Auto merge of #125507 - compiler-errors:type-length-limit, r=lcnr

Re-implement a type-size based limit

r? lcnr

This PR reintroduces the type length limit added in #37789, which was accidentally made practically useless by the caching changes to `Ty::walk` in #72412, which caused the `walk` function to no longer walk over identical elements.

Hitting this length limit is not fatal unless we are in codegen -- so it shouldn't affect passes like the mir inliner which creates potentially very large types (which we observed, for example, when the new trait solver compiles `itertools` in `--release` mode).

This also increases the type length limit from `1048576 == 2 ** 20` to `2 ** 24`, which covers all of the code that can be reached with craterbot-check. Individual crates can increase the length limit further if desired.

Perf regression is mild and I think we should accept it -- reinstating this limit is important for the new trait solver and to make sure we don't accidentally hit more type-size related regressions in the future.

Fixes #125460

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -3733,7 +3733,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
             if tcx.is_diagnostic_item(sym::deref_method, method_did) {
                 let deref_target =
                     tcx.get_diagnostic_item(sym::deref_target).and_then(|deref_target| {
-                        Instance::resolve(tcx, self.param_env, deref_target, method_args)
+                        Instance::try_resolve(tcx, self.param_env, deref_target, method_args)
                             .transpose()
                     });
                 if let Some(Ok(instance)) = deref_target {

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -949,7 +949,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
                 return;
             }
 
-            if let Ok(Some(instance)) = ty::Instance::resolve(
+            if let Ok(Some(instance)) = ty::Instance::try_resolve(
                 tcx,
                 self.param_env,
                 *fn_did,

compiler/rustc_codegen_cranelift/src/abi/mod.rs

@@ -371,9 +371,14 @@ pub(crate) fn codegen_terminator_call<'tcx>(
 
     // Handle special calls like intrinsics and empty drop glue.
     let instance = if let ty::FnDef(def_id, fn_args) = *func.layout().ty.kind() {
-        let instance =
+        let instance = ty::Instance::expect_resolve(
-            ty::Instance::expect_resolve(fx.tcx, ty::ParamEnv::reveal_all(), def_id, fn_args)
+            fx.tcx,
-                .polymorphize(fx.tcx);
+            ty::ParamEnv::reveal_all(),
+            def_id,
+            fn_args,
+            source_info.span,
+        )
+        .polymorphize(fx.tcx);
 
         if is_call_from_compiler_builtins_to_upstream_monomorphization(fx.tcx, instance) {
             if target.is_some() {

compiler/rustc_codegen_cranelift/src/main_shim.rs

@@ -4,6 +4,7 @@ use rustc_middle::ty::AssocKind;
 use rustc_middle::ty::GenericArg;
 use rustc_session::config::{sigpipe, EntryFnType};
 use rustc_span::symbol::Ident;
+use rustc_span::DUMMY_SP;
 
 use crate::prelude::*;
 
@@ -119,6 +120,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     ParamEnv::reveal_all(),
                     report.def_id,
                     tcx.mk_args(&[GenericArg::from(main_ret_ty)]),
+                    DUMMY_SP,
                 )
                 .polymorphize(tcx);
 
@@ -144,6 +146,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     ParamEnv::reveal_all(),
                     start_def_id,
                     tcx.mk_args(&[main_ret_ty.into()]),
+                    DUMMY_SP,
                 )
                 .polymorphize(tcx);
                 let start_func_id = import_function(tcx, m, start_instance);

compiler/rustc_codegen_gcc/src/context.rs

@@ -17,7 +17,7 @@ use rustc_middle::ty::layout::{
 };
 use rustc_middle::ty::{self, Instance, ParamEnv, PolyExistentialTraitRef, Ty, TyCtxt};
 use rustc_session::Session;
-use rustc_span::{source_map::respan, Span};
+use rustc_span::{source_map::respan, Span, DUMMY_SP};
 use rustc_target::abi::{
     call::FnAbi, HasDataLayout, PointeeInfo, Size, TargetDataLayout, VariantIdx,
 };
@@ -479,6 +479,7 @@ impl<'gcc, 'tcx> MiscMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
                     ty::ParamEnv::reveal_all(),
                     def_id,
                     ty::List::empty(),
+                    DUMMY_SP,
                 );
 
                 let symbol_name = tcx.symbol_name(instance).name;

compiler/rustc_codegen_llvm/src/context.rs

@@ -28,7 +28,7 @@ use rustc_session::config::{BranchProtection, CFGuard, CFProtection};
 use rustc_session::config::{CrateType, DebugInfo, PAuthKey, PacRet};
 use rustc_session::Session;
 use rustc_span::source_map::Spanned;
-use rustc_span::Span;
+use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi::{call::FnAbi, HasDataLayout, TargetDataLayout, VariantIdx};
 use rustc_target::spec::{HasTargetSpec, RelocModel, Target, TlsModel};
 use smallvec::SmallVec;
@@ -580,6 +580,7 @@ impl<'ll, 'tcx> MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 ty::ParamEnv::reveal_all(),
                 def_id,
                 ty::List::empty(),
+                DUMMY_SP,
             )),
             _ => {
                 let name = name.unwrap_or("rust_eh_personality");

compiler/rustc_codegen_ssa/src/base.rs

@@ -37,7 +37,7 @@ use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_session::config::{self, CrateType, EntryFnType, OptLevel, OutputType};
 use rustc_session::Session;
 use rustc_span::symbol::sym;
-use rustc_span::Symbol;
+use rustc_span::{Symbol, DUMMY_SP};
 use rustc_target::abi::FIRST_VARIANT;
 
 use std::cmp;
@@ -467,6 +467,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 ty::ParamEnv::reveal_all(),
                 start_def_id,
                 cx.tcx().mk_args(&[main_ret_ty.into()]),
+                DUMMY_SP,
             );
             let start_fn = cx.get_fn_addr(start_instance);
 

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -842,6 +842,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         ty::ParamEnv::reveal_all(),
                         def_id,
                         args,
+                        fn_span,
                     )
                     .polymorphize(bx.tcx()),
                 ),

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -768,7 +768,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                         is_trait = true;
 
                         if let Ok(Some(instance)) =
-                            Instance::resolve(tcx, param_env, callee, fn_args)
+                            Instance::try_resolve(tcx, param_env, callee, fn_args)
                             && let InstanceKind::Item(def) = instance.def
                         {
                             // Resolve a trait method call to its concrete implementation, which may be in a

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -253,6 +253,7 @@ impl<'tcx> CompileTimeInterpCx<'tcx> {
                 ty::ParamEnv::reveal_all(),
                 const_def_id,
                 instance.args,
+                self.cur_span(),
             );
 
             return Ok(Some(new_instance));

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -618,7 +618,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         trace!("resolve: {:?}, {:#?}", def, args);
         trace!("param_env: {:#?}", self.param_env);
         trace!("args: {:#?}", args);
-        match ty::Instance::resolve(*self.tcx, self.param_env, def, args) {
+        match ty::Instance::try_resolve(*self.tcx, self.param_env, def, args) {
             Ok(Some(instance)) => Ok(instance),
             Ok(None) => throw_inval!(TooGeneric),
 

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -883,13 +883,13 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                         ty::ExistentialTraitRef::erase_self_ty(tcx, virtual_trait_ref);
                     let concrete_trait_ref = existential_trait_ref.with_self_ty(tcx, dyn_ty);
 
-                    let concrete_method = Instance::resolve_for_vtable(
+                    let concrete_method = Instance::expect_resolve_for_vtable(
                         tcx,
                         self.param_env,
                         def_id,
                         instance.args.rebase_onto(tcx, trait_def_id, concrete_trait_ref.args),
-                    )
+                        self.cur_span(),
-                    .unwrap();
+                    );
                     assert_eq!(fn_inst, concrete_method);
                 }
 

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -534,7 +534,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let tcx = self.tcx();
 
         // Find the method being called.
-        let Ok(Some(instance)) = ty::Instance::resolve(
+        let Ok(Some(instance)) = ty::Instance::try_resolve(
             tcx,
             ctxt.param_env,
             ctxt.assoc_item.def_id,

compiler/rustc_lint/src/internal.rs

@@ -88,7 +88,7 @@ declare_lint_pass!(QueryStability => [POTENTIAL_QUERY_INSTABILITY]);
 impl LateLintPass<'_> for QueryStability {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
         let Some((span, def_id, args)) = typeck_results_of_method_fn(cx, expr) else { return };
-        if let Ok(Some(instance)) = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, args) {
+        if let Ok(Some(instance)) = ty::Instance::try_resolve(cx.tcx, cx.param_env, def_id, args) {
             let def_id = instance.def_id();
             if cx.tcx.has_attr(def_id, sym::rustc_lint_query_instability) {
                 cx.emit_span_lint(
@@ -393,7 +393,7 @@ impl LateLintPass<'_> for Diagnostics {
         };
 
         // Is the callee marked with `#[rustc_lint_diagnostics]`?
-        let has_attr = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, fn_gen_args)
+        let has_attr = ty::Instance::try_resolve(cx.tcx, cx.param_env, def_id, fn_gen_args)
             .ok()
             .flatten()
             .is_some_and(|inst| cx.tcx.has_attr(inst.def_id(), sym::rustc_lint_diagnostics));

compiler/rustc_lint/src/noop_method_call.rs

@@ -96,7 +96,9 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
             .tcx
             .normalize_erasing_regions(cx.param_env, cx.typeck_results().node_args(expr.hir_id));
         // Resolve the trait method instance.
-        let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, cx.param_env, did, args) else { return };
+        let Ok(Some(i)) = ty::Instance::try_resolve(cx.tcx, cx.param_env, did, args) else {
+            return;
+        };
         // (Re)check that it implements the noop diagnostic.
         let Some(name) = cx.tcx.get_diagnostic_name(i.def_id()) else { return };
         if !matches!(

compiler/rustc_middle/messages.ftl

@@ -41,6 +41,9 @@ middle_cannot_be_normalized =
 middle_conflict_types =
     this expression supplies two conflicting concrete types for the same opaque type
 
+middle_consider_type_length_limit =
+    consider adding a `#![type_length_limit="{$type_length}"]` attribute to your crate
+
 middle_const_eval_non_int =
     constant evaluation of enum discriminant resulted in non-integer
 
@@ -94,8 +97,11 @@ middle_strict_coherence_needs_negative_coherence =
     to use `strict_coherence` on this trait, the `with_negative_coherence` feature must be enabled
     .label = due to this attribute
 
+middle_type_length_limit = reached the type-length limit while instantiating `{$shrunk}`
+
 middle_unknown_layout =
     the type `{$ty}` has an unknown layout
 
 middle_values_too_big =
     values of the type `{$ty}` are too big for the current architecture
+middle_written_to_path = the full type name has been written to '{$path}'

compiler/rustc_middle/src/error.rs

@@ -1,4 +1,5 @@
 use std::fmt;
+use std::path::PathBuf;
 
 use rustc_errors::{codes::*, DiagArgName, DiagArgValue, DiagMessage};
 use rustc_macros::{Diagnostic, Subdiagnostic};
@@ -149,3 +150,16 @@ pub struct ErroneousConstant {
 
 /// Used by `rustc_const_eval`
 pub use crate::fluent_generated::middle_adjust_for_foreign_abi_error;
+
+#[derive(Diagnostic)]
+#[diag(middle_type_length_limit)]
+#[help(middle_consider_type_length_limit)]
+pub struct TypeLengthLimit {
+    #[primary_span]
+    pub span: Span,
+    pub shrunk: String,
+    #[note(middle_written_to_path)]
+    pub was_written: Option<()>,
+    pub path: PathBuf,
+    pub type_length: usize,
+}

compiler/rustc_middle/src/middle/limits.rs

@@ -30,7 +30,7 @@ pub fn provide(providers: &mut Providers) {
             tcx.hir().krate_attrs(),
             tcx.sess,
             sym::type_length_limit,
-            1048576,
+            2usize.pow(24),
         ),
     }
 }

compiler/rustc_middle/src/mir/interpret/queries.rs

@@ -73,7 +73,7 @@ impl<'tcx> TyCtxt<'tcx> {
             bug!("did not expect inference variables here");
         }
 
-        match ty::Instance::resolve(
+        match ty::Instance::try_resolve(
             self, param_env,
             // FIXME: maybe have a separate version for resolving mir::UnevaluatedConst?
             ct.def, ct.args,
@@ -106,7 +106,7 @@ impl<'tcx> TyCtxt<'tcx> {
             bug!("did not expect inference variables here");
         }
 
-        match ty::Instance::resolve(self, param_env, ct.def, ct.args) {
+        match ty::Instance::try_resolve(self, param_env, ct.def, ct.args) {
             Ok(Some(instance)) => {
                 let cid = GlobalId { instance, promoted: None };
                 self.const_eval_global_id_for_typeck(param_env, cid, span).inspect(|_| {

compiler/rustc_middle/src/query/mod.rs

@@ -2197,8 +2197,8 @@ rustc_queries! {
     ///  * `Err(ErrorGuaranteed)` when the `Instance` resolution process
     ///    couldn't complete due to errors elsewhere - this is distinct
     ///    from `Ok(None)` to avoid misleading diagnostics when an error
-    ///    has already been/will be emitted, for the original cause
+    ///    has already been/will be emitted, for the original cause.
-    query resolve_instance(
+    query resolve_instance_raw(
         key: ty::ParamEnvAnd<'tcx, (DefId, GenericArgsRef<'tcx>)>
     ) -> Result<Option<ty::Instance<'tcx>>, ErrorGuaranteed> {
         desc { "resolving instance `{}`", ty::Instance::new(key.value.0, key.value.1) }

compiler/rustc_middle/src/ty/instance.rs

@@ -1,23 +1,25 @@
+use crate::error;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
-use crate::ty::print::{FmtPrinter, Printer};
+use crate::ty::print::{shrunk_instance_name, FmtPrinter, Printer};
-use crate::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
+use crate::ty::{
-use crate::ty::{EarlyBinder, GenericArgs, GenericArgsRef, TypeVisitableExt};
+    self, EarlyBinder, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable,
+    TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
+};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_hir::lang_items::LangItem;
 use rustc_index::bit_set::FiniteBitSet;
-use rustc_macros::{
+use rustc_macros::{Decodable, Encodable, HashStable, Lift, TyDecodable, TyEncodable};
-    Decodable, Encodable, HashStable, Lift, TyDecodable, TyEncodable, TypeVisitable,
-};
 use rustc_middle::ty::normalize_erasing_regions::NormalizationError;
 use rustc_span::def_id::LOCAL_CRATE;
-use rustc_span::Symbol;
+use rustc_span::{Span, Symbol, DUMMY_SP};
 use tracing::{debug, instrument};
 
 use std::assert_matches::assert_matches;
 use std::fmt;
+use std::path::PathBuf;
 
 /// An `InstanceKind` along with the args that are needed to substitute the instance.
 ///
@@ -385,7 +387,28 @@ impl<'tcx> InstanceKind<'tcx> {
     }
 }
 
-fn fmt_instance(
+fn type_length<'tcx>(item: impl TypeVisitable<TyCtxt<'tcx>>) -> usize {
+    struct Visitor {
+        type_length: usize,
+    }
+    impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for Visitor {
+        fn visit_ty(&mut self, t: Ty<'tcx>) {
+            self.type_length += 1;
+            t.super_visit_with(self);
+        }
+
+        fn visit_const(&mut self, ct: ty::Const<'tcx>) {
+            self.type_length += 1;
+            ct.super_visit_with(self);
+        }
+    }
+    let mut visitor = Visitor { type_length: 0 };
+    item.visit_with(&mut visitor);
+
+    visitor.type_length
+}
+
+pub fn fmt_instance(
     f: &mut fmt::Formatter<'_>,
     instance: Instance<'_>,
     type_length: Option<rustc_session::Limit>,
@@ -485,19 +508,30 @@ impl<'tcx> Instance<'tcx> {
     ///
     /// Presuming that coherence and type-check have succeeded, if this method is invoked
     /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
-    /// `Ok(Some(instance))`.
+    /// `Ok(Some(instance))`, **except** for when the instance's inputs hit the type size limit,
+    /// in which case it may bail out and return `Ok(None)`.
     ///
     /// Returns `Err(ErrorGuaranteed)` when the `Instance` resolution process
     /// couldn't complete due to errors elsewhere - this is distinct
     /// from `Ok(None)` to avoid misleading diagnostics when an error
     /// has already been/will be emitted, for the original cause
     #[instrument(level = "debug", skip(tcx), ret)]
-    pub fn resolve(
+    pub fn try_resolve(
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         def_id: DefId,
         args: GenericArgsRef<'tcx>,
     ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
+        // Rust code can easily create exponentially-long types using only a
+        // polynomial recursion depth. Even with the default recursion
+        // depth, you can easily get cases that take >2^60 steps to run,
+        // which means that rustc basically hangs.
+        //
+        // Bail out in these cases to avoid that bad user experience.
+        if !tcx.type_length_limit().value_within_limit(type_length(args)) {
+            return Ok(None);
+        }
+
         // All regions in the result of this query are erased, so it's
         // fine to erase all of the input regions.
 
@@ -505,7 +539,7 @@ impl<'tcx> Instance<'tcx> {
         // below is more likely to ignore the bounds in scope (e.g. if the only
         // generic parameters mentioned by `args` were lifetime ones).
         let args = tcx.erase_regions(args);
-        tcx.resolve_instance(tcx.erase_regions(param_env.and((def_id, args))))
+        tcx.resolve_instance_raw(tcx.erase_regions(param_env.and((def_id, args))))
     }
 
     pub fn expect_resolve(
@@ -513,10 +547,48 @@ impl<'tcx> Instance<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         def_id: DefId,
         args: GenericArgsRef<'tcx>,
+        span: Span,
     ) -> Instance<'tcx> {
-        match ty::Instance::resolve(tcx, param_env, def_id, args) {
+        // We compute the span lazily, to avoid unnecessary query calls.
+        // If `span` is a DUMMY_SP, and the def id is local, then use the
+        // def span of the def id.
+        let span_or_local_def_span =
+            || if span.is_dummy() && def_id.is_local() { tcx.def_span(def_id) } else { span };
+
+        match ty::Instance::try_resolve(tcx, param_env, def_id, args) {
             Ok(Some(instance)) => instance,
-            instance => bug!(
+            Ok(None) => {
+                let type_length = type_length(args);
+                if !tcx.type_length_limit().value_within_limit(type_length) {
+                    let (shrunk, written_to_path) =
+                        shrunk_instance_name(tcx, Instance::new(def_id, args));
+                    let mut path = PathBuf::new();
+                    let was_written = if let Some(path2) = written_to_path {
+                        path = path2;
+                        Some(())
+                    } else {
+                        None
+                    };
+                    tcx.dcx().emit_fatal(error::TypeLengthLimit {
+                        // We don't use `def_span(def_id)` so that diagnostics point
+                        // to the crate root during mono instead of to foreign items.
+                        // This is arguably better.
+                        span: span_or_local_def_span(),
+                        shrunk,
+                        was_written,
+                        path,
+                        type_length,
+                    });
+                } else {
+                    span_bug!(
+                        span_or_local_def_span(),
+                        "failed to resolve instance for {}",
+                        tcx.def_path_str_with_args(def_id, args)
+                    )
+                }
+            }
+            instance => span_bug!(
+                span_or_local_def_span(),
                 "failed to resolve instance for {}: {instance:#?}",
                 tcx.def_path_str_with_args(def_id, args)
             ),
@@ -533,7 +605,7 @@ impl<'tcx> Instance<'tcx> {
         // Use either `resolve_closure` or `resolve_for_vtable`
         assert!(!tcx.is_closure_like(def_id), "Called `resolve_for_fn_ptr` on closure: {def_id:?}");
         let reason = tcx.sess.is_sanitizer_kcfi_enabled().then_some(ReifyReason::FnPtr);
-        Instance::resolve(tcx, param_env, def_id, args).ok().flatten().map(|mut resolved| {
+        Instance::try_resolve(tcx, param_env, def_id, args).ok().flatten().map(|mut resolved| {
             match resolved.def {
                 InstanceKind::Item(def) if resolved.def.requires_caller_location(tcx) => {
                     debug!(" => fn pointer created for function with #[track_caller]");
@@ -571,77 +643,82 @@ impl<'tcx> Instance<'tcx> {
         })
     }
 
-    pub fn resolve_for_vtable(
+    pub fn expect_resolve_for_vtable(
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         def_id: DefId,
         args: GenericArgsRef<'tcx>,
-    ) -> Option<Instance<'tcx>> {
+        span: Span,
+    ) -> Instance<'tcx> {
         debug!("resolve_for_vtable(def_id={:?}, args={:?})", def_id, args);
         let fn_sig = tcx.fn_sig(def_id).instantiate_identity();
         let is_vtable_shim = !fn_sig.inputs().skip_binder().is_empty()
             && fn_sig.input(0).skip_binder().is_param(0)
             && tcx.generics_of(def_id).has_self;
+
         if is_vtable_shim {
             debug!(" => associated item with unsizeable self: Self");
-            Some(Instance { def: InstanceKind::VTableShim(def_id), args })
+            return Instance { def: InstanceKind::VTableShim(def_id), args };
-        } else {
-            let reason = tcx.sess.is_sanitizer_kcfi_enabled().then_some(ReifyReason::Vtable);
-            Instance::resolve(tcx, param_env, def_id, args).ok().flatten().map(|mut resolved| {
-                match resolved.def {
-                    InstanceKind::Item(def) => {
-                        // We need to generate a shim when we cannot guarantee that
-                        // the caller of a trait object method will be aware of
-                        // `#[track_caller]` - this ensures that the caller
-                        // and callee ABI will always match.
-                        //
-                        // The shim is generated when all of these conditions are met:
-                        //
-                        // 1) The underlying method expects a caller location parameter
-                        // in the ABI
-                        if resolved.def.requires_caller_location(tcx)
-                            // 2) The caller location parameter comes from having `#[track_caller]`
-                            // on the implementation, and *not* on the trait method.
-                            && !tcx.should_inherit_track_caller(def)
-                            // If the method implementation comes from the trait definition itself
-                            // (e.g. `trait Foo { #[track_caller] my_fn() { /* impl */ } }`),
-                            // then we don't need to generate a shim. This check is needed because
-                            // `should_inherit_track_caller` returns `false` if our method
-                            // implementation comes from the trait block, and not an impl block
-                            && !matches!(
-                                tcx.opt_associated_item(def),
-                                Some(ty::AssocItem {
-                                    container: ty::AssocItemContainer::TraitContainer,
-                                    ..
-                                })
-                            )
-                        {
-                            if tcx.is_closure_like(def) {
-                                debug!(" => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}",
-                                       def, def_id, args);
-
-                                // Create a shim for the `FnOnce/FnMut/Fn` method we are calling
-                                // - unlike functions, invoking a closure always goes through a
-                                // trait.
-                                resolved = Instance { def: InstanceKind::ReifyShim(def_id, reason), args };
-                            } else {
-                                debug!(
-                                    " => vtable fn pointer created for function with #[track_caller]: {:?}", def
-                                );
-                                resolved.def = InstanceKind::ReifyShim(def, reason);
-                            }
-                        }
-                    }
-                    InstanceKind::Virtual(def_id, _) => {
-                        debug!(" => vtable fn pointer created for virtual call");
-                        resolved.def = InstanceKind::ReifyShim(def_id, reason)
-                    }
-                    _ => {}
-                }
-
-                resolved
-            })
         }
+
+        let mut resolved = Instance::expect_resolve(tcx, param_env, def_id, args, span);
+
+        let reason = tcx.sess.is_sanitizer_kcfi_enabled().then_some(ReifyReason::Vtable);
+        match resolved.def {
+            InstanceKind::Item(def) => {
+                // We need to generate a shim when we cannot guarantee that
+                // the caller of a trait object method will be aware of
+                // `#[track_caller]` - this ensures that the caller
+                // and callee ABI will always match.
+                //
+                // The shim is generated when all of these conditions are met:
+                //
+                // 1) The underlying method expects a caller location parameter
+                // in the ABI
+                if resolved.def.requires_caller_location(tcx)
+                        // 2) The caller location parameter comes from having `#[track_caller]`
+                        // on the implementation, and *not* on the trait method.
+                        && !tcx.should_inherit_track_caller(def)
+                        // If the method implementation comes from the trait definition itself
+                        // (e.g. `trait Foo { #[track_caller] my_fn() { /* impl */ } }`),
+                        // then we don't need to generate a shim. This check is needed because
+                        // `should_inherit_track_caller` returns `false` if our method
+                        // implementation comes from the trait block, and not an impl block
+                        && !matches!(
+                            tcx.opt_associated_item(def),
+                            Some(ty::AssocItem {
+                                container: ty::AssocItemContainer::TraitContainer,
+                                ..
+                            })
+                        )
+                {
+                    if tcx.is_closure_like(def) {
+                        debug!(
+                            " => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}",
+                            def, def_id, args
+                        );
+
+                        // Create a shim for the `FnOnce/FnMut/Fn` method we are calling
+                        // - unlike functions, invoking a closure always goes through a
+                        // trait.
+                        resolved = Instance { def: InstanceKind::ReifyShim(def_id, reason), args };
+                    } else {
+                        debug!(
+                            " => vtable fn pointer created for function with #[track_caller]: {:?}",
+                            def
+                        );
+                        resolved.def = InstanceKind::ReifyShim(def, reason);
+                    }
+                }
+            }
+            InstanceKind::Virtual(def_id, _) => {
+                debug!(" => vtable fn pointer created for virtual call");
+                resolved.def = InstanceKind::ReifyShim(def_id, reason)
+            }
+            _ => {}
+        }
+
+        resolved
     }
 
     pub fn resolve_closure(
@@ -661,13 +738,25 @@ impl<'tcx> Instance<'tcx> {
     pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
         let def_id = tcx.require_lang_item(LangItem::DropInPlace, None);
         let args = tcx.mk_args(&[ty.into()]);
-        Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args)
+        Instance::expect_resolve(
+            tcx,
+            ty::ParamEnv::reveal_all(),
+            def_id,
+            args,
+            ty.ty_adt_def().and_then(|adt| tcx.hir().span_if_local(adt.did())).unwrap_or(DUMMY_SP),
+        )
     }
 
     pub fn resolve_async_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
         let def_id = tcx.require_lang_item(LangItem::AsyncDropInPlace, None);
         let args = tcx.mk_args(&[ty.into()]);
-        Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args)
+        Instance::expect_resolve(
+            tcx,
+            ty::ParamEnv::reveal_all(),
+            def_id,
+            args,
+            ty.ty_adt_def().and_then(|adt| tcx.hir().span_if_local(adt.did())).unwrap_or(DUMMY_SP),
+        )
     }
 
     #[instrument(level = "debug", skip(tcx), ret)]

compiler/rustc_middle/src/ty/print/mod.rs

@@ -1,5 +1,7 @@
+use std::path::PathBuf;
+
 use crate::ty::GenericArg;
-use crate::ty::{self, Ty, TyCtxt};
+use crate::ty::{self, ShortInstance, Ty, TyCtxt};
 
 use hir::def::Namespace;
 use rustc_data_structures::fx::FxHashSet;
@@ -356,3 +358,31 @@ where
         with_no_trimmed_paths!(Self::print(t, fmt))
     }
 }
+
+/// Format instance name that is already known to be too long for rustc.
+/// Show only the first 2 types if it is longer than 32 characters to avoid blasting
+/// the user's terminal with thousands of lines of type-name.
+///
+/// If the type name is longer than before+after, it will be written to a file.
+pub fn shrunk_instance_name<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    instance: ty::Instance<'tcx>,
+) -> (String, Option<PathBuf>) {
+    let s = instance.to_string();
+
+    // Only use the shrunk version if it's really shorter.
+    // This also avoids the case where before and after slices overlap.
+    if s.chars().nth(33).is_some() {
+        let shrunk = format!("{}", ShortInstance(instance, 4));
+        if shrunk == s {
+            return (s, None);
+        }
+
+        let path = tcx.output_filenames(()).temp_path_ext("long-type.txt", None);
+        let written_to_path = std::fs::write(&path, s).ok().map(|_| path);
+
+        (shrunk, written_to_path)
+    } else {
+        (s, None)
+    }
+}

compiler/rustc_middle/src/util/call_kind.rs

@@ -98,7 +98,7 @@ pub fn call_kind<'tcx>(
         Some(CallKind::Operator { self_arg, trait_id, self_ty: method_args.type_at(0) })
     } else if is_deref {
         let deref_target = tcx.get_diagnostic_item(sym::deref_target).and_then(|deref_target| {
-            Instance::resolve(tcx, param_env, deref_target, method_args).transpose()
+            Instance::try_resolve(tcx, param_env, deref_target, method_args).transpose()
         });
         if let Some(Ok(instance)) = deref_target {
             let deref_target_ty = instance.ty(tcx, param_env);

compiler/rustc_mir_build/src/lints.rs

@@ -141,7 +141,7 @@ impl<'tcx> TerminatorClassifier<'tcx> for CallRecursion<'tcx> {
                 return false;
             };
             let (callee, call_args) = if let Ok(Some(instance)) =
-                Instance::resolve(tcx, param_env, callee, normalized_args)
+                Instance::try_resolve(tcx, param_env, callee, normalized_args)
             {
                 (instance.def_id(), instance.args)
             } else {

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -558,7 +558,8 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         let args = self
             .tcx
             .normalize_erasing_regions(param_env_reveal_all, self.typeck_results.node_args(id));
-        let instance = match ty::Instance::resolve(self.tcx, param_env_reveal_all, def_id, args) {
+        let instance = match ty::Instance::try_resolve(self.tcx, param_env_reveal_all, def_id, args)
+        {
             Ok(Some(i)) => i,
             Ok(None) => {
                 // It should be assoc consts if there's no error but we cannot resolve it.

compiler/rustc_mir_transform/src/inline.rs

@@ -389,7 +389,7 @@ impl<'tcx> Inliner<'tcx> {
                 // To resolve an instance its args have to be fully normalized.
                 let args = self.tcx.try_normalize_erasing_regions(self.param_env, args).ok()?;
                 let callee =
-                    Instance::resolve(self.tcx, self.param_env, def_id, args).ok().flatten()?;
+                    Instance::try_resolve(self.tcx, self.param_env, def_id, args).ok().flatten()?;
 
                 if let InstanceKind::Virtual(..) | InstanceKind::Intrinsic(_) = callee.def {
                     return None;

compiler/rustc_mir_transform/src/inline/cycle.rs

@@ -53,7 +53,7 @@ pub(crate) fn mir_callgraph_reachable<'tcx>(
                 trace!(?caller, ?param_env, ?args, "cannot normalize, skipping");
                 continue;
             };
-            let Ok(Some(callee)) = ty::Instance::resolve(tcx, param_env, callee, args) else {
+            let Ok(Some(callee)) = ty::Instance::try_resolve(tcx, param_env, callee, args) else {
                 trace!(?callee, "cannot resolve, skipping");
                 continue;
             };

compiler/rustc_monomorphize/messages.ftl

@@ -1,6 +1,3 @@
-monomorphize_consider_type_length_limit =
-    consider adding a `#![type_length_limit="{$type_length}"]` attribute to your crate
-
 monomorphize_couldnt_dump_mono_stats =
     unexpected error occurred while dumping monomorphization stats: {$error}
 
@@ -25,8 +22,6 @@ monomorphize_start_not_found = using `fn main` requires the standard library
 
 monomorphize_symbol_already_defined = symbol `{$symbol}` is already defined
 
-monomorphize_type_length_limit = reached the type-length limit while instantiating `{$shrunk}`
-
 monomorphize_unknown_cgu_collection_mode =
     unknown codegen-item collection mode '{$mode}', falling back to 'lazy' mode
 

compiler/rustc_monomorphize/src/collector.rs

@@ -222,12 +222,12 @@ use rustc_middle::mir::{self, Location, MentionedItem};
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::adjustment::{CustomCoerceUnsized, PointerCoercion};
 use rustc_middle::ty::layout::ValidityRequirement;
-use rustc_middle::ty::print::with_no_trimmed_paths;
+use rustc_middle::ty::print::{shrunk_instance_name, with_no_trimmed_paths};
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{
     self, AssocKind, GenericParamDefKind, Instance, InstanceKind, Ty, TyCtxt, TypeFoldable,
     TypeVisitableExt, VtblEntry,
 };
-use rustc_middle::ty::{GenericArgKind, GenericArgs};
 use rustc_middle::{bug, span_bug};
 use rustc_session::config::EntryFnType;
 use rustc_session::Limit;
@@ -238,9 +238,7 @@ use rustc_target::abi::Size;
 use std::path::PathBuf;
 use tracing::{debug, instrument, trace};
 
-use crate::errors::{
+use crate::errors::{self, EncounteredErrorWhileInstantiating, NoOptimizedMir, RecursionLimit};
-    self, EncounteredErrorWhileInstantiating, NoOptimizedMir, RecursionLimit, TypeLengthLimit,
-};
 use move_check::MoveCheckState;
 
 #[derive(PartialEq)]
@@ -443,7 +441,6 @@ fn collect_items_rec<'tcx>(
                 recursion_depths,
                 recursion_limit,
             ));
-            check_type_length_limit(tcx, instance);
 
             rustc_data_structures::stack::ensure_sufficient_stack(|| {
                 collect_items_of_instance(
@@ -554,34 +551,6 @@ fn collect_items_rec<'tcx>(
     }
 }
 
-/// Format instance name that is already known to be too long for rustc.
-/// Show only the first 2 types if it is longer than 32 characters to avoid blasting
-/// the user's terminal with thousands of lines of type-name.
-///
-/// If the type name is longer than before+after, it will be written to a file.
-fn shrunk_instance_name<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    instance: Instance<'tcx>,
-) -> (String, Option<PathBuf>) {
-    let s = instance.to_string();
-
-    // Only use the shrunk version if it's really shorter.
-    // This also avoids the case where before and after slices overlap.
-    if s.chars().nth(33).is_some() {
-        let shrunk = format!("{}", ty::ShortInstance(instance, 4));
-        if shrunk == s {
-            return (s, None);
-        }
-
-        let path = tcx.output_filenames(()).temp_path_ext("long-type.txt", None);
-        let written_to_path = std::fs::write(&path, s).ok().map(|_| path);
-
-        (shrunk, written_to_path)
-    } else {
-        (s, None)
-    }
-}
-
 fn check_recursion_limit<'tcx>(
     tcx: TyCtxt<'tcx>,
     instance: Instance<'tcx>,
@@ -630,38 +599,6 @@ fn check_recursion_limit<'tcx>(
     (def_id, recursion_depth)
 }
 
-fn check_type_length_limit<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) {
-    let type_length = instance
-        .args
-        .iter()
-        .flat_map(|arg| arg.walk())
-        .filter(|arg| match arg.unpack() {
-            GenericArgKind::Type(_) | GenericArgKind::Const(_) => true,
-            GenericArgKind::Lifetime(_) => false,
-        })
-        .count();
-    debug!(" => type length={}", type_length);
-
-    // Rust code can easily create exponentially-long types using only a
-    // polynomial recursion depth. Even with the default recursion
-    // depth, you can easily get cases that take >2^60 steps to run,
-    // which means that rustc basically hangs.
-    //
-    // Bail out in these cases to avoid that bad user experience.
-    if !tcx.type_length_limit().value_within_limit(type_length) {
-        let (shrunk, written_to_path) = shrunk_instance_name(tcx, instance);
-        let span = tcx.def_span(instance.def_id());
-        let mut path = PathBuf::new();
-        let was_written = if let Some(path2) = written_to_path {
-            path = path2;
-            Some(())
-        } else {
-            None
-        };
-        tcx.dcx().emit_fatal(TypeLengthLimit { span, shrunk, was_written, path, type_length });
-    }
-}
-
 struct MirUsedCollector<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     body: &'a mir::Body<'tcx>,
@@ -916,7 +853,7 @@ fn visit_fn_use<'tcx>(
 ) {
     if let ty::FnDef(def_id, args) = *ty.kind() {
         let instance = if is_direct_call {
-            ty::Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args)
+            ty::Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args, source)
         } else {
             match ty::Instance::resolve_for_fn_ptr(tcx, ty::ParamEnv::reveal_all(), def_id, args) {
                 Some(instance) => instance,
@@ -1319,7 +1256,7 @@ fn visit_mentioned_item<'tcx>(
         MentionedItem::Fn(ty) => {
             if let ty::FnDef(def_id, args) = *ty.kind() {
                 let instance =
-                    Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args);
+                    Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args, span);
                 // `visit_instance_use` was written for "used" item collection but works just as well
                 // for "mentioned" item collection.
                 // We can set `is_direct_call`; that just means we'll skip a bunch of shims that anyway
@@ -1544,6 +1481,7 @@ impl<'v> RootCollector<'_, 'v> {
             ty::ParamEnv::reveal_all(),
             start_def_id,
             self.tcx.mk_args(&[main_ret_ty.into()]),
+            DUMMY_SP,
         );
 
         self.output.push(create_fn_mono_item(self.tcx, start_instance, DUMMY_SP));
@@ -1612,9 +1550,10 @@ fn create_mono_items_for_default_impls<'tcx>(
         }
 
         // As mentioned above, the method is legal to eagerly instantiate if it
-        // only has lifetime generic parameters. This is validated by
+        // only has lifetime generic parameters. This is validated by calling
+        // `own_requires_monomorphization` on both the impl and method.
         let args = trait_ref.args.extend_to(tcx, method.def_id, only_region_params);
-        let instance = ty::Instance::expect_resolve(tcx, param_env, method.def_id, args);
+        let instance = ty::Instance::expect_resolve(tcx, param_env, method.def_id, args, DUMMY_SP);
 
         let mono_item = create_fn_mono_item(tcx, instance, DUMMY_SP);
         if mono_item.node.is_instantiable(tcx) && should_codegen_locally(tcx, instance) {

compiler/rustc_monomorphize/src/errors.rs

@@ -19,19 +19,6 @@ pub struct RecursionLimit {
     pub path: PathBuf,
 }
 
-#[derive(Diagnostic)]
-#[diag(monomorphize_type_length_limit)]
-#[help(monomorphize_consider_type_length_limit)]
-pub struct TypeLengthLimit {
-    #[primary_span]
-    pub span: Span,
-    pub shrunk: String,
-    #[note(monomorphize_written_to_path)]
-    pub was_written: Option<()>,
-    pub path: PathBuf,
-    pub type_length: usize,
-}
-
 #[derive(Diagnostic)]
 #[diag(monomorphize_no_optimized_mir)]
 pub struct NoOptimizedMir {

compiler/rustc_passes/src/abi_test.rs

@@ -61,7 +61,7 @@ fn unwrap_fn_abi<'tcx>(
 fn dump_abi_of_fn_item(tcx: TyCtxt<'_>, item_def_id: LocalDefId, attr: &Attribute) {
     let param_env = tcx.param_env(item_def_id);
     let args = GenericArgs::identity_for_item(tcx, item_def_id);
-    let instance = match Instance::resolve(tcx, param_env, item_def_id.into(), args) {
+    let instance = match Instance::try_resolve(tcx, param_env, item_def_id.into(), args) {
         Ok(Some(instance)) => instance,
         Ok(None) => {
             // Not sure what to do here, but `LayoutError::Unknown` seems reasonable?

compiler/rustc_smir/src/rustc_smir/context.rs

@@ -629,7 +629,7 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         let tcx = tables.tcx;
         let def_id = def.0.internal(&mut *tables, tcx);
         let args_ref = args.internal(&mut *tables, tcx);
-        match Instance::resolve(tables.tcx, ParamEnv::reveal_all(), def_id, args_ref) {
+        match Instance::try_resolve(tables.tcx, ParamEnv::reveal_all(), def_id, args_ref) {
             Ok(Some(instance)) => Some(instance.stable(&mut *tables)),
             Ok(None) | Err(_) => None,
         }

compiler/rustc_trait_selection/src/traits/vtable.rs

@@ -6,7 +6,7 @@ use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, GenericParamDefKind, Ty, TyCtxt, Upcast, VtblEntry};
 use rustc_middle::ty::{GenericArgs, TypeVisitableExt};
-use rustc_span::{sym, Span};
+use rustc_span::{sym, Span, DUMMY_SP};
 use smallvec::{smallvec, SmallVec};
 
 use std::fmt::Debug;
@@ -285,13 +285,14 @@ fn vtable_entries<'tcx>(
                         return VtblEntry::Vacant;
                     }
 
-                    let instance = ty::Instance::resolve_for_vtable(
+                    let instance = ty::Instance::expect_resolve_for_vtable(
                         tcx,
                         ty::ParamEnv::reveal_all(),
                         def_id,
                         args,
-                    )
+                        DUMMY_SP,
-                    .expect("resolution failed during building vtable representation");
+                    );
+
                     VtblEntry::Method(instance)
                 });
 

compiler/rustc_ty_utils/src/instance.rs

@@ -16,7 +16,7 @@ use traits::{translate_args, Reveal};
 
 use crate::errors::UnexpectedFnPtrAssociatedItem;
 
-fn resolve_instance<'tcx>(
+fn resolve_instance_raw<'tcx>(
     tcx: TyCtxt<'tcx>,
     key: ty::ParamEnvAnd<'tcx, (DefId, GenericArgsRef<'tcx>)>,
 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
@@ -364,5 +364,5 @@ fn resolve_associated_item<'tcx>(
 }
 
 pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { resolve_instance, ..*providers };
+    *providers = Providers { resolve_instance_raw, ..*providers };
 }

src/tools/clippy/clippy_lints/src/assigning_clones.rs

@@ -103,7 +103,7 @@ fn extract_call<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Option<
             let args = cx.typeck_results().node_args(expr.hir_id);
 
             // If we could not resolve the method, don't apply the lint
-            let Ok(Some(resolved_method)) = Instance::resolve(cx.tcx, cx.param_env, fn_def_id, args) else {
+            let Ok(Some(resolved_method)) = Instance::try_resolve(cx.tcx, cx.param_env, fn_def_id, args) else {
                 return None;
             };
             if is_trait_method(cx, expr, sym::Clone) && path.ident.name == sym::clone {
@@ -119,7 +119,7 @@ fn extract_call<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Option<
 
             // If we could not resolve the method, don't apply the lint
             let Ok(Some(resolved_method)) = (match kind {
-                ty::FnDef(_, args) => Instance::resolve(cx.tcx, cx.param_env, fn_def_id, args),
+                ty::FnDef(_, args) => Instance::try_resolve(cx.tcx, cx.param_env, fn_def_id, args),
                 _ => Ok(None),
             }) else {
                 return None;

src/tools/clippy/clippy_lints/src/non_copy_const.rs

@@ -293,7 +293,7 @@ impl<'tcx> NonCopyConst<'tcx> {
         ct: ty::UnevaluatedConst<'tcx>,
         span: Span,
     ) -> EvalToValTreeResult<'tcx> {
-        match ty::Instance::resolve(tcx, param_env, ct.def, ct.args) {
+        match ty::Instance::try_resolve(tcx, param_env, ct.def, ct.args) {
             Ok(Some(instance)) => {
                 let cid = GlobalId {
                     instance,

src/tools/miri/src/eval.rs

@@ -375,7 +375,7 @@ pub fn create_ecx<'tcx>(
             });
             let main_ret_ty = tcx.fn_sig(entry_id).no_bound_vars().unwrap().output();
             let main_ret_ty = main_ret_ty.no_bound_vars().unwrap();
-            let start_instance = ty::Instance::resolve(
+            let start_instance = ty::Instance::try_resolve(
                 tcx,
                 ty::ParamEnv::reveal_all(),
                 start_id,

tests/ui/closures/issue-72408-nested-closures-exponential.rs

@@ -1,5 +1,4 @@
-//@ build-pass
+//@ build-fail
-//@ ignore-compare-mode-next-solver (hangs)
 
 // Closures include captured types twice in a type tree.
 //
@@ -46,6 +45,7 @@ fn main() {
 
     let f = dup(f);
     let f = dup(f);
+    //~^ ERROR reached the type-length limit
     let f = dup(f);
     let f = dup(f);
     let f = dup(f);

tests/ui/closures/issue-72408-nested-closures-exponential.stderr

@@ -0,0 +1,10 @@
+error: reached the type-length limit while instantiating `dup::<{closure@$DIR/issue-72408-nested-closures-exponential.rs:13:5: 13:13}>`
+  --> $DIR/issue-72408-nested-closures-exponential.rs:47:13
+   |
+LL |     let f = dup(f);
+   |             ^^^^^^
+   |
+   = help: consider adding a `#![type_length_limit="29360121"]` attribute to your crate
+
+error: aborting due to 1 previous error
+

tests/ui/codegen/overflow-during-mono.rs

@@ -1,5 +1,5 @@
 //@ build-fail
-//~^ ERROR overflow evaluating the requirement
+//@ error-pattern: reached the type-length limit while instantiating
 
 #![recursion_limit = "32"]
 

tests/ui/codegen/overflow-during-mono.stderr

@@ -1,11 +1,8 @@
-error[E0275]: overflow evaluating the requirement `{closure@$DIR/overflow-during-mono.rs:13:41: 13:44}: Sized`
+error: reached the type-length limit while instantiating `<Filter<Filter<std::array::IntoIter<i32, 11>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, ...> as Iterator>::try_fold::<..., ..., ...>`
+  --> $SRC_DIR/core/src/iter/adapters/filter.rs:LL:COL
    |
-   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "64"]` attribute to your crate (`overflow_during_mono`)
+   = help: consider adding a `#![type_length_limit="20156994"]` attribute to your crate
-   = note: required for `Filter<std::array::IntoIter<i32, 11>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>` to implement `Iterator`
+   = note: the full type name has been written to '$TEST_BUILD_DIR/codegen/overflow-during-mono/overflow-during-mono.long-type.txt'
-   = note: 31 redundant requirements hidden
-   = note: required for `Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<std::array::IntoIter<i32, 11>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>` to implement `Iterator`
-   = note: required for `Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<std::array::IntoIter<i32, 11>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>` to implement `IntoIterator`
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0275`.

tests/ui/issues/issue-22638.rs

@@ -1,7 +1,4 @@
 //@ build-fail
-//@ normalize-stderr-test: "<\{closure@.+`" -> "$$CLOSURE`"
-//@ normalize-stderr-test: ".nll/" -> "/"
-//@ ignore-compare-mode-next-solver (hangs)
 
 #![allow(unused)]
 
@@ -43,6 +40,7 @@ impl C {
     pub fn matches<F: Fn()>(&self, f: &F) {
         let &C(ref base) = self;
         base.matches(&|| {
+            //~^ ERROR reached the type-length limit
             C(base.clone()).matches(f)
         })
     }
@@ -55,7 +53,6 @@ impl D {
     pub fn matches<F: Fn()>(&self, f: &F) {
         let &D(ref a) = self;
         a.matches(f)
-        //~^ ERROR reached the recursion limit while instantiating `A::matches::<{closure
     }
 }
 

tests/ui/issues/issue-22638.stderr

@@ -1,14 +1,13 @@
-error: reached the recursion limit while instantiating `A::matches::$CLOSURE`
+error: reached the type-length limit while instantiating `D::matches::<{closure@$DIR/issue-22638.rs:42:23: 42:25}>`
-  --> $DIR/issue-22638.rs:57:9
+  --> $DIR/issue-22638.rs:42:9
    |
-LL |         a.matches(f)
+LL | /         base.matches(&|| {
-   |         ^^^^^^^^^^^^
+LL | |
+LL | |             C(base.clone()).matches(f)
+LL | |         })
+   | |__________^
    |
-note: `A::matches` defined here
+   = help: consider adding a `#![type_length_limit="30408681"]` attribute to your crate
-  --> $DIR/issue-22638.rs:16:5
-   |
-LL |     pub fn matches<F: Fn()>(&self, f: &F) {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 1 previous error
 

tests/ui/issues/issue-37311-type-length-limit/issue-37311.rs

@@ -1,6 +1,5 @@
 //@ build-fail
 //@ normalize-stderr-test: ".nll/" -> "/"
-//@ ignore-compare-mode-next-solver (hangs)
 
 trait Mirror {
     type Image;
@@ -15,7 +14,8 @@ trait Foo {
 impl<T> Foo for T {
     #[allow(unconditional_recursion)]
     fn recurse(&self) {
-        (self, self).recurse(); //~ ERROR reached the recursion limit
+        (self, self).recurse();
+        //~^ ERROR reached the type-length limit
     }
 }
 

tests/ui/issues/issue-37311-type-length-limit/issue-37311.stderr

@@ -1,14 +1,10 @@
-error: reached the recursion limit while instantiating `<(&(&(..., ...), ...), ...) as Foo>::recurse`
+error: reached the type-length limit while instantiating `<(&(&(..., ...), ...), ...) as Foo>::recurse`
-  --> $DIR/issue-37311.rs:18:9
+  --> $DIR/issue-37311.rs:17:9
    |
 LL |         (self, self).recurse();
    |         ^^^^^^^^^^^^^^^^^^^^^^
    |
-note: `<T as Foo>::recurse` defined here
+   = help: consider adding a `#![type_length_limit="33554429"]` attribute to your crate
-  --> $DIR/issue-37311.rs:17:5
-   |
-LL |     fn recurse(&self) {
-   |     ^^^^^^^^^^^^^^^^^
    = note: the full type name has been written to '$TEST_BUILD_DIR/issues/issue-37311-type-length-limit/issue-37311/issue-37311.long-type.txt'
 
 error: aborting due to 1 previous error

tests/ui/iterators/issue-58952-filter-type-length.rs

@@ -1,5 +1,5 @@
-//@ run-pass
+//@ build-fail
-//@ ignore-compare-mode-next-solver (hangs)
+//@ error-pattern: reached the type-length limit while instantiating
 
 //! This snippet causes the type length to blowup exponentially,
 //! so check that we don't accidentally exceed the type length limit.
@@ -30,5 +30,9 @@ fn main() {
         .filter(|a| b.clone().any(|b| *b == *a))
         .filter(|a| b.clone().any(|b| *b == *a))
         .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
         .collect::<VecDeque<_>>();
 }

tests/ui/iterators/issue-58952-filter-type-length.stderr

@@ -0,0 +1,8 @@
+error: reached the type-length limit while instantiating `<std::vec::IntoIter<i32> as Iterator>::try_fold::<vec::in_place_drop::InPlaceDrop<i32>, {closure@iter::adapters::filter::filter_try_fold<'_, ..., ..., ..., ..., ...>::{closure#0}}, ...>`
+  --> $SRC_DIR/core/src/iter/adapters/filter.rs:LL:COL
+   |
+   = help: consider adding a `#![type_length_limit="21233607"]` attribute to your crate
+   = note: the full type name has been written to '$TEST_BUILD_DIR/iterators/issue-58952-filter-type-length/issue-58952-filter-type-length.long-type.txt'
+
+error: aborting due to 1 previous error
+

tests/ui/iterators/iter-map-fold-type-length.rs

@@ -3,7 +3,7 @@
 //!
 //! The normal limit is a million, and this test used to exceed 1.5 million, but
 //! now we can survive an even tighter limit. Still seems excessive though...
-#![type_length_limit = "256000"]
+#![type_length_limit = "1327047"]
 
 // Custom wrapper so Iterator methods aren't specialized.
 struct Iter<I>(I);

tests/ui/recursion/issue-83150.rs

@@ -1,7 +1,6 @@
 //@ build-fail
 //@ compile-flags: -Copt-level=0
 //@ normalize-stderr-test: "long-type-\d+" -> "long-type-hash"
-//~^^^ ERROR overflow evaluating the requirement
 //@ ignore-compare-mode-next-solver (hangs)
 
 fn main() {
@@ -9,6 +8,8 @@ fn main() {
     func(&mut iter)
 }
 
-fn func<T: Iterator<Item = u8>>(iter: &mut T) { //~ WARN function cannot return without recursing
+fn func<T: Iterator<Item = u8>>(iter: &mut T) {
+    //~^ WARN function cannot return without recursing
     func(&mut iter.map(|x| x + 1))
+    //~^ ERROR reached the type-length limit
 }

tests/ui/recursion/issue-83150.stderr

@@ -1,21 +1,23 @@
 warning: function cannot return without recursing
-  --> $DIR/issue-83150.rs:12:1
+  --> $DIR/issue-83150.rs:11:1
    |
 LL | fn func<T: Iterator<Item = u8>>(iter: &mut T) {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot return without recursing
+LL |
 LL |     func(&mut iter.map(|x| x + 1))
    |     ------------------------------ recursive call site
    |
    = help: a `loop` may express intention better if this is on purpose
    = note: `#[warn(unconditional_recursion)]` on by default
 
-error[E0275]: overflow evaluating the requirement `Map<&mut std::ops::Range<u8>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>: Iterator`
+error: reached the type-length limit while instantiating `<&mut Map<&mut Map<&mut ..., ...>, ...> as Iterator>::map::<..., ...>`
+  --> $DIR/issue-83150.rs:13:15
    |
-   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_83150`)
+LL |     func(&mut iter.map(|x| x + 1))
-   = note: required for `&mut Map<&mut std::ops::Range<u8>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>` to implement `Iterator`
+   |               ^^^^^^^^^^^^^^^^^^^
-   = note: 65 redundant requirements hidden
+   |
-   = note: required for `&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut std::ops::Range<u8>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>, {closure@$DIR/issue-83150.rs:13:24: 13:27}>` to implement `Iterator`
+   = help: consider adding a `#![type_length_limit="23068663"]` attribute to your crate
+   = note: the full type name has been written to '$TEST_BUILD_DIR/recursion/issue-83150/issue-83150.long-type.txt'
 
 error: aborting due to 1 previous error; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0275`.

tests/ui/traits/issue-91949-hangs-on-recursion.rs

@@ -1,9 +1,5 @@
 //@ build-fail
 //@ compile-flags: -Zinline-mir=no
-//@ error-pattern: overflow evaluating the requirement `<std::iter::Empty<()> as Iterator>::Item == ()`
-//@ error-pattern: function cannot return without recursing
-//@ normalize-stderr-test: "long-type-\d+" -> "long-type-hash"
-//@ ignore-compare-mode-next-solver (hangs)
 
 // Regression test for #91949.
 // This hanged *forever* on 1.56, fixed by #90423.
@@ -22,10 +18,12 @@ impl<T, I: Iterator<Item = T>> Iterator for IteratorOfWrapped<T, I> {
 }
 
 fn recurse<T>(elements: T) -> Vec<char>
+//~^ WARN function cannot return without recursing
 where
     T: Iterator<Item = ()>,
 {
     recurse(IteratorOfWrapped(elements).map(|t| t.0))
+    //~^ ERROR reached the type-length limit
 }
 
 fn main() {

tests/ui/type_length_limit.rs

@@ -1,7 +1,6 @@
 //@ build-fail
-//@ error-pattern: reached the type-length limit while instantiating
 //@ compile-flags: -Copt-level=0
-//@ normalize-stderr-test: ".nll/" -> "/"
+//~^^ ERROR reached the type-length limit
 
 // Test that the type length limit can be changed.
 // The exact type depends on optimizations, so disable them.
@@ -31,4 +30,5 @@ pub struct G<T, K>(std::marker::PhantomData::<(T, K)>);
 
 fn main() {
     drop::<Option<A>>(None);
+    //~^ ERROR reached the type-length limit
 }

tests/ui/type_length_limit.stderr

@@ -1,8 +1,15 @@
 error: reached the type-length limit while instantiating `std::mem::drop::<Option<((((..., ..., ...), ..., ...), ..., ...), ..., ...)>>`
-  --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
+  --> $DIR/type_length_limit.rs:32:5
    |
-   = help: consider adding a `#![type_length_limit="10"]` attribute to your crate
+LL |     drop::<Option<A>>(None);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider adding a `#![type_length_limit="4010"]` attribute to your crate
    = note: the full type name has been written to '$TEST_BUILD_DIR/type_length_limit/type_length_limit.long-type.txt'
 
-error: aborting due to 1 previous error
+error: reached the type-length limit while instantiating `<{closure@rt::lang_start<()>::{closure#0}} as FnMut<()>>::call_mut`
+   |
+   = help: consider adding a `#![type_length_limit="10"]` attribute to your crate
+
+error: aborting due to 2 previous errors