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-rw-r--r--compiler/rustc_lint/messages.ftl3
-rw-r--r--compiler/rustc_lint/src/internal.rs128
-rw-r--r--compiler/rustc_lint/src/lib.rs1
-rw-r--r--compiler/rustc_lint/src/lints.rs5
-rw-r--r--compiler/rustc_monomorphize/src/collector.rs6
-rw-r--r--compiler/rustc_next_trait_solver/src/lib.rs1
-rw-r--r--compiler/rustc_span/src/symbol.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs6
-rw-r--r--compiler/rustc_type_ir/src/infer_ctxt.rs1
-rw-r--r--compiler/rustc_type_ir/src/interner.rs1
-rw-r--r--compiler/rustc_type_ir/src/lib.rs1
-rw-r--r--tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.rs16
-rw-r--r--tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.stderr15
13 files changed, 139 insertions, 47 deletions
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index d51865810b9..0a3eb434d3f 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -799,6 +799,9 @@ lint_tykind_kind = usage of `ty::TyKind::<kind>`
 lint_type_ir_inherent_usage = do not use `rustc_type_ir::inherent` unless you're inside of the trait solver
     .note = the method or struct you're looking for is likely defined somewhere else downstream in the compiler
 
+lint_type_ir_trait_usage = do not use `rustc_type_ir::Interner` or `rustc_type_ir::InferCtxtLike` unless you're inside of the trait solver
+    .note = the method or struct you're looking for is likely defined somewhere else downstream in the compiler
+
 lint_undropped_manually_drops = calls to `std::mem::drop` with `std::mem::ManuallyDrop` instead of the inner value does nothing
     .label = argument has type `{$arg_ty}`
     .suggestion = use `std::mem::ManuallyDrop::into_inner` to get the inner value
diff --git a/compiler/rustc_lint/src/internal.rs b/compiler/rustc_lint/src/internal.rs
index b359ee790a5..1d4be24ea9f 100644
--- a/compiler/rustc_lint/src/internal.rs
+++ b/compiler/rustc_lint/src/internal.rs
@@ -1,24 +1,21 @@
 //! Some lints that are only useful in the compiler or crates that use compiler internals, such as
 //! Clippy.
 
-use rustc_ast as ast;
+use rustc_hir::HirId;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::DefId;
-use rustc_hir::{
-    AmbigArg, BinOp, BinOpKind, Expr, ExprKind, GenericArg, HirId, Impl, Item, ItemKind, Node, Pat,
-    PatExpr, PatExprKind, PatKind, Path, PathSegment, QPath, Ty, TyKind,
-};
 use rustc_middle::ty::{self, GenericArgsRef, Ty as MiddleTy};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::hygiene::{ExpnKind, MacroKind};
 use rustc_span::{Span, sym};
 use tracing::debug;
+use {rustc_ast as ast, rustc_hir as hir};
 
 use crate::lints::{
     BadOptAccessDiag, DefaultHashTypesDiag, DiagOutOfImpl, LintPassByHand,
     NonGlobImportTypeIrInherent, QueryInstability, QueryUntracked, SpanUseEqCtxtDiag,
     SymbolInternStringLiteralDiag, TyQualified, TykindDiag, TykindKind, TypeIrInherentUsage,
-    UntranslatableDiag,
+    TypeIrTraitUsage, UntranslatableDiag,
 };
 use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
 
@@ -37,9 +34,12 @@ declare_tool_lint! {
 declare_lint_pass!(DefaultHashTypes => [DEFAULT_HASH_TYPES]);
 
 impl LateLintPass<'_> for DefaultHashTypes {
-    fn check_path(&mut self, cx: &LateContext<'_>, path: &Path<'_>, hir_id: HirId) {
+    fn check_path(&mut self, cx: &LateContext<'_>, path: &hir::Path<'_>, hir_id: HirId) {
         let Res::Def(rustc_hir::def::DefKind::Struct, def_id) = path.res else { return };
-        if matches!(cx.tcx.hir_node(hir_id), Node::Item(Item { kind: ItemKind::Use(..), .. })) {
+        if matches!(
+            cx.tcx.hir_node(hir_id),
+            hir::Node::Item(hir::Item { kind: hir::ItemKind::Use(..), .. })
+        ) {
             // Don't lint imports, only actual usages.
             return;
         }
@@ -60,10 +60,10 @@ impl LateLintPass<'_> for DefaultHashTypes {
 /// get the `DefId` and `GenericArgsRef` of the function.
 fn typeck_results_of_method_fn<'tcx>(
     cx: &LateContext<'tcx>,
-    expr: &Expr<'_>,
+    expr: &hir::Expr<'_>,
 ) -> Option<(Span, DefId, ty::GenericArgsRef<'tcx>)> {
     match expr.kind {
-        ExprKind::MethodCall(segment, ..)
+        hir::ExprKind::MethodCall(segment, ..)
             if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) =>
         {
             Some((segment.ident.span, def_id, cx.typeck_results().node_args(expr.hir_id)))
@@ -102,7 +102,7 @@ declare_tool_lint! {
 declare_lint_pass!(QueryStability => [POTENTIAL_QUERY_INSTABILITY, UNTRACKED_QUERY_INFORMATION]);
 
 impl LateLintPass<'_> for QueryStability {
-    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
         let Some((span, def_id, args)) = typeck_results_of_method_fn(cx, expr) else { return };
         if let Ok(Some(instance)) = ty::Instance::try_resolve(cx.tcx, cx.typing_env(), def_id, args)
         {
@@ -164,21 +164,25 @@ impl<'tcx> LateLintPass<'tcx> for TyTyKind {
         }
     }
 
-    fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx Ty<'tcx, AmbigArg>) {
+    fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx hir::Ty<'tcx, hir::AmbigArg>) {
         match &ty.kind {
-            TyKind::Path(QPath::Resolved(_, path)) => {
+            hir::TyKind::Path(hir::QPath::Resolved(_, path)) => {
                 if lint_ty_kind_usage(cx, &path.res) {
                     let span = match cx.tcx.parent_hir_node(ty.hir_id) {
-                        Node::PatExpr(PatExpr { kind: PatExprKind::Path(qpath), .. })
-                        | Node::Pat(Pat {
-                            kind: PatKind::TupleStruct(qpath, ..) | PatKind::Struct(qpath, ..),
+                        hir::Node::PatExpr(hir::PatExpr {
+                            kind: hir::PatExprKind::Path(qpath),
+                            ..
+                        })
+                        | hir::Node::Pat(hir::Pat {
+                            kind:
+                                hir::PatKind::TupleStruct(qpath, ..) | hir::PatKind::Struct(qpath, ..),
                             ..
                         })
-                        | Node::Expr(
-                            Expr { kind: ExprKind::Path(qpath), .. }
-                            | &Expr { kind: ExprKind::Struct(qpath, ..), .. },
+                        | hir::Node::Expr(
+                            hir::Expr { kind: hir::ExprKind::Path(qpath), .. }
+                            | &hir::Expr { kind: hir::ExprKind::Struct(qpath, ..), .. },
                         ) => {
-                            if let QPath::TypeRelative(qpath_ty, ..) = qpath
+                            if let hir::QPath::TypeRelative(qpath_ty, ..) = qpath
                                 && qpath_ty.hir_id == ty.hir_id
                             {
                                 Some(path.span)
@@ -223,7 +227,7 @@ fn lint_ty_kind_usage(cx: &LateContext<'_>, res: &Res) -> bool {
     }
 }
 
-fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, path: &Path<'_>) -> Option<String> {
+fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, path: &hir::Path<'_>) -> Option<String> {
     match &path.res {
         Res::Def(_, def_id) => {
             if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(*def_id) {
@@ -244,13 +248,17 @@ fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, path: &Path<'_>) -> Option<String> {
     None
 }
 
-fn gen_args(segment: &PathSegment<'_>) -> String {
+fn gen_args(segment: &hir::PathSegment<'_>) -> String {
     if let Some(args) = &segment.args {
         let lifetimes = args
             .args
             .iter()
             .filter_map(|arg| {
-                if let GenericArg::Lifetime(lt) = arg { Some(lt.ident.to_string()) } else { None }
+                if let hir::GenericArg::Lifetime(lt) = arg {
+                    Some(lt.ident.to_string())
+                } else {
+                    None
+                }
             })
             .collect::<Vec<_>>();
 
@@ -272,7 +280,7 @@ declare_tool_lint! {
 }
 
 declare_tool_lint! {
-    /// The `usage_of_type_ir_inherent` lint detects usage `rustc_type_ir::inherent`.
+    /// The `usage_of_type_ir_inherent` lint detects usage of `rustc_type_ir::inherent`.
     ///
     /// This module should only be used within the trait solver.
     pub rustc::USAGE_OF_TYPE_IR_INHERENT,
@@ -281,10 +289,43 @@ declare_tool_lint! {
     report_in_external_macro: true
 }
 
-declare_lint_pass!(TypeIr => [NON_GLOB_IMPORT_OF_TYPE_IR_INHERENT, USAGE_OF_TYPE_IR_INHERENT]);
+declare_tool_lint! {
+    /// The `usage_of_type_ir_traits` lint detects usage of `rustc_type_ir::Interner`,
+    /// or `rustc_infer::InferCtxtLike`.
+    ///
+    /// Methods of this trait should only be used within the type system abstraction layer,
+    /// and in the generic next trait solver implementation. Look for an analogously named
+    /// method on `TyCtxt` or `InferCtxt` (respectively).
+    pub rustc::USAGE_OF_TYPE_IR_TRAITS,
+    Allow,
+    "usage `rustc_type_ir`-specific abstraction traits outside of trait system",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(TypeIr => [NON_GLOB_IMPORT_OF_TYPE_IR_INHERENT, USAGE_OF_TYPE_IR_INHERENT, USAGE_OF_TYPE_IR_TRAITS]);
 
 impl<'tcx> LateLintPass<'tcx> for TypeIr {
-    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
+        let res_def_id = match expr.kind {
+            hir::ExprKind::Path(hir::QPath::Resolved(_, path)) => path.res.opt_def_id(),
+            hir::ExprKind::Path(hir::QPath::TypeRelative(..)) | hir::ExprKind::MethodCall(..) => {
+                cx.typeck_results().type_dependent_def_id(expr.hir_id)
+            }
+            _ => return,
+        };
+        let Some(res_def_id) = res_def_id else {
+            return;
+        };
+        if let Some(assoc_item) = cx.tcx.opt_associated_item(res_def_id)
+            && let Some(trait_def_id) = assoc_item.trait_container(cx.tcx)
+            && (cx.tcx.is_diagnostic_item(sym::type_ir_interner, trait_def_id)
+                | cx.tcx.is_diagnostic_item(sym::type_ir_infer_ctxt_like, trait_def_id))
+        {
+            cx.emit_span_lint(USAGE_OF_TYPE_IR_TRAITS, expr.span, TypeIrTraitUsage);
+        }
+    }
+
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
         let rustc_hir::ItemKind::Use(path, kind) = item.kind else { return };
 
         let is_mod_inherent = |def_id| cx.tcx.is_diagnostic_item(sym::type_ir_inherent, def_id);
@@ -394,15 +435,15 @@ declare_tool_lint! {
 declare_lint_pass!(Diagnostics => [UNTRANSLATABLE_DIAGNOSTIC, DIAGNOSTIC_OUTSIDE_OF_IMPL]);
 
 impl LateLintPass<'_> for Diagnostics {
-    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
-        let collect_args_tys_and_spans = |args: &[Expr<'_>], reserve_one_extra: bool| {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
+        let collect_args_tys_and_spans = |args: &[hir::Expr<'_>], reserve_one_extra: bool| {
             let mut result = Vec::with_capacity(args.len() + usize::from(reserve_one_extra));
             result.extend(args.iter().map(|arg| (cx.typeck_results().expr_ty(arg), arg.span)));
             result
         };
         // Only check function calls and method calls.
         let (span, def_id, fn_gen_args, arg_tys_and_spans) = match expr.kind {
-            ExprKind::Call(callee, args) => {
+            hir::ExprKind::Call(callee, args) => {
                 match cx.typeck_results().node_type(callee.hir_id).kind() {
                     &ty::FnDef(def_id, fn_gen_args) => {
                         (callee.span, def_id, fn_gen_args, collect_args_tys_and_spans(args, false))
@@ -410,7 +451,7 @@ impl LateLintPass<'_> for Diagnostics {
                     _ => return, // occurs for fns passed as args
                 }
             }
-            ExprKind::MethodCall(_segment, _recv, args, _span) => {
+            hir::ExprKind::MethodCall(_segment, _recv, args, _span) => {
                 let Some((span, def_id, fn_gen_args)) = typeck_results_of_method_fn(cx, expr)
                 else {
                     return;
@@ -514,8 +555,8 @@ impl Diagnostics {
         let mut is_inside_appropriate_impl = false;
         for (_hir_id, parent) in cx.tcx.hir_parent_iter(current_id) {
             debug!(?parent);
-            if let Node::Item(Item { kind: ItemKind::Impl(impl_), .. }) = parent
-                && let Impl { of_trait: Some(of_trait), .. } = impl_
+            if let hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) = parent
+                && let hir::Impl { of_trait: Some(of_trait), .. } = impl_
                 && let Some(def_id) = of_trait.trait_def_id()
                 && let Some(name) = cx.tcx.get_diagnostic_name(def_id)
                 && matches!(name, sym::Diagnostic | sym::Subdiagnostic | sym::LintDiagnostic)
@@ -543,8 +584,8 @@ declare_tool_lint! {
 declare_lint_pass!(BadOptAccess => [BAD_OPT_ACCESS]);
 
 impl LateLintPass<'_> for BadOptAccess {
-    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
-        let ExprKind::Field(base, target) = expr.kind else { return };
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
+        let hir::ExprKind::Field(base, target) = expr.kind else { return };
         let Some(adt_def) = cx.typeck_results().expr_ty(base).ty_adt_def() else { return };
         // Skip types without `#[rustc_lint_opt_ty]` - only so that the rest of the lint can be
         // avoided.
@@ -581,9 +622,12 @@ declare_tool_lint! {
 declare_lint_pass!(SpanUseEqCtxt => [SPAN_USE_EQ_CTXT]);
 
 impl<'tcx> LateLintPass<'tcx> for SpanUseEqCtxt {
-    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) {
-        if let ExprKind::Binary(BinOp { node: BinOpKind::Eq | BinOpKind::Ne, .. }, lhs, rhs) =
-            expr.kind
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
+        if let hir::ExprKind::Binary(
+            hir::BinOp { node: hir::BinOpKind::Eq | hir::BinOpKind::Ne, .. },
+            lhs,
+            rhs,
+        ) = expr.kind
         {
             if is_span_ctxt_call(cx, lhs) && is_span_ctxt_call(cx, rhs) {
                 cx.emit_span_lint(SPAN_USE_EQ_CTXT, expr.span, SpanUseEqCtxtDiag);
@@ -592,9 +636,9 @@ impl<'tcx> LateLintPass<'tcx> for SpanUseEqCtxt {
     }
 }
 
-fn is_span_ctxt_call(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
+fn is_span_ctxt_call(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
     match &expr.kind {
-        ExprKind::MethodCall(..) => cx
+        hir::ExprKind::MethodCall(..) => cx
             .typeck_results()
             .type_dependent_def_id(expr.hir_id)
             .is_some_and(|call_did| cx.tcx.is_diagnostic_item(sym::SpanCtxt, call_did)),
@@ -617,11 +661,11 @@ declare_lint_pass!(SymbolInternStringLiteral => [SYMBOL_INTERN_STRING_LITERAL]);
 
 impl<'tcx> LateLintPass<'tcx> for SymbolInternStringLiteral {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx rustc_hir::Expr<'tcx>) {
-        if let ExprKind::Call(path, [arg]) = expr.kind
-            && let ExprKind::Path(ref qpath) = path.kind
+        if let hir::ExprKind::Call(path, [arg]) = expr.kind
+            && let hir::ExprKind::Path(ref qpath) = path.kind
             && let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
             && cx.tcx.is_diagnostic_item(sym::SymbolIntern, def_id)
-            && let ExprKind::Lit(kind) = arg.kind
+            && let hir::ExprKind::Lit(kind) = arg.kind
             && let rustc_ast::LitKind::Str(_, _) = kind.node
         {
             cx.emit_span_lint(
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index c38a7540018..cd474f1b7db 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -645,6 +645,7 @@ fn register_internals(store: &mut LintStore) {
             LintId::of(USAGE_OF_QUALIFIED_TY),
             LintId::of(NON_GLOB_IMPORT_OF_TYPE_IR_INHERENT),
             LintId::of(USAGE_OF_TYPE_IR_INHERENT),
+            LintId::of(USAGE_OF_TYPE_IR_TRAITS),
             LintId::of(BAD_OPT_ACCESS),
             LintId::of(SPAN_USE_EQ_CTXT),
         ],
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 00586309572..036d68d13fa 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -944,6 +944,11 @@ pub(crate) struct TyQualified {
 pub(crate) struct TypeIrInherentUsage;
 
 #[derive(LintDiagnostic)]
+#[diag(lint_type_ir_trait_usage)]
+#[note]
+pub(crate) struct TypeIrTraitUsage;
+
+#[derive(LintDiagnostic)]
 #[diag(lint_non_glob_import_type_ir_inherent)]
 pub(crate) struct NonGlobImportTypeIrInherent {
     #[suggestion(code = "{snippet}", applicability = "maybe-incorrect")]
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 67fca1d7c29..679c614e9fa 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -225,8 +225,8 @@ use rustc_middle::ty::adjustment::{CustomCoerceUnsized, PointerCoercion};
 use rustc_middle::ty::layout::ValidityRequirement;
 use rustc_middle::ty::print::{shrunk_instance_name, with_no_trimmed_paths};
 use rustc_middle::ty::{
-    self, GenericArgs, GenericParamDefKind, Instance, InstanceKind, Interner, Ty, TyCtxt,
-    TypeFoldable, TypeVisitableExt, VtblEntry,
+    self, GenericArgs, GenericParamDefKind, Instance, InstanceKind, Ty, TyCtxt, TypeFoldable,
+    TypeVisitableExt, VtblEntry,
 };
 use rustc_middle::util::Providers;
 use rustc_middle::{bug, span_bug};
@@ -967,7 +967,7 @@ fn should_codegen_locally<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) ->
     {
         // `#[rustc_force_inline]` items should never be codegened. This should be caught by
         // the MIR validator.
-        tcx.delay_bug("attempt to codegen `#[rustc_force_inline]` item");
+        tcx.dcx().delayed_bug("attempt to codegen `#[rustc_force_inline]` item");
     }
 
     if def_id.is_local() {
diff --git a/compiler/rustc_next_trait_solver/src/lib.rs b/compiler/rustc_next_trait_solver/src/lib.rs
index f6963a79067..f575fe03019 100644
--- a/compiler/rustc_next_trait_solver/src/lib.rs
+++ b/compiler/rustc_next_trait_solver/src/lib.rs
@@ -6,6 +6,7 @@
 
 // tidy-alphabetical-start
 #![allow(rustc::usage_of_type_ir_inherent)]
+#![cfg_attr(not(bootstrap), allow(rustc::usage_of_type_ir_traits))]
 // tidy-alphabetical-end
 
 pub mod canonicalizer;
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 3e474243965..555764c26a6 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -2118,7 +2118,9 @@ symbols! {
         type_changing_struct_update,
         type_const,
         type_id,
+        type_ir_infer_ctxt_like,
         type_ir_inherent,
+        type_ir_interner,
         type_length_limit,
         type_macros,
         type_name,
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index fc352499146..4cfd8149b1e 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -16,7 +16,7 @@ use rustc_infer::traits::{Obligation, PolyTraitObligation, SelectionError};
 use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::{self, Ty, TypeVisitableExt, TypingMode};
 use rustc_middle::{bug, span_bug};
-use rustc_type_ir::{Interner, elaborate};
+use rustc_type_ir::elaborate;
 use tracing::{debug, instrument, trace};
 
 use super::SelectionCandidate::*;
@@ -802,7 +802,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 | ty::UnsafeBinder(_) => {
                     // Only consider auto impls of unsafe traits when there are
                     // no unsafe fields.
-                    if self.tcx().trait_is_unsafe(def_id) && self_ty.has_unsafe_fields() {
+                    if self.tcx().trait_def(def_id).safety.is_unsafe()
+                        && self_ty.has_unsafe_fields()
+                    {
                         return;
                     }
 
diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs
index 26c49510696..e512e8fc838 100644
--- a/compiler/rustc_type_ir/src/infer_ctxt.rs
+++ b/compiler/rustc_type_ir/src/infer_ctxt.rs
@@ -102,6 +102,7 @@ impl<I: Interner> TypingMode<I> {
     }
 }
 
+#[cfg_attr(feature = "nightly", rustc_diagnostic_item = "type_ir_infer_ctxt_like")]
 pub trait InferCtxtLike: Sized {
     type Interner: Interner;
     fn cx(&self) -> Self::Interner;
diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs
index e765cb66d00..8f86270d7dc 100644
--- a/compiler/rustc_type_ir/src/interner.rs
+++ b/compiler/rustc_type_ir/src/interner.rs
@@ -15,6 +15,7 @@ use crate::solve::{CanonicalInput, ExternalConstraintsData, PredefinedOpaquesDat
 use crate::visit::{Flags, TypeSuperVisitable, TypeVisitable};
 use crate::{self as ty, search_graph};
 
+#[cfg_attr(feature = "nightly", rustc_diagnostic_item = "type_ir_interner")]
 pub trait Interner:
     Sized
     + Copy
diff --git a/compiler/rustc_type_ir/src/lib.rs b/compiler/rustc_type_ir/src/lib.rs
index 62912189509..4e2baca2785 100644
--- a/compiler/rustc_type_ir/src/lib.rs
+++ b/compiler/rustc_type_ir/src/lib.rs
@@ -6,6 +6,7 @@
     feature(associated_type_defaults, never_type, rustc_attrs, negative_impls)
 )]
 #![cfg_attr(feature = "nightly", allow(internal_features))]
+#![cfg_attr(not(bootstrap), allow(rustc::usage_of_type_ir_traits))]
 // tidy-alphabetical-end
 
 extern crate self as rustc_type_ir;
diff --git a/tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.rs b/tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.rs
new file mode 100644
index 00000000000..3fdd65d6c87
--- /dev/null
+++ b/tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.rs
@@ -0,0 +1,16 @@
+//@ compile-flags: -Z unstable-options
+//@ ignore-stage1
+
+#![feature(rustc_private)]
+#![deny(rustc::usage_of_type_ir_traits)]
+
+extern crate rustc_type_ir;
+
+use rustc_type_ir::Interner;
+
+fn foo<I: Interner>(cx: I, did: I::DefId) {
+    let _ = cx.trait_is_unsafe(did);
+    //~^ ERROR do not use `rustc_type_ir::Interner` or `rustc_type_ir::InferCtxtLike` unless you're inside of the trait solver
+}
+
+fn main() {}
diff --git a/tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.stderr b/tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.stderr
new file mode 100644
index 00000000000..df29a494558
--- /dev/null
+++ b/tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.stderr
@@ -0,0 +1,15 @@
+error: do not use `rustc_type_ir::Interner` or `rustc_type_ir::InferCtxtLike` unless you're inside of the trait solver
+  --> $DIR/import-of-type-ir-traits.rs:12:13
+   |
+LL |     let _ = cx.trait_is_unsafe(did);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the method or struct you're looking for is likely defined somewhere else downstream in the compiler
+note: the lint level is defined here
+  --> $DIR/import-of-type-ir-traits.rs:5:9
+   |
+LL | #![deny(rustc::usage_of_type_ir_traits)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
generated by cgit-pink 1.4.1-3-g733a5 (git 2.37.1) at 2026-01-11 14:04:22 +0000