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::HasAttrs;
 use feature_gate::{feature_err, EXPLAIN_STMT_ATTR_SYNTAX, Features, get_features, GateIssue};
 use {fold, attr};
 use ast;
 use codemap::Spanned;
 use parse::{token, ParseSess};

 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 should_test: bool,
     pub sess: &'a ParseSess,
     pub features: Option<&'a Features>,
 }

 // `cfg_attr`-process the crate's attributes and compute the crate's features.
 pub fn features(mut krate: ast::Crate, sess: &ParseSess, should_test: bool)
                 -> (ast::Crate, Features) {
     let features;
     {
         let mut strip_unconfigured = StripUnconfigured {
             should_test,
             sess,
             features: None,
         };

         let unconfigured_attrs = krate.attrs.clone();
         let err_count = sess.span_diagnostic.err_count();
         if let Some(attrs) = strip_unconfigured.configure(krate.attrs) {
             krate.attrs = attrs;
         } else { // the entire crate is unconfigured
             krate.attrs = Vec::new();
             krate.module.items = Vec::new();
             return (krate, Features::new());
         }

         features = get_features(&sess.span_diagnostic, &krate.attrs);

         // Avoid reconfiguring malformed `cfg_attr`s
         if err_count == sess.span_diagnostic.err_count() {
             strip_unconfigured.features = Some(&features);
             strip_unconfigured.configure(unconfigured_attrs);
         }
     }

     (krate, features)
 }

 macro_rules! configure {
     ($this:ident, $node:ident) => {
         match $this.configure($node) {
             Some(node) => node,
             None => return Default::default(),
         }
     }
 }

 impl<'a> StripUnconfigured<'a> {
     pub 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 (cfg, path, tokens, span) = match attr.parse(self.sess, |parser| {
             parser.expect(&token::OpenDelim(token::Paren))?;
             let cfg = parser.parse_meta_item()?;
             parser.expect(&token::Comma)?;
             let lo = parser.span.lo();
             let (path, tokens) = parser.parse_path_and_tokens()?;
             parser.expect(&token::CloseDelim(token::Paren))?;
             Ok((cfg, path, tokens, parser.prev_span.with_lo(lo)))
         }) {
             Ok(result) => result,
             Err(mut e) => {
                 e.emit();
                 return None;
             }
         };

         if attr::cfg_matches(&cfg, self.sess, self.features) {
             self.process_cfg_attr(ast::Attribute {
                 id: attr::mk_attr_id(),
                 style: attr.style,
                 path,
                 tokens,
                 is_sugared_doc: false,
                 span,
             })
         } else {
             None
         }
     }

     // Determine if a node with the given attributes should be included in this configuation.
     pub 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 = if !is_cfg(attr) {
                 return true;
             } else if let Some(mis) = attr.meta_item_list() {
                 mis
             } else {
                 return true;
             };

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

             if !mis[0].is_meta_item() {
                 self.sess.span_diagnostic.span_err(mis[0].span, "unexpected literal");
                 return true;
             }

             attr::cfg_matches(mis[0].meta_item().unwrap(), self.sess, self.features)
         })
     }

     // Visit attributes on expression and statements (but not attributes on items in blocks).
     fn visit_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) {
                 let mut err = feature_err(self.sess,
                                           "stmt_expr_attributes",
                                           attr.span,
                                           GateIssue::Language,
                                           EXPLAIN_STMT_ATTR_SYNTAX);
                 if attr.is_sugared_doc {
                     err.help("`///` is for documentation comments. For a plain comment, use `//`.");
                 }
                 err.emit();
             }
         }
     }

     pub fn configure_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)).collect(),
         }
     }

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

     pub fn configure_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
         match item {
             ast::ItemKind::Struct(def, generics) => {
                 ast::ItemKind::Struct(self.configure_variant_data(def), generics)
             }
             ast::ItemKind::Union(def, generics) => {
                 ast::ItemKind::Union(self.configure_variant_data(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: self.configure_variant_data(v.node.data),
                                 disr_expr: v.node.disr_expr,
                             },
                             span: v.span
                         }
                     })
                 });
                 ast::ItemKind::Enum(ast::EnumDef {
                     variants: variants.collect(),
                 }, generics)
             }
             item => item,
         }
     }

     pub fn configure_expr_kind(&mut self, expr_kind: ast::ExprKind) -> ast::ExprKind {
         match expr_kind {
             ast::ExprKind::Match(m, arms) => {
                 let arms = arms.into_iter().filter_map(|a| self.configure(a)).collect();
                 ast::ExprKind::Match(m, arms)
             }
             ast::ExprKind::Struct(path, fields, base) => {
                 let fields = fields.into_iter()
                     .filter_map(|field| {
                         self.configure(field)
                     })
                     .collect();
                 ast::ExprKind::Struct(path, fields, base)
             }
             _ => expr_kind,
         }
     }

     pub fn configure_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
         self.visit_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);
         }

         self.process_cfg_attrs(expr)
     }

     pub fn configure_stmt(&mut self, stmt: ast::Stmt) -> Option<ast::Stmt> {
         self.configure(stmt)
     }

     pub fn configure_struct_expr_field(&mut self, field: ast::Field) -> Option<ast::Field> {
         self.configure(field)
     }

     pub fn configure_pat(&mut self, pattern: P<ast::Pat>) -> P<ast::Pat> {
         pattern.map(|mut pattern| {
             if let ast::PatKind::Struct(path, fields, etc) = pattern.node {
                 let fields = fields.into_iter()
                     .filter_map(|field| {
                         self.configure(field)
                     })
                     .collect();
                 pattern.node = ast::PatKind::Struct(path, fields, etc);
             }
             pattern
         })
     }
 }

 impl<'a> fold::Folder for StripUnconfigured<'a> {
     fn fold_foreign_mod(&mut self, foreign_mod: ast::ForeignMod) -> ast::ForeignMod {
         let foreign_mod = self.configure_foreign_mod(foreign_mod);
         fold::noop_fold_foreign_mod(foreign_mod, self)
     }

     fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
         let item = self.configure_item_kind(item);
         fold::noop_fold_item_kind(item, self)
     }

     fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
         let mut expr = self.configure_expr(expr).into_inner();
         expr.node = self.configure_expr_kind(expr.node);
         P(fold::noop_fold_expr(expr, self))
     }

     fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
         let mut expr = configure!(self, expr).into_inner();
         expr.node = self.configure_expr_kind(expr.node);
         Some(P(fold::noop_fold_expr(expr, self)))
     }

     fn fold_stmt(&mut self, stmt: ast::Stmt) -> SmallVector<ast::Stmt> {
         match self.configure_stmt(stmt) {
             Some(stmt) => fold::noop_fold_stmt(stmt, self),
             None => return SmallVector::new(),
         }
     }

     fn fold_item(&mut self, item: P<ast::Item>) -> SmallVector<P<ast::Item>> {
         fold::noop_fold_item(configure!(self, item), self)
     }

     fn fold_impl_item(&mut self, item: ast::ImplItem) -> SmallVector<ast::ImplItem> {
         fold::noop_fold_impl_item(configure!(self, item), self)
     }

     fn fold_trait_item(&mut self, item: ast::TraitItem) -> SmallVector<ast::TraitItem> {
         fold::noop_fold_trait_item(configure!(self, item), self)
     }

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

     fn fold_pat(&mut self, pattern: P<ast::Pat>) -> P<ast::Pat> {
         fold::noop_fold_pat(self.configure_pat(pattern), self)
     }
 }

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

 pub 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::HasAttrs;
	use feature_gate::{feature_err, EXPLAIN_STMT_ATTR_SYNTAX, Features, get_features, GateIssue};
	use {fold, attr};
	use ast;
	use codemap::Spanned;
	use parse::{token, ParseSess};

	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 should_test: bool,
	pub sess: &'a ParseSess,
	pub features: Option<&'a Features>,
	}

	// `cfg_attr`-process the crate's attributes and compute the crate's features.
	pub fn features(mut krate: ast::Crate, sess: &ParseSess, should_test: bool)
	-> (ast::Crate, Features) {
	let features;
	{
	let mut strip_unconfigured = StripUnconfigured {
	should_test,
	sess,
	features: None,
	};

	let unconfigured_attrs = krate.attrs.clone();
	let err_count = sess.span_diagnostic.err_count();
	if let Some(attrs) = strip_unconfigured.configure(krate.attrs) {
	krate.attrs = attrs;
	} else { // the entire crate is unconfigured
	krate.attrs = Vec::new();
	krate.module.items = Vec::new();
	return (krate, Features::new());
	}

	features = get_features(&sess.span_diagnostic, &krate.attrs);

	// Avoid reconfiguring malformed `cfg_attr`s
	if err_count == sess.span_diagnostic.err_count() {
	strip_unconfigured.features = Some(&features);
	strip_unconfigured.configure(unconfigured_attrs);
	}
	}

	(krate, features)
	}

	macro_rules! configure {
	($this:ident, $node:ident) => {
	match $this.configure($node) {
	Some(node) => node,
	None => return Default::default(),
	}
	}
	}

	impl<'a> StripUnconfigured<'a> {
	pub 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 (cfg, path, tokens, span) = match attr.parse(self.sess, \|parser\| {
	parser.expect(&token::OpenDelim(token::Paren))?;
	let cfg = parser.parse_meta_item()?;
	parser.expect(&token::Comma)?;
	let lo = parser.span.lo();
	let (path, tokens) = parser.parse_path_and_tokens()?;
	parser.expect(&token::CloseDelim(token::Paren))?;
	Ok((cfg, path, tokens, parser.prev_span.with_lo(lo)))
	}) {
	Ok(result) => result,
	Err(mut e) => {
	e.emit();
	return None;
	}
	};

	if attr::cfg_matches(&cfg, self.sess, self.features) {
	self.process_cfg_attr(ast::Attribute {
	id: attr::mk_attr_id(),
	style: attr.style,
	path,
	tokens,
	is_sugared_doc: false,
	span,
	})
	} else {
	None
	}
	}

	// Determine if a node with the given attributes should be included in this configuation.
	pub 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 = if !is_cfg(attr) {
	return true;
	} else if let Some(mis) = attr.meta_item_list() {
	mis
	} else {
	return true;
	};

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

	if !mis[0].is_meta_item() {
	self.sess.span_diagnostic.span_err(mis[0].span, "unexpected literal");
	return true;
	}

	attr::cfg_matches(mis[0].meta_item().unwrap(), self.sess, self.features)
	})
	}

	// Visit attributes on expression and statements (but not attributes on items in blocks).
	fn visit_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) {
	let mut err = feature_err(self.sess,
	"stmt_expr_attributes",
	attr.span,
	GateIssue::Language,
	EXPLAIN_STMT_ATTR_SYNTAX);
	if attr.is_sugared_doc {
	err.help("`///` is for documentation comments. For a plain comment, use `//`.");
	}
	err.emit();
	}
	}
	}

	pub fn configure_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)).collect(),
	}
	}

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

	pub fn configure_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
	match item {
	ast::ItemKind::Struct(def, generics) => {
	ast::ItemKind::Struct(self.configure_variant_data(def), generics)
	}
	ast::ItemKind::Union(def, generics) => {
	ast::ItemKind::Union(self.configure_variant_data(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: self.configure_variant_data(v.node.data),
	disr_expr: v.node.disr_expr,
	},
	span: v.span
	}
	})
	});
	ast::ItemKind::Enum(ast::EnumDef {
	variants: variants.collect(),
	}, generics)
	}
	item => item,
	}
	}

	pub fn configure_expr_kind(&mut self, expr_kind: ast::ExprKind) -> ast::ExprKind {
	match expr_kind {
	ast::ExprKind::Match(m, arms) => {
	let arms = arms.into_iter().filter_map(\|a\| self.configure(a)).collect();
	ast::ExprKind::Match(m, arms)
	}
	ast::ExprKind::Struct(path, fields, base) => {
	let fields = fields.into_iter()
	.filter_map(\|field\| {
	self.configure(field)
	})
	.collect();
	ast::ExprKind::Struct(path, fields, base)
	}
	_ => expr_kind,
	}
	}

	pub fn configure_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
	self.visit_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);
	}

	self.process_cfg_attrs(expr)
	}

	pub fn configure_stmt(&mut self, stmt: ast::Stmt) -> Option<ast::Stmt> {
	self.configure(stmt)
	}

	pub fn configure_struct_expr_field(&mut self, field: ast::Field) -> Option<ast::Field> {
	self.configure(field)
	}

	pub fn configure_pat(&mut self, pattern: P<ast::Pat>) -> P<ast::Pat> {
	pattern.map(\|mut pattern\| {
	if let ast::PatKind::Struct(path, fields, etc) = pattern.node {
	let fields = fields.into_iter()
	.filter_map(\|field\| {
	self.configure(field)
	})
	.collect();
	pattern.node = ast::PatKind::Struct(path, fields, etc);
	}
	pattern
	})
	}
	}

	impl<'a> fold::Folder for StripUnconfigured<'a> {
	fn fold_foreign_mod(&mut self, foreign_mod: ast::ForeignMod) -> ast::ForeignMod {
	let foreign_mod = self.configure_foreign_mod(foreign_mod);
	fold::noop_fold_foreign_mod(foreign_mod, self)
	}

	fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
	let item = self.configure_item_kind(item);
	fold::noop_fold_item_kind(item, self)
	}

	fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
	let mut expr = self.configure_expr(expr).into_inner();
	expr.node = self.configure_expr_kind(expr.node);
	P(fold::noop_fold_expr(expr, self))
	}

	fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
	let mut expr = configure!(self, expr).into_inner();
	expr.node = self.configure_expr_kind(expr.node);
	Some(P(fold::noop_fold_expr(expr, self)))
	}

	fn fold_stmt(&mut self, stmt: ast::Stmt) -> SmallVector<ast::Stmt> {
	match self.configure_stmt(stmt) {
	Some(stmt) => fold::noop_fold_stmt(stmt, self),
	None => return SmallVector::new(),
	}
	}

	fn fold_item(&mut self, item: P<ast::Item>) -> SmallVector<P<ast::Item>> {
	fold::noop_fold_item(configure!(self, item), self)
	}

	fn fold_impl_item(&mut self, item: ast::ImplItem) -> SmallVector<ast::ImplItem> {
	fold::noop_fold_impl_item(configure!(self, item), self)
	}

	fn fold_trait_item(&mut self, item: ast::TraitItem) -> SmallVector<ast::TraitItem> {
	fold::noop_fold_trait_item(configure!(self, item), self)
	}

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

	fn fold_pat(&mut self, pattern: P<ast::Pat>) -> P<ast::Pat> {
	fold::noop_fold_pat(self.configure_pat(pattern), self)
	}
	}

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

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