diff options
Diffstat (limited to 'compiler/rustc_ast_lowering/src/lib.rs')
| -rw-r--r-- | compiler/rustc_ast_lowering/src/lib.rs | 66 |
1 files changed, 45 insertions, 21 deletions
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs index d1ea76b3922..51e5c3384a7 100644 --- a/compiler/rustc_ast_lowering/src/lib.rs +++ b/compiler/rustc_ast_lowering/src/lib.rs @@ -46,7 +46,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_data_structures::sorted_map::SortedMap; use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; use rustc_data_structures::sync::Lrc; -use rustc_errors::struct_span_err; +use rustc_errors::{struct_span_err, Applicability}; use rustc_hir as hir; use rustc_hir::def::{DefKind, Namespace, PartialRes, PerNS, Res}; use rustc_hir::def_id::{DefId, DefPathHash, LocalDefId, CRATE_DEF_ID}; @@ -253,7 +253,7 @@ enum ImplTraitContext { /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`. /// /// Newly generated parameters should be inserted into the given `Vec`. - Universal(LocalDefId), + Universal, /// Treat `impl Trait` as shorthand for a new opaque type. /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually @@ -857,7 +857,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { itctx: ImplTraitContext, ) -> hir::TypeBinding<'hir> { debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx); - // lower generic arguments of identifier in constraint let gen_args = if let Some(ref gen_args) = constraint.gen_args { let gen_args_ctor = match gen_args { @@ -865,12 +864,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { self.lower_angle_bracketed_parameter_data(data, ParamMode::Explicit, itctx).0 } GenericArgs::Parenthesized(ref data) => { - let mut err = self.sess.struct_span_err( - gen_args.span(), - "parenthesized generic arguments cannot be used in associated type constraints" - ); - // FIXME: try to write a suggestion here - err.emit(); + self.assoc_ty_contraint_param_error_emit(data); self.lower_angle_bracketed_parameter_data( &data.as_angle_bracketed_args(), ParamMode::Explicit, @@ -893,7 +887,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { hir::TypeBindingKind::Equality { term } } AssocConstraintKind::Bound { ref bounds } => { - let mut parent_def_id = self.current_hir_id_owner; // Piggy-back on the `impl Trait` context to figure out the correct behavior. let (desugar_to_impl_trait, itctx) = match itctx { // We are in the return position: @@ -913,10 +906,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { // so desugar to // // fn foo(x: dyn Iterator<Item = impl Debug>) - ImplTraitContext::Universal(parent) if self.is_in_dyn_type => { - parent_def_id = parent; - (true, itctx) - } + ImplTraitContext::Universal if self.is_in_dyn_type => (true, itctx), // In `type Foo = dyn Iterator<Item: Debug>` we desugar to // `type Foo = dyn Iterator<Item = impl Debug>` but we have to override the @@ -942,6 +932,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { // Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by // constructing the HIR for `impl bounds...` and then lowering that. + let parent_def_id = self.current_hir_id_owner; let impl_trait_node_id = self.resolver.next_node_id(); self.resolver.create_def( parent_def_id, @@ -984,6 +975,42 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { } } + fn assoc_ty_contraint_param_error_emit(&self, data: &ParenthesizedArgs) -> () { + let mut err = self.sess.struct_span_err( + data.span, + "parenthesized generic arguments cannot be used in associated type constraints", + ); + // Suggest removing empty parentheses: "Trait()" -> "Trait" + if data.inputs.is_empty() { + let parentheses_span = + data.inputs_span.shrink_to_lo().to(data.inputs_span.shrink_to_hi()); + err.multipart_suggestion( + "remove these parentheses", + vec![(parentheses_span, String::new())], + Applicability::MaybeIncorrect, + ); + } + // Suggest replacing parentheses with angle brackets `Trait(params...)` to `Trait<params...>` + else { + // Start of parameters to the 1st argument + let open_param = data.inputs_span.shrink_to_lo().to(data + .inputs + .first() + .unwrap() + .span + .shrink_to_lo()); + // End of last argument to end of parameters + let close_param = + data.inputs.last().unwrap().span.shrink_to_hi().to(data.inputs_span.shrink_to_hi()); + err.multipart_suggestion( + &format!("use angle brackets instead",), + vec![(open_param, String::from("<")), (close_param, String::from(">"))], + Applicability::MaybeIncorrect, + ); + } + err.emit(); + } + fn lower_generic_arg( &mut self, arg: &ast::GenericArg, @@ -1184,12 +1211,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { |this| this.lower_param_bounds(bounds, nested_itctx), ) } - ImplTraitContext::Universal(parent_def_id) => { + ImplTraitContext::Universal => { // Add a definition for the in-band `Param`. let def_id = self.resolver.local_def_id(def_node_id); - let hir_bounds = self - .lower_param_bounds(bounds, ImplTraitContext::Universal(parent_def_id)); + let hir_bounds = + self.lower_param_bounds(bounds, ImplTraitContext::Universal); // Set the name to `impl Bound1 + Bound2`. let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span); let param = hir::GenericParam { @@ -1399,10 +1426,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { } let inputs = self.arena.alloc_from_iter(inputs.iter().map(|param| { if fn_node_id.is_some() { - self.lower_ty_direct( - ¶m.ty, - ImplTraitContext::Universal(self.current_hir_id_owner), - ) + self.lower_ty_direct(¶m.ty, ImplTraitContext::Universal) } else { self.lower_ty_direct( ¶m.ty, |