Use fewer origins when creating type variables.

`InferCtxt::next_{ty,const}_var*` all take an origin, but the
`param_def_id` is almost always `None`. This commit changes them to just
take a `Span` and build the origin within the method, and adds new
methods for the rare cases where `param_def_id` might not be `None`.
This avoids a lot of tedious origin building.

Specifically:
- next_ty_var{,_id_in_universe,_in_universe}: now take `Span` instead of
  `TypeVariableOrigin`
- next_ty_var_with_origin: added

- next_const_var{,_in_universe}: takes Span instead of ConstVariableOrigin
- next_const_var_with_origin: added

- next_region_var, next_region_var_in_universe: these are unchanged,
  still take RegionVariableOrigin

The API inconsistency (ty/const vs region) seems worth it for the
large conciseness improvements.

9 files changed, 15 insertions, 55 deletions

diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
index 5f73432750d..c43026f7971 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
@@ -19,12 +19,10 @@ use rustc_infer::infer::canonical::query_response::make_query_region_constraints
 use rustc_infer::infer::canonical::CanonicalVarValues;
 use rustc_infer::infer::canonical::{CanonicalExt, QueryRegionConstraints};
 use rustc_infer::infer::resolve::EagerResolver;
-use rustc_infer::infer::type_variable::TypeVariableOrigin;
 use rustc_infer::infer::RegionVariableOrigin;
 use rustc_infer::infer::{InferCtxt, InferOk};
 use rustc_infer::traits::solve::NestedNormalizationGoals;
 use rustc_middle::infer::canonical::Canonical;
-use rustc_middle::infer::unify_key::ConstVariableOrigin;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::solve::{
     ExternalConstraintsData, MaybeCause, PredefinedOpaquesData, QueryInput,
@@ -424,12 +422,8 @@ pub(in crate::solve) fn instantiate_canonical_state<'tcx, T: TypeFoldable<TyCtxt
             ty::GenericArgKind::Lifetime(_) => {
                 infcx.next_region_var(RegionVariableOrigin::MiscVariable(span)).into()
             }
-            ty::GenericArgKind::Type(_) => {
-                infcx.next_ty_var(TypeVariableOrigin { param_def_id: None, span }).into()
-            }
-            ty::GenericArgKind::Const(ct) => infcx
-                .next_const_var(ct.ty(), ConstVariableOrigin { param_def_id: None, span })
-                .into(),
+            ty::GenericArgKind::Type(_) => infcx.next_ty_var(span).into(),
+            ty::GenericArgKind::Const(ct) => infcx.next_const_var(ct.ty(), span).into(),
         };
 
         orig_values.push(unconstrained);
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
index 98aac581c6e..9cd1841051d 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
@@ -2,7 +2,6 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::def_id::DefId;
 use rustc_infer::infer::at::ToTrace;
 use rustc_infer::infer::canonical::CanonicalVarValues;
-use rustc_infer::infer::type_variable::TypeVariableOrigin;
 use rustc_infer::infer::{
     BoundRegionConversionTime, DefineOpaqueTypes, InferCtxt, InferOk, TyCtxtInferExt,
 };
@@ -11,7 +10,6 @@ use rustc_infer::traits::solve::{MaybeCause, NestedNormalizationGoals};
 use rustc_infer::traits::ObligationCause;
 use rustc_macros::{extension, HashStable};
 use rustc_middle::infer::canonical::CanonicalVarInfos;
-use rustc_middle::infer::unify_key::ConstVariableOrigin;
 use rustc_middle::traits::solve::inspect;
 use rustc_middle::traits::solve::{
     CanonicalInput, CanonicalResponse, Certainty, PredefinedOpaques, PredefinedOpaquesData,
@@ -600,15 +598,13 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
     }
 
     pub(super) fn next_ty_infer(&mut self) -> Ty<'tcx> {
-        let ty = self.infcx.next_ty_var(TypeVariableOrigin { param_def_id: None, span: DUMMY_SP });
+        let ty = self.infcx.next_ty_var(DUMMY_SP);
         self.inspect.add_var_value(ty);
         ty
     }
 
     pub(super) fn next_const_infer(&mut self, ty: Ty<'tcx>) -> ty::Const<'tcx> {
-        let ct = self
-            .infcx
-            .next_const_var(ty, ConstVariableOrigin { param_def_id: None, span: DUMMY_SP });
+        let ct = self.infcx.next_const_var(ty, DUMMY_SP);
         self.inspect.add_var_value(ct);
         ct
     }
diff --git a/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs b/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
index fa4323a3a94..e6760837937 100644
--- a/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
+++ b/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
@@ -12,10 +12,8 @@
 use rustc_ast_ir::try_visit;
 use rustc_ast_ir::visit::VisitorResult;
 use rustc_infer::infer::resolve::EagerResolver;
-use rustc_infer::infer::type_variable::TypeVariableOrigin;
 use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, InferOk};
 use rustc_macros::extension;
-use rustc_middle::infer::unify_key::ConstVariableOrigin;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::solve::{inspect, QueryResult};
 use rustc_middle::traits::solve::{Certainty, Goal};
@@ -201,15 +199,8 @@ impl<'a, 'tcx> InspectCandidate<'a, 'tcx> {
             .map(|(source, goal)| match goal.predicate.kind().no_bound_vars() {
                 Some(ty::PredicateKind::NormalizesTo(ty::NormalizesTo { alias, term })) => {
                     let unconstrained_term = match term.unpack() {
-                        ty::TermKind::Ty(_) => infcx
-                            .next_ty_var(TypeVariableOrigin { param_def_id: None, span })
-                            .into(),
-                        ty::TermKind::Const(ct) => infcx
-                            .next_const_var(
-                                ct.ty(),
-                                ConstVariableOrigin { param_def_id: None, span },
-                            )
-                            .into(),
+                        ty::TermKind::Ty(_) => infcx.next_ty_var(span).into(),
+                        ty::TermKind::Const(ct) => infcx.next_const_var(ct.ty(), span).into(),
                     };
                     let goal =
                         goal.with(infcx.tcx, ty::NormalizesTo { alias, term: unconstrained_term });
diff --git a/compiler/rustc_trait_selection/src/solve/normalize.rs b/compiler/rustc_trait_selection/src/solve/normalize.rs
index 65ef4659907..cd1add9e0fa 100644
--- a/compiler/rustc_trait_selection/src/solve/normalize.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalize.rs
@@ -3,11 +3,9 @@ use crate::traits::query::evaluate_obligation::InferCtxtExt;
 use crate::traits::{BoundVarReplacer, PlaceholderReplacer};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_infer::infer::at::At;
-use rustc_infer::infer::type_variable::TypeVariableOrigin;
 use rustc_infer::infer::InferCtxt;
 use rustc_infer::traits::TraitEngineExt;
 use rustc_infer::traits::{FulfillmentError, Obligation, TraitEngine};
-use rustc_middle::infer::unify_key::ConstVariableOrigin;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::{self, AliasTy, Ty, TyCtxt, UniverseIndex};
 use rustc_middle::ty::{FallibleTypeFolder, TypeFolder, TypeSuperFoldable};
@@ -74,8 +72,7 @@ impl<'tcx> NormalizationFolder<'_, 'tcx> {
 
         self.depth += 1;
 
-        let new_infer_ty =
-            infcx.next_ty_var(TypeVariableOrigin { param_def_id: None, span: self.at.cause.span });
+        let new_infer_ty = infcx.next_ty_var(self.at.cause.span);
         let obligation = Obligation::new(
             tcx,
             self.at.cause.clone(),
@@ -120,10 +117,7 @@ impl<'tcx> NormalizationFolder<'_, 'tcx> {
 
         self.depth += 1;
 
-        let new_infer_ct = infcx.next_const_var(
-            ty,
-            ConstVariableOrigin { param_def_id: None, span: self.at.cause.span },
-        );
+        let new_infer_ct = infcx.next_const_var(ty, self.at.cause.span);
         let obligation = Obligation::new(
             tcx,
             self.at.cause.clone(),
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/infer_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/infer_ctxt_ext.rs
index 9e5701ffffc..4b5b1d77b30 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/infer_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/infer_ctxt_ext.rs
@@ -1,4 +1,3 @@
-use crate::infer::type_variable::TypeVariableOrigin;
 use crate::infer::InferCtxt;
 use crate::traits::{Obligation, ObligationCause, ObligationCtxt};
 use rustc_errors::{codes::*, pluralize, struct_span_code_err, Applicability, Diag};
@@ -218,8 +217,7 @@ impl<'tcx> InferCtxt<'tcx> {
                 let Some(trait_def_id) = trait_def_id else { continue };
                 // Make a fresh inference variable so we can determine what the generic parameters
                 // of the trait are.
-                let var =
-                    self.next_ty_var(TypeVariableOrigin { span: DUMMY_SP, param_def_id: None });
+                let var = self.next_ty_var(DUMMY_SP);
                 // FIXME(effects)
                 let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, [ty.skip_binder(), var]);
                 let obligation = Obligation::new(
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 3d2574ac92b..88c00ba1794 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -24,7 +24,6 @@ use rustc_hir::is_range_literal;
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, HirId, Node};
 use rustc_infer::infer::error_reporting::TypeErrCtxt;
-use rustc_infer::infer::type_variable::TypeVariableOrigin;
 use rustc_infer::infer::{BoundRegionConversionTime, DefineOpaqueTypes, InferOk};
 use rustc_macros::extension;
 use rustc_middle::hir::map;
@@ -1893,8 +1892,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 ty::Tuple(inputs) if infcx.tcx.is_fn_trait(trait_ref.def_id) => {
                     infcx.tcx.mk_fn_sig(
                         *inputs,
-                        infcx
-                            .next_ty_var(TypeVariableOrigin { span: DUMMY_SP, param_def_id: None }),
+                        infcx.next_ty_var(DUMMY_SP),
                         false,
                         hir::Unsafety::Normal,
                         abi::Abi::Rust,
@@ -1902,7 +1900,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 }
                 _ => infcx.tcx.mk_fn_sig(
                     [inputs],
-                    infcx.next_ty_var(TypeVariableOrigin { span: DUMMY_SP, param_def_id: None }),
+                    infcx.next_ty_var(DUMMY_SP),
                     false,
                     hir::Unsafety::Normal,
                     abi::Abi::Rust,
@@ -4263,7 +4261,6 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 continue;
             };
 
-            let origin = TypeVariableOrigin { param_def_id: None, span };
             // Make `Self` be equivalent to the type of the call chain
             // expression we're looking at now, so that we can tell what
             // for example `Iterator::Item` is at this point in the chain.
@@ -4277,7 +4274,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             // This will hold the resolved type of the associated type, if the
             // current expression implements the trait that associated type is
             // in. For example, this would be what `Iterator::Item` is here.
-            let ty = self.infcx.next_ty_var(origin);
+            let ty = self.infcx.next_ty_var(span);
             // This corresponds to `<ExprTy as Iterator>::Item = _`.
             let projection = ty::Binder::dummy(ty::PredicateKind::Clause(
                 ty::ClauseKind::Projection(ty::ProjectionPredicate {
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index e50cb2af4b8..0966bb16d3e 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -6,7 +6,6 @@ use crate::errors::{
     AsyncClosureNotFn, ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch,
 };
 use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
-use crate::infer::type_variable::TypeVariableOrigin;
 use crate::infer::InferCtxtExt as _;
 use crate::infer::{self, InferCtxt};
 use crate::traits::error_reporting::infer_ctxt_ext::InferCtxtExt;
@@ -2826,9 +2825,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
                 if let ty::Param(_) = *ty.kind() {
                     let infcx = self.infcx;
-                    *self.var_map.entry(ty).or_insert_with(|| {
-                        infcx.next_ty_var(TypeVariableOrigin { param_def_id: None, span: DUMMY_SP })
-                    })
+                    *self.var_map.entry(ty).or_insert_with(|| infcx.next_ty_var(DUMMY_SP))
                 } else {
                     ty.super_fold_with(self)
                 }
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 116e17c7e43..587f2f72207 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -18,7 +18,6 @@ use rustc_middle::traits::ImplSource;
 use rustc_middle::traits::ImplSourceUserDefinedData;
 
 use crate::errors::InherentProjectionNormalizationOverflow;
-use crate::infer::type_variable::TypeVariableOrigin;
 use crate::infer::{BoundRegionConversionTime, InferOk};
 use crate::traits::normalize::normalize_with_depth;
 use crate::traits::normalize::normalize_with_depth_to;
@@ -521,10 +520,7 @@ fn normalize_to_error<'a, 'tcx>(
         predicate: trait_ref.to_predicate(selcx.tcx()),
     };
     let tcx = selcx.infcx.tcx;
-    let new_value = selcx.infcx.next_ty_var(TypeVariableOrigin {
-        param_def_id: None,
-        span: tcx.def_span(projection_ty.def_id),
-    });
+    let new_value = selcx.infcx.next_ty_var(tcx.def_span(projection_ty.def_id));
     Normalized { value: new_value, obligations: vec![trait_obligation] }
 }
 
diff --git a/compiler/rustc_trait_selection/src/traits/structural_normalize.rs b/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
index 64ab8378abb..96a06e0c169 100644
--- a/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
@@ -1,5 +1,4 @@
 use rustc_infer::infer::at::At;
-use rustc_infer::infer::type_variable::TypeVariableOrigin;
 use rustc_infer::traits::{FulfillmentError, TraitEngine};
 use rustc_macros::extension;
 use rustc_middle::ty::{self, Ty};
@@ -20,9 +19,7 @@ impl<'tcx> At<'_, 'tcx> {
                 return Ok(ty);
             };
 
-            let new_infer_ty = self
-                .infcx
-                .next_ty_var(TypeVariableOrigin { param_def_id: None, span: self.cause.span });
+            let new_infer_ty = self.infcx.next_ty_var(self.cause.span);
 
             // We simply emit an `alias-eq` goal here, since that will take care of
             // normalizing the LHS of the projection until it is a rigid projection