compiler/rustc_parse/src/validate_attr.rs

   1 //! Meta-syntax validation logic of attributes for post-expansion.
   2
   3 use crate::parse_in;
   4
   5 use rustc_ast::tokenstream::DelimSpan;
   6 use rustc_ast::{self as ast, Attribute, MacArgs, MacDelimiter, MetaItem, MetaItemKind};
   7 use rustc_errors::{Applicability, PResult};
   8 use rustc_feature::{AttributeTemplate, BUILTIN_ATTRIBUTE_MAP};
   9 use rustc_session::lint::builtin::ILL_FORMED_ATTRIBUTE_INPUT;
  10 use rustc_session::parse::ParseSess;
  11 use rustc_span::{sym, Symbol};
  12
  13 pub fn check_meta(sess: &ParseSess, attr: &Attribute) {
  14     if attr.is_doc_comment() {
  15         return;
  16     }
  17
  18     let attr_info =
  19         attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
  20
  21     // Check input tokens for built-in and key-value attributes.
  22     match attr_info {
  23         // `rustc_dummy` doesn't have any restrictions specific to built-in attributes.
  24         Some((name, _, template, _)) if name != sym::rustc_dummy => {
  25             check_builtin_attribute(sess, attr, name, template)
  26         }
  27         _ => {
  28             if let MacArgs::Eq(..) = attr.get_normal_item().args {
  29                 // All key-value attributes are restricted to meta-item syntax.
  30                 parse_meta(sess, attr)
  31                     .map_err(|mut err| {
  32                         err.emit();
  33                     })
  34                     .ok();
  35             }
  36         }
  37     }
  38 }
  39
  40 pub fn parse_meta<'a>(sess: &'a ParseSess, attr: &Attribute) -> PResult<'a, MetaItem> {
  41     let item = attr.get_normal_item();
  42     Ok(MetaItem {
  43         span: attr.span,
  44         path: item.path.clone(),
  45         kind: match &item.args {
  46             MacArgs::Empty => MetaItemKind::Word,
  47             MacArgs::Eq(_, t) => {
  48                 let v = parse_in(sess, t.clone(), "name value", |p| p.parse_unsuffixed_lit())?;
  49                 MetaItemKind::NameValue(v)
  50             }
  51             MacArgs::Delimited(dspan, delim, t) => {
  52                 check_meta_bad_delim(sess, *dspan, *delim, "wrong meta list delimiters");
  53                 let nmis = parse_in(sess, t.clone(), "meta list", |p| p.parse_meta_seq_top())?;
  54                 MetaItemKind::List(nmis)
  55             }
  56         },
  57     })
  58 }
  59
  60 pub fn check_meta_bad_delim(sess: &ParseSess, span: DelimSpan, delim: MacDelimiter, msg: &str) {
  61     if let ast::MacDelimiter::Parenthesis = delim {
  62         return;
  63     }
  64
  65     sess.span_diagnostic
  66         .struct_span_err(span.entire(), msg)
  67         .multipart_suggestion(
  68             "the delimiters should be `(` and `)`",
  69             vec![(span.open, "(".to_string()), (span.close, ")".to_string())],
  70             Applicability::MachineApplicable,
  71         )
  72         .emit();
  73 }
  74
  75 /// Checks that the given meta-item is compatible with this `AttributeTemplate`.
  76 fn is_attr_template_compatible(template: &AttributeTemplate, meta: &ast::MetaItemKind) -> bool {
  77     match meta {
  78         MetaItemKind::Word => template.word,
  79         MetaItemKind::List(..) => template.list.is_some(),
  80         MetaItemKind::NameValue(lit) if lit.kind.is_str() => template.name_value_str.is_some(),
  81         MetaItemKind::NameValue(..) => false,
  82     }
  83 }
  84
  85 pub fn check_builtin_attribute(
  86     sess: &ParseSess,
  87     attr: &Attribute,
  88     name: Symbol,
  89     template: AttributeTemplate,
  90 ) {
  91     // Some special attributes like `cfg` must be checked
  92     // before the generic check, so we skip them here.
  93     let should_skip = |name| name == sym::cfg;
  94     // Some of previously accepted forms were used in practice,
  95     // report them as warnings for now.
  96     let should_warn = |name| {
  97         name == sym::doc
  98             || name == sym::ignore
  99             || name == sym::inline
 100             || name == sym::link
 101             || name == sym::test
 102             || name == sym::bench
 103     };
 104
 105     match parse_meta(sess, attr) {
 106         Ok(meta) => {
 107             if !should_skip(name) && !is_attr_template_compatible(&template, &meta.kind) {
 108                 let error_msg = format!("malformed `{}` attribute input", name);
 109                 let mut msg = "attribute must be of the form ".to_owned();
 110                 let mut suggestions = vec![];
 111                 let mut first = true;
 112                 if template.word {
 113                     first = false;
 114                     let code = format!("#[{}]", name);
 115                     msg.push_str(&format!("`{}`", &code));
 116                     suggestions.push(code);
 117                 }
 118                 if let Some(descr) = template.list {
 119                     if !first {
 120                         msg.push_str(" or ");
 121                     }
 122                     first = false;
 123                     let code = format!("#[{}({})]", name, descr);
 124                     msg.push_str(&format!("`{}`", &code));
 125                     suggestions.push(code);
 126                 }
 127                 if let Some(descr) = template.name_value_str {
 128                     if !first {
 129                         msg.push_str(" or ");
 130                     }
 131                     let code = format!("#[{} = \"{}\"]", name, descr);
 132                     msg.push_str(&format!("`{}`", &code));
 133                     suggestions.push(code);
 134                 }
 135                 if should_warn(name) {
 136                     sess.buffer_lint(
 137                         &ILL_FORMED_ATTRIBUTE_INPUT,
 138                         meta.span,
 139                         ast::CRATE_NODE_ID,
 140                         &msg,
 141                     );
 142                 } else {
 143                     sess.span_diagnostic
 144                         .struct_span_err(meta.span, &error_msg)
 145                         .span_suggestions(
 146                             meta.span,
 147                             if suggestions.len() == 1 {
 148                                 "must be of the form"
 149                             } else {
 150                                 "the following are the possible correct uses"
 151                             },
 152                             suggestions.into_iter(),
 153                             Applicability::HasPlaceholders,
 154                         )
 155                         .emit();
 156                 }
 157             }
 158         }
 159         Err(mut err) => {
 160             err.emit();
 161         }
 162     }
 163 }