src/librustc/traits/on_unimplemented.rs

   1 use fmt_macros::{Parser, Piece, Position};
   2
   3 use crate::hir::def_id::DefId;
   4 use crate::ty::{self, TyCtxt, GenericParamDefKind};
   5 use crate::util::common::ErrorReported;
   6 use crate::util::nodemap::FxHashMap;
   7
   8 use syntax::ast::{MetaItem, NestedMetaItem};
   9 use syntax::attr;
  10 use syntax::symbol::{Symbol, kw, sym};
  11 use syntax_pos::Span;
  12
  13 #[derive(Clone, Debug)]
  14 pub struct OnUnimplementedFormatString(Symbol);
  15
  16 #[derive(Debug)]
  17 pub struct OnUnimplementedDirective {
  18     pub condition: Option<MetaItem>,
  19     pub subcommands: Vec<OnUnimplementedDirective>,
  20     pub message: Option<OnUnimplementedFormatString>,
  21     pub label: Option<OnUnimplementedFormatString>,
  22     pub note: Option<OnUnimplementedFormatString>,
  23 }
  24
  25 pub struct OnUnimplementedNote {
  26     pub message: Option<String>,
  27     pub label: Option<String>,
  28     pub note: Option<String>,
  29 }
  30
  31 impl OnUnimplementedNote {
  32     pub fn empty() -> Self {
  33         OnUnimplementedNote { message: None, label: None, note: None }
  34     }
  35 }
  36
  37 fn parse_error(
  38     tcx: TyCtxt<'_>,
  39     span: Span,
  40     message: &str,
  41     label: &str,
  42     note: Option<&str>,
  43 ) -> ErrorReported {
  44     let mut diag = struct_span_err!(
  45         tcx.sess, span, E0232, "{}", message);
  46     diag.span_label(span, label);
  47     if let Some(note) = note {
  48         diag.note(note);
  49     }
  50     diag.emit();
  51     ErrorReported
  52 }
  53
  54 impl<'tcx> OnUnimplementedDirective {
  55     fn parse(
  56         tcx: TyCtxt<'tcx>,
  57         trait_def_id: DefId,
  58         items: &[NestedMetaItem],
  59         span: Span,
  60         is_root: bool,
  61     ) -> Result<Self, ErrorReported> {
  62         let mut errored = false;
  63         let mut item_iter = items.iter();
  64
  65         let condition = if is_root {
  66             None
  67         } else {
  68             let cond = item_iter.next().ok_or_else(||
  69                 parse_error(tcx, span,
  70                             "empty `on`-clause in `#[rustc_on_unimplemented]`",
  71                             "empty on-clause here",
  72                             None)
  73             )?.meta_item().ok_or_else(||
  74                 parse_error(tcx, span,
  75                             "invalid `on`-clause in `#[rustc_on_unimplemented]`",
  76                             "invalid on-clause here",
  77                             None)
  78             )?;
  79             attr::eval_condition(cond, &tcx.sess.parse_sess, &mut |_| true);
  80             Some(cond.clone())
  81         };
  82
  83         let mut message = None;
  84         let mut label = None;
  85         let mut note = None;
  86         let mut subcommands = vec![];
  87         for item in item_iter {
  88             if item.check_name(sym::message) && message.is_none() {
  89                 if let Some(message_) = item.value_str() {
  90                     message = Some(OnUnimplementedFormatString::try_parse(
  91                         tcx, trait_def_id, message_, span)?);
  92                     continue;
  93                 }
  94             } else if item.check_name(sym::label) && label.is_none() {
  95                 if let Some(label_) = item.value_str() {
  96                     label = Some(OnUnimplementedFormatString::try_parse(
  97                         tcx, trait_def_id, label_, span)?);
  98                     continue;
  99                 }
 100             } else if item.check_name(sym::note) && note.is_none() {
 101                 if let Some(note_) = item.value_str() {
 102                     note = Some(OnUnimplementedFormatString::try_parse(
 103                         tcx, trait_def_id, note_, span)?);
 104                     continue;
 105                 }
 106             } else if item.check_name(sym::on) && is_root &&
 107                 message.is_none() && label.is_none() && note.is_none()
 108             {
 109                 if let Some(items) = item.meta_item_list() {
 110                     if let Ok(subcommand) =
 111                         Self::parse(tcx, trait_def_id, &items, item.span(), false)
 112                     {
 113                         subcommands.push(subcommand);
 114                     } else {
 115                         errored = true;
 116                     }
 117                     continue
 118                 }
 119             }
 120
 121             // nothing found
 122             parse_error(tcx, item.span(),
 123                         "this attribute must have a valid value",
 124                         "expected value here",
 125                         Some(r#"eg `#[rustc_on_unimplemented(message="foo")]`"#));
 126         }
 127
 128         if errored {
 129             Err(ErrorReported)
 130         } else {
 131             Ok(OnUnimplementedDirective { condition, message, label, subcommands, note })
 132         }
 133     }
 134
 135     pub fn of_item(
 136         tcx: TyCtxt<'tcx>,
 137         trait_def_id: DefId,
 138         impl_def_id: DefId,
 139     ) -> Result<Option<Self>, ErrorReported> {
 140         let attrs = tcx.get_attrs(impl_def_id);
 141
 142         let attr = if let Some(item) = attr::find_by_name(&attrs, sym::rustc_on_unimplemented) {
 143             item
 144         } else {
 145             return Ok(None);
 146         };
 147
 148         let result = if let Some(items) = attr.meta_item_list() {
 149             Self::parse(tcx, trait_def_id, &items, attr.span, true).map(Some)
 150         } else if let Some(value) = attr.value_str() {
 151             Ok(Some(OnUnimplementedDirective {
 152                 condition: None,
 153                 message: None,
 154                 subcommands: vec![],
 155                 label: Some(OnUnimplementedFormatString::try_parse(
 156                     tcx, trait_def_id, value, attr.span)?),
 157                 note: None,
 158             }))
 159         } else {
 160             return Err(ErrorReported);
 161         };
 162         debug!("of_item({:?}/{:?}) = {:?}", trait_def_id, impl_def_id, result);
 163         result
 164     }
 165
 166     pub fn evaluate(
 167         &self,
 168         tcx: TyCtxt<'tcx>,
 169         trait_ref: ty::TraitRef<'tcx>,
 170         options: &[(Symbol, Option<String>)],
 171     ) -> OnUnimplementedNote {
 172         let mut message = None;
 173         let mut label = None;
 174         let mut note = None;
 175         info!("evaluate({:?}, trait_ref={:?}, options={:?})", self, trait_ref, options);
 176
 177         for command in self.subcommands.iter().chain(Some(self)).rev() {
 178             if let Some(ref condition) = command.condition {
 179                 if !attr::eval_condition(condition, &tcx.sess.parse_sess, &mut |c| {
 180                     c.ident().map_or(false, |ident| {
 181                         options.contains(&(
 182                             ident.name,
 183                             c.value_str().map(|s| s.as_str().to_string())
 184                         ))
 185                     })
 186                 }) {
 187                     debug!("evaluate: skipping {:?} due to condition", command);
 188                     continue
 189                 }
 190             }
 191             debug!("evaluate: {:?} succeeded", command);
 192             if let Some(ref message_) = command.message {
 193                 message = Some(message_.clone());
 194             }
 195
 196             if let Some(ref label_) = command.label {
 197                 label = Some(label_.clone());
 198             }
 199
 200             if let Some(ref note_) = command.note {
 201                 note = Some(note_.clone());
 202             }
 203         }
 204
 205         let options: FxHashMap<Symbol, String> = options.into_iter()
 206             .filter_map(|(k, v)| v.as_ref().map(|v| (*k, v.to_owned())))
 207             .collect();
 208         OnUnimplementedNote {
 209             label: label.map(|l| l.format(tcx, trait_ref, &options)),
 210             message: message.map(|m| m.format(tcx, trait_ref, &options)),
 211             note: note.map(|n| n.format(tcx, trait_ref, &options)),
 212         }
 213     }
 214 }
 215
 216 impl<'tcx> OnUnimplementedFormatString {
 217     fn try_parse(
 218         tcx: TyCtxt<'tcx>,
 219         trait_def_id: DefId,
 220         from: Symbol,
 221         err_sp: Span,
 222     ) -> Result<Self, ErrorReported> {
 223         let result = OnUnimplementedFormatString(from);
 224         result.verify(tcx, trait_def_id, err_sp)?;
 225         Ok(result)
 226     }
 227
 228     fn verify(
 229         &self,
 230         tcx: TyCtxt<'tcx>,
 231         trait_def_id: DefId,
 232         span: Span,
 233     ) -> Result<(), ErrorReported> {
 234         let name = tcx.item_name(trait_def_id);
 235         let generics = tcx.generics_of(trait_def_id);
 236         let s = self.0.as_str();
 237         let parser = Parser::new(&s, None, vec![], false);
 238         let mut result = Ok(());
 239         for token in parser {
 240             match token {
 241                 Piece::String(_) => (), // Normal string, no need to check it
 242                 Piece::NextArgument(a) => match a.position {
 243                     // `{Self}` is allowed
 244                     Position::ArgumentNamed(s) if s == kw::SelfUpper => (),
 245                     // `{ThisTraitsName}` is allowed
 246                     Position::ArgumentNamed(s) if s == name => (),
 247                     // `{from_method}` is allowed
 248                     Position::ArgumentNamed(s) if s == sym::from_method => (),
 249                     // `{from_desugaring}` is allowed
 250                     Position::ArgumentNamed(s) if s == sym::from_desugaring => (),
 251                     // So is `{A}` if A is a type parameter
 252                     Position::ArgumentNamed(s) => match generics.params.iter().find(|param| {
 253                         param.name == s
 254                     }) {
 255                         Some(_) => (),
 256                         None => {
 257                             span_err!(tcx.sess, span, E0230,
 258                                       "there is no parameter `{}` on trait `{}`", s, name);
 259                             result = Err(ErrorReported);
 260                         }
 261                     },
 262                     // `{:1}` and `{}` are not to be used
 263                     Position::ArgumentIs(_) | Position::ArgumentImplicitlyIs(_) => {
 264                         span_err!(tcx.sess, span, E0231,
 265                                   "only named substitution parameters are allowed");
 266                         result = Err(ErrorReported);
 267                     }
 268                 }
 269             }
 270         }
 271
 272         result
 273     }
 274
 275     pub fn format(
 276         &self,
 277         tcx: TyCtxt<'tcx>,
 278         trait_ref: ty::TraitRef<'tcx>,
 279         options: &FxHashMap<Symbol, String>,
 280     ) -> String {
 281         let name = tcx.item_name(trait_ref.def_id);
 282         let trait_str = tcx.def_path_str(trait_ref.def_id);
 283         let generics = tcx.generics_of(trait_ref.def_id);
 284         let generic_map = generics.params.iter().filter_map(|param| {
 285             let value = match param.kind {
 286                 GenericParamDefKind::Type { .. } |
 287                 GenericParamDefKind::Const => {
 288                     trait_ref.substs[param.index as usize].to_string()
 289                 },
 290                 GenericParamDefKind::Lifetime => return None
 291             };
 292             let name = param.name;
 293             Some((name, value))
 294         }).collect::<FxHashMap<Symbol, String>>();
 295         let empty_string = String::new();
 296
 297         let s = self.0.as_str();
 298         let parser = Parser::new(&s, None, vec![], false);
 299         parser.map(|p|
 300             match p {
 301                 Piece::String(s) => s,
 302                 Piece::NextArgument(a) => match a.position {
 303                     Position::ArgumentNamed(s) => match generic_map.get(&s) {
 304                         Some(val) => val,
 305                         None if s == name => {
 306                             &trait_str
 307                         }
 308                         None => {
 309                             if let Some(val) = options.get(&s) {
 310                                 val
 311                             } else if s == sym::from_desugaring || s == sym::from_method {
 312                                 // don't break messages using these two arguments incorrectly
 313                                 &empty_string
 314                             } else {
 315                                 bug!("broken on_unimplemented {:?} for {:?}: \
 316                                       no argument matching {:?}",
 317                                      self.0, trait_ref, s)
 318                             }
 319                         }
 320                     },
 321                     _ => bug!("broken on_unimplemented {:?} - bad format arg", self.0)
 322                 }
 323             }
 324         ).collect()
 325     }
 326 }