360 lines
12 KiB
Rust
360 lines
12 KiB
Rust
// Copyright 2015 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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//! This module implements some validity checks for attributes.
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//! In particular it verifies that `#[inline]` and `#[repr]` attributes are
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//! attached to items that actually support them and if there are
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//! conflicts between multiple such attributes attached to the same
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//! item.
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use syntax_pos::Span;
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use ty::TyCtxt;
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use hir;
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use hir::intravisit::{self, Visitor, NestedVisitorMap};
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#[derive(Copy, Clone, PartialEq)]
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enum Target {
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Fn,
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Struct,
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Union,
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Enum,
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Const,
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ForeignMod,
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Expression,
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Statement,
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Closure,
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Static,
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Other,
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}
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impl Target {
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fn from_item(item: &hir::Item) -> Target {
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match item.node {
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hir::ItemFn(..) => Target::Fn,
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hir::ItemStruct(..) => Target::Struct,
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hir::ItemUnion(..) => Target::Union,
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hir::ItemEnum(..) => Target::Enum,
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hir::ItemConst(..) => Target::Const,
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hir::ItemForeignMod(..) => Target::ForeignMod,
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hir::ItemStatic(..) => Target::Static,
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_ => Target::Other,
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}
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}
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}
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struct CheckAttrVisitor<'a, 'tcx: 'a> {
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tcx: TyCtxt<'a, 'tcx, 'tcx>,
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}
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impl<'a, 'tcx> CheckAttrVisitor<'a, 'tcx> {
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/// Check any attribute.
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fn check_attributes(&self, item: &hir::Item, target: Target) {
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if target == Target::Fn {
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self.tcx.codegen_fn_attrs(self.tcx.hir.local_def_id(item.id));
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} else if let Some(a) = item.attrs.iter().find(|a| a.check_name("target_feature")) {
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self.tcx.sess.struct_span_err(a.span, "attribute should be applied to a function")
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.span_label(item.span, "not a function")
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.emit();
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}
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let mut has_wasm_import_module = false;
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for attr in &item.attrs {
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if attr.check_name("inline") {
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self.check_inline(attr, &item.span, target)
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} else if attr.check_name("non_exhaustive") {
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self.check_non_exhaustive(attr, item, target)
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} else if attr.check_name("wasm_import_module") {
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has_wasm_import_module = true;
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if attr.value_str().is_none() {
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self.tcx.sess.span_err(attr.span, "\
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must be of the form #[wasm_import_module = \"...\"]");
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}
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if target != Target::ForeignMod {
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self.tcx.sess.span_err(attr.span, "\
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must only be attached to foreign modules");
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}
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} else if attr.check_name("wasm_custom_section") {
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if target != Target::Const {
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self.tcx.sess.span_err(attr.span, "only allowed on consts");
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}
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if attr.value_str().is_none() {
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self.tcx.sess.span_err(attr.span, "must be of the form \
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#[wasm_custom_section = \"foo\"]");
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}
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}
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}
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if target == Target::ForeignMod &&
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!has_wasm_import_module &&
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self.tcx.sess.target.target.arch == "wasm32" &&
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false // FIXME: eventually enable this warning when stable
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{
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self.tcx.sess.span_warn(item.span, "\
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must have a #[wasm_import_module = \"...\"] attribute, this \
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will become a hard error before too long");
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}
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self.check_repr(item, target);
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self.check_used(item, target);
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}
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/// Check if an `#[inline]` is applied to a function or a closure.
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fn check_inline(&self, attr: &hir::Attribute, span: &Span, target: Target) {
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if target != Target::Fn && target != Target::Closure {
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struct_span_err!(self.tcx.sess,
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attr.span,
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E0518,
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"attribute should be applied to function or closure")
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.span_label(*span, "not a function or closure")
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.emit();
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}
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}
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/// Check if the `#[non_exhaustive]` attribute on an `item` is valid.
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fn check_non_exhaustive(&self, attr: &hir::Attribute, item: &hir::Item, target: Target) {
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match target {
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Target::Struct | Target::Enum => { /* Valid */ },
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_ => {
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struct_span_err!(self.tcx.sess,
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attr.span,
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E0910,
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"attribute can only be applied to a struct or enum")
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.span_label(item.span, "not a struct or enum")
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.emit();
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return;
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}
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}
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if attr.meta_item_list().is_some() || attr.value_str().is_some() {
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struct_span_err!(self.tcx.sess,
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attr.span,
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E0911,
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"attribute should be empty")
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.span_label(item.span, "not empty")
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.emit();
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}
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}
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/// Check if the `#[repr]` attributes on `item` are valid.
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fn check_repr(&self, item: &hir::Item, target: Target) {
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// Extract the names of all repr hints, e.g., [foo, bar, align] for:
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// ```
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// #[repr(foo)]
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// #[repr(bar, align(8))]
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// ```
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let hints: Vec<_> = item.attrs
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.iter()
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.filter(|attr| attr.name() == "repr")
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.filter_map(|attr| attr.meta_item_list())
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.flat_map(|hints| hints)
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.collect();
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let mut int_reprs = 0;
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let mut is_c = false;
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let mut is_simd = false;
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let mut is_transparent = false;
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for hint in &hints {
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let name = if let Some(name) = hint.name() {
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name
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} else {
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// Invalid repr hint like repr(42). We don't check for unrecognized hints here
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// (libsyntax does that), so just ignore it.
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continue;
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};
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let (article, allowed_targets) = match &*name.as_str() {
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"C" => {
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is_c = true;
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if target != Target::Struct &&
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target != Target::Union &&
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target != Target::Enum {
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("a", "struct, enum or union")
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} else {
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continue
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}
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}
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"packed" => {
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if target != Target::Struct &&
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target != Target::Union {
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("a", "struct or union")
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} else {
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continue
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}
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}
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"simd" => {
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is_simd = true;
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if target != Target::Struct {
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("a", "struct")
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} else {
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continue
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}
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}
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"align" => {
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if target != Target::Struct &&
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target != Target::Union {
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("a", "struct or union")
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} else {
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continue
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}
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}
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"transparent" => {
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is_transparent = true;
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if target != Target::Struct {
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("a", "struct")
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} else {
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continue
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}
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}
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"i8" | "u8" | "i16" | "u16" |
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"i32" | "u32" | "i64" | "u64" |
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"isize" | "usize" => {
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int_reprs += 1;
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if target != Target::Enum {
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("an", "enum")
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} else {
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continue
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}
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}
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_ => continue,
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};
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self.emit_repr_error(
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hint.span,
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item.span,
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&format!("attribute should be applied to {}", allowed_targets),
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&format!("not {} {}", article, allowed_targets),
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)
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}
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// Just point at all repr hints if there are any incompatibilities.
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// This is not ideal, but tracking precisely which ones are at fault is a huge hassle.
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let hint_spans = hints.iter().map(|hint| hint.span);
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// Error on repr(transparent, <anything else>).
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if is_transparent && hints.len() > 1 {
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let hint_spans: Vec<_> = hint_spans.clone().collect();
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span_err!(self.tcx.sess, hint_spans, E0692,
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"transparent struct cannot have other repr hints");
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}
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// Warn on repr(u8, u16), repr(C, simd), and c-like-enum-repr(C, u8)
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if (int_reprs > 1)
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|| (is_simd && is_c)
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|| (int_reprs == 1 && is_c && is_c_like_enum(item)) {
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let hint_spans: Vec<_> = hint_spans.collect();
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span_warn!(self.tcx.sess, hint_spans, E0566,
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"conflicting representation hints");
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}
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}
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fn emit_repr_error(
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&self,
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hint_span: Span,
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label_span: Span,
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hint_message: &str,
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label_message: &str,
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) {
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struct_span_err!(self.tcx.sess, hint_span, E0517, "{}", hint_message)
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.span_label(label_span, label_message)
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.emit();
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}
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fn check_stmt_attributes(&self, stmt: &hir::Stmt) {
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// When checking statements ignore expressions, they will be checked later
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if let hir::Stmt_::StmtDecl(_, _) = stmt.node {
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for attr in stmt.node.attrs() {
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if attr.check_name("inline") {
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self.check_inline(attr, &stmt.span, Target::Statement);
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}
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if attr.check_name("repr") {
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self.emit_repr_error(
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attr.span,
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stmt.span,
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&format!("attribute should not be applied to a statement"),
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&format!("not a struct, enum or union"),
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);
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}
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}
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}
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}
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fn check_expr_attributes(&self, expr: &hir::Expr) {
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let target = match expr.node {
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hir::ExprClosure(..) => Target::Closure,
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_ => Target::Expression,
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};
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for attr in expr.attrs.iter() {
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if attr.check_name("inline") {
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self.check_inline(attr, &expr.span, target);
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}
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if attr.check_name("repr") {
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self.emit_repr_error(
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attr.span,
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expr.span,
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&format!("attribute should not be applied to an expression"),
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&format!("not defining a struct, enum or union"),
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);
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}
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}
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}
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fn check_used(&self, item: &hir::Item, target: Target) {
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for attr in &item.attrs {
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if attr.name() == "used" && target != Target::Static {
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self.tcx.sess
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.span_err(attr.span, "attribute must be applied to a `static` variable");
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}
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}
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}
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}
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impl<'a, 'tcx> Visitor<'tcx> for CheckAttrVisitor<'a, 'tcx> {
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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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NestedVisitorMap::OnlyBodies(&self.tcx.hir)
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}
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fn visit_item(&mut self, item: &'tcx hir::Item) {
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let target = Target::from_item(item);
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self.check_attributes(item, target);
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intravisit::walk_item(self, item)
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}
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fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt) {
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self.check_stmt_attributes(stmt);
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intravisit::walk_stmt(self, stmt)
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}
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fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
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self.check_expr_attributes(expr);
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intravisit::walk_expr(self, expr)
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}
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}
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pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
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let mut checker = CheckAttrVisitor { tcx };
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tcx.hir.krate().visit_all_item_likes(&mut checker.as_deep_visitor());
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}
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fn is_c_like_enum(item: &hir::Item) -> bool {
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if let hir::ItemEnum(ref def, _) = item.node {
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for variant in &def.variants {
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match variant.node.data {
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hir::VariantData::Unit(_) => { /* continue */ }
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_ => { return false; }
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}
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}
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true
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} else {
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false
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}
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}
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