383 lines
14 KiB
Rust
383 lines
14 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Feature gating
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//!
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//! This modules implements the gating necessary for preventing certain compiler
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//! features from being used by default. This module will crawl a pre-expanded
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//! AST to ensure that there are no features which are used that are not
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//! enabled.
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//!
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//! Features are enabled in programs via the crate-level attributes of
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//! #![feature(...)] with a comma-separated list of features.
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use middle::lint;
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use syntax::ast;
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use syntax::attr;
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use syntax::attr::AttrMetaMethods;
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use syntax::codemap::Span;
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use syntax::visit;
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use syntax::visit::Visitor;
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use syntax::parse::token;
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use driver::session::Session;
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use std::cell::Cell;
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/// This is a list of all known features since the beginning of time. This list
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/// can never shrink, it may only be expanded (in order to prevent old programs
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/// from failing to compile). The status of each feature may change, however.
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static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
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("globs", Active),
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("macro_rules", Active),
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("struct_variant", Active),
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("once_fns", Active),
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("asm", Active),
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("managed_boxes", Active),
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("non_ascii_idents", Active),
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("thread_local", Active),
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("link_args", Active),
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("phase", Active),
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("plugin_registrar", Active),
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("log_syntax", Active),
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("trace_macros", Active),
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("concat_idents", Active),
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("simd", Active),
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("default_type_params", Active),
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("quote", Active),
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("linkage", Active),
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("struct_inherit", Active),
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("overloaded_calls", Active),
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("quad_precision_float", Active),
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// A temporary feature gate used to enable parser extensions needed
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// to bootstrap fix for #5723.
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("issue_5723_bootstrap", Active),
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// These are used to test this portion of the compiler, they don't actually
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// mean anything
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("test_accepted_feature", Accepted),
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("test_removed_feature", Removed),
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];
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enum Status {
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/// Represents an active feature that is currently being implemented or
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/// currently being considered for addition/removal.
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Active,
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/// Represents a feature which has since been removed (it was once Active)
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Removed,
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/// This language feature has since been Accepted (it was once Active)
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Accepted,
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}
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/// A set of features to be used by later passes.
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pub struct Features {
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pub default_type_params: Cell<bool>,
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pub quad_precision_float: Cell<bool>,
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pub issue_5723_bootstrap: Cell<bool>,
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pub overloaded_calls: Cell<bool>,
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}
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impl Features {
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pub fn new() -> Features {
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Features {
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default_type_params: Cell::new(false),
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quad_precision_float: Cell::new(false),
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issue_5723_bootstrap: Cell::new(false),
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overloaded_calls: Cell::new(false),
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}
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}
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}
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struct Context<'a> {
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features: Vec<&'static str>,
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sess: &'a Session,
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}
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impl<'a> Context<'a> {
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fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
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if !self.has_feature(feature) {
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self.sess.span_err(span, explain);
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self.sess.span_note(span, format!("add \\#![feature({})] to the \
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crate attributes to enable",
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feature).as_slice());
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}
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}
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fn gate_box(&self, span: Span) {
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self.gate_feature("managed_boxes", span,
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"The managed box syntax is being replaced by the \
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`std::gc::Gc` and `std::rc::Rc` types. Equivalent \
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functionality to managed trait objects will be \
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implemented but is currently missing.");
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}
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fn has_feature(&self, feature: &str) -> bool {
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self.features.iter().any(|n| n.as_slice() == feature)
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}
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}
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impl<'a> Visitor<()> for Context<'a> {
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fn visit_ident(&mut self, sp: Span, id: ast::Ident, _: ()) {
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if !token::get_ident(id).get().is_ascii() {
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self.gate_feature("non_ascii_idents", sp,
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"non-ascii idents are not fully supported.");
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}
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}
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fn visit_view_item(&mut self, i: &ast::ViewItem, _: ()) {
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match i.node {
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ast::ViewItemUse(ref path) => {
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match path.node {
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ast::ViewPathGlob(..) => {
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self.gate_feature("globs", path.span,
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"glob import statements are \
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experimental and possibly buggy");
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}
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_ => {}
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}
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}
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ast::ViewItemExternCrate(..) => {
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for attr in i.attrs.iter() {
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if attr.name().get() == "phase"{
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self.gate_feature("phase", attr.span,
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"compile time crate loading is \
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experimental and possibly buggy");
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}
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}
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}
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}
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visit::walk_view_item(self, i, ())
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}
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fn visit_item(&mut self, i: &ast::Item, _:()) {
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for attr in i.attrs.iter() {
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if attr.name().equiv(&("thread_local")) {
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self.gate_feature("thread_local", i.span,
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"`#[thread_local]` is an experimental feature, and does not \
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currently handle destructors. There is no corresponding \
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`#[task_local]` mapping to the task model");
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}
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}
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match i.node {
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ast::ItemEnum(ref def, _) => {
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for variant in def.variants.iter() {
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match variant.node.kind {
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ast::StructVariantKind(..) => {
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self.gate_feature("struct_variant", variant.span,
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"enum struct variants are \
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experimental and possibly buggy");
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}
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_ => {}
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}
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}
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}
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ast::ItemForeignMod(..) => {
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if attr::contains_name(i.attrs.as_slice(), "link_args") {
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self.gate_feature("link_args", i.span,
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"the `link_args` attribute is not portable \
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across platforms, it is recommended to \
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use `#[link(name = \"foo\")]` instead")
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}
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}
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ast::ItemFn(..) => {
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if attr::contains_name(i.attrs.as_slice(), "plugin_registrar") {
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self.gate_feature("plugin_registrar", i.span,
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"compiler plugins are experimental and possibly buggy");
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}
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}
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ast::ItemStruct(struct_definition, _) => {
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if attr::contains_name(i.attrs.as_slice(), "simd") {
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self.gate_feature("simd", i.span,
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"SIMD types are experimental and possibly buggy");
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}
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match struct_definition.super_struct {
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Some(ref path) => self.gate_feature("struct_inherit", path.span,
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"struct inheritance is experimental \
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and possibly buggy"),
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None => {}
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}
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if struct_definition.is_virtual {
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self.gate_feature("struct_inherit", i.span,
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"struct inheritance (`virtual` keyword) is \
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experimental and possibly buggy");
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}
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}
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_ => {}
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}
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visit::walk_item(self, i, ());
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}
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fn visit_mac(&mut self, macro: &ast::Mac, _: ()) {
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let ast::MacInvocTT(ref path, _, _) = macro.node;
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let id = path.segments.last().unwrap().identifier;
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let quotes = ["quote_tokens", "quote_expr", "quote_ty",
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"quote_item", "quote_pat", "quote_stmt"];
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let msg = " is not stable enough for use and are subject to change";
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if id == token::str_to_ident("macro_rules") {
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self.gate_feature("macro_rules", path.span, "macro definitions are \
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not stable enough for use and are subject to change");
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}
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else if id == token::str_to_ident("asm") {
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self.gate_feature("asm", path.span, "inline assembly is not \
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stable enough for use and is subject to change");
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}
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else if id == token::str_to_ident("log_syntax") {
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self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
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stable enough for use and is subject to change");
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}
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else if id == token::str_to_ident("trace_macros") {
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self.gate_feature("trace_macros", path.span, "`trace_macros` is not \
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stable enough for use and is subject to change");
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}
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else if id == token::str_to_ident("concat_idents") {
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self.gate_feature("concat_idents", path.span, "`concat_idents` is not \
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stable enough for use and is subject to change");
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}
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else {
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for "e in quotes.iter() {
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if id == token::str_to_ident(quote) {
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self.gate_feature("quote",
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path.span,
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format!("{}{}", quote, msg).as_slice());
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}
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}
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}
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}
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fn visit_foreign_item(&mut self, i: &ast::ForeignItem, _: ()) {
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match i.node {
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ast::ForeignItemFn(..) | ast::ForeignItemStatic(..) => {
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if attr::contains_name(i.attrs.as_slice(), "linkage") {
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self.gate_feature("linkage", i.span,
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"the `linkage` attribute is experimental \
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and not portable across platforms")
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}
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}
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}
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visit::walk_foreign_item(self, i, ())
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}
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fn visit_ty(&mut self, t: &ast::Ty, _: ()) {
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match t.node {
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ast::TyClosure(closure, _) if closure.onceness == ast::Once => {
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self.gate_feature("once_fns", t.span,
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"once functions are \
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experimental and likely to be removed");
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},
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ast::TyBox(_) => { self.gate_box(t.span); }
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_ => {}
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}
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visit::walk_ty(self, t, ());
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}
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fn visit_expr(&mut self, e: &ast::Expr, _: ()) {
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match e.node {
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ast::ExprUnary(ast::UnBox, _) => {
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self.gate_box(e.span);
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}
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_ => {}
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}
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visit::walk_expr(self, e, ());
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}
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fn visit_generics(&mut self, generics: &ast::Generics, _: ()) {
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for type_parameter in generics.ty_params.iter() {
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match type_parameter.default {
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Some(ty) => {
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self.gate_feature("default_type_params", ty.span,
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"default type parameters are \
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experimental and possibly buggy");
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}
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None => {}
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}
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}
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visit::walk_generics(self, generics, ());
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}
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}
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pub fn check_crate(sess: &Session, krate: &ast::Crate) {
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let mut cx = Context {
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features: Vec::new(),
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sess: sess,
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};
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for attr in krate.attrs.iter() {
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if !attr.check_name("feature") {
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continue
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}
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match attr.meta_item_list() {
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None => {
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sess.span_err(attr.span, "malformed feature attribute, \
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expected #![feature(...)]");
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}
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Some(list) => {
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for &mi in list.iter() {
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let name = match mi.node {
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ast::MetaWord(ref word) => (*word).clone(),
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_ => {
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sess.span_err(mi.span,
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"malformed feature, expected just \
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one word");
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continue
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}
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};
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match KNOWN_FEATURES.iter()
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.find(|& &(n, _)| name.equiv(&n)) {
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Some(&(name, Active)) => { cx.features.push(name); }
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Some(&(_, Removed)) => {
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sess.span_err(mi.span, "feature has been removed");
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}
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Some(&(_, Accepted)) => {
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sess.span_warn(mi.span, "feature has added to rust, \
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directive not necessary");
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}
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None => {
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sess.add_lint(lint::UnknownFeatures,
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ast::CRATE_NODE_ID,
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mi.span,
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"unknown feature".to_string());
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}
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}
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}
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}
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}
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}
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visit::walk_crate(&mut cx, krate, ());
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sess.abort_if_errors();
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sess.features.default_type_params.set(cx.has_feature("default_type_params"));
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sess.features.quad_precision_float.set(cx.has_feature("quad_precision_float"));
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sess.features.issue_5723_bootstrap.set(cx.has_feature("issue_5723_bootstrap"));
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sess.features.overloaded_calls.set(cx.has_feature("overloaded_calls"));
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}
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