/
feature_gate.rs
483 lines (431 loc) · 17.7 KB
/
feature_gate.rs
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// Copyright 2013 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.
//! Feature gating
//!
//! This modules implements the gating necessary for preventing certain compiler
//! features from being used by default. This module will crawl a pre-expanded
//! AST to ensure that there are no features which are used that are not
//! enabled.
//!
//! Features are enabled in programs via the crate-level attributes of
//! `#![feature(...)]` with a comma-separated list of features.
use abi::RustIntrinsic;
use ast::NodeId;
use ast;
use attr;
use attr::AttrMetaMethods;
use codemap::Span;
use diagnostic::SpanHandler;
use visit;
use visit::Visitor;
use parse::token;
use std::slice;
/// This is a list of all known features since the beginning of time. This list
/// can never shrink, it may only be expanded (in order to prevent old programs
/// from failing to compile). The status of each feature may change, however.
static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
("globs", Active),
("macro_rules", Active),
("struct_variant", Active),
("once_fns", Active),
("asm", Active),
("managed_boxes", Removed),
("non_ascii_idents", Active),
("thread_local", Active),
("link_args", Active),
("phase", Active),
("plugin_registrar", Active),
("log_syntax", Active),
("trace_macros", Active),
("concat_idents", Active),
("unsafe_destructor", Active),
("intrinsics", Active),
("lang_items", Active),
("simd", Active),
("default_type_params", Active),
("quote", Active),
("linkage", Active),
("struct_inherit", Active),
("overloaded_calls", Active),
("unboxed_closure_sugar", Active),
("quad_precision_float", Removed),
("rustc_diagnostic_macros", Active),
("unboxed_closures", Active),
("import_shadowing", Active),
("advanced_slice_patterns", Active),
("tuple_indexing", Active),
("associated_types", Active),
("visible_private_types", Active),
("slicing_syntax", Active),
("if_let", Active),
("while_let", Active),
// if you change this list without updating src/doc/reference.md, cmr will be sad
// A temporary feature gate used to enable parser extensions needed
// to bootstrap fix for #5723.
("issue_5723_bootstrap", Accepted),
// These are used to test this portion of the compiler, they don't actually
// mean anything
("test_accepted_feature", Accepted),
("test_removed_feature", Removed),
];
enum Status {
/// Represents an active feature that is currently being implemented or
/// currently being considered for addition/removal.
Active,
/// Represents a feature which has since been removed (it was once Active)
Removed,
/// This language feature has since been Accepted (it was once Active)
Accepted,
}
/// A set of features to be used by later passes.
pub struct Features {
pub default_type_params: bool,
pub overloaded_calls: bool,
pub rustc_diagnostic_macros: bool,
pub import_shadowing: bool,
pub visible_private_types: bool,
pub quote: bool,
}
impl Features {
pub fn new() -> Features {
Features {
default_type_params: false,
overloaded_calls: false,
rustc_diagnostic_macros: false,
import_shadowing: false,
visible_private_types: false,
quote: false,
}
}
}
struct Context<'a> {
features: Vec<&'static str>,
span_handler: &'a SpanHandler,
}
impl<'a> Context<'a> {
fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
if !self.has_feature(feature) {
self.span_handler.span_err(span, explain);
self.span_handler.span_note(span, format!("add #![feature({})] to the \
crate attributes to enable",
feature).as_slice());
}
}
fn has_feature(&self, feature: &str) -> bool {
self.features.iter().any(|n| n.as_slice() == feature)
}
}
impl<'a, 'v> Visitor<'v> for Context<'a> {
fn visit_ident(&mut self, sp: Span, id: ast::Ident) {
if !token::get_ident(id).get().is_ascii() {
self.gate_feature("non_ascii_idents", sp,
"non-ascii idents are not fully supported.");
}
}
fn visit_view_item(&mut self, i: &ast::ViewItem) {
match i.node {
ast::ViewItemUse(ref path) => {
match path.node {
ast::ViewPathGlob(..) => {
self.gate_feature("globs", path.span,
"glob import statements are \
experimental and possibly buggy");
}
_ => {}
}
}
ast::ViewItemExternCrate(..) => {
for attr in i.attrs.iter() {
if attr.name().get() == "phase"{
self.gate_feature("phase", attr.span,
"compile time crate loading is \
experimental and possibly buggy");
}
}
}
}
visit::walk_view_item(self, i)
}
fn visit_item(&mut self, i: &ast::Item) {
for attr in i.attrs.iter() {
if attr.name().equiv(&("thread_local")) {
self.gate_feature("thread_local", i.span,
"`#[thread_local]` is an experimental feature, and does not \
currently handle destructors. There is no corresponding \
`#[task_local]` mapping to the task model");
}
}
match i.node {
ast::ItemEnum(ref def, _) => {
for variant in def.variants.iter() {
match variant.node.kind {
ast::StructVariantKind(..) => {
self.gate_feature("struct_variant", variant.span,
"enum struct variants are \
experimental and possibly buggy");
}
_ => {}
}
}
}
ast::ItemForeignMod(ref foreign_module) => {
if attr::contains_name(i.attrs.as_slice(), "link_args") {
self.gate_feature("link_args", i.span,
"the `link_args` attribute is not portable \
across platforms, it is recommended to \
use `#[link(name = \"foo\")]` instead")
}
if foreign_module.abi == RustIntrinsic {
self.gate_feature("intrinsics",
i.span,
"intrinsics are subject to change")
}
}
ast::ItemFn(..) => {
if attr::contains_name(i.attrs.as_slice(), "plugin_registrar") {
self.gate_feature("plugin_registrar", i.span,
"compiler plugins are experimental and possibly buggy");
}
}
ast::ItemStruct(ref struct_definition, _) => {
if attr::contains_name(i.attrs.as_slice(), "simd") {
self.gate_feature("simd", i.span,
"SIMD types are experimental and possibly buggy");
}
match struct_definition.super_struct {
Some(ref path) => self.gate_feature("struct_inherit", path.span,
"struct inheritance is experimental \
and possibly buggy"),
None => {}
}
if struct_definition.is_virtual {
self.gate_feature("struct_inherit", i.span,
"struct inheritance (`virtual` keyword) is \
experimental and possibly buggy");
}
}
ast::ItemImpl(_, _, _, ref items) => {
if attr::contains_name(i.attrs.as_slice(),
"unsafe_destructor") {
self.gate_feature("unsafe_destructor",
i.span,
"`#[unsafe_destructor]` allows too \
many unsafe patterns and may be \
removed in the future");
}
for item in items.iter() {
match *item {
ast::MethodImplItem(_) => {}
ast::TypeImplItem(ref typedef) => {
self.gate_feature("associated_types",
typedef.span,
"associated types are \
experimental")
}
}
}
}
_ => {}
}
visit::walk_item(self, i);
}
fn visit_trait_item(&mut self, trait_item: &ast::TraitItem) {
match *trait_item {
ast::RequiredMethod(_) | ast::ProvidedMethod(_) => {}
ast::TypeTraitItem(ref ti) => {
self.gate_feature("associated_types",
ti.span,
"associated types are experimental")
}
}
}
fn visit_mac(&mut self, macro: &ast::Mac) {
let ast::MacInvocTT(ref path, _, _) = macro.node;
let id = path.segments.last().unwrap().identifier;
if id == token::str_to_ident("macro_rules") {
self.gate_feature("macro_rules", path.span, "macro definitions are \
not stable enough for use and are subject to change");
}
else if id == token::str_to_ident("asm") {
self.gate_feature("asm", path.span, "inline assembly is not \
stable enough for use and is subject to change");
}
else if id == token::str_to_ident("log_syntax") {
self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
stable enough for use and is subject to change");
}
else if id == token::str_to_ident("trace_macros") {
self.gate_feature("trace_macros", path.span, "`trace_macros` is not \
stable enough for use and is subject to change");
}
else if id == token::str_to_ident("concat_idents") {
self.gate_feature("concat_idents", path.span, "`concat_idents` is not \
stable enough for use and is subject to change");
}
}
fn visit_foreign_item(&mut self, i: &ast::ForeignItem) {
if attr::contains_name(i.attrs.as_slice(), "linkage") {
self.gate_feature("linkage", i.span,
"the `linkage` attribute is experimental \
and not portable across platforms")
}
visit::walk_foreign_item(self, i)
}
fn visit_ty(&mut self, t: &ast::Ty) {
match t.node {
ast::TyClosure(ref closure) if closure.onceness == ast::Once => {
self.gate_feature("once_fns", t.span,
"once functions are \
experimental and likely to be removed");
},
ast::TyUnboxedFn(..) => {
self.gate_feature("unboxed_closure_sugar",
t.span,
"unboxed closure trait sugar is experimental");
}
_ => {}
}
visit::walk_ty(self, t);
}
fn visit_expr(&mut self, e: &ast::Expr) {
match e.node {
ast::ExprUnboxedFn(..) => {
self.gate_feature("unboxed_closures",
e.span,
"unboxed closures are a work-in-progress \
feature with known bugs");
}
ast::ExprTupField(..) => {
self.gate_feature("tuple_indexing",
e.span,
"tuple indexing is experimental");
}
ast::ExprIfLet(..) => {
self.gate_feature("if_let", e.span,
"`if let` syntax is experimental");
}
ast::ExprSlice(..) => {
self.gate_feature("slicing_syntax",
e.span,
"slicing syntax is experimental");
}
ast::ExprWhileLet(..) => {
self.gate_feature("while_let", e.span,
"`while let` syntax is experimental");
}
_ => {}
}
visit::walk_expr(self, e);
}
fn visit_generics(&mut self, generics: &ast::Generics) {
for type_parameter in generics.ty_params.iter() {
match type_parameter.default {
Some(ref ty) => {
self.gate_feature("default_type_params", ty.span,
"default type parameters are \
experimental and possibly buggy");
}
None => {}
}
}
visit::walk_generics(self, generics);
}
fn visit_attribute(&mut self, attr: &ast::Attribute) {
if attr::contains_name(slice::ref_slice(attr), "lang") {
self.gate_feature("lang_items",
attr.span,
"language items are subject to change");
}
}
fn visit_pat(&mut self, pattern: &ast::Pat) {
match pattern.node {
ast::PatVec(_, Some(_), ref last) if !last.is_empty() => {
self.gate_feature("advanced_slice_patterns",
pattern.span,
"multiple-element slice matches anywhere \
but at the end of a slice (e.g. \
`[0, ..xs, 0]` are experimental")
}
_ => {}
}
visit::walk_pat(self, pattern)
}
fn visit_fn(&mut self,
fn_kind: visit::FnKind<'v>,
fn_decl: &'v ast::FnDecl,
block: &'v ast::Block,
span: Span,
_: NodeId) {
match fn_kind {
visit::FkItemFn(_, _, _, abi) if abi == RustIntrinsic => {
self.gate_feature("intrinsics",
span,
"intrinsics are subject to change")
}
_ => {}
}
visit::walk_fn(self, fn_kind, fn_decl, block, span);
}
}
pub fn check_crate(span_handler: &SpanHandler, krate: &ast::Crate) -> (Features, Vec<Span>) {
let mut cx = Context {
features: Vec::new(),
span_handler: span_handler,
};
let mut unknown_features = Vec::new();
for attr in krate.attrs.iter() {
if !attr.check_name("feature") {
continue
}
match attr.meta_item_list() {
None => {
span_handler.span_err(attr.span, "malformed feature attribute, \
expected #![feature(...)]");
}
Some(list) => {
for mi in list.iter() {
let name = match mi.node {
ast::MetaWord(ref word) => (*word).clone(),
_ => {
span_handler.span_err(mi.span,
"malformed feature, expected just \
one word");
continue
}
};
match KNOWN_FEATURES.iter()
.find(|& &(n, _)| name.equiv(&n)) {
Some(&(name, Active)) => { cx.features.push(name); }
Some(&(_, Removed)) => {
span_handler.span_err(mi.span, "feature has been removed");
}
Some(&(_, Accepted)) => {
span_handler.span_warn(mi.span, "feature has been added to Rust, \
directive not necessary");
}
None => {
unknown_features.push(mi.span);
}
}
}
}
}
}
visit::walk_crate(&mut cx, krate);
(Features {
default_type_params: cx.has_feature("default_type_params"),
overloaded_calls: cx.has_feature("overloaded_calls"),
rustc_diagnostic_macros: cx.has_feature("rustc_diagnostic_macros"),
import_shadowing: cx.has_feature("import_shadowing"),
visible_private_types: cx.has_feature("visible_private_types"),
quote: cx.has_feature("quote"),
},
unknown_features)
}