Move trait selection error reporting to its own top-level module

17 files changed, 80 insertions, 76 deletions

diff --git a/compiler/rustc_trait_selection/src/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/mod.rs
new file mode 100644
index 00000000000..f6ac8fc7b61
--- /dev/null
+++ b/compiler/rustc_trait_selection/src/error_reporting/mod.rs
@@ -0,0 +1 @@
+pub mod traits;
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/ambiguity.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
index e6cb28df593..e6cb28df593 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/ambiguity.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/infer_ctxt_ext.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/infer_ctxt_ext.rs
index 34da8e576ce..34da8e576ce 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/infer_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/infer_ctxt_ext.rs
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
index 633d488f7be..438b25056c3 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
@@ -6,10 +6,12 @@ pub mod on_unimplemented;
 pub mod suggestions;
 mod type_err_ctxt_ext;
 
-use super::{Obligation, ObligationCause, ObligationCauseCode, PredicateObligation};
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::Visitor;
+use rustc_infer::traits::{Obligation, ObligationCause, ObligationCauseCode, PredicateObligation};
+use rustc_middle::ty::print::PrintTraitRefExt as _;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
 use std::ops::ControlFlow;
@@ -180,3 +182,61 @@ pub enum DefIdOrName {
     DefId(DefId),
     Name(&'static str),
 }
+
+/// Recovers the "impl X for Y" signature from `impl_def_id` and returns it as a
+/// string.
+pub(crate) fn to_pretty_impl_header(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Option<String> {
+    use std::fmt::Write;
+
+    let trait_ref = tcx.impl_trait_ref(impl_def_id)?.instantiate_identity();
+    let mut w = "impl".to_owned();
+
+    let args = ty::GenericArgs::identity_for_item(tcx, impl_def_id);
+
+    // FIXME: Currently only handles ?Sized.
+    //        Needs to support ?Move and ?DynSized when they are implemented.
+    let mut types_without_default_bounds = FxIndexSet::default();
+    let sized_trait = tcx.lang_items().sized_trait();
+
+    let arg_names = args.iter().map(|k| k.to_string()).filter(|k| k != "'_").collect::<Vec<_>>();
+    if !arg_names.is_empty() {
+        types_without_default_bounds.extend(args.types());
+        w.push('<');
+        w.push_str(&arg_names.join(", "));
+        w.push('>');
+    }
+
+    write!(
+        w,
+        " {} for {}",
+        trait_ref.print_only_trait_path(),
+        tcx.type_of(impl_def_id).instantiate_identity()
+    )
+    .unwrap();
+
+    // The predicates will contain default bounds like `T: Sized`. We need to
+    // remove these bounds, and add `T: ?Sized` to any untouched type parameters.
+    let predicates = tcx.predicates_of(impl_def_id).predicates;
+    let mut pretty_predicates =
+        Vec::with_capacity(predicates.len() + types_without_default_bounds.len());
+
+    for (p, _) in predicates {
+        if let Some(poly_trait_ref) = p.as_trait_clause() {
+            if Some(poly_trait_ref.def_id()) == sized_trait {
+                // FIXME(#120456) - is `swap_remove` correct?
+                types_without_default_bounds.swap_remove(&poly_trait_ref.self_ty().skip_binder());
+                continue;
+            }
+        }
+        pretty_predicates.push(p.to_string());
+    }
+
+    pretty_predicates.extend(types_without_default_bounds.iter().map(|ty| format!("{ty}: ?Sized")));
+
+    if !pretty_predicates.is_empty() {
+        write!(w, "\n  where {}", pretty_predicates.join(", ")).unwrap();
+    }
+
+    w.push(';');
+    Some(w)
+}
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
index 94b28426f43..83c6798ba2e 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
@@ -1,10 +1,10 @@
 use super::{ObligationCauseCode, PredicateObligation};
+use crate::error_reporting::traits::type_err_ctxt_ext::InferCtxtPrivExt;
 use crate::errors::{
     EmptyOnClauseInOnUnimplemented, InvalidOnClauseInOnUnimplemented, NoValueInOnUnimplemented,
 };
 use crate::infer::error_reporting::TypeErrCtxt;
 use crate::infer::InferCtxtExt;
-use crate::traits::error_reporting::type_err_ctxt_ext::InferCtxtPrivExt;
 use rustc_ast::AttrArgs;
 use rustc_ast::AttrArgsEq;
 use rustc_ast::AttrKind;
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index 52edffce614..fdc6db4abec 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -44,8 +44,8 @@ use std::assert_matches::debug_assert_matches;
 use std::borrow::Cow;
 use std::iter;
 
+use crate::error_reporting::traits::type_err_ctxt_ext::InferCtxtPrivExt;
 use crate::infer::InferCtxtExt as _;
-use crate::traits::error_reporting::type_err_ctxt_ext::InferCtxtPrivExt;
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
 use rustc_middle::ty::print::{
     with_forced_trimmed_paths, with_no_trimmed_paths, PrintPolyTraitPredicateExt as _,
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/type_err_ctxt_ext.rs
index 5461f9e65af..7843a95d966 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/type_err_ctxt_ext.rs
@@ -2,16 +2,16 @@
 
 use super::on_unimplemented::{AppendConstMessage, OnUnimplementedNote, TypeErrCtxtExt as _};
 use super::suggestions::{get_explanation_based_on_obligation, TypeErrCtxtExt as _};
+use crate::error_reporting::traits::infer_ctxt_ext::InferCtxtExt;
+use crate::error_reporting::traits::to_pretty_impl_header;
+use crate::error_reporting::traits::{ambiguity, ambiguity::CandidateSource::*};
 use crate::errors::{
     AsyncClosureNotFn, ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch,
 };
 use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
 use crate::infer::InferCtxtExt as _;
 use crate::infer::{self, InferCtxt};
-use crate::traits::error_reporting::infer_ctxt_ext::InferCtxtExt;
-use crate::traits::error_reporting::{ambiguity, ambiguity::CandidateSource::*};
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
-use crate::traits::specialize::to_pretty_impl_header;
 use crate::traits::NormalizeExt;
 use crate::traits::{
     elaborate, FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes, Obligation,
diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs
index 37008baca28..d0a12d73941 100644
--- a/compiler/rustc_trait_selection/src/lib.rs
+++ b/compiler/rustc_trait_selection/src/lib.rs
@@ -33,6 +33,7 @@
 #[macro_use]
 extern crate tracing;
 
+pub mod error_reporting;
 pub mod errors;
 pub mod infer;
 pub mod regions;
diff --git a/compiler/rustc_trait_selection/src/solve/normalize.rs b/compiler/rustc_trait_selection/src/solve/normalize.rs
index 2679da942b7..bda2137fa73 100644
--- a/compiler/rustc_trait_selection/src/solve/normalize.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalize.rs
@@ -1,7 +1,7 @@
 use std::fmt::Debug;
 use std::marker::PhantomData;
 
-use crate::traits::error_reporting::{OverflowCause, TypeErrCtxtExt};
+use crate::error_reporting::traits::{OverflowCause, TypeErrCtxtExt};
 use crate::traits::query::evaluate_obligation::InferCtxtExt;
 use crate::traits::{BoundVarReplacer, PlaceholderReplacer, ScrubbedTraitError};
 use rustc_data_structures::stack::ensure_sufficient_stack;
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index fc390bf318d..7e996c5c5ef 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -30,8 +30,8 @@ use rustc_span::symbol::sym;
 use rustc_span::{Span, DUMMY_SP};
 use std::fmt::Debug;
 
-use super::error_reporting::suggest_new_overflow_limit;
 use super::ObligationCtxt;
+use crate::error_reporting::traits::suggest_new_overflow_limit;
 
 pub struct OverlapResult<'tcx> {
     pub impl_header: ty::ImplHeader<'tcx>,
diff --git a/compiler/rustc_trait_selection/src/traits/engine.rs b/compiler/rustc_trait_selection/src/traits/engine.rs
index 811f61d2bf3..bdc27e734f9 100644
--- a/compiler/rustc_trait_selection/src/traits/engine.rs
+++ b/compiler/rustc_trait_selection/src/traits/engine.rs
@@ -3,10 +3,10 @@ use std::fmt::Debug;
 
 use super::{FromSolverError, TraitEngine};
 use super::{FulfillmentContext, ScrubbedTraitError};
+use crate::error_reporting::traits::TypeErrCtxtExt;
 use crate::regions::InferCtxtRegionExt;
 use crate::solve::FulfillmentCtxt as NextFulfillmentCtxt;
 use crate::solve::NextSolverError;
-use crate::traits::error_reporting::TypeErrCtxtExt;
 use crate::traits::fulfill::OldSolverError;
 use crate::traits::NormalizeExt;
 use crate::traits::StructurallyNormalizeExt;
diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
index bce5c7101cc..6f7e69798ee 100644
--- a/compiler/rustc_trait_selection/src/traits/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -1,5 +1,5 @@
+use crate::error_reporting::traits::TypeErrCtxtExt;
 use crate::infer::{InferCtxt, TyOrConstInferVar};
-use crate::traits::error_reporting::TypeErrCtxtExt;
 use crate::traits::normalize::normalize_with_depth_to;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::obligation_forest::ProcessResult;
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index 662d95db8ba..703ff2f7f16 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -6,7 +6,6 @@ pub mod auto_trait;
 pub(crate) mod coherence;
 pub mod const_evaluatable;
 mod engine;
-pub mod error_reporting;
 mod fulfill;
 pub mod misc;
 pub mod normalize;
@@ -24,10 +23,10 @@ mod util;
 pub mod vtable;
 pub mod wf;
 
+use crate::error_reporting::traits::TypeErrCtxtExt as _;
 use crate::infer::outlives::env::OutlivesEnvironment;
 use crate::infer::{InferCtxt, TyCtxtInferExt};
 use crate::regions::InferCtxtRegionExt;
-use crate::traits::error_reporting::TypeErrCtxtExt as _;
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
 use rustc_errors::ErrorGuaranteed;
 use rustc_middle::query::Providers;
diff --git a/compiler/rustc_trait_selection/src/traits/normalize.rs b/compiler/rustc_trait_selection/src/traits/normalize.rs
index a9ac0f7eb25..a34fd804467 100644
--- a/compiler/rustc_trait_selection/src/traits/normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/normalize.rs
@@ -1,9 +1,9 @@
 //! Deeply normalize types using the old trait solver.
 
-use super::error_reporting::OverflowCause;
-use super::error_reporting::TypeErrCtxtExt;
 use super::SelectionContext;
 use super::{project, with_replaced_escaping_bound_vars, BoundVarReplacer, PlaceholderReplacer};
+use crate::error_reporting::traits::OverflowCause;
+use crate::error_reporting::traits::TypeErrCtxtExt;
 use crate::solve::NextSolverError;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_infer::infer::at::At;
diff --git a/compiler/rustc_trait_selection/src/traits/query/normalize.rs b/compiler/rustc_trait_selection/src/traits/query/normalize.rs
index bed76b84ee0..da4e4fef3cf 100644
--- a/compiler/rustc_trait_selection/src/traits/query/normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/normalize.rs
@@ -2,11 +2,11 @@
 //! which folds deeply, invoking the underlying
 //! `normalize_canonicalized_projection_ty` query when it encounters projections.
 
+use crate::error_reporting::traits::OverflowCause;
+use crate::error_reporting::traits::TypeErrCtxtExt;
 use crate::infer::at::At;
 use crate::infer::canonical::OriginalQueryValues;
 use crate::infer::{InferCtxt, InferOk};
-use crate::traits::error_reporting::OverflowCause;
-use crate::traits::error_reporting::TypeErrCtxtExt;
 use crate::traits::normalize::needs_normalization;
 use crate::traits::Normalized;
 use crate::traits::{BoundVarReplacer, PlaceholderReplacer, ScrubbedTraitError};
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index cc082ad98aa..1e55b2d0150 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -18,9 +18,9 @@ use super::{
     TraitQueryMode,
 };
 
+use crate::error_reporting::traits::TypeErrCtxtExt;
 use crate::infer::{InferCtxt, InferCtxtExt, InferOk, TypeFreshener};
 use crate::solve::InferCtxtSelectExt as _;
-use crate::traits::error_reporting::TypeErrCtxtExt;
 use crate::traits::normalize::normalize_with_depth;
 use crate::traits::normalize::normalize_with_depth_to;
 use crate::traits::project::ProjectAndUnifyResult;
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index c9bb0d330e1..6a904ef487e 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -14,6 +14,7 @@ use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_middle::ty::print::PrintTraitRefExt as _;
 use specialization_graph::GraphExt;
 
+use crate::error_reporting::traits::to_pretty_impl_header;
 use crate::errors::NegativePositiveConflict;
 use crate::infer::{InferCtxt, InferOk, TyCtxtInferExt};
 use crate::traits::select::IntercrateAmbiguityCause;
@@ -25,8 +26,8 @@ use rustc_errors::{codes::*, Diag, EmissionGuarantee};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::bug;
 use rustc_middle::query::LocalCrate;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, ImplSubject, Ty, TyCtxt, TypeVisitableExt};
-use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_session::lint::builtin::COHERENCE_LEAK_CHECK;
 use rustc_session::lint::builtin::ORDER_DEPENDENT_TRAIT_OBJECTS;
 use rustc_span::{sym, ErrorGuaranteed, Span, DUMMY_SP};
@@ -485,61 +486,3 @@ fn report_conflicting_impls<'tcx>(
         }
     }
 }
-
-/// Recovers the "impl X for Y" signature from `impl_def_id` and returns it as a
-/// string.
-pub(crate) fn to_pretty_impl_header(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Option<String> {
-    use std::fmt::Write;
-
-    let trait_ref = tcx.impl_trait_ref(impl_def_id)?.instantiate_identity();
-    let mut w = "impl".to_owned();
-
-    let args = GenericArgs::identity_for_item(tcx, impl_def_id);
-
-    // FIXME: Currently only handles ?Sized.
-    //        Needs to support ?Move and ?DynSized when they are implemented.
-    let mut types_without_default_bounds = FxIndexSet::default();
-    let sized_trait = tcx.lang_items().sized_trait();
-
-    let arg_names = args.iter().map(|k| k.to_string()).filter(|k| k != "'_").collect::<Vec<_>>();
-    if !arg_names.is_empty() {
-        types_without_default_bounds.extend(args.types());
-        w.push('<');
-        w.push_str(&arg_names.join(", "));
-        w.push('>');
-    }
-
-    write!(
-        w,
-        " {} for {}",
-        trait_ref.print_only_trait_path(),
-        tcx.type_of(impl_def_id).instantiate_identity()
-    )
-    .unwrap();
-
-    // The predicates will contain default bounds like `T: Sized`. We need to
-    // remove these bounds, and add `T: ?Sized` to any untouched type parameters.
-    let predicates = tcx.predicates_of(impl_def_id).predicates;
-    let mut pretty_predicates =
-        Vec::with_capacity(predicates.len() + types_without_default_bounds.len());
-
-    for (p, _) in predicates {
-        if let Some(poly_trait_ref) = p.as_trait_clause() {
-            if Some(poly_trait_ref.def_id()) == sized_trait {
-                // FIXME(#120456) - is `swap_remove` correct?
-                types_without_default_bounds.swap_remove(&poly_trait_ref.self_ty().skip_binder());
-                continue;
-            }
-        }
-        pretty_predicates.push(p.to_string());
-    }
-
-    pretty_predicates.extend(types_without_default_bounds.iter().map(|ty| format!("{ty}: ?Sized")));
-
-    if !pretty_predicates.is_empty() {
-        write!(w, "\n  where {}", pretty_predicates.join(", ")).unwrap();
-    }
-
-    w.push(';');
-    Some(w)
-}