Split astconv's error report code in check functions to mod errors.

Move some error report codes to mod `astconv/errors.rs`

Author: surechen

compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

@@ -1,13 +1,14 @@
 use crate::errors::{
     self, AssocTypeBindingNotAllowed, ManualImplementation, MissingTypeParams,
-    ParenthesizedFnTraitExpansion,
+    ParenthesizedFnTraitExpansion, TraitObjectDeclaredWithNoTraits,
 };
 use crate::fluent_generated as fluent;
 use crate::hir_ty_lowering::HirTyLowerer;
 use crate::traits::error_reporting::report_object_safety_error;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::unord::UnordMap;
+use rustc_errors::MultiSpan;
 use rustc_errors::{
     codes::*, pluralize, struct_span_code_err, Applicability, Diag, ErrorGuaranteed,
 };
@@ -16,11 +17,14 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_infer::traits::FulfillmentError;
 use rustc_middle::query::Key;
 use rustc_middle::ty::{self, suggest_constraining_type_param, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{Binder, TraitRef};
 use rustc_session::parse::feature_err;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::{Span, Symbol, DUMMY_SP};
-use rustc_trait_selection::traits::object_safety_violations_for_assoc_item;
+use rustc_trait_selection::traits::{
+    object_safety_violations_for_assoc_item, TraitAliasExpansionInfo,
+};
 
 impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// On missing type parameters, emit an E0393 error and provide a structured suggestion using
@@ -1024,15 +1028,179 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             Ok(())
         }
     }
+
+    pub fn report_prohibit_generics_error<'a>(
+        &self,
+        segments: impl Iterator<Item = &'a hir::PathSegment<'a>> + Clone,
+        args_visitors: impl Iterator<Item = &'a hir::GenericArg<'a>> + Clone,
+        extend: impl Fn(&mut Diag<'_>),
+    ) -> ErrorGuaranteed {
+        #[derive(PartialEq, Eq, Hash)]
+        enum ProhibitGenericsArg {
+            Lifetime,
+            Type,
+            Const,
+            Infer,
+        }
+
+        let mut prohibit_args = FxIndexSet::default();
+        args_visitors.for_each(|arg| {
+            match arg {
+                hir::GenericArg::Lifetime(_) => prohibit_args.insert(ProhibitGenericsArg::Lifetime),
+                hir::GenericArg::Type(_) => prohibit_args.insert(ProhibitGenericsArg::Type),
+                hir::GenericArg::Const(_) => prohibit_args.insert(ProhibitGenericsArg::Const),
+                hir::GenericArg::Infer(_) => prohibit_args.insert(ProhibitGenericsArg::Infer),
+            };
+        });
+
+        let types_and_spans: Vec<_> = segments
+            .clone()
+            .flat_map(|segment| {
+                if segment.args().args.is_empty() {
+                    None
+                } else {
+                    Some((
+                        match segment.res {
+                            hir::def::Res::PrimTy(ty) => {
+                                format!("{} `{}`", segment.res.descr(), ty.name())
+                            }
+                            hir::def::Res::Def(_, def_id)
+                                if let Some(name) = self.tcx().opt_item_name(def_id) =>
+                            {
+                                format!("{} `{name}`", segment.res.descr())
+                            }
+                            hir::def::Res::Err => "this type".to_string(),
+                            _ => segment.res.descr().to_string(),
+                        },
+                        segment.ident.span,
+                    ))
+                }
+            })
+            .collect();
+        let this_type = match &types_and_spans[..] {
+            [.., _, (last, _)] => format!(
+                "{} and {last}",
+                types_and_spans[..types_and_spans.len() - 1]
+                    .iter()
+                    .map(|(x, _)| x.as_str())
+                    .intersperse(", ")
+                    .collect::<String>()
+            ),
+            [(only, _)] => only.to_string(),
+            [] => "this type".to_string(),
+        };
+
+        let arg_spans: Vec<Span> = segments
+            .clone()
+            .flat_map(|segment| segment.args().args)
+            .map(|arg| arg.span())
+            .collect();
+
+        let mut kinds = Vec::with_capacity(4);
+        prohibit_args.iter().for_each(|arg| match arg {
+            ProhibitGenericsArg::Lifetime => kinds.push("lifetime"),
+            ProhibitGenericsArg::Type => kinds.push("type"),
+            ProhibitGenericsArg::Const => kinds.push("const"),
+            ProhibitGenericsArg::Infer => kinds.push("generic"),
+        });
+
+        let (kind, s) = match kinds[..] {
+            [.., _, last] => (
+                format!(
+                    "{} and {last}",
+                    kinds[..kinds.len() - 1]
+                        .iter()
+                        .map(|&x| x)
+                        .intersperse(", ")
+                        .collect::<String>()
+                ),
+                "s",
+            ),
+            [only] => (only.to_string(), ""),
+            [] => unreachable!("expected at least one generic to prohibit"),
+        };
+        let last_span = *arg_spans.last().unwrap();
+        let span: MultiSpan = arg_spans.into();
+        let mut err = struct_span_code_err!(
+            self.tcx().dcx(),
+            span,
+            E0109,
+            "{kind} arguments are not allowed on {this_type}",
+        );
+        err.span_label(last_span, format!("{kind} argument{s} not allowed"));
+        for (what, span) in types_and_spans {
+            err.span_label(span, format!("not allowed on {what}"));
+        }
+        extend(&mut err);
+        let reported = err.emit();
+        self.set_tainted_by_errors(reported);
+        reported
+    }
+
+    pub fn report_trait_object_addition_traits_error(
+        &self,
+        regular_traits: &Vec<TraitAliasExpansionInfo<'_>>,
+    ) -> ErrorGuaranteed {
+        let tcx = self.tcx();
+        let first_trait = &regular_traits[0];
+        let additional_trait = &regular_traits[1];
+        let mut err = struct_span_code_err!(
+            tcx.dcx(),
+            additional_trait.bottom().1,
+            E0225,
+            "only auto traits can be used as additional traits in a trait object"
+        );
+        additional_trait.label_with_exp_info(
+            &mut err,
+            "additional non-auto trait",
+            "additional use",
+        );
+        first_trait.label_with_exp_info(&mut err, "first non-auto trait", "first use");
+        err.help(format!(
+            "consider creating a new trait with all of these as supertraits and using that \
+             trait here instead: `trait NewTrait: {} {{}}`",
+            regular_traits
+                .iter()
+                // FIXME: This should `print_sugared`, but also needs to integrate projection bounds...
+                .map(|t| t.trait_ref().print_only_trait_path().to_string())
+                .collect::<Vec<_>>()
+                .join(" + "),
+        ));
+        err.note(
+            "auto-traits like `Send` and `Sync` are traits that have special properties; \
+             for more information on them, visit \
+             <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>",
+        );
+        let reported = err.emit();
+        self.set_tainted_by_errors(reported);
+        reported
+    }
+
+    pub fn report_trait_object_with_no_traits_error(
+        &self,
+        span: Span,
+        trait_bounds: &Vec<(Binder<'tcx, TraitRef<'tcx>>, Span)>,
+    ) -> ErrorGuaranteed {
+        let tcx = self.tcx();
+        let trait_alias_span = trait_bounds
+            .iter()
+            .map(|&(trait_ref, _)| trait_ref.def_id())
+            .find(|&trait_ref| tcx.is_trait_alias(trait_ref))
+            .map(|trait_ref| tcx.def_span(trait_ref));
+        let reported =
+            tcx.dcx().emit_err(TraitObjectDeclaredWithNoTraits { span, trait_alias_span });
+        self.set_tainted_by_errors(reported);
+        reported
+    }
 }
 
 /// Emits an error regarding forbidden type binding associations
 pub fn prohibit_assoc_item_binding(
     tcx: TyCtxt<'_>,
     span: Span,
     segment: Option<(&hir::PathSegment<'_>, Span)>,
-) {
-    tcx.dcx().emit_err(AssocTypeBindingNotAllowed {
+) -> ErrorGuaranteed {
+    return tcx.dcx().emit_err(AssocTypeBindingNotAllowed {
         span,
         fn_trait_expansion: if let Some((segment, span)) = segment
             && segment.args().parenthesized == hir::GenericArgsParentheses::ParenSugar