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 |item| {
  93                 if let Some(symbol) = item.value_str() && let Err(guar) = parse_value(symbol) {
  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 |c| {
 230                     c.ident().map_or(false, |ident| {
 231                         let value = c.value_str().map(|s| {
 232                             OnUnimplementedFormatString(s).format(tcx, trait_ref, &options_map)
 233                         });
 234
 235                         options.contains(&(ident.name, value))
 236                     })
 237                 },
 238             ) {
 239                 debug!("evaluate: skipping {:?} due to condition", command);
 240                 continue;
 241             }
 242             debug!("evaluate: {:?} succeeded", command);
 243             if let Some(ref message_) = command.message {
 244                 message = Some(message_.clone());
 245             }
 246
 247             if let Some(ref label_) = command.label {
 248                 label = Some(label_.clone());
 249             }
 250
 251             if let Some(ref note_) = command.note {
 252                 note = Some(note_.clone());
 253             }
 254
 255             if let Some(ref enclosing_scope_) = command.enclosing_scope {
 256                 enclosing_scope = Some(enclosing_scope_.clone());
 257             }
 258
 259             append_const_msg = command.append_const_msg;
 260         }
 261
 262         OnUnimplementedNote {
 263             label: label.map(|l| l.format(tcx, trait_ref, &options_map)),
 264             message: message.map(|m| m.format(tcx, trait_ref, &options_map)),
 265             note: note.map(|n| n.format(tcx, trait_ref, &options_map)),
 266             enclosing_scope: enclosing_scope.map(|e_s| e_s.format(tcx, trait_ref, &options_map)),
 267             append_const_msg,
 268         }
 269     }
 270 }
 271
 272 impl<'tcx> OnUnimplementedFormatString {
 273     fn try_parse(
 274         tcx: TyCtxt<'tcx>,
 275         item_def_id: DefId,
 276         from: Symbol,
 277         err_sp: Span,
 278     ) -> Result<Self, ErrorGuaranteed> {
 279         let result = OnUnimplementedFormatString(from);
 280         result.verify(tcx, item_def_id, err_sp)?;
 281         Ok(result)
 282     }
 283
 284     fn verify(
 285         &self,
 286         tcx: TyCtxt<'tcx>,
 287         item_def_id: DefId,
 288         span: Span,
 289     ) -> Result<(), ErrorGuaranteed> {
 290         let trait_def_id = if tcx.is_trait(item_def_id) {
 291             item_def_id
 292         } else {
 293             tcx.trait_id_of_impl(item_def_id)
 294                 .expect("expected `on_unimplemented` to correspond to a trait")
 295         };
 296         let trait_name = tcx.item_name(trait_def_id);
 297         let generics = tcx.generics_of(item_def_id);
 298         let s = self.0.as_str();
 299         let parser = Parser::new(s, None, None, false, ParseMode::Format);
 300         let mut result = Ok(());
 301         for token in parser {
 302             match token {
 303                 Piece::String(_) => (), // Normal string, no need to check it
 304                 Piece::NextArgument(a) => match a.position {
 305                     Position::ArgumentNamed(s, _) => {
 306                         match Symbol::intern(s) {
 307                             // `{Self}` is allowed
 308                             kw::SelfUpper => (),
 309                             // `{ThisTraitsName}` is allowed
 310                             s if s == trait_name => (),
 311                             // `{from_method}` is allowed
 312                             sym::from_method => (),
 313                             // `{from_desugaring}` is allowed
 314                             sym::from_desugaring => (),
 315                             // `{ItemContext}` is allowed
 316                             sym::ItemContext => (),
 317                             // `{integral}` and `{integer}` and `{float}` are allowed
 318                             sym::integral | sym::integer_ | sym::float => (),
 319                             // So is `{A}` if A is a type parameter
 320                             s => match generics.params.iter().find(|param| param.name == s) {
 321                                 Some(_) => (),
 322                                 None => {
 323                                     let reported = struct_span_err!(
 324                                         tcx.sess,
 325                                         span,
 326                                         E0230,
 327                                         "there is no parameter `{}` on {}",
 328                                         s,
 329                                         if trait_def_id == item_def_id {
 330                                             format!("trait `{}`", trait_name)
 331                                         } else {
 332                                             "impl".to_string()
 333                                         }
 334                                     )
 335                                     .emit();
 336                                     result = Err(reported);
 337                                 }
 338                             },
 339                         }
 340                     }
 341                     // `{:1}` and `{}` are not to be used
 342                     Position::ArgumentIs(_) | Position::ArgumentImplicitlyIs(_) => {
 343                         let reported = struct_span_err!(
 344                             tcx.sess,
 345                             span,
 346                             E0231,
 347                             "only named substitution parameters are allowed"
 348                         )
 349                         .emit();
 350                         result = Err(reported);
 351                     }
 352                 },
 353             }
 354         }
 355
 356         result
 357     }
 358
 359     pub fn format(
 360         &self,
 361         tcx: TyCtxt<'tcx>,
 362         trait_ref: ty::TraitRef<'tcx>,
 363         options: &FxHashMap<Symbol, String>,
 364     ) -> String {
 365         let name = tcx.item_name(trait_ref.def_id);
 366         let trait_str = tcx.def_path_str(trait_ref.def_id);
 367         let generics = tcx.generics_of(trait_ref.def_id);
 368         let generic_map = generics
 369             .params
 370             .iter()
 371             .filter_map(|param| {
 372                 let value = match param.kind {
 373                     GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
 374                         trait_ref.substs[param.index as usize].to_string()
 375                     }
 376                     GenericParamDefKind::Lifetime => return None,
 377                 };
 378                 let name = param.name;
 379                 Some((name, value))
 380             })
 381             .collect::<FxHashMap<Symbol, String>>();
 382         let empty_string = String::new();
 383
 384         let s = self.0.as_str();
 385         let parser = Parser::new(s, None, None, false, ParseMode::Format);
 386         let item_context = (options.get(&sym::ItemContext)).unwrap_or(&empty_string);
 387         parser
 388             .map(|p| match p {
 389                 Piece::String(s) => s,
 390                 Piece::NextArgument(a) => match a.position {
 391                     Position::ArgumentNamed(s, _) => {
 392                         let s = Symbol::intern(s);
 393                         match generic_map.get(&s) {
 394                             Some(val) => val,
 395                             None if s == name => &trait_str,
 396                             None => {
 397                                 if let Some(val) = options.get(&s) {
 398                                     val
 399                                 } else if s == sym::from_desugaring || s == sym::from_method {
 400                                     // don't break messages using these two arguments incorrectly
 401                                     &empty_string
 402                                 } else if s == sym::ItemContext {
 403                                     &item_context
 404                                 } else if s == sym::integral {
 405                                     "{integral}"
 406                                 } else if s == sym::integer_ {
 407                                     "{integer}"
 408                                 } else if s == sym::float {
 409                                     "{float}"
 410                                 } else {
 411                                     bug!(
 412                                         "broken on_unimplemented {:?} for {:?}: \
 413                                       no argument matching {:?}",
 414                                         self.0,
 415                                         trait_ref,
 416                                         s
 417                                     )
 418                                 }
 419                             }
 420                         }
 421                     }
 422                     _ => bug!("broken on_unimplemented {:?} - bad format arg", self.0),
 423                 },
 424             })
 425             .collect()
 426     }
 427 }