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),
71 ("import_shadowing", Active),
72 ("advanced_slice_patterns", Active),
74 // if you change this list without updating src/doc/rust.md, cmr will be sad
76 // A temporary feature gate used to enable parser extensions needed
77 // to bootstrap fix for #5723.
78 ("issue_5723_bootstrap", Accepted),
80 // These are used to test this portion of the compiler, they don't actually
82 ("test_accepted_feature", Accepted),
83 ("test_removed_feature", Removed),
87 /// Represents an active feature that is currently being implemented or
88 /// currently being considered for addition/removal.
91 /// Represents a feature which has since been removed (it was once Active)
94 /// This language feature has since been Accepted (it was once Active)
98 /// A set of features to be used by later passes.
100 pub default_type_params: Cell<bool>,
101 pub overloaded_calls: Cell<bool>,
102 pub rustc_diagnostic_macros: Cell<bool>,
103 pub import_shadowing: Cell<bool>,
107 pub fn new() -> Features {
109 default_type_params: Cell::new(false),
110 overloaded_calls: Cell::new(false),
111 rustc_diagnostic_macros: Cell::new(false),
112 import_shadowing: Cell::new(false),
118 features: Vec<&'static str>,
122 impl<'a> Context<'a> {
123 fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
124 if !self.has_feature(feature) {
125 self.sess.span_err(span, explain);
126 self.sess.span_note(span, format!("add #![feature({})] to the \
127 crate attributes to enable",
128 feature).as_slice());
132 fn gate_box(&self, span: Span) {
133 self.gate_feature("managed_boxes", span,
134 "The managed box syntax is being replaced by the \
135 `std::gc::Gc` and `std::rc::Rc` types. Equivalent \
136 functionality to managed trait objects will be \
137 implemented but is currently missing.");
140 fn has_feature(&self, feature: &str) -> bool {
141 self.features.iter().any(|n| n.as_slice() == feature)
145 impl<'a> Visitor<()> for Context<'a> {
146 fn visit_ident(&mut self, sp: Span, id: ast::Ident, _: ()) {
147 if !token::get_ident(id).get().is_ascii() {
148 self.gate_feature("non_ascii_idents", sp,
149 "non-ascii idents are not fully supported.");
153 fn visit_view_item(&mut self, i: &ast::ViewItem, _: ()) {
155 ast::ViewItemUse(ref path) => {
157 ast::ViewPathGlob(..) => {
158 self.gate_feature("globs", path.span,
159 "glob import statements are \
160 experimental and possibly buggy");
165 ast::ViewItemExternCrate(..) => {
166 for attr in i.attrs.iter() {
167 if attr.name().get() == "phase"{
168 self.gate_feature("phase", attr.span,
169 "compile time crate loading is \
170 experimental and possibly buggy");
175 visit::walk_view_item(self, i, ())
178 fn visit_item(&mut self, i: &ast::Item, _:()) {
179 for attr in i.attrs.iter() {
180 if attr.name().equiv(&("thread_local")) {
181 self.gate_feature("thread_local", i.span,
182 "`#[thread_local]` is an experimental feature, and does not \
183 currently handle destructors. There is no corresponding \
184 `#[task_local]` mapping to the task model");
188 ast::ItemEnum(ref def, _) => {
189 for variant in def.variants.iter() {
190 match variant.node.kind {
191 ast::StructVariantKind(..) => {
192 self.gate_feature("struct_variant", variant.span,
193 "enum struct variants are \
194 experimental and possibly buggy");
201 ast::ItemForeignMod(ref foreign_module) => {
202 if attr::contains_name(i.attrs.as_slice(), "link_args") {
203 self.gate_feature("link_args", i.span,
204 "the `link_args` attribute is not portable \
205 across platforms, it is recommended to \
206 use `#[link(name = \"foo\")]` instead")
208 if foreign_module.abi == RustIntrinsic {
209 self.gate_feature("intrinsics",
211 "intrinsics are subject to change")
216 if attr::contains_name(i.attrs.as_slice(), "plugin_registrar") {
217 self.gate_feature("plugin_registrar", i.span,
218 "compiler plugins are experimental and possibly buggy");
222 ast::ItemStruct(struct_definition, _) => {
223 if attr::contains_name(i.attrs.as_slice(), "simd") {
224 self.gate_feature("simd", i.span,
225 "SIMD types are experimental and possibly buggy");
227 match struct_definition.super_struct {
228 Some(ref path) => self.gate_feature("struct_inherit", path.span,
229 "struct inheritance is experimental \
230 and possibly buggy"),
233 if struct_definition.is_virtual {
234 self.gate_feature("struct_inherit", i.span,
235 "struct inheritance (`virtual` keyword) is \
236 experimental and possibly buggy");
240 ast::ItemImpl(..) => {
241 if attr::contains_name(i.attrs.as_slice(),
242 "unsafe_destructor") {
243 self.gate_feature("unsafe_destructor",
245 "`#[unsafe_destructor]` allows too \
246 many unsafe patterns and may be \
247 removed in the future");
254 visit::walk_item(self, i, ());
257 fn visit_mac(&mut self, macro: &ast::Mac, _: ()) {
258 let ast::MacInvocTT(ref path, _, _) = macro.node;
259 let id = path.segments.last().unwrap().identifier;
260 let quotes = ["quote_tokens", "quote_expr", "quote_ty",
261 "quote_item", "quote_pat", "quote_stmt"];
262 let msg = " is not stable enough for use and are subject to change";
265 if id == token::str_to_ident("macro_rules") {
266 self.gate_feature("macro_rules", path.span, "macro definitions are \
267 not stable enough for use and are subject to change");
270 else if id == token::str_to_ident("asm") {
271 self.gate_feature("asm", path.span, "inline assembly is not \
272 stable enough for use and is subject to change");
275 else if id == token::str_to_ident("log_syntax") {
276 self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
277 stable enough for use and is subject to change");
280 else if id == token::str_to_ident("trace_macros") {
281 self.gate_feature("trace_macros", path.span, "`trace_macros` is not \
282 stable enough for use and is subject to change");
285 else if id == token::str_to_ident("concat_idents") {
286 self.gate_feature("concat_idents", path.span, "`concat_idents` is not \
287 stable enough for use and is subject to change");
291 for "e in quotes.iter() {
292 if id == token::str_to_ident(quote) {
293 self.gate_feature("quote",
295 format!("{}{}", quote, msg).as_slice());
301 fn visit_foreign_item(&mut self, i: &ast::ForeignItem, _: ()) {
302 if attr::contains_name(i.attrs.as_slice(), "linkage") {
303 self.gate_feature("linkage", i.span,
304 "the `linkage` attribute is experimental \
305 and not portable across platforms")
307 visit::walk_foreign_item(self, i, ())
310 fn visit_ty(&mut self, t: &ast::Ty, _: ()) {
312 ast::TyClosure(closure) if closure.onceness == ast::Once => {
313 self.gate_feature("once_fns", t.span,
314 "once functions are \
315 experimental and likely to be removed");
318 ast::TyBox(_) => { self.gate_box(t.span); }
319 ast::TyUnboxedFn(..) => {
320 self.gate_feature("unboxed_closure_sugar",
322 "unboxed closure trait sugar is experimental");
327 visit::walk_ty(self, t, ());
330 fn visit_expr(&mut self, e: &ast::Expr, _: ()) {
332 ast::ExprUnary(ast::UnBox, _) => {
333 self.gate_box(e.span);
335 ast::ExprUnboxedFn(..) => {
336 self.gate_feature("unboxed_closures",
338 "unboxed closures are a work-in-progress \
339 feature with known bugs");
343 visit::walk_expr(self, e, ());
346 fn visit_generics(&mut self, generics: &ast::Generics, _: ()) {
347 for type_parameter in generics.ty_params.iter() {
348 match type_parameter.default {
350 self.gate_feature("default_type_params", ty.span,
351 "default type parameters are \
352 experimental and possibly buggy");
357 visit::walk_generics(self, generics, ());
360 fn visit_attribute(&mut self, attr: &ast::Attribute, _: ()) {
361 if attr::contains_name([*attr], "lang") {
362 self.gate_feature("lang_items",
364 "language items are subject to change");
368 fn visit_pat(&mut self, pattern: &ast::Pat, (): ()) {
370 ast::PatVec(_, Some(_), ref last) if !last.is_empty() => {
371 self.gate_feature("advanced_slice_patterns",
373 "multiple-element slice matches anywhere \
374 but at the end of a slice (e.g. \
375 `[0, ..xs, 0]` are experimental")
379 visit::walk_pat(self, pattern, ())
382 fn visit_fn(&mut self,
383 fn_kind: &visit::FnKind,
384 fn_decl: &ast::FnDecl,
390 visit::FkItemFn(_, _, _, ref abi) if *abi == RustIntrinsic => {
391 self.gate_feature("intrinsics",
393 "intrinsics are subject to change")
397 visit::walk_fn(self, fn_kind, fn_decl, block, span, ());
401 pub fn check_crate(sess: &Session, krate: &ast::Crate) {
402 let mut cx = Context {
403 features: Vec::new(),
407 for attr in krate.attrs.iter() {
408 if !attr.check_name("feature") {
412 match attr.meta_item_list() {
414 sess.span_err(attr.span, "malformed feature attribute, \
415 expected #![feature(...)]");
418 for &mi in list.iter() {
419 let name = match mi.node {
420 ast::MetaWord(ref word) => (*word).clone(),
422 sess.span_err(mi.span,
423 "malformed feature, expected just \
428 match KNOWN_FEATURES.iter()
429 .find(|& &(n, _)| name.equiv(&n)) {
430 Some(&(name, Active)) => { cx.features.push(name); }
431 Some(&(_, Removed)) => {
432 sess.span_err(mi.span, "feature has been removed");
434 Some(&(_, Accepted)) => {
435 sess.span_warn(mi.span, "feature has been added to Rust, \
436 directive not necessary");
439 sess.add_lint(lint::builtin::UNKNOWN_FEATURES,
442 "unknown feature".to_string());
450 visit::walk_crate(&mut cx, krate, ());
452 sess.abort_if_errors();
454 sess.features.default_type_params.set(cx.has_feature("default_type_params"));
455 sess.features.overloaded_calls.set(cx.has_feature("overloaded_calls"));
456 sess.features.rustc_diagnostic_macros.set(cx.has_feature("rustc_diagnostic_macros"));
457 sess.features.import_shadowing.set(cx.has_feature("import_shadowing"));