compiler/rustc_typeck/src/check/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::{Ref, Ty};
   8 use rustc_session::lint::builtin::FUTURE_PRELUDE_COLLISION;
   9 use rustc_span::symbol::kw::Underscore;
  10 use rustc_span::symbol::{sym, Ident};
  11 use rustc_span::Span;
  12
  13 use crate::check::{
  14     method::probe::{self, Pick},
  15     FnCtxt,
  16 };
  17
  18 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  19     pub(super) fn lint_dot_call_from_2018(
  20         &self,
  21         self_ty: Ty<'tcx>,
  22         segment: &hir::PathSegment<'_>,
  23         span: Span,
  24         call_expr: &'tcx hir::Expr<'tcx>,
  25         self_expr: &'tcx hir::Expr<'tcx>,
  26         pick: &Pick<'tcx>,
  27         args: &'tcx [hir::Expr<'tcx>],
  28     ) {
  29         debug!(
  30             "lookup(method_name={}, self_ty={:?}, call_expr={:?}, self_expr={:?})",
  31             segment.ident, self_ty, call_expr, self_expr
  32         );
  33
  34         // Rust 2021 and later is already using the new prelude
  35         if span.rust_2021() {
  36             return;
  37         }
  38
  39         // These are the method names that were added to prelude in Rust 2021
  40         if !matches!(segment.ident.name, sym::try_into) {
  41             return;
  42         }
  43
  44         // No need to lint if method came from std/core, as that will now be in the prelude
  45         if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) {
  46             return;
  47         }
  48
  49         if matches!(pick.kind, probe::PickKind::InherentImplPick | probe::PickKind::ObjectPick) {
  50             // avoid repeatedly adding unneeded `&*`s
  51             if pick.autoderefs == 1
  52                 && matches!(
  53                     pick.autoref_or_ptr_adjustment,
  54                     Some(probe::AutorefOrPtrAdjustment::Autoref { .. })
  55                 )
  56                 && matches!(self_ty.kind(), Ref(..))
  57             {
  58                 return;
  59             }
  60             // Inherent impls only require not relying on autoref and autoderef in order to
  61             // ensure that the trait implementation won't be used
  62             self.tcx.struct_span_lint_hir(
  63                 FUTURE_PRELUDE_COLLISION,
  64                 self_expr.hir_id,
  65                 self_expr.span,
  66                 |lint| {
  67                     let sp = self_expr.span;
  68
  69                     let mut lint = lint.build(&format!(
  70                         "trait method `{}` will become ambiguous in Rust 2021",
  71                         segment.ident.name
  72                     ));
  73
  74                     let derefs = "*".repeat(pick.autoderefs);
  75
  76                     let autoref = match pick.autoref_or_ptr_adjustment {
  77                         Some(probe::AutorefOrPtrAdjustment::Autoref {
  78                             mutbl: Mutability::Mut,
  79                             ..
  80                         }) => "&mut ",
  81                         Some(probe::AutorefOrPtrAdjustment::Autoref {
  82                             mutbl: Mutability::Not,
  83                             ..
  84                         }) => "&",
  85                         Some(probe::AutorefOrPtrAdjustment::ToConstPtr) | None => "",
  86                     };
  87                     if let Ok(self_expr) = self.sess().source_map().span_to_snippet(self_expr.span)
  88                     {
  89                         let self_adjusted = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) =
  90                             pick.autoref_or_ptr_adjustment
  91                         {
  92                             format!("{}{} as *const _", derefs, self_expr)
  93                         } else {
  94                             format!("{}{}{}", autoref, derefs, self_expr)
  95                         };
  96
  97                         lint.span_suggestion(
  98                             sp,
  99                             "disambiguate the method call",
 100                             format!("({})", self_adjusted),
 101                             Applicability::MachineApplicable,
 102                         );
 103                     } else {
 104                         let self_adjusted = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) =
 105                             pick.autoref_or_ptr_adjustment
 106                         {
 107                             format!("{}(...) as *const _", derefs)
 108                         } else {
 109                             format!("{}{}...", autoref, derefs)
 110                         };
 111                         lint.span_help(
 112                             sp,
 113                             &format!("disambiguate the method call with `({})`", self_adjusted,),
 114                         );
 115                     }
 116
 117                     lint.emit();
 118                 },
 119             );
 120         } else {
 121             // trait implementations require full disambiguation to not clash with the new prelude
 122             // additions (i.e. convert from dot-call to fully-qualified call)
 123             self.tcx.struct_span_lint_hir(
 124                 FUTURE_PRELUDE_COLLISION,
 125                 call_expr.hir_id,
 126                 call_expr.span,
 127                 |lint| {
 128                     let sp = call_expr.span;
 129                     let trait_name = self.trait_path_or_bare_name(
 130                         span,
 131                         call_expr.hir_id,
 132                         pick.item.container.id(),
 133                     );
 134
 135                     let mut lint = lint.build(&format!(
 136                         "trait method `{}` will become ambiguous in Rust 2021",
 137                         segment.ident.name
 138                     ));
 139
 140                     let (self_adjusted, precise) = self.adjust_expr(pick, self_expr);
 141                     if precise {
 142                         let args = args
 143                             .iter()
 144                             .skip(1)
 145                             .map(|arg| {
 146                                 format!(
 147                                     ", {}",
 148                                     self.sess().source_map().span_to_snippet(arg.span).unwrap()
 149                                 )
 150                             })
 151                             .collect::<String>();
 152
 153                         lint.span_suggestion(
 154                             sp,
 155                             "disambiguate the associated function",
 156                             format!(
 157                                 "{}::{}({}{})",
 158                                 trait_name, segment.ident.name, self_adjusted, args
 159                             ),
 160                             Applicability::MachineApplicable,
 161                         );
 162                     } else {
 163                         lint.span_help(
 164                             sp,
 165                             &format!(
 166                                 "disambiguate the associated function with `{}::{}(...)`",
 167                                 trait_name, segment.ident,
 168                             ),
 169                         );
 170                     }
 171
 172                     lint.emit();
 173                 },
 174             );
 175         }
 176     }
 177
 178     pub(super) fn lint_fully_qualified_call_from_2018(
 179         &self,
 180         span: Span,
 181         method_name: Ident,
 182         self_ty: Ty<'tcx>,
 183         self_ty_span: Span,
 184         expr_id: hir::HirId,
 185         pick: &Pick<'tcx>,
 186     ) {
 187         // Rust 2021 and later is already using the new prelude
 188         if span.rust_2021() {
 189             return;
 190         }
 191
 192         // These are the fully qualified methods added to prelude in Rust 2021
 193         if !matches!(method_name.name, sym::try_into | sym::try_from | sym::from_iter) {
 194             return;
 195         }
 196
 197         // No need to lint if method came from std/core, as that will now be in the prelude
 198         if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) {
 199             return;
 200         }
 201
 202         // No need to lint if this is an inherent method called on a specific type, like `Vec::foo(...)`,
 203         // since such methods take precedence over trait methods.
 204         if matches!(pick.kind, probe::PickKind::InherentImplPick) {
 205             return;
 206         }
 207
 208         self.tcx.struct_span_lint_hir(FUTURE_PRELUDE_COLLISION, expr_id, span, |lint| {
 209             // "type" refers to either a type or, more likely, a trait from which
 210             // the associated function or method is from.
 211             let trait_path = self.trait_path_or_bare_name(span, expr_id, pick.item.container.id());
 212             let trait_generics = self.tcx.generics_of(pick.item.container.id());
 213
 214             let parameter_count = trait_generics.count() - (trait_generics.has_self as usize);
 215             let trait_name = if parameter_count == 0 {
 216                 trait_path
 217             } else {
 218                 format!(
 219                     "{}<{}>",
 220                     trait_path,
 221                     std::iter::repeat("_").take(parameter_count).collect::<Vec<_>>().join(", ")
 222                 )
 223             };
 224
 225             let mut lint = lint.build(&format!(
 226                 "trait-associated function `{}` will become ambiguous in Rust 2021",
 227                 method_name.name
 228             ));
 229
 230             let self_ty = self
 231                 .sess()
 232                 .source_map()
 233                 .span_to_snippet(self_ty_span)
 234                 .unwrap_or_else(|_| self_ty.to_string());
 235
 236             lint.span_suggestion(
 237                 span,
 238                 "disambiguate the associated function",
 239                 format!("<{} as {}>::{}", self_ty, trait_name, method_name.name,),
 240                 Applicability::MachineApplicable,
 241             );
 242
 243             lint.emit();
 244         });
 245     }
 246
 247     fn trait_path_or_bare_name(
 248         &self,
 249         span: Span,
 250         expr_hir_id: HirId,
 251         trait_def_id: DefId,
 252     ) -> String {
 253         self.trait_path(span, expr_hir_id, trait_def_id).unwrap_or_else(|| {
 254             let key = self.tcx.def_key(trait_def_id);
 255             format!("{}", key.disambiguated_data.data)
 256         })
 257     }
 258
 259     fn trait_path(&self, span: Span, expr_hir_id: HirId, trait_def_id: DefId) -> Option<String> {
 260         let applicable_traits = self.tcx.in_scope_traits(expr_hir_id)?;
 261         let applicable_trait = applicable_traits.iter().find(|t| t.def_id == trait_def_id)?;
 262         if applicable_trait.import_ids.is_empty() {
 263             // The trait was declared within the module, we only need to use its name.
 264             return None;
 265         }
 266
 267         let import_items: Vec<_> = applicable_trait
 268             .import_ids
 269             .iter()
 270             .map(|&import_id| {
 271                 let hir_id = self.tcx.hir().local_def_id_to_hir_id(import_id);
 272                 self.tcx.hir().expect_item(hir_id)
 273             })
 274             .collect();
 275
 276         // Find an identifier with which this trait was imported (note that `_` doesn't count).
 277         let any_id = import_items
 278             .iter()
 279             .filter_map(|item| if item.ident.name != Underscore { Some(item.ident) } else { None })
 280             .next();
 281         if let Some(any_id) = any_id {
 282             return Some(format!("{}", any_id));
 283         }
 284
 285         // All that is left is `_`! We need to use the full path. It doesn't matter which one we pick,
 286         // so just take the first one.
 287         match import_items[0].kind {
 288             ItemKind::Use(path, _) => Some(
 289                 path.segments
 290                     .iter()
 291                     .map(|segment| segment.ident.to_string())
 292                     .collect::<Vec<_>>()
 293                     .join("::"),
 294             ),
 295             _ => {
 296                 span_bug!(span, "unexpected item kind, expected a use: {:?}", import_items[0].kind);
 297             }
 298         }
 299     }
 300
 301     /// Creates a string version of the `expr` that includes explicit adjustments.
 302     /// Returns the string and also a bool indicating whther this is a *precise*
 303     /// suggestion.
 304     fn adjust_expr(&self, pick: &Pick<'tcx>, expr: &hir::Expr<'tcx>) -> (String, bool) {
 305         let derefs = "*".repeat(pick.autoderefs);
 306
 307         let autoref = match pick.autoref_or_ptr_adjustment {
 308             Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl: Mutability::Mut, .. }) => "&mut ",
 309             Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl: Mutability::Not, .. }) => "&",
 310             Some(probe::AutorefOrPtrAdjustment::ToConstPtr) | None => "",
 311         };
 312
 313         let (expr_text, precise) =
 314             if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
 315                 (expr_text, true)
 316             } else {
 317                 (format!("(..)"), false)
 318             };
 319
 320         let adjusted_text = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) =
 321             pick.autoref_or_ptr_adjustment
 322         {
 323             format!("{}{} as *const _", derefs, expr_text)
 324         } else {
 325             format!("{}{}{}", autoref, derefs, expr_text)
 326         };
 327
 328         (adjusted_text, precise)
 329     }
 330 }