compiler/rustc_hir_typeck/src/method/prelude2021.rs

   1 use hir::def_id::DefId;
   2 use hir::HirId;
   3 use hir::ItemKind;
   4 use rustc_ast::Mutability;
   5 use rustc_errors::Applicability;
   6 use rustc_hir as hir;
   7 use rustc_middle::ty::subst::InternalSubsts;
   8 use rustc_middle::ty::{Adt, Array, Ref, Ty};
   9 use rustc_session::lint::builtin::RUST_2021_PRELUDE_COLLISIONS;
  10 use rustc_span::symbol::kw::{Empty, Underscore};
  11 use rustc_span::symbol::{sym, Ident};
  12 use rustc_span::Span;
  13 use rustc_trait_selection::infer::InferCtxtExt;
  14
  15 use crate::check::{
  16     method::probe::{self, Pick},
  17     FnCtxt,
  18 };
  19
  20 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  21     pub(super) fn lint_dot_call_from_2018(
  22         &self,
  23         self_ty: Ty<'tcx>,
  24         segment: &hir::PathSegment<'_>,
  25         span: Span,
  26         call_expr: &'tcx hir::Expr<'tcx>,
  27         self_expr: &'tcx hir::Expr<'tcx>,
  28         pick: &Pick<'tcx>,
  29         args: &'tcx [hir::Expr<'tcx>],
  30     ) {
  31         debug!(
  32             "lookup(method_name={}, self_ty={:?}, call_expr={:?}, self_expr={:?})",
  33             segment.ident, self_ty, call_expr, self_expr
  34         );
  35
  36         // Rust 2021 and later is already using the new prelude
  37         if span.rust_2021() {
  38             return;
  39         }
  40
  41         let prelude_or_array_lint = match segment.ident.name {
  42             // `try_into` was added to the prelude in Rust 2021.
  43             sym::try_into => RUST_2021_PRELUDE_COLLISIONS,
  44             // `into_iter` wasn't added to the prelude,
  45             // but `[T; N].into_iter()` doesn't resolve to IntoIterator::into_iter
  46             // before Rust 2021, which results in the same problem.
  47             // It is only a problem for arrays.
  48             sym::into_iter if let Array(..) = self_ty.kind() => {
  49                 // In this case, it wasn't really a prelude addition that was the problem.
  50                 // Instead, the problem is that the array-into_iter hack will no longer apply in Rust 2021.
  51                 rustc_lint::ARRAY_INTO_ITER
  52             }
  53             _ => return,
  54         };
  55
  56         // No need to lint if method came from std/core, as that will now be in the prelude
  57         if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) {
  58             return;
  59         }
  60
  61         if matches!(pick.kind, probe::PickKind::InherentImplPick | probe::PickKind::ObjectPick) {
  62             // avoid repeatedly adding unneeded `&*`s
  63             if pick.autoderefs == 1
  64                 && matches!(
  65                     pick.autoref_or_ptr_adjustment,
  66                     Some(probe::AutorefOrPtrAdjustment::Autoref { .. })
  67                 )
  68                 && matches!(self_ty.kind(), Ref(..))
  69             {
  70                 return;
  71             }
  72
  73             // if it's an inherent `self` method (not `&self` or `&mut self`), it will take
  74             // precedence over the `TryInto` impl, and thus won't break in 2021 edition
  75             if pick.autoderefs == 0 && pick.autoref_or_ptr_adjustment.is_none() {
  76                 return;
  77             }
  78
  79             // Inherent impls only require not relying on autoref and autoderef in order to
  80             // ensure that the trait implementation won't be used
  81             self.tcx.struct_span_lint_hir(
  82                 prelude_or_array_lint,
  83                 self_expr.hir_id,
  84                 self_expr.span,
  85                 format!("trait method `{}` will become ambiguous in Rust 2021", segment.ident.name),
  86                 |lint| {
  87                     let sp = self_expr.span;
  88
  89                     let derefs = "*".repeat(pick.autoderefs);
  90
  91                     let autoref = match pick.autoref_or_ptr_adjustment {
  92                         Some(probe::AutorefOrPtrAdjustment::Autoref {
  93                             mutbl: Mutability::Mut,
  94                             ..
  95                         }) => "&mut ",
  96                         Some(probe::AutorefOrPtrAdjustment::Autoref {
  97                             mutbl: Mutability::Not,
  98                             ..
  99                         }) => "&",
 100                         Some(probe::AutorefOrPtrAdjustment::ToConstPtr) | None => "",
 101                     };
 102                     if let Ok(self_expr) = self.sess().source_map().span_to_snippet(self_expr.span)
 103                     {
 104                         let self_adjusted = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) =
 105                             pick.autoref_or_ptr_adjustment
 106                         {
 107                             format!("{}{} as *const _", derefs, self_expr)
 108                         } else {
 109                             format!("{}{}{}", autoref, derefs, self_expr)
 110                         };
 111
 112                         lint.span_suggestion(
 113                             sp,
 114                             "disambiguate the method call",
 115                             format!("({})", self_adjusted),
 116                             Applicability::MachineApplicable,
 117                         );
 118                     } else {
 119                         let self_adjusted = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) =
 120                             pick.autoref_or_ptr_adjustment
 121                         {
 122                             format!("{}(...) as *const _", derefs)
 123                         } else {
 124                             format!("{}{}...", autoref, derefs)
 125                         };
 126                         lint.span_help(
 127                             sp,
 128                             &format!("disambiguate the method call with `({})`", self_adjusted,),
 129                         );
 130                     }
 131
 132                     lint
 133                 },
 134             );
 135         } else {
 136             // trait implementations require full disambiguation to not clash with the new prelude
 137             // additions (i.e. convert from dot-call to fully-qualified call)
 138             self.tcx.struct_span_lint_hir(
 139                 prelude_or_array_lint,
 140                 call_expr.hir_id,
 141                 call_expr.span,
 142                 format!("trait method `{}` will become ambiguous in Rust 2021", segment.ident.name),
 143                 |lint| {
 144                     let sp = call_expr.span;
 145                     let trait_name = self.trait_path_or_bare_name(
 146                         span,
 147                         call_expr.hir_id,
 148                         pick.item.container_id(self.tcx),
 149                     );
 150
 151                     let (self_adjusted, precise) = self.adjust_expr(pick, self_expr, sp);
 152                     if precise {
 153                         let args = args
 154                             .iter()
 155                             .map(|arg| {
 156                                 let span = arg.span.find_ancestor_inside(sp).unwrap_or_default();
 157                                 format!(
 158                                     ", {}",
 159                                     self.sess().source_map().span_to_snippet(span).unwrap()
 160                                 )
 161                             })
 162                             .collect::<String>();
 163
 164                         lint.span_suggestion(
 165                             sp,
 166                             "disambiguate the associated function",
 167                             format!(
 168                                 "{}::{}{}({}{})",
 169                                 trait_name,
 170                                 segment.ident.name,
 171                                 if let Some(args) = segment.args.as_ref().and_then(|args| self
 172                                     .sess()
 173                                     .source_map()
 174                                     .span_to_snippet(args.span_ext)
 175                                     .ok())
 176                                 {
 177                                     // Keep turbofish.
 178                                     format!("::{}", args)
 179                                 } else {
 180                                     String::new()
 181                                 },
 182                                 self_adjusted,
 183                                 args,
 184                             ),
 185                             Applicability::MachineApplicable,
 186                         );
 187                     } else {
 188                         lint.span_help(
 189                             sp,
 190                             &format!(
 191                                 "disambiguate the associated function with `{}::{}(...)`",
 192                                 trait_name, segment.ident,
 193                             ),
 194                         );
 195                     }
 196
 197                     lint
 198                 },
 199             );
 200         }
 201     }
 202
 203     pub(super) fn lint_fully_qualified_call_from_2018(
 204         &self,
 205         span: Span,
 206         method_name: Ident,
 207         self_ty: Ty<'tcx>,
 208         self_ty_span: Span,
 209         expr_id: hir::HirId,
 210         pick: &Pick<'tcx>,
 211     ) {
 212         // Rust 2021 and later is already using the new prelude
 213         if span.rust_2021() {
 214             return;
 215         }
 216
 217         // These are the fully qualified methods added to prelude in Rust 2021
 218         if !matches!(method_name.name, sym::try_into | sym::try_from | sym::from_iter) {
 219             return;
 220         }
 221
 222         // No need to lint if method came from std/core, as that will now be in the prelude
 223         if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) {
 224             return;
 225         }
 226
 227         // For from_iter, check if the type actually implements FromIterator.
 228         // If we know it does not, we don't need to warn.
 229         if method_name.name == sym::from_iter {
 230             if let Some(trait_def_id) = self.tcx.get_diagnostic_item(sym::FromIterator) {
 231                 if !self
 232                     .infcx
 233                     .type_implements_trait(
 234                         trait_def_id,
 235                         self_ty,
 236                         InternalSubsts::empty(),
 237                         self.param_env,
 238                     )
 239                     .may_apply()
 240                 {
 241                     return;
 242                 }
 243             }
 244         }
 245
 246         // No need to lint if this is an inherent method called on a specific type, like `Vec::foo(...)`,
 247         // since such methods take precedence over trait methods.
 248         if matches!(pick.kind, probe::PickKind::InherentImplPick) {
 249             return;
 250         }
 251
 252         self.tcx.struct_span_lint_hir(
 253             RUST_2021_PRELUDE_COLLISIONS,
 254             expr_id,
 255             span,
 256             format!(
 257                 "trait-associated function `{}` will become ambiguous in Rust 2021",
 258                 method_name.name
 259             ),
 260             |lint| {
 261                 // "type" refers to either a type or, more likely, a trait from which
 262                 // the associated function or method is from.
 263                 let container_id = pick.item.container_id(self.tcx);
 264                 let trait_path = self.trait_path_or_bare_name(span, expr_id, container_id);
 265                 let trait_generics = self.tcx.generics_of(container_id);
 266
 267                 let trait_name = if trait_generics.params.len() <= trait_generics.has_self as usize
 268                 {
 269                     trait_path
 270                 } else {
 271                     let counts = trait_generics.own_counts();
 272                     format!(
 273                         "{}<{}>",
 274                         trait_path,
 275                         std::iter::repeat("'_")
 276                             .take(counts.lifetimes)
 277                             .chain(std::iter::repeat("_").take(
 278                                 counts.types + counts.consts - trait_generics.has_self as usize
 279                             ))
 280                             .collect::<Vec<_>>()
 281                             .join(", ")
 282                     )
 283                 };
 284
 285                 let mut self_ty_name = self_ty_span
 286                     .find_ancestor_inside(span)
 287                     .and_then(|span| self.sess().source_map().span_to_snippet(span).ok())
 288                     .unwrap_or_else(|| self_ty.to_string());
 289
 290                 // Get the number of generics the self type has (if an Adt) unless we can determine that
 291                 // the user has written the self type with generics already which we (naively) do by looking
 292                 // for a "<" in `self_ty_name`.
 293                 if !self_ty_name.contains('<') {
 294                     if let Adt(def, _) = self_ty.kind() {
 295                         let generics = self.tcx.generics_of(def.did());
 296                         if !generics.params.is_empty() {
 297                             let counts = generics.own_counts();
 298                             self_ty_name += &format!(
 299                                 "<{}>",
 300                                 std::iter::repeat("'_")
 301                                     .take(counts.lifetimes)
 302                                     .chain(
 303                                         std::iter::repeat("_").take(counts.types + counts.consts)
 304                                     )
 305                                     .collect::<Vec<_>>()
 306                                     .join(", ")
 307                             );
 308                         }
 309                     }
 310                 }
 311                 lint.span_suggestion(
 312                     span,
 313                     "disambiguate the associated function",
 314                     format!("<{} as {}>::{}", self_ty_name, trait_name, method_name.name,),
 315                     Applicability::MachineApplicable,
 316                 );
 317
 318                 lint
 319             },
 320         );
 321     }
 322
 323     fn trait_path_or_bare_name(
 324         &self,
 325         span: Span,
 326         expr_hir_id: HirId,
 327         trait_def_id: DefId,
 328     ) -> String {
 329         self.trait_path(span, expr_hir_id, trait_def_id).unwrap_or_else(|| {
 330             let key = self.tcx.def_key(trait_def_id);
 331             format!("{}", key.disambiguated_data.data)
 332         })
 333     }
 334
 335     fn trait_path(&self, span: Span, expr_hir_id: HirId, trait_def_id: DefId) -> Option<String> {
 336         let applicable_traits = self.tcx.in_scope_traits(expr_hir_id)?;
 337         let applicable_trait = applicable_traits.iter().find(|t| t.def_id == trait_def_id)?;
 338         if applicable_trait.import_ids.is_empty() {
 339             // The trait was declared within the module, we only need to use its name.
 340             return None;
 341         }
 342
 343         let import_items: Vec<_> = applicable_trait
 344             .import_ids
 345             .iter()
 346             .map(|&import_id| self.tcx.hir().expect_item(import_id))
 347             .collect();
 348
 349         // Find an identifier with which this trait was imported (note that `_` doesn't count).
 350         let any_id = import_items
 351             .iter()
 352             .filter_map(|item| if item.ident.name != Underscore { Some(item.ident) } else { None })
 353             .next();
 354         if let Some(any_id) = any_id {
 355             if any_id.name == Empty {
 356                 // Glob import, so just use its name.
 357                 return None;
 358             } else {
 359                 return Some(format!("{}", any_id));
 360             }
 361         }
 362
 363         // All that is left is `_`! We need to use the full path. It doesn't matter which one we pick,
 364         // so just take the first one.
 365         match import_items[0].kind {
 366             ItemKind::Use(path, _) => Some(
 367                 path.segments
 368                     .iter()
 369                     .map(|segment| segment.ident.to_string())
 370                     .collect::<Vec<_>>()
 371                     .join("::"),
 372             ),
 373             _ => {
 374                 span_bug!(span, "unexpected item kind, expected a use: {:?}", import_items[0].kind);
 375             }
 376         }
 377     }
 378
 379     /// Creates a string version of the `expr` that includes explicit adjustments.
 380     /// Returns the string and also a bool indicating whether this is a *precise*
 381     /// suggestion.
 382     fn adjust_expr(
 383         &self,
 384         pick: &Pick<'tcx>,
 385         expr: &hir::Expr<'tcx>,
 386         outer: Span,
 387     ) -> (String, bool) {
 388         let derefs = "*".repeat(pick.autoderefs);
 389
 390         let autoref = match pick.autoref_or_ptr_adjustment {
 391             Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl: Mutability::Mut, .. }) => "&mut ",
 392             Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl: Mutability::Not, .. }) => "&",
 393             Some(probe::AutorefOrPtrAdjustment::ToConstPtr) | None => "",
 394         };
 395
 396         let (expr_text, precise) = if let Some(expr_text) = expr
 397             .span
 398             .find_ancestor_inside(outer)
 399             .and_then(|span| self.sess().source_map().span_to_snippet(span).ok())
 400         {
 401             (expr_text, true)
 402         } else {
 403             ("(..)".to_string(), false)
 404         };
 405
 406         let adjusted_text = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) =
 407             pick.autoref_or_ptr_adjustment
 408         {
 409             format!("{}{} as *const _", derefs, expr_text)
 410         } else {
 411             format!("{}{}{}", autoref, derefs, expr_text)
 412         };
 413
 414         (adjusted_text, precise)
 415     }
 416 }