1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 //! This modules implements the gating necessary for preventing certain compiler
14 //! features from being used by default. This module will crawl a pre-expanded
15 //! AST to ensure that there are no features which are used that are not
18 //! Features are enabled in programs via the crate-level attributes of
19 //! `#![feature(...)]` with a comma-separated list of features.
23 use syntax::abi::RustIntrinsic;
24 use syntax::ast::NodeId;
27 use syntax::attr::AttrMetaMethods;
28 use syntax::codemap::Span;
30 use syntax::visit::Visitor;
31 use syntax::parse::token;
33 use driver::session::Session;
37 /// This is a list of all known features since the beginning of time. This list
38 /// can never shrink, it may only be expanded (in order to prevent old programs
39 /// from failing to compile). The status of each feature may change, however.
40 static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
42 ("macro_rules", Active),
43 ("struct_variant", Active),
46 ("managed_boxes", Active),
47 ("non_ascii_idents", Active),
48 ("thread_local", Active),
49 ("link_args", Active),
51 ("plugin_registrar", Active),
52 ("log_syntax", Active),
53 ("trace_macros", Active),
54 ("concat_idents", Active),
55 ("unsafe_destructor", Active),
56 ("intrinsics", Active),
57 ("lang_items", Active),
60 ("default_type_params", Active),
63 ("struct_inherit", Active),
64 ("overloaded_calls", Active),
65 ("unboxed_closure_sugar", Active),
67 ("quad_precision_float", Removed),
69 ("rustc_diagnostic_macros", Active),
70 ("unboxed_closures", Active),
72 // A temporary feature gate used to enable parser extensions needed
73 // to bootstrap fix for #5723.
74 ("issue_5723_bootstrap", Active),
76 // These are used to test this portion of the compiler, they don't actually
78 ("test_accepted_feature", Accepted),
79 ("test_removed_feature", Removed),
83 /// Represents an active feature that is currently being implemented or
84 /// currently being considered for addition/removal.
87 /// Represents a feature which has since been removed (it was once Active)
90 /// This language feature has since been Accepted (it was once Active)
94 /// A set of features to be used by later passes.
96 pub default_type_params: Cell<bool>,
97 pub issue_5723_bootstrap: Cell<bool>,
98 pub overloaded_calls: Cell<bool>,
99 pub rustc_diagnostic_macros: Cell<bool>
103 pub fn new() -> Features {
105 default_type_params: Cell::new(false),
106 issue_5723_bootstrap: Cell::new(false),
107 overloaded_calls: Cell::new(false),
108 rustc_diagnostic_macros: Cell::new(false)
114 features: Vec<&'static str>,
118 impl<'a> Context<'a> {
119 fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
120 if !self.has_feature(feature) {
121 self.sess.span_err(span, explain);
122 self.sess.span_note(span, format!("add #![feature({})] to the \
123 crate attributes to enable",
124 feature).as_slice());
128 fn gate_box(&self, span: Span) {
129 self.gate_feature("managed_boxes", span,
130 "The managed box syntax is being replaced by the \
131 `std::gc::Gc` and `std::rc::Rc` types. Equivalent \
132 functionality to managed trait objects will be \
133 implemented but is currently missing.");
136 fn has_feature(&self, feature: &str) -> bool {
137 self.features.iter().any(|n| n.as_slice() == feature)
141 impl<'a> Visitor<()> for Context<'a> {
142 fn visit_ident(&mut self, sp: Span, id: ast::Ident, _: ()) {
143 if !token::get_ident(id).get().is_ascii() {
144 self.gate_feature("non_ascii_idents", sp,
145 "non-ascii idents are not fully supported.");
149 fn visit_view_item(&mut self, i: &ast::ViewItem, _: ()) {
151 ast::ViewItemUse(ref path) => {
153 ast::ViewPathGlob(..) => {
154 self.gate_feature("globs", path.span,
155 "glob import statements are \
156 experimental and possibly buggy");
161 ast::ViewItemExternCrate(..) => {
162 for attr in i.attrs.iter() {
163 if attr.name().get() == "phase"{
164 self.gate_feature("phase", attr.span,
165 "compile time crate loading is \
166 experimental and possibly buggy");
171 visit::walk_view_item(self, i, ())
174 fn visit_item(&mut self, i: &ast::Item, _:()) {
175 for attr in i.attrs.iter() {
176 if attr.name().equiv(&("thread_local")) {
177 self.gate_feature("thread_local", i.span,
178 "`#[thread_local]` is an experimental feature, and does not \
179 currently handle destructors. There is no corresponding \
180 `#[task_local]` mapping to the task model");
184 ast::ItemEnum(ref def, _) => {
185 for variant in def.variants.iter() {
186 match variant.node.kind {
187 ast::StructVariantKind(..) => {
188 self.gate_feature("struct_variant", variant.span,
189 "enum struct variants are \
190 experimental and possibly buggy");
197 ast::ItemForeignMod(ref foreign_module) => {
198 if attr::contains_name(i.attrs.as_slice(), "link_args") {
199 self.gate_feature("link_args", i.span,
200 "the `link_args` attribute is not portable \
201 across platforms, it is recommended to \
202 use `#[link(name = \"foo\")]` instead")
204 if foreign_module.abi == RustIntrinsic {
205 self.gate_feature("intrinsics",
207 "intrinsics are subject to change")
212 if attr::contains_name(i.attrs.as_slice(), "plugin_registrar") {
213 self.gate_feature("plugin_registrar", i.span,
214 "compiler plugins are experimental and possibly buggy");
218 ast::ItemStruct(struct_definition, _) => {
219 if attr::contains_name(i.attrs.as_slice(), "simd") {
220 self.gate_feature("simd", i.span,
221 "SIMD types are experimental and possibly buggy");
223 match struct_definition.super_struct {
224 Some(ref path) => self.gate_feature("struct_inherit", path.span,
225 "struct inheritance is experimental \
226 and possibly buggy"),
229 if struct_definition.is_virtual {
230 self.gate_feature("struct_inherit", i.span,
231 "struct inheritance (`virtual` keyword) is \
232 experimental and possibly buggy");
236 ast::ItemImpl(..) => {
237 if attr::contains_name(i.attrs.as_slice(),
238 "unsafe_destructor") {
239 self.gate_feature("unsafe_destructor",
241 "`#[unsafe_destructor]` allows too \
242 many unsafe patterns and may be \
243 removed in the future");
250 visit::walk_item(self, i, ());
253 fn visit_mac(&mut self, macro: &ast::Mac, _: ()) {
254 let ast::MacInvocTT(ref path, _, _) = macro.node;
255 let id = path.segments.last().unwrap().identifier;
256 let quotes = ["quote_tokens", "quote_expr", "quote_ty",
257 "quote_item", "quote_pat", "quote_stmt"];
258 let msg = " is not stable enough for use and are subject to change";
261 if id == token::str_to_ident("macro_rules") {
262 self.gate_feature("macro_rules", path.span, "macro definitions are \
263 not stable enough for use and are subject to change");
266 else if id == token::str_to_ident("asm") {
267 self.gate_feature("asm", path.span, "inline assembly is not \
268 stable enough for use and is subject to change");
271 else if id == token::str_to_ident("log_syntax") {
272 self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
273 stable enough for use and is subject to change");
276 else if id == token::str_to_ident("trace_macros") {
277 self.gate_feature("trace_macros", path.span, "`trace_macros` is not \
278 stable enough for use and is subject to change");
281 else if id == token::str_to_ident("concat_idents") {
282 self.gate_feature("concat_idents", path.span, "`concat_idents` is not \
283 stable enough for use and is subject to change");
287 for "e in quotes.iter() {
288 if id == token::str_to_ident(quote) {
289 self.gate_feature("quote",
291 format!("{}{}", quote, msg).as_slice());
297 fn visit_foreign_item(&mut self, i: &ast::ForeignItem, _: ()) {
298 if attr::contains_name(i.attrs.as_slice(), "linkage") {
299 self.gate_feature("linkage", i.span,
300 "the `linkage` attribute is experimental \
301 and not portable across platforms")
303 visit::walk_foreign_item(self, i, ())
306 fn visit_ty(&mut self, t: &ast::Ty, _: ()) {
308 ast::TyClosure(closure, _) if closure.onceness == ast::Once => {
309 self.gate_feature("once_fns", t.span,
310 "once functions are \
311 experimental and likely to be removed");
314 ast::TyBox(_) => { self.gate_box(t.span); }
315 ast::TyUnboxedFn(_) => {
316 self.gate_feature("unboxed_closure_sugar",
318 "unboxed closure trait sugar is experimental");
323 visit::walk_ty(self, t, ());
326 fn visit_expr(&mut self, e: &ast::Expr, _: ()) {
328 ast::ExprUnary(ast::UnBox, _) => {
329 self.gate_box(e.span);
331 ast::ExprUnboxedFn(..) => {
332 self.gate_feature("unboxed_closures",
334 "unboxed closures are a work-in-progress \
335 feature with known bugs");
339 visit::walk_expr(self, e, ());
342 fn visit_generics(&mut self, generics: &ast::Generics, _: ()) {
343 for type_parameter in generics.ty_params.iter() {
344 match type_parameter.default {
346 self.gate_feature("default_type_params", ty.span,
347 "default type parameters are \
348 experimental and possibly buggy");
353 visit::walk_generics(self, generics, ());
356 fn visit_attribute(&mut self, attr: &ast::Attribute, _: ()) {
357 if attr::contains_name([*attr], "lang") {
358 self.gate_feature("lang_items",
360 "language items are subject to change");
364 fn visit_fn(&mut self,
365 fn_kind: &visit::FnKind,
366 fn_decl: &ast::FnDecl,
372 visit::FkItemFn(_, _, _, ref abi) if *abi == RustIntrinsic => {
373 self.gate_feature("intrinsics",
375 "intrinsics are subject to change")
379 visit::walk_fn(self, fn_kind, fn_decl, block, span, ());
383 pub fn check_crate(sess: &Session, krate: &ast::Crate) {
384 let mut cx = Context {
385 features: Vec::new(),
389 for attr in krate.attrs.iter() {
390 if !attr.check_name("feature") {
394 match attr.meta_item_list() {
396 sess.span_err(attr.span, "malformed feature attribute, \
397 expected #![feature(...)]");
400 for &mi in list.iter() {
401 let name = match mi.node {
402 ast::MetaWord(ref word) => (*word).clone(),
404 sess.span_err(mi.span,
405 "malformed feature, expected just \
410 match KNOWN_FEATURES.iter()
411 .find(|& &(n, _)| name.equiv(&n)) {
412 Some(&(name, Active)) => { cx.features.push(name); }
413 Some(&(_, Removed)) => {
414 sess.span_err(mi.span, "feature has been removed");
416 Some(&(_, Accepted)) => {
417 sess.span_warn(mi.span, "feature has added to rust, \
418 directive not necessary");
421 sess.add_lint(lint::builtin::UNKNOWN_FEATURES,
424 "unknown feature".to_string());
432 visit::walk_crate(&mut cx, krate, ());
434 sess.abort_if_errors();
436 sess.features.default_type_params.set(cx.has_feature("default_type_params"));
437 sess.features.issue_5723_bootstrap.set(cx.has_feature("issue_5723_bootstrap"));
438 sess.features.overloaded_calls.set(cx.has_feature("overloaded_calls"));
439 sess.features.rustc_diagnostic_macros.set(cx.has_feature("rustc_diagnostic_macros"));