compiler/rustc_trait_selection/src/traits/on_unimplemented.rs

   1 use rustc_ast::{MetaItem, NestedMetaItem};
   2 use rustc_attr as attr;
   3 use rustc_data_structures::fx::FxHashMap;
   4 use rustc_errors::{struct_span_err, ErrorGuaranteed};
   5 use rustc_hir::def_id::DefId;
   6 use rustc_middle::ty::{self, GenericParamDefKind, TyCtxt};
   7 use rustc_parse_format::{ParseMode, Parser, Piece, Position};
   8 use rustc_span::symbol::{kw, sym, Symbol};
   9 use rustc_span::{Span, DUMMY_SP};
  10
  11 #[derive(Clone, Debug)]
  12 pub struct OnUnimplementedFormatString(Symbol);
  13
  14 #[derive(Debug)]
  15 pub struct OnUnimplementedDirective {
  16     pub condition: Option<MetaItem>,
  17     pub subcommands: Vec<OnUnimplementedDirective>,
  18     pub message: Option<OnUnimplementedFormatString>,
  19     pub label: Option<OnUnimplementedFormatString>,
  20     pub note: Option<OnUnimplementedFormatString>,
  21     pub enclosing_scope: Option<OnUnimplementedFormatString>,
  22     pub append_const_msg: Option<Option<Symbol>>,
  23 }
  24
  25 #[derive(Default)]
  26 pub struct OnUnimplementedNote {
  27     pub message: Option<String>,
  28     pub label: Option<String>,
  29     pub note: Option<String>,
  30     pub enclosing_scope: Option<String>,
  31     /// Append a message for `~const Trait` errors. `None` means not requested and
  32     /// should fallback to a generic message, `Some(None)` suggests using the default
  33     /// appended message, `Some(Some(s))` suggests use the `s` message instead of the
  34     /// default one..
  35     pub append_const_msg: Option<Option<Symbol>>,
  36 }
  37
  38 fn parse_error(
  39     tcx: TyCtxt<'_>,
  40     span: Span,
  41     message: &str,
  42     label: &str,
  43     note: Option<&str>,
  44 ) -> ErrorGuaranteed {
  45     let mut diag = struct_span_err!(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 }
  52
  53 impl<'tcx> OnUnimplementedDirective {
  54     fn parse(
  55         tcx: TyCtxt<'tcx>,
  56         item_def_id: DefId,
  57         items: &[NestedMetaItem],
  58         span: Span,
  59         is_root: bool,
  60     ) -> Result<Self, ErrorGuaranteed> {
  61         let mut errored = None;
  62         let mut item_iter = items.iter();
  63
  64         let parse_value = |value_str| {
  65             OnUnimplementedFormatString::try_parse(tcx, item_def_id, value_str, span).map(Some)
  66         };
  67
  68         let condition = if is_root {
  69             None
  70         } else {
  71             let cond = item_iter
  72                 .next()
  73                 .ok_or_else(|| {
  74                     parse_error(
  75                         tcx,
  76                         span,
  77                         "empty `on`-clause in `#[rustc_on_unimplemented]`",
  78                         "empty on-clause here",
  79                         None,
  80                     )
  81                 })?
  82                 .meta_item()
  83                 .ok_or_else(|| {
  84                     parse_error(
  85                         tcx,
  86                         span,
  87                         "invalid `on`-clause in `#[rustc_on_unimplemented]`",
  88                         "invalid on-clause here",
  89                         None,
  90                     )
  91                 })?;
  92             attr::eval_condition(cond, &tcx.sess.parse_sess, Some(tcx.features()), &mut |cfg| {
  93                 if let Some(value) = cfg.value && let Err(guar) = parse_value(value) {
  94                     errored = Some(guar);
  95                 }
  96                 true
  97             });
  98             Some(cond.clone())
  99         };
 100
 101         let mut message = None;
 102         let mut label = None;
 103         let mut note = None;
 104         let mut enclosing_scope = None;
 105         let mut subcommands = vec![];
 106         let mut append_const_msg = None;
 107
 108         for item in item_iter {
 109             if item.has_name(sym::message) && message.is_none() {
 110                 if let Some(message_) = item.value_str() {
 111                     message = parse_value(message_)?;
 112                     continue;
 113                 }
 114             } else if item.has_name(sym::label) && label.is_none() {
 115                 if let Some(label_) = item.value_str() {
 116                     label = parse_value(label_)?;
 117                     continue;
 118                 }
 119             } else if item.has_name(sym::note) && note.is_none() {
 120                 if let Some(note_) = item.value_str() {
 121                     note = parse_value(note_)?;
 122                     continue;
 123                 }
 124             } else if item.has_name(sym::enclosing_scope) && enclosing_scope.is_none() {
 125                 if let Some(enclosing_scope_) = item.value_str() {
 126                     enclosing_scope = parse_value(enclosing_scope_)?;
 127                     continue;
 128                 }
 129             } else if item.has_name(sym::on)
 130                 && is_root
 131                 && message.is_none()
 132                 && label.is_none()
 133                 && note.is_none()
 134             {
 135                 if let Some(items) = item.meta_item_list() {
 136                     match Self::parse(tcx, item_def_id, &items, item.span(), false) {
 137                         Ok(subcommand) => subcommands.push(subcommand),
 138                         Err(reported) => errored = Some(reported),
 139                     };
 140                     continue;
 141                 }
 142             } else if item.has_name(sym::append_const_msg) && append_const_msg.is_none() {
 143                 if let Some(msg) = item.value_str() {
 144                     append_const_msg = Some(Some(msg));
 145                     continue;
 146                 } else if item.is_word() {
 147                     append_const_msg = Some(None);
 148                     continue;
 149                 }
 150             }
 151
 152             // nothing found
 153             parse_error(
 154                 tcx,
 155                 item.span(),
 156                 "this attribute must have a valid value",
 157                 "expected value here",
 158                 Some(r#"eg `#[rustc_on_unimplemented(message="foo")]`"#),
 159             );
 160         }
 161
 162         if let Some(reported) = errored {
 163             Err(reported)
 164         } else {
 165             Ok(OnUnimplementedDirective {
 166                 condition,
 167                 subcommands,
 168                 message,
 169                 label,
 170                 note,
 171                 enclosing_scope,
 172                 append_const_msg,
 173             })
 174         }
 175     }
 176
 177     pub fn of_item(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> Result<Option<Self>, ErrorGuaranteed> {
 178         let Some(attr) = tcx.get_attr(item_def_id, sym::rustc_on_unimplemented) else {
 179             return Ok(None);
 180         };
 181
 182         let result = if let Some(items) = attr.meta_item_list() {
 183             Self::parse(tcx, item_def_id, &items, attr.span, true).map(Some)
 184         } else if let Some(value) = attr.value_str() {
 185             Ok(Some(OnUnimplementedDirective {
 186                 condition: None,
 187                 message: None,
 188                 subcommands: vec![],
 189                 label: Some(OnUnimplementedFormatString::try_parse(
 190                     tcx,
 191                     item_def_id,
 192                     value,
 193                     attr.span,
 194                 )?),
 195                 note: None,
 196                 enclosing_scope: None,
 197                 append_const_msg: None,
 198             }))
 199         } else {
 200             let reported =
 201                 tcx.sess.delay_span_bug(DUMMY_SP, "of_item: neither meta_item_list nor value_str");
 202             return Err(reported);
 203         };
 204         debug!("of_item({:?}) = {:?}", item_def_id, result);
 205         result
 206     }
 207
 208     pub fn evaluate(
 209         &self,
 210         tcx: TyCtxt<'tcx>,
 211         trait_ref: ty::TraitRef<'tcx>,
 212         options: &[(Symbol, Option<String>)],
 213     ) -> OnUnimplementedNote {
 214         let mut message = None;
 215         let mut label = None;
 216         let mut note = None;
 217         let mut enclosing_scope = None;
 218         let mut append_const_msg = None;
 219         info!("evaluate({:?}, trait_ref={:?}, options={:?})", self, trait_ref, options);
 220
 221         let options_map: FxHashMap<Symbol, String> =
 222             options.iter().filter_map(|(k, v)| v.as_ref().map(|v| (*k, v.to_owned()))).collect();
 223
 224         for command in self.subcommands.iter().chain(Some(self)).rev() {
 225             if let Some(ref condition) = command.condition && !attr::eval_condition(
 226                 condition,
 227                 &tcx.sess.parse_sess,
 228                 Some(tcx.features()),
 229                 &mut |cfg| {
 230                     let value = cfg.value.map(|v| {
 231                         OnUnimplementedFormatString(v).format(tcx, trait_ref, &options_map)
 232                     });
 233
 234                     options.contains(&(cfg.name, value))
 235                 },
 236             ) {
 237                 debug!("evaluate: skipping {:?} due to condition", command);
 238                 continue;
 239             }
 240             debug!("evaluate: {:?} succeeded", command);
 241             if let Some(ref message_) = command.message {
 242                 message = Some(message_.clone());
 243             }
 244
 245             if let Some(ref label_) = command.label {
 246                 label = Some(label_.clone());
 247             }
 248
 249             if let Some(ref note_) = command.note {
 250                 note = Some(note_.clone());
 251             }
 252
 253             if let Some(ref enclosing_scope_) = command.enclosing_scope {
 254                 enclosing_scope = Some(enclosing_scope_.clone());
 255             }
 256
 257             append_const_msg = command.append_const_msg;
 258         }
 259
 260         OnUnimplementedNote {
 261             label: label.map(|l| l.format(tcx, trait_ref, &options_map)),
 262             message: message.map(|m| m.format(tcx, trait_ref, &options_map)),
 263             note: note.map(|n| n.format(tcx, trait_ref, &options_map)),
 264             enclosing_scope: enclosing_scope.map(|e_s| e_s.format(tcx, trait_ref, &options_map)),
 265             append_const_msg,
 266         }
 267     }
 268 }
 269
 270 impl<'tcx> OnUnimplementedFormatString {
 271     fn try_parse(
 272         tcx: TyCtxt<'tcx>,
 273         item_def_id: DefId,
 274         from: Symbol,
 275         err_sp: Span,
 276     ) -> Result<Self, ErrorGuaranteed> {
 277         let result = OnUnimplementedFormatString(from);
 278         result.verify(tcx, item_def_id, err_sp)?;
 279         Ok(result)
 280     }
 281
 282     fn verify(
 283         &self,
 284         tcx: TyCtxt<'tcx>,
 285         item_def_id: DefId,
 286         span: Span,
 287     ) -> Result<(), ErrorGuaranteed> {
 288         let trait_def_id = if tcx.is_trait(item_def_id) {
 289             item_def_id
 290         } else {
 291             tcx.trait_id_of_impl(item_def_id)
 292                 .expect("expected `on_unimplemented` to correspond to a trait")
 293         };
 294         let trait_name = tcx.item_name(trait_def_id);
 295         let generics = tcx.generics_of(item_def_id);
 296         let s = self.0.as_str();
 297         let parser = Parser::new(s, None, None, false, ParseMode::Format);
 298         let mut result = Ok(());
 299         for token in parser {
 300             match token {
 301                 Piece::String(_) => (), // Normal string, no need to check it
 302                 Piece::NextArgument(a) => match a.position {
 303                     Position::ArgumentNamed(s) => {
 304                         match Symbol::intern(s) {
 305                             // `{Self}` is allowed
 306                             kw::SelfUpper => (),
 307                             // `{ThisTraitsName}` is allowed
 308                             s if s == trait_name => (),
 309                             // `{from_method}` is allowed
 310                             sym::from_method => (),
 311                             // `{from_desugaring}` is allowed
 312                             sym::from_desugaring => (),
 313                             // `{ItemContext}` is allowed
 314                             sym::ItemContext => (),
 315                             // `{integral}` and `{integer}` and `{float}` are allowed
 316                             sym::integral | sym::integer_ | sym::float => (),
 317                             // So is `{A}` if A is a type parameter
 318                             s => match generics.params.iter().find(|param| param.name == s) {
 319                                 Some(_) => (),
 320                                 None => {
 321                                     let reported = struct_span_err!(
 322                                         tcx.sess,
 323                                         span,
 324                                         E0230,
 325                                         "there is no parameter `{}` on {}",
 326                                         s,
 327                                         if trait_def_id == item_def_id {
 328                                             format!("trait `{}`", trait_name)
 329                                         } else {
 330                                             "impl".to_string()
 331                                         }
 332                                     )
 333                                     .emit();
 334                                     result = Err(reported);
 335                                 }
 336                             },
 337                         }
 338                     }
 339                     // `{:1}` and `{}` are not to be used
 340                     Position::ArgumentIs(..) | Position::ArgumentImplicitlyIs(_) => {
 341                         let reported = struct_span_err!(
 342                             tcx.sess,
 343                             span,
 344                             E0231,
 345                             "only named substitution parameters are allowed"
 346                         )
 347                         .emit();
 348                         result = Err(reported);
 349                     }
 350                 },
 351             }
 352         }
 353
 354         result
 355     }
 356
 357     pub fn format(
 358         &self,
 359         tcx: TyCtxt<'tcx>,
 360         trait_ref: ty::TraitRef<'tcx>,
 361         options: &FxHashMap<Symbol, String>,
 362     ) -> String {
 363         let name = tcx.item_name(trait_ref.def_id);
 364         let trait_str = tcx.def_path_str(trait_ref.def_id);
 365         let generics = tcx.generics_of(trait_ref.def_id);
 366         let generic_map = generics
 367             .params
 368             .iter()
 369             .filter_map(|param| {
 370                 let value = match param.kind {
 371                     GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
 372                         trait_ref.substs[param.index as usize].to_string()
 373                     }
 374                     GenericParamDefKind::Lifetime => return None,
 375                 };
 376                 let name = param.name;
 377                 Some((name, value))
 378             })
 379             .collect::<FxHashMap<Symbol, String>>();
 380         let empty_string = String::new();
 381
 382         let s = self.0.as_str();
 383         let parser = Parser::new(s, None, None, false, ParseMode::Format);
 384         let item_context = (options.get(&sym::ItemContext)).unwrap_or(&empty_string);
 385         parser
 386             .map(|p| match p {
 387                 Piece::String(s) => s,
 388                 Piece::NextArgument(a) => match a.position {
 389                     Position::ArgumentNamed(s) => {
 390                         let s = Symbol::intern(s);
 391                         match generic_map.get(&s) {
 392                             Some(val) => val,
 393                             None if s == name => &trait_str,
 394                             None => {
 395                                 if let Some(val) = options.get(&s) {
 396                                     val
 397                                 } else if s == sym::from_desugaring || s == sym::from_method {
 398                                     // don't break messages using these two arguments incorrectly
 399                                     &empty_string
 400                                 } else if s == sym::ItemContext {
 401                                     &item_context
 402                                 } else if s == sym::integral {
 403                                     "{integral}"
 404                                 } else if s == sym::integer_ {
 405                                     "{integer}"
 406                                 } else if s == sym::float {
 407                                     "{float}"
 408                                 } else {
 409                                     bug!(
 410                                         "broken on_unimplemented {:?} for {:?}: \
 411                                       no argument matching {:?}",
 412                                         self.0,
 413                                         trait_ref,
 414                                         s
 415                                     )
 416                                 }
 417                             }
 418                         }
 419                     }
 420                     _ => bug!("broken on_unimplemented {:?} - bad format arg", self.0),
 421                 },
 422             })
 423             .collect()
 424     }
 425 }