Auto merge of rust-lang#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 rust-lang#37789, which was accidentally made practically useless by the caching changes to `Ty::walk` in rust-lang#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 rust-lang#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 =
-            ty::Instance::expect_resolve(fx.tcx, ty::ParamEnv::reveal_all(), def_id, fn_args)
-                .polymorphize(fx.tcx);
+        let instance = ty::Instance::expect_resolve(
+            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),
-                    )
-                    .unwrap();
+                        self.cur_span(),
+                    );
                     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
-    query resolve_instance(
+    ///    has already been/will be emitted, for the original cause.
+    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) }