diff options
Diffstat (limited to 'compiler/rustc_typeck/src/check/method/prelude2021.rs')
| -rw-r--r-- | compiler/rustc_typeck/src/check/method/prelude2021.rs | 419 |
1 files changed, 419 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/check/method/prelude2021.rs b/compiler/rustc_typeck/src/check/method/prelude2021.rs new file mode 100644 index 000000000..7c68d9304 --- /dev/null +++ b/compiler/rustc_typeck/src/check/method/prelude2021.rs @@ -0,0 +1,419 @@ +use hir::def_id::DefId; +use hir::HirId; +use hir::ItemKind; +use rustc_ast::Mutability; +use rustc_errors::Applicability; +use rustc_hir as hir; +use rustc_middle::ty::subst::InternalSubsts; +use rustc_middle::ty::{Adt, Array, Ref, Ty}; +use rustc_session::lint::builtin::RUST_2021_PRELUDE_COLLISIONS; +use rustc_span::symbol::kw::{Empty, Underscore}; +use rustc_span::symbol::{sym, Ident}; +use rustc_span::Span; +use rustc_trait_selection::infer::InferCtxtExt; + +use crate::check::{ + method::probe::{self, Pick}, + FnCtxt, +}; + +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + pub(super) fn lint_dot_call_from_2018( + &self, + self_ty: Ty<'tcx>, + segment: &hir::PathSegment<'_>, + span: Span, + call_expr: &'tcx hir::Expr<'tcx>, + self_expr: &'tcx hir::Expr<'tcx>, + pick: &Pick<'tcx>, + args: &'tcx [hir::Expr<'tcx>], + ) { + debug!( + "lookup(method_name={}, self_ty={:?}, call_expr={:?}, self_expr={:?})", + segment.ident, self_ty, call_expr, self_expr + ); + + // Rust 2021 and later is already using the new prelude + if span.rust_2021() { + return; + } + + let prelude_or_array_lint = match segment.ident.name { + // `try_into` was added to the prelude in Rust 2021. + sym::try_into => RUST_2021_PRELUDE_COLLISIONS, + // `into_iter` wasn't added to the prelude, + // but `[T; N].into_iter()` doesn't resolve to IntoIterator::into_iter + // before Rust 2021, which results in the same problem. + // It is only a problem for arrays. + sym::into_iter if let Array(..) = self_ty.kind() => { + // In this case, it wasn't really a prelude addition that was the problem. + // Instead, the problem is that the array-into_iter hack will no longer apply in Rust 2021. + rustc_lint::ARRAY_INTO_ITER + } + _ => return, + }; + + // No need to lint if method came from std/core, as that will now be in the prelude + if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) { + return; + } + + if matches!(pick.kind, probe::PickKind::InherentImplPick | probe::PickKind::ObjectPick) { + // avoid repeatedly adding unneeded `&*`s + if pick.autoderefs == 1 + && matches!( + pick.autoref_or_ptr_adjustment, + Some(probe::AutorefOrPtrAdjustment::Autoref { .. }) + ) + && matches!(self_ty.kind(), Ref(..)) + { + return; + } + + // if it's an inherent `self` method (not `&self` or `&mut self`), it will take + // precedence over the `TryInto` impl, and thus won't break in 2021 edition + if pick.autoderefs == 0 && pick.autoref_or_ptr_adjustment.is_none() { + return; + } + + // Inherent impls only require not relying on autoref and autoderef in order to + // ensure that the trait implementation won't be used + self.tcx.struct_span_lint_hir( + prelude_or_array_lint, + self_expr.hir_id, + self_expr.span, + |lint| { + let sp = self_expr.span; + + let mut lint = lint.build(&format!( + "trait method `{}` will become ambiguous in Rust 2021", + segment.ident.name + )); + + let derefs = "*".repeat(pick.autoderefs); + + let autoref = match pick.autoref_or_ptr_adjustment { + Some(probe::AutorefOrPtrAdjustment::Autoref { + mutbl: Mutability::Mut, + .. + }) => "&mut ", + Some(probe::AutorefOrPtrAdjustment::Autoref { + mutbl: Mutability::Not, + .. + }) => "&", + Some(probe::AutorefOrPtrAdjustment::ToConstPtr) | None => "", + }; + if let Ok(self_expr) = self.sess().source_map().span_to_snippet(self_expr.span) + { + let self_adjusted = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) = + pick.autoref_or_ptr_adjustment + { + format!("{}{} as *const _", derefs, self_expr) + } else { + format!("{}{}{}", autoref, derefs, self_expr) + }; + + lint.span_suggestion( + sp, + "disambiguate the method call", + format!("({})", self_adjusted), + Applicability::MachineApplicable, + ); + } else { + let self_adjusted = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) = + pick.autoref_or_ptr_adjustment + { + format!("{}(...) as *const _", derefs) + } else { + format!("{}{}...", autoref, derefs) + }; + lint.span_help( + sp, + &format!("disambiguate the method call with `({})`", self_adjusted,), + ); + } + + lint.emit(); + }, + ); + } else { + // trait implementations require full disambiguation to not clash with the new prelude + // additions (i.e. convert from dot-call to fully-qualified call) + self.tcx.struct_span_lint_hir( + prelude_or_array_lint, + call_expr.hir_id, + call_expr.span, + |lint| { + let sp = call_expr.span; + let trait_name = self.trait_path_or_bare_name( + span, + call_expr.hir_id, + pick.item.container_id(self.tcx), + ); + + let mut lint = lint.build(&format!( + "trait method `{}` will become ambiguous in Rust 2021", + segment.ident.name + )); + + let (self_adjusted, precise) = self.adjust_expr(pick, self_expr, sp); + if precise { + let args = args + .iter() + .skip(1) + .map(|arg| { + let span = arg.span.find_ancestor_inside(sp).unwrap_or_default(); + format!( + ", {}", + self.sess().source_map().span_to_snippet(span).unwrap() + ) + }) + .collect::<String>(); + + lint.span_suggestion( + sp, + "disambiguate the associated function", + format!( + "{}::{}{}({}{})", + trait_name, + segment.ident.name, + if let Some(args) = segment.args.as_ref().and_then(|args| self + .sess() + .source_map() + .span_to_snippet(args.span_ext) + .ok()) + { + // Keep turbofish. + format!("::{}", args) + } else { + String::new() + }, + self_adjusted, + args, + ), + Applicability::MachineApplicable, + ); + } else { + lint.span_help( + sp, + &format!( + "disambiguate the associated function with `{}::{}(...)`", + trait_name, segment.ident, + ), + ); + } + + lint.emit(); + }, + ); + } + } + + pub(super) fn lint_fully_qualified_call_from_2018( + &self, + span: Span, + method_name: Ident, + self_ty: Ty<'tcx>, + self_ty_span: Span, + expr_id: hir::HirId, + pick: &Pick<'tcx>, + ) { + // Rust 2021 and later is already using the new prelude + if span.rust_2021() { + return; + } + + // These are the fully qualified methods added to prelude in Rust 2021 + if !matches!(method_name.name, sym::try_into | sym::try_from | sym::from_iter) { + return; + } + + // No need to lint if method came from std/core, as that will now be in the prelude + if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) { + return; + } + + // For from_iter, check if the type actually implements FromIterator. + // If we know it does not, we don't need to warn. + if method_name.name == sym::from_iter { + if let Some(trait_def_id) = self.tcx.get_diagnostic_item(sym::FromIterator) { + if !self + .infcx + .type_implements_trait( + trait_def_id, + self_ty, + InternalSubsts::empty(), + self.param_env, + ) + .may_apply() + { + return; + } + } + } + + // No need to lint if this is an inherent method called on a specific type, like `Vec::foo(...)`, + // since such methods take precedence over trait methods. + if matches!(pick.kind, probe::PickKind::InherentImplPick) { + return; + } + + self.tcx.struct_span_lint_hir(RUST_2021_PRELUDE_COLLISIONS, expr_id, span, |lint| { + // "type" refers to either a type or, more likely, a trait from which + // the associated function or method is from. + let container_id = pick.item.container_id(self.tcx); + let trait_path = self.trait_path_or_bare_name(span, expr_id, container_id); + let trait_generics = self.tcx.generics_of(container_id); + + let trait_name = + if trait_generics.params.len() <= trait_generics.has_self as usize { + trait_path + } else { + let counts = trait_generics.own_counts(); + format!( + "{}<{}>", + trait_path, + std::iter::repeat("'_") + .take(counts.lifetimes) + .chain(std::iter::repeat("_").take( + counts.types + counts.consts - trait_generics.has_self as usize + )) + .collect::<Vec<_>>() + .join(", ") + ) + }; + + let mut lint = lint.build(&format!( + "trait-associated function `{}` will become ambiguous in Rust 2021", + method_name.name + )); + + let mut self_ty_name = self_ty_span + .find_ancestor_inside(span) + .and_then(|span| self.sess().source_map().span_to_snippet(span).ok()) + .unwrap_or_else(|| self_ty.to_string()); + + // Get the number of generics the self type has (if an Adt) unless we can determine that + // the user has written the self type with generics already which we (naively) do by looking + // for a "<" in `self_ty_name`. + if !self_ty_name.contains('<') { + if let Adt(def, _) = self_ty.kind() { + let generics = self.tcx.generics_of(def.did()); + if !generics.params.is_empty() { + let counts = generics.own_counts(); + self_ty_name += &format!( + "<{}>", + std::iter::repeat("'_") + .take(counts.lifetimes) + .chain(std::iter::repeat("_").take(counts.types + counts.consts)) + .collect::<Vec<_>>() + .join(", ") + ); + } + } + } + lint.span_suggestion( + span, + "disambiguate the associated function", + format!("<{} as {}>::{}", self_ty_name, trait_name, method_name.name,), + Applicability::MachineApplicable, + ); + + lint.emit(); + }); + } + + fn trait_path_or_bare_name( + &self, + span: Span, + expr_hir_id: HirId, + trait_def_id: DefId, + ) -> String { + self.trait_path(span, expr_hir_id, trait_def_id).unwrap_or_else(|| { + let key = self.tcx.def_key(trait_def_id); + format!("{}", key.disambiguated_data.data) + }) + } + + fn trait_path(&self, span: Span, expr_hir_id: HirId, trait_def_id: DefId) -> Option<String> { + let applicable_traits = self.tcx.in_scope_traits(expr_hir_id)?; + let applicable_trait = applicable_traits.iter().find(|t| t.def_id == trait_def_id)?; + if applicable_trait.import_ids.is_empty() { + // The trait was declared within the module, we only need to use its name. + return None; + } + + let import_items: Vec<_> = applicable_trait + .import_ids + .iter() + .map(|&import_id| self.tcx.hir().expect_item(import_id)) + .collect(); + + // Find an identifier with which this trait was imported (note that `_` doesn't count). + let any_id = import_items + .iter() + .filter_map(|item| if item.ident.name != Underscore { Some(item.ident) } else { None }) + .next(); + if let Some(any_id) = any_id { + if any_id.name == Empty { + // Glob import, so just use its name. + return None; + } else { + return Some(format!("{}", any_id)); + } + } + + // All that is left is `_`! We need to use the full path. It doesn't matter which one we pick, + // so just take the first one. + match import_items[0].kind { + ItemKind::Use(path, _) => Some( + path.segments + .iter() + .map(|segment| segment.ident.to_string()) + .collect::<Vec<_>>() + .join("::"), + ), + _ => { + span_bug!(span, "unexpected item kind, expected a use: {:?}", import_items[0].kind); + } + } + } + + /// Creates a string version of the `expr` that includes explicit adjustments. + /// Returns the string and also a bool indicating whether this is a *precise* + /// suggestion. + fn adjust_expr( + &self, + pick: &Pick<'tcx>, + expr: &hir::Expr<'tcx>, + outer: Span, + ) -> (String, bool) { + let derefs = "*".repeat(pick.autoderefs); + + let autoref = match pick.autoref_or_ptr_adjustment { + Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl: Mutability::Mut, .. }) => "&mut ", + Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl: Mutability::Not, .. }) => "&", + Some(probe::AutorefOrPtrAdjustment::ToConstPtr) | None => "", + }; + + let (expr_text, precise) = if let Some(expr_text) = expr + .span + .find_ancestor_inside(outer) + .and_then(|span| self.sess().source_map().span_to_snippet(span).ok()) + { + (expr_text, true) + } else { + ("(..)".to_string(), false) + }; + + let adjusted_text = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) = + pick.autoref_or_ptr_adjustment + { + format!("{}{} as *const _", derefs, expr_text) + } else { + format!("{}{}{}", autoref, derefs, expr_text) + }; + + (adjusted_text, precise) + } +} |