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", Active),
69 // A temporary feature gate used to enable parser extensions needed
70 // to bootstrap fix for #5723.
71 ("issue_5723_bootstrap", Active),
73 // These are used to test this portion of the compiler, they don't actually
75 ("test_accepted_feature", Accepted),
76 ("test_removed_feature", Removed),
80 /// Represents an active feature that is currently being implemented or
81 /// currently being considered for addition/removal.
84 /// Represents a feature which has since been removed (it was once Active)
87 /// This language feature has since been Accepted (it was once Active)
91 /// A set of features to be used by later passes.
93 pub default_type_params: Cell<bool>,
94 pub quad_precision_float: Cell<bool>,
95 pub issue_5723_bootstrap: Cell<bool>,
96 pub overloaded_calls: Cell<bool>,
100 pub fn new() -> Features {
102 default_type_params: Cell::new(false),
103 quad_precision_float: Cell::new(false),
104 issue_5723_bootstrap: Cell::new(false),
105 overloaded_calls: Cell::new(false),
111 features: Vec<&'static str>,
115 impl<'a> Context<'a> {
116 fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
117 if !self.has_feature(feature) {
118 self.sess.span_err(span, explain);
119 self.sess.span_note(span, format!("add #![feature({})] to the \
120 crate attributes to enable",
121 feature).as_slice());
125 fn gate_box(&self, span: Span) {
126 self.gate_feature("managed_boxes", span,
127 "The managed box syntax is being replaced by the \
128 `std::gc::Gc` and `std::rc::Rc` types. Equivalent \
129 functionality to managed trait objects will be \
130 implemented but is currently missing.");
133 fn has_feature(&self, feature: &str) -> bool {
134 self.features.iter().any(|n| n.as_slice() == feature)
138 impl<'a> Visitor<()> for Context<'a> {
139 fn visit_ident(&mut self, sp: Span, id: ast::Ident, _: ()) {
140 if !token::get_ident(id).get().is_ascii() {
141 self.gate_feature("non_ascii_idents", sp,
142 "non-ascii idents are not fully supported.");
146 fn visit_view_item(&mut self, i: &ast::ViewItem, _: ()) {
148 ast::ViewItemUse(ref path) => {
150 ast::ViewPathGlob(..) => {
151 self.gate_feature("globs", path.span,
152 "glob import statements are \
153 experimental and possibly buggy");
158 ast::ViewItemExternCrate(..) => {
159 for attr in i.attrs.iter() {
160 if attr.name().get() == "phase"{
161 self.gate_feature("phase", attr.span,
162 "compile time crate loading is \
163 experimental and possibly buggy");
168 visit::walk_view_item(self, i, ())
171 fn visit_item(&mut self, i: &ast::Item, _:()) {
172 for attr in i.attrs.iter() {
173 if attr.name().equiv(&("thread_local")) {
174 self.gate_feature("thread_local", i.span,
175 "`#[thread_local]` is an experimental feature, and does not \
176 currently handle destructors. There is no corresponding \
177 `#[task_local]` mapping to the task model");
181 ast::ItemEnum(ref def, _) => {
182 for variant in def.variants.iter() {
183 match variant.node.kind {
184 ast::StructVariantKind(..) => {
185 self.gate_feature("struct_variant", variant.span,
186 "enum struct variants are \
187 experimental and possibly buggy");
194 ast::ItemForeignMod(ref foreign_module) => {
195 if attr::contains_name(i.attrs.as_slice(), "link_args") {
196 self.gate_feature("link_args", i.span,
197 "the `link_args` attribute is not portable \
198 across platforms, it is recommended to \
199 use `#[link(name = \"foo\")]` instead")
201 if foreign_module.abi == RustIntrinsic {
202 self.gate_feature("intrinsics",
204 "intrinsics are subject to change")
209 if attr::contains_name(i.attrs.as_slice(), "plugin_registrar") {
210 self.gate_feature("plugin_registrar", i.span,
211 "compiler plugins are experimental and possibly buggy");
215 ast::ItemStruct(struct_definition, _) => {
216 if attr::contains_name(i.attrs.as_slice(), "simd") {
217 self.gate_feature("simd", i.span,
218 "SIMD types are experimental and possibly buggy");
220 match struct_definition.super_struct {
221 Some(ref path) => self.gate_feature("struct_inherit", path.span,
222 "struct inheritance is experimental \
223 and possibly buggy"),
226 if struct_definition.is_virtual {
227 self.gate_feature("struct_inherit", i.span,
228 "struct inheritance (`virtual` keyword) is \
229 experimental and possibly buggy");
233 ast::ItemImpl(..) => {
234 if attr::contains_name(i.attrs.as_slice(),
235 "unsafe_destructor") {
236 self.gate_feature("unsafe_destructor",
238 "`#[unsafe_destructor]` allows too \
239 many unsafe patterns and may be \
240 removed in the future");
247 visit::walk_item(self, i, ());
250 fn visit_mac(&mut self, macro: &ast::Mac, _: ()) {
251 let ast::MacInvocTT(ref path, _, _) = macro.node;
252 let id = path.segments.last().unwrap().identifier;
253 let quotes = ["quote_tokens", "quote_expr", "quote_ty",
254 "quote_item", "quote_pat", "quote_stmt"];
255 let msg = " is not stable enough for use and are subject to change";
258 if id == token::str_to_ident("macro_rules") {
259 self.gate_feature("macro_rules", path.span, "macro definitions are \
260 not stable enough for use and are subject to change");
263 else if id == token::str_to_ident("asm") {
264 self.gate_feature("asm", path.span, "inline assembly is not \
265 stable enough for use and is subject to change");
268 else if id == token::str_to_ident("log_syntax") {
269 self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
270 stable enough for use and is subject to change");
273 else if id == token::str_to_ident("trace_macros") {
274 self.gate_feature("trace_macros", path.span, "`trace_macros` is not \
275 stable enough for use and is subject to change");
278 else if id == token::str_to_ident("concat_idents") {
279 self.gate_feature("concat_idents", path.span, "`concat_idents` is not \
280 stable enough for use and is subject to change");
284 for "e in quotes.iter() {
285 if id == token::str_to_ident(quote) {
286 self.gate_feature("quote",
288 format!("{}{}", quote, msg).as_slice());
294 fn visit_foreign_item(&mut self, i: &ast::ForeignItem, _: ()) {
295 if attr::contains_name(i.attrs.as_slice(), "linkage") {
296 self.gate_feature("linkage", i.span,
297 "the `linkage` attribute is experimental \
298 and not portable across platforms")
300 visit::walk_foreign_item(self, i, ())
303 fn visit_ty(&mut self, t: &ast::Ty, _: ()) {
305 ast::TyClosure(closure, _) if closure.onceness == ast::Once => {
306 self.gate_feature("once_fns", t.span,
307 "once functions are \
308 experimental and likely to be removed");
311 ast::TyBox(_) => { self.gate_box(t.span); }
312 ast::TyUnboxedFn(_) => {
313 self.gate_feature("unboxed_closure_sugar",
315 "unboxed closure trait sugar is experimental");
320 visit::walk_ty(self, t, ());
323 fn visit_expr(&mut self, e: &ast::Expr, _: ()) {
325 ast::ExprUnary(ast::UnBox, _) => {
326 self.gate_box(e.span);
330 visit::walk_expr(self, e, ());
333 fn visit_generics(&mut self, generics: &ast::Generics, _: ()) {
334 for type_parameter in generics.ty_params.iter() {
335 match type_parameter.default {
337 self.gate_feature("default_type_params", ty.span,
338 "default type parameters are \
339 experimental and possibly buggy");
344 visit::walk_generics(self, generics, ());
347 fn visit_attribute(&mut self, attr: &ast::Attribute, _: ()) {
348 if attr::contains_name([*attr], "lang") {
349 self.gate_feature("lang_items",
351 "language items are subject to change");
355 fn visit_fn(&mut self,
356 fn_kind: &visit::FnKind,
357 fn_decl: &ast::FnDecl,
363 visit::FkItemFn(_, _, _, ref abi) if *abi == RustIntrinsic => {
364 self.gate_feature("intrinsics",
366 "intrinsics are subject to change")
370 visit::walk_fn(self, fn_kind, fn_decl, block, span, ());
374 pub fn check_crate(sess: &Session, krate: &ast::Crate) {
375 let mut cx = Context {
376 features: Vec::new(),
380 for attr in krate.attrs.iter() {
381 if !attr.check_name("feature") {
385 match attr.meta_item_list() {
387 sess.span_err(attr.span, "malformed feature attribute, \
388 expected #![feature(...)]");
391 for &mi in list.iter() {
392 let name = match mi.node {
393 ast::MetaWord(ref word) => (*word).clone(),
395 sess.span_err(mi.span,
396 "malformed feature, expected just \
401 match KNOWN_FEATURES.iter()
402 .find(|& &(n, _)| name.equiv(&n)) {
403 Some(&(name, Active)) => { cx.features.push(name); }
404 Some(&(_, Removed)) => {
405 sess.span_err(mi.span, "feature has been removed");
407 Some(&(_, Accepted)) => {
408 sess.span_warn(mi.span, "feature has added to rust, \
409 directive not necessary");
412 sess.add_lint(lint::UnknownFeatures,
415 "unknown feature".to_string());
423 visit::walk_crate(&mut cx, krate, ());
425 sess.abort_if_errors();
427 sess.features.default_type_params.set(cx.has_feature("default_type_params"));
428 sess.features.quad_precision_float.set(cx.has_feature("quad_precision_float"));
429 sess.features.issue_5723_bootstrap.set(cx.has_feature("issue_5723_bootstrap"));
430 sess.features.overloaded_calls.set(cx.has_feature("overloaded_calls"));