUnconfigured<'a> {
     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
         let node = self.process_cfg_attrs(node);
         if self.in_cfg(node.attrs()) { Some(node) } else { None }
     }

     pub fn process_cfg_attrs<T: HasAttrs>(&mut self, node: T) -> T {
         node.map_attrs(|attrs| {
             attrs.into_iter().filter_map(|attr| self.process_cfg_attr(attr)).collect()
         })
     }

     fn process_cfg_attr(&mut self, attr: ast::Attribute) -> Option<ast::Attribute> {
         if !attr.check_name("cfg_attr") {
             return Some(attr);
         }

         let attr_list = match attr.meta_item_list() {
             Some(attr_list) => attr_list,
             None => {
                 let msg = "expected `#[cfg_attr(<cfg pattern>, <attr>)]`";
                 self.sess.span_diagnostic.span_err(attr.span, msg);
                 return None;
             }
         };
         let (cfg, mi) = match (attr_list.len(), attr_list.get(0), attr_list.get(1)) {
             (2, Some(cfg), Some(mi)) => (cfg, mi),
             _ => {
                 let msg = "expected `#[cfg_attr(<cfg pattern>, <attr>)]`";
                 self.sess.span_diagnostic.span_err(attr.span, msg);
                 return None;
             }
         };

         if attr::cfg_matches(self.config, &cfg, self.sess, self.features) {
             self.process_cfg_attr(respan(mi.span, ast::Attribute_ {
                 id: attr::mk_attr_id(),
                 style: attr.node.style,
                 value: mi.clone(),
                 is_sugared_doc: false,
             }))
         } else {
             None
         }
     }

     // Determine if a node with the given attributes should be included in this configuation.
     fn in_cfg(&mut self, attrs: &[ast::Attribute]) -> bool {
         attrs.iter().all(|attr| {
             // When not compiling with --test we should not compile the #[test] functions
             if !self.should_test && is_test_or_bench(attr) {
                 return false;
             }

             let mis = match attr.node.value.node {
                 ast::MetaItemKind::List(_, ref mis) if is_cfg(&attr) => mis,
                 _ => return true
             };

             if mis.len() != 1 {
                 self.sess.span_diagnostic.span_err(attr.span, "expected 1 cfg-pattern");
                 return true;
             }

             attr::cfg_matches(self.config, &mis[0], self.sess, self.features)
         })
     }

     // Visit attributes on expression and statements (but not attributes on items in blocks).
     fn visit_stmt_or_expr_attrs(&mut self, attrs: &[ast::Attribute]) {
         // flag the offending attributes
         for attr in attrs.iter() {
             if !self.features.map(|features| features.stmt_expr_attributes).unwrap_or(true) {
                 emit_feature_err(&self.sess.span_diagnostic,
                                  "stmt_expr_attributes",
                                  attr.span,
                                  GateIssue::Language,
                                  EXPLAIN_STMT_ATTR_SYNTAX);
             }
         }
     }
 }

 // Support conditional compilation by transforming the AST, stripping out
 // any items that do not belong in the current configuration
 pub fn strip_unconfigured_items(mut krate: ast::Crate, sess: &ParseSess, should_test: bool)
                                 -> (ast::Crate, Features) {
     let features;
     {
         let mut strip_unconfigured = StripUnconfigured {
             config: &krate.config.clone(),
             should_test: should_test,
             sess: sess,
             features: None,
         };

         let err_count = sess.span_diagnostic.err_count();
         let krate_attrs = strip_unconfigured.process_cfg_attrs(krate.attrs.clone());
         features = get_features(&sess.span_diagnostic, &krate_attrs);
         if err_count < sess.span_diagnostic.err_count() {
             krate.attrs = krate_attrs.clone(); // Avoid reconfiguring malformed `cfg_attr`s
         }

         strip_unconfigured.features = Some(&features);
         krate = strip_unconfigured.fold_crate(krate);
         krate.attrs = krate_attrs;
     }

     (krate, features)
 }

 impl<'a> fold::Folder for StripUnconfigured<'a> {
     fn fold_foreign_mod(&mut self, foreign_mod: ast::ForeignMod) -> ast::ForeignMod {
         ast::ForeignMod {
             abi: foreign_mod.abi,
             items: foreign_mod.items.into_iter().filter_map(|item| {
                 self.configure(item).map(|item| fold::noop_fold_foreign_item(item, self))
             }).collect(),
         }
     }

     fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
         let fold_struct = |this: &mut Self, vdata| match vdata {
             ast::VariantData::Struct(fields, id) => {
                 let fields = fields.into_iter().filter_map(|field| this.configure(field));
                 ast::VariantData::Struct(fields.collect(), id)
             }
             ast::VariantData::Tuple(fields, id) => {
                 let fields = fields.into_iter().filter_map(|field| this.configure(field));
                 ast::VariantData::Tuple(fields.collect(), id)
             }
             ast::VariantData::Unit(id) => ast::VariantData::Unit(id)
         };

         let item = match item {
             ast::ItemKind::Struct(def, generics) => {
                 ast::ItemKind::Struct(fold_struct(self, def), generics)
             }
             ast::ItemKind::Enum(def, generics) => {
                 let variants = def.variants.into_iter().filter_map(|v| {
                     self.configure(v).map(|v| {
                         Spanned {
                             node: ast::Variant_ {
                                 name: v.node.name,
                                 attrs: v.node.attrs,
                                 data: fold_struct(self, v.node.data),
                                 disr_expr: v.node.disr_expr,
                             },
                             span: v.span
                         }
                     })
                 });
                 ast::ItemKind::Enum(ast::EnumDef {
                     variants: variants.collect(),
                 }, generics)
             }
             item => item,
         };

         fold::noop_fold_item_kind(item, self)
     }

     fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
         self.visit_stmt_or_expr_attrs(expr.attrs());

         // If an expr is valid to cfg away it will have been removed by the
         // outer stmt or expression folder before descending in here.
         // Anything else is always required, and thus has to error out
         // in case of a cfg attr.
         //
         // NB: This is intentionally not part of the fold_expr() function
         //     in order for fold_opt_expr() to be able to avoid this check
         if let Some(attr) = expr.attrs().iter().find(|a| is_cfg(a) || is_test_or_bench(a)) {
             let msg = "removing an expression is not supported in this position";
             self.sess.span_diagnostic.span_err(attr.span, msg);
         }

         let expr = self.process_cfg_attrs(expr);
         fold_expr(self, expr)
     }

     fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
         self.configure(expr).map(|expr| fold_expr(self, expr))
     }

     fn fold_stmt(&mut self, stmt: ast::Stmt) -> SmallVector<ast::Stmt> {
         self.visit_stmt_or_expr_attrs(stmt.attrs());
         self.configure(stmt).map(|stmt| fold::noop_fold_stmt(stmt, self))
                             .unwrap_or(SmallVector::zero())
     }

     fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
         fold::noop_fold_mac(mac, self)
     }

     fn fold_item(&mut self, item: P<ast::Item>) -> SmallVector<P<ast::Item>> {
         self.configure(item).map(|item| fold::noop_fold_item(item, self))
                             .unwrap_or(SmallVector::zero())
     }

     fn fold_impl_item(&mut self, item: ast::ImplItem) -> SmallVector<ast::ImplItem> {
         self.configure(item).map(|item| fold::noop_fold_impl_item(item, self))
                             .unwrap_or(SmallVector::zero())
     }

     fn fold_trait_item(&mut self, item: ast::TraitItem) -> SmallVector<ast::TraitItem> {
         self.configure(item).map(|item| fold::noop_fold_trait_item(item, self))
                             .unwrap_or(SmallVector::zero())
     }

     fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
         // Don't configure interpolated AST (c.f. #34171).
         // Interpolated AST will get configured once the surrounding tokens are parsed.
         nt
     }
 }

 fn fold_expr(folder: &mut StripUnconfigured, expr: P<ast::Expr>) -> P<ast::Expr> {
     expr.map(|ast::Expr {id, span, node, attrs}| {
         fold::noop_fold_expr(ast::Expr {
             id: id,
             node: match node {
                 ast::ExprKind::Match(m, arms) => {
                     ast::ExprKind::Match(m, arms.into_iter()
                                         .filter_map(|a| folder.configure(a))
                                         .collect())
                 }
                 _ => node
             },
             span: span,
             attrs: attrs,
         }, folder)
     })
 }

 fn is_cfg(attr: &ast::Attribute) -> bool {
     attr.check_name("cfg")
 }

 fn is_test_or_bench(attr: &ast::Attribute) -> bool {
     attr.check_name("test") || attr.check_name("bench")
 }
	// 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 attr::{AttrMetaMethods, HasAttrs};
	use feature_gate::{emit_feature_err, EXPLAIN_STMT_ATTR_SYNTAX, Features, get_features, GateIssue};
	use fold::Folder;
	use {fold, attr};
	use ast;
	use codemap::{Spanned, respan};
	use parse::{ParseSess, token};
	use ptr::P;

	use util::small_vector::SmallVector;

	/// A folder that strips out items that do not belong in the current configuration.
	pub struct StripUnconfigured<'a> {
	pub config: &'a ast::CrateConfig,
	pub should_test: bool,
	pub sess: &'a ParseSess,
	pub features: Option<&'a Features>,
	}

	impl<'a> StripUnconfigured<'a> {
	fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
	let node = self.process_cfg_attrs(node);
	if self.in_cfg(node.attrs()) { Some(node) } else { None }
	}

	pub fn process_cfg_attrs<T: HasAttrs>(&mut self, node: T) -> T {
	node.map_attrs(\|attrs\| {
	attrs.into_iter().filter_map(\|attr\| self.process_cfg_attr(attr)).collect()
	})
	}

	fn process_cfg_attr(&mut self, attr: ast::Attribute) -> Option<ast::Attribute> {
	if !attr.check_name("cfg_attr") {
	return Some(attr);
	}

	let attr_list = match attr.meta_item_list() {
	Some(attr_list) => attr_list,
	None => {
	let msg = "expected `#[cfg_attr(<cfg pattern>, <attr>)]`";
	self.sess.span_diagnostic.span_err(attr.span, msg);
	return None;
	}
	};
	let (cfg, mi) = match (attr_list.len(), attr_list.get(0), attr_list.get(1)) {
	(2, Some(cfg), Some(mi)) => (cfg, mi),
	_ => {
	let msg = "expected `#[cfg_attr(<cfg pattern>, <attr>)]`";
	self.sess.span_diagnostic.span_err(attr.span, msg);
	return None;
	}
	};

	if attr::cfg_matches(self.config, &cfg, self.sess, self.features) {
	self.process_cfg_attr(respan(mi.span, ast::Attribute_ {
	id: attr::mk_attr_id(),
	style: attr.node.style,
	value: mi.clone(),
	is_sugared_doc: false,
	}))
	} else {
	None
	}
	}

	// Determine if a node with the given attributes should be included in this configuation.
	fn in_cfg(&mut self, attrs: &[ast::Attribute]) -> bool {
	attrs.iter().all(\|attr\| {
	// When not compiling with --test we should not compile the #[test] functions
	if !self.should_test && is_test_or_bench(attr) {
	return false;
	}

	let mis = match attr.node.value.node {
	ast::MetaItemKind::List(_, ref mis) if is_cfg(&attr) => mis,
	_ => return true
	};

	if mis.len() != 1 {
	self.sess.span_diagnostic.span_err(attr.span, "expected 1 cfg-pattern");
	return true;
	}

	attr::cfg_matches(self.config, &mis[0], self.sess, self.features)
	})
	}

	// Visit attributes on expression and statements (but not attributes on items in blocks).
	fn visit_stmt_or_expr_attrs(&mut self, attrs: &[ast::Attribute]) {
	// flag the offending attributes
	for attr in attrs.iter() {
	if !self.features.map(\|features\| features.stmt_expr_attributes).unwrap_or(true) {
	emit_feature_err(&self.sess.span_diagnostic,
	"stmt_expr_attributes",
	attr.span,
	GateIssue::Language,
	EXPLAIN_STMT_ATTR_SYNTAX);
	}
	}
	}
	}

	// Support conditional compilation by transforming the AST, stripping out
	// any items that do not belong in the current configuration
	pub fn strip_unconfigured_items(mut krate: ast::Crate, sess: &ParseSess, should_test: bool)
	-> (ast::Crate, Features) {
	let features;
	{
	let mut strip_unconfigured = StripUnconfigured {
	config: &krate.config.clone(),
	should_test: should_test,
	sess: sess,
	features: None,
	};

	let err_count = sess.span_diagnostic.err_count();
	let krate_attrs = strip_unconfigured.process_cfg_attrs(krate.attrs.clone());
	features = get_features(&sess.span_diagnostic, &krate_attrs);
	if err_count < sess.span_diagnostic.err_count() {
	krate.attrs = krate_attrs.clone(); // Avoid reconfiguring malformed `cfg_attr`s
	}

	strip_unconfigured.features = Some(&features);
	krate = strip_unconfigured.fold_crate(krate);
	krate.attrs = krate_attrs;
	}

	(krate, features)
	}

	impl<'a> fold::Folder for StripUnconfigured<'a> {
	fn fold_foreign_mod(&mut self, foreign_mod: ast::ForeignMod) -> ast::ForeignMod {
	ast::ForeignMod {
	abi: foreign_mod.abi,
	items: foreign_mod.items.into_iter().filter_map(\|item\| {
	self.configure(item).map(\|item\| fold::noop_fold_foreign_item(item, self))
	}).collect(),
	}
	}

	fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
	let fold_struct = \|this: &mut Self, vdata\| match vdata {
	ast::VariantData::Struct(fields, id) => {
	let fields = fields.into_iter().filter_map(\|field\| this.configure(field));
	ast::VariantData::Struct(fields.collect(), id)
	}
	ast::VariantData::Tuple(fields, id) => {
	let fields = fields.into_iter().filter_map(\|field\| this.configure(field));
	ast::VariantData::Tuple(fields.collect(), id)
	}
	ast::VariantData::Unit(id) => ast::VariantData::Unit(id)
	};

	let item = match item {
	ast::ItemKind::Struct(def, generics) => {
	ast::ItemKind::Struct(fold_struct(self, def), generics)
	}
	ast::ItemKind::Enum(def, generics) => {
	let variants = def.variants.into_iter().filter_map(\|v\| {
	self.configure(v).map(\|v\| {
	Spanned {
	node: ast::Variant_ {
	name: v.node.name,
	attrs: v.node.attrs,
	data: fold_struct(self, v.node.data),
	disr_expr: v.node.disr_expr,
	},
	span: v.span
	}
	})
	});
	ast::ItemKind::Enum(ast::EnumDef {
	variants: variants.collect(),
	}, generics)
	}
	item => item,
	};

	fold::noop_fold_item_kind(item, self)
	}

	fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
	self.visit_stmt_or_expr_attrs(expr.attrs());

	// If an expr is valid to cfg away it will have been removed by the
	// outer stmt or expression folder before descending in here.
	// Anything else is always required, and thus has to error out
	// in case of a cfg attr.
	//
	// NB: This is intentionally not part of the fold_expr() function
	// in order for fold_opt_expr() to be able to avoid this check
	if let Some(attr) = expr.attrs().iter().find(\|a\| is_cfg(a) \|\| is_test_or_bench(a)) {
	let msg = "removing an expression is not supported in this position";
	self.sess.span_diagnostic.span_err(attr.span, msg);
	}

	let expr = self.process_cfg_attrs(expr);
	fold_expr(self, expr)
	}

	fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
	self.configure(expr).map(\|expr\| fold_expr(self, expr))
	}

	fn fold_stmt(&mut self, stmt: ast::Stmt) -> SmallVector<ast::Stmt> {
	self.visit_stmt_or_expr_attrs(stmt.attrs());
	self.configure(stmt).map(\|stmt\| fold::noop_fold_stmt(stmt, self))
	.unwrap_or(SmallVector::zero())
	}

	fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
	fold::noop_fold_mac(mac, self)
	}

	fn fold_item(&mut self, item: P<ast::Item>) -> SmallVector<P<ast::Item>> {
	self.configure(item).map(\|item\| fold::noop_fold_item(item, self))
	.unwrap_or(SmallVector::zero())
	}

	fn fold_impl_item(&mut self, item: ast::ImplItem) -> SmallVector<ast::ImplItem> {
	self.configure(item).map(\|item\| fold::noop_fold_impl_item(item, self))
	.unwrap_or(SmallVector::zero())
	}

	fn fold_trait_item(&mut self, item: ast::TraitItem) -> SmallVector<ast::TraitItem> {
	self.configure(item).map(\|item\| fold::noop_fold_trait_item(item, self))
	.unwrap_or(SmallVector::zero())
	}

	fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
	// Don't configure interpolated AST (c.f. #34171).
	// Interpolated AST will get configured once the surrounding tokens are parsed.
	nt
	}
	}

	fn fold_expr(folder: &mut StripUnconfigured, expr: P<ast::Expr>) -> P<ast::Expr> {
	expr.map(\|ast::Expr {id, span, node, attrs}\| {
	fold::noop_fold_expr(ast::Expr {
	id: id,
	node: match node {
	ast::ExprKind::Match(m, arms) => {
	ast::ExprKind::Match(m, arms.into_iter()
	.filter_map(\|a\| folder.configure(a))
	.collect())
	}
	_ => node
	},
	span: span,
	attrs: attrs,
	}, folder)
	})
	}

	fn is_cfg(attr: &ast::Attribute) -> bool {
	attr.check_name("cfg")
	}

	fn is_test_or_bench(attr: &ast::Attribute) -> bool {
	attr.check_name("test") \|\| attr.check_name("bench")
	}