DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Git (4fb54ed484)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163
//! Meta-syntax validation logic of attributes for post-expansion.

use crate::parse_in;

use rustc_ast::ast::{self, Attribute, MacArgs, MacDelimiter, MetaItem, MetaItemKind};
use rustc_ast::tokenstream::DelimSpan;
use rustc_errors::{Applicability, PResult};
use rustc_feature::{AttributeTemplate, BUILTIN_ATTRIBUTE_MAP};
use rustc_session::lint::builtin::ILL_FORMED_ATTRIBUTE_INPUT;
use rustc_session::parse::ParseSess;
use rustc_span::{sym, Symbol};

pub fn check_meta(sess: &ParseSess, attr: &Attribute) {
    if attr.is_doc_comment() {
        return;
    }

    let attr_info =
        attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);

    // Check input tokens for built-in and key-value attributes.
    match attr_info {
        // `rustc_dummy` doesn't have any restrictions specific to built-in attributes.
        Some((name, _, template, _)) if name != sym::rustc_dummy => {
            check_builtin_attribute(sess, attr, name, template)
        }
        _ => {
            if let MacArgs::Eq(..) = attr.get_normal_item().args {
                // All key-value attributes are restricted to meta-item syntax.
                parse_meta(sess, attr)
                    .map_err(|mut err| {
                        err.emit();
                    })
                    .ok();
            }
        }
    }
}

pub fn parse_meta<'a>(sess: &'a ParseSess, attr: &Attribute) -> PResult<'a, MetaItem> {
    let item = attr.get_normal_item();
    Ok(MetaItem {
        span: attr.span,
        path: item.path.clone(),
        kind: match &item.args {
            MacArgs::Empty => MetaItemKind::Word,
            MacArgs::Eq(_, t) => {
                let v = parse_in(sess, t.clone(), "name value", |p| p.parse_unsuffixed_lit())?;
                MetaItemKind::NameValue(v)
            }
            MacArgs::Delimited(dspan, delim, t) => {
                check_meta_bad_delim(sess, *dspan, *delim, "wrong meta list delimiters");
                let nmis = parse_in(sess, t.clone(), "meta list", |p| p.parse_meta_seq_top())?;
                MetaItemKind::List(nmis)
            }
        },
    })
}

pub fn check_meta_bad_delim(sess: &ParseSess, span: DelimSpan, delim: MacDelimiter, msg: &str) {
    if let ast::MacDelimiter::Parenthesis = delim {
        return;
    }

    sess.span_diagnostic
        .struct_span_err(span.entire(), msg)
        .multipart_suggestion(
            "the delimiters should be `(` and `)`",
            vec![(span.open, "(".to_string()), (span.close, ")".to_string())],
            Applicability::MachineApplicable,
        )
        .emit();
}

/// Checks that the given meta-item is compatible with this `AttributeTemplate`.
fn is_attr_template_compatible(template: &AttributeTemplate, meta: &ast::MetaItemKind) -> bool {
    match meta {
        MetaItemKind::Word => template.word,
        MetaItemKind::List(..) => template.list.is_some(),
        MetaItemKind::NameValue(lit) if lit.kind.is_str() => template.name_value_str.is_some(),
        MetaItemKind::NameValue(..) => false,
    }
}

pub fn check_builtin_attribute(
    sess: &ParseSess,
    attr: &Attribute,
    name: Symbol,
    template: AttributeTemplate,
) {
    // Some special attributes like `cfg` must be checked
    // before the generic check, so we skip them here.
    let should_skip = |name| name == sym::cfg;
    // Some of previously accepted forms were used in practice,
    // report them as warnings for now.
    let should_warn = |name| {
        name == sym::doc
            || name == sym::ignore
            || name == sym::inline
            || name == sym::link
            || name == sym::test
            || name == sym::bench
    };

    match parse_meta(sess, attr) {
        Ok(meta) => {
            if !should_skip(name) && !is_attr_template_compatible(&template, &meta.kind) {
                let error_msg = format!("malformed `{}` attribute input", name);
                let mut msg = "attribute must be of the form ".to_owned();
                let mut suggestions = vec![];
                let mut first = true;
                if template.word {
                    first = false;
                    let code = format!("#[{}]", name);
                    msg.push_str(&format!("`{}`", &code));
                    suggestions.push(code);
                }
                if let Some(descr) = template.list {
                    if !first {
                        msg.push_str(" or ");
                    }
                    first = false;
                    let code = format!("#[{}({})]", name, descr);
                    msg.push_str(&format!("`{}`", &code));
                    suggestions.push(code);
                }
                if let Some(descr) = template.name_value_str {
                    if !first {
                        msg.push_str(" or ");
                    }
                    let code = format!("#[{} = \"{}\"]", name, descr);
                    msg.push_str(&format!("`{}`", &code));
                    suggestions.push(code);
                }
                if should_warn(name) {
                    sess.buffer_lint(
                        &ILL_FORMED_ATTRIBUTE_INPUT,
                        meta.span,
                        ast::CRATE_NODE_ID,
                        &msg,
                    );
                } else {
                    sess.span_diagnostic
                        .struct_span_err(meta.span, &error_msg)
                        .span_suggestions(
                            meta.span,
                            if suggestions.len() == 1 {
                                "must be of the form"
                            } else {
                                "the following are the possible correct uses"
                            },
                            suggestions.into_iter(),
                            Applicability::HasPlaceholders,
                        )
                        .emit();
                }
            }
        }
        Err(mut err) => {
            err.emit();
        }
    }
}