Add support for shortening Instance and use it

Replace ad-hoc type path shortening logic for recursive mono instantiation errors to use `tcx.short_string()` instead.

Author: estebank

compiler/rustc_middle/messages.ftl

@@ -122,8 +122,6 @@ 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 `{$shrunk}`
+middle_type_length_limit = reached the type-length limit while instantiating `{$instance}`
 
 middle_unsupported_union = we don't support unions yet: '{$ty_name}'
-
-middle_written_to_path = the full type name has been written to '{$path}'

compiler/rustc_middle/src/error.rs

@@ -1,12 +1,12 @@
-use std::path::{Path, PathBuf};
+use std::path::Path;
 use std::{fmt, io};
 
 use rustc_errors::codes::*;
 use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
 
-use crate::ty::Ty;
+use crate::ty::{Instance, Ty};
 
 #[derive(Diagnostic)]
 #[diag(middle_drop_check_overflow, code = E0320)]
@@ -161,13 +161,10 @@ pub(crate) struct ErroneousConstant {
 #[derive(Diagnostic)]
 #[diag(middle_type_length_limit)]
 #[help(middle_consider_type_length_limit)]
-pub(crate) struct TypeLengthLimit {
+pub(crate) struct TypeLengthLimit<'tcx> {
     #[primary_span]
     pub span: Span,
-    pub shrunk: String,
-    #[note(middle_written_to_path)]
-    pub was_written: bool,
-    pub path: PathBuf,
+    pub instance: Instance<'tcx>,
     pub type_length: usize,
 }
 

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -14,7 +14,7 @@ use rustc_span::{BytePos, Span};
 use rustc_type_ir::TyKind::*;
 
 use crate::ty::{
-    self, AliasTy, Const, ConstKind, FallibleTypeFolder, InferConst, InferTy, Opaque,
+    self, AliasTy, Const, ConstKind, FallibleTypeFolder, InferConst, InferTy, Instance, Opaque,
     PolyTraitPredicate, Projection, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable,
     TypeSuperVisitable, TypeVisitable, TypeVisitor,
 };
@@ -28,6 +28,15 @@ impl IntoDiagArg for Ty<'_> {
     }
 }
 
+impl IntoDiagArg for Instance<'_> {
+    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> rustc_errors::DiagArgValue {
+        ty::tls::with(|tcx| {
+            let instance = tcx.short_string(self, path);
+            rustc_errors::DiagArgValue::Str(std::borrow::Cow::Owned(instance))
+        })
+    }
+}
+
 into_diag_arg_using_display! {
     ty::Region<'_>,
 }

compiler/rustc_middle/src/ty/instance.rs

@@ -1,6 +1,5 @@
 use std::assert_matches::assert_matches;
 use std::fmt;
-use std::path::PathBuf;
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::ErrorGuaranteed;
@@ -17,7 +16,7 @@ use tracing::{debug, instrument};
 use crate::error;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::ty::normalize_erasing_regions::NormalizationError;
-use crate::ty::print::{FmtPrinter, Printer, shrunk_instance_name};
+use crate::ty::print::{FmtPrinter, Printer};
 use crate::ty::{
     self, EarlyBinder, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
     TypeVisitable, TypeVisitableExt, TypeVisitor,
@@ -431,14 +430,6 @@ pub fn fmt_instance(
     }
 }
 
-pub struct ShortInstance<'tcx>(pub Instance<'tcx>, pub usize);
-
-impl<'tcx> fmt::Display for ShortInstance<'tcx> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt_instance(f, self.0, Some(rustc_session::Limit(self.1)))
-    }
-}
-
 impl<'tcx> fmt::Display for Instance<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt_instance(f, *self, None)
@@ -610,23 +601,12 @@ impl<'tcx> Instance<'tcx> {
             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_raw(def_id, args));
-                    let mut path = PathBuf::new();
-                    let was_written = if let Some(path2) = written_to_path {
-                        path = path2;
-                        true
-                    } else {
-                        false
-                    };
                     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,
+                        instance: Instance::new_raw(def_id, args),
                         type_length,
                     });
                 } else {

compiler/rustc_middle/src/ty/mod.rs

@@ -82,7 +82,7 @@ pub use self::context::{
     TyCtxtFeed, tls,
 };
 pub use self::fold::*;
-pub use self::instance::{Instance, InstanceKind, ReifyReason, ShortInstance, UnusedGenericParams};
+pub use self::instance::{Instance, InstanceKind, ReifyReason, UnusedGenericParams};
 pub use self::list::{List, ListWithCachedTypeInfo};
 pub use self::opaque_types::OpaqueTypeKey;
 pub use self::parameterized::ParameterizedOverTcx;

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

@@ -1,5 +1,3 @@
-use std::path::PathBuf;
-
 use hir::def::Namespace;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sso::SsoHashSet;
@@ -8,7 +6,7 @@ use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
 use tracing::{debug, instrument, trace};
 
-use crate::ty::{self, GenericArg, ShortInstance, Ty, TyCtxt};
+use crate::ty::{self, GenericArg, Ty, TyCtxt};
 
 // `pretty` is a separate module only for organization.
 mod pretty;
@@ -323,6 +321,43 @@ impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for Ty<'tcx> {
     }
 }
 
+impl<'tcx, P: Printer<'tcx> + std::fmt::Write> Print<'tcx, P> for ty::Instance<'tcx> {
+    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
+        cx.print_def_path(self.def_id(), self.args)?;
+        match self.def {
+            ty::InstanceKind::Item(_) => {}
+            ty::InstanceKind::VTableShim(_) => cx.write_str(" - shim(vtable)")?,
+            ty::InstanceKind::ReifyShim(_, None) => cx.write_str(" - shim(reify)")?,
+            ty::InstanceKind::ReifyShim(_, Some(ty::ReifyReason::FnPtr)) => {
+                cx.write_str(" - shim(reify-fnptr)")?
+            }
+            ty::InstanceKind::ReifyShim(_, Some(ty::ReifyReason::Vtable)) => {
+                cx.write_str(" - shim(reify-vtable)")?
+            }
+            ty::InstanceKind::ThreadLocalShim(_) => cx.write_str(" - shim(tls)")?,
+            ty::InstanceKind::Intrinsic(_) => cx.write_str(" - intrinsic")?,
+            ty::InstanceKind::Virtual(_, num) => cx.write_str(&format!(" - virtual#{num}"))?,
+            ty::InstanceKind::FnPtrShim(_, ty) => cx.write_str(&format!(" - shim({ty})"))?,
+            ty::InstanceKind::ClosureOnceShim { .. } => cx.write_str(" - shim")?,
+            ty::InstanceKind::ConstructCoroutineInClosureShim { .. } => cx.write_str(" - shim")?,
+            ty::InstanceKind::DropGlue(_, None) => cx.write_str(" - shim(None)")?,
+            ty::InstanceKind::DropGlue(_, Some(ty)) => {
+                cx.write_str(&format!(" - shim(Some({ty}))"))?
+            }
+            ty::InstanceKind::CloneShim(_, ty) => cx.write_str(&format!(" - shim({ty})"))?,
+            ty::InstanceKind::FnPtrAddrShim(_, ty) => cx.write_str(&format!(" - shim({ty})"))?,
+            ty::InstanceKind::FutureDropPollShim(_, proxy_ty, impl_ty) => {
+                cx.write_str(&format!(" - dropshim({proxy_ty}-{impl_ty})"))?
+            }
+            ty::InstanceKind::AsyncDropGlue(_, ty) => cx.write_str(&format!(" - shim({ty})"))?,
+            ty::InstanceKind::AsyncDropGlueCtorShim(_, ty) => {
+                cx.write_str(&format!(" - shim(Some({ty}))"))?
+            }
+        };
+        Ok(())
+    }
+}
+
 impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
     fn print(&self, cx: &mut P) -> Result<(), PrintError> {
         cx.print_dyn_existential(self)
@@ -362,31 +397,3 @@ 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_for_diagnostic("long-type.txt");
-        let written_to_path = std::fs::write(&path, s).ok().map(|_| path);
-
-        (shrunk, written_to_path)
-    } else {
-        (s, None)
-    }
-}

compiler/rustc_monomorphize/messages.ftl

@@ -40,7 +40,10 @@ monomorphize_couldnt_dump_mono_stats =
     unexpected error occurred while dumping monomorphization stats: {$error}
 
 monomorphize_encountered_error_while_instantiating =
-    the above error was encountered while instantiating `{$formatted_item}`
+    the above error was encountered while instantiating `{$kind} {$instance}`
+
+monomorphize_encountered_error_while_instantiating_global_asm =
+    the above error was encountered while instantiating `global_asm`
 
 monomorphize_large_assignments =
     moving {$size} bytes
@@ -52,12 +55,10 @@ monomorphize_no_optimized_mir =
     .note = missing optimized MIR for this item (was the crate `{$crate_name}` compiled with `--emit=metadata`?)
 
 monomorphize_recursion_limit =
-    reached the recursion limit while instantiating `{$shrunk}`
+    reached the recursion limit while instantiating `{$instance}`
     .note = `{$def_path_str}` defined here
 
 monomorphize_start_not_found = using `fn main` requires the standard library
     .help = use `#![no_main]` to bypass the Rust generated entrypoint and declare a platform specific entrypoint yourself, usually with `#[no_mangle]`
 
 monomorphize_symbol_already_defined = symbol `{$symbol}` is already defined
-
-monomorphize_written_to_path = the full type name has been written to '{$path}'

compiler/rustc_monomorphize/src/collector.rs

@@ -206,7 +206,6 @@
 //! regardless of whether it is actually needed or not.
 
 use std::cell::OnceCell;
-use std::path::PathBuf;
 
 use rustc_attr_data_structures::InlineAttr;
 use rustc_data_structures::fx::FxIndexMap;
@@ -224,7 +223,6 @@ use rustc_middle::mir::{self, Location, MentionedItem, traversal};
 use rustc_middle::query::TyCtxtAt;
 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, Ty, TyCtxt, TypeFoldable,
     TypeVisitableExt, VtblEntry,
@@ -237,7 +235,10 @@ use rustc_span::source_map::{Spanned, dummy_spanned, respan};
 use rustc_span::{DUMMY_SP, Span};
 use tracing::{debug, instrument, trace};
 
-use crate::errors::{self, EncounteredErrorWhileInstantiating, NoOptimizedMir, RecursionLimit};
+use crate::errors::{
+    self, EncounteredErrorWhileInstantiating, EncounteredErrorWhileInstantiatingGlobalAsm,
+    NoOptimizedMir, RecursionLimit,
+};
 
 #[derive(PartialEq)]
 pub(crate) enum MonoItemCollectionStrategy {
@@ -525,11 +526,23 @@ fn collect_items_rec<'tcx>(
         && starting_item.node.is_generic_fn()
         && starting_item.node.is_user_defined()
     {
-        let formatted_item = with_no_trimmed_paths!(starting_item.node.to_string());
-        tcx.dcx().emit_note(EncounteredErrorWhileInstantiating {
-            span: starting_item.span,
-            formatted_item,
-        });
+        match starting_item.node {
+            MonoItem::Fn(instance) => tcx.dcx().emit_note(EncounteredErrorWhileInstantiating {
+                span: starting_item.span,
+                kind: "fn",
+                instance,
+            }),
+            MonoItem::Static(def_id) => tcx.dcx().emit_note(EncounteredErrorWhileInstantiating {
+                span: starting_item.span,
+                kind: "static",
+                instance: Instance::new_raw(def_id, GenericArgs::empty()),
+            }),
+            MonoItem::GlobalAsm(_) => {
+                tcx.dcx().emit_note(EncounteredErrorWhileInstantiatingGlobalAsm {
+                    span: starting_item.span,
+                })
+            }
+        }
     }
     // Only updating `usage_map` for used items as otherwise we may be inserting the same item
     // multiple times (if it is first 'mentioned' and then later actually used), and the usage map
@@ -612,22 +625,7 @@ fn check_recursion_limit<'tcx>(
     if !recursion_limit.value_within_limit(adjusted_recursion_depth) {
         let def_span = tcx.def_span(def_id);
         let def_path_str = tcx.def_path_str(def_id);
-        let (shrunk, written_to_path) = shrunk_instance_name(tcx, instance);
-        let mut path = PathBuf::new();
-        let was_written = if let Some(written_to_path) = written_to_path {
-            path = written_to_path;
-            true
-        } else {
-            false
-        };
-        tcx.dcx().emit_fatal(RecursionLimit {
-            span,
-            shrunk,
-            def_span,
-            def_path_str,
-            was_written,
-            path,
-        });
+        tcx.dcx().emit_fatal(RecursionLimit { span, instance, def_span, def_path_str });
     }
 
     recursion_depths.insert(def_id, recursion_depth + 1);

compiler/rustc_monomorphize/src/errors.rs

@@ -1,21 +1,16 @@
-use std::path::PathBuf;
-
 use rustc_macros::{Diagnostic, LintDiagnostic};
-use rustc_middle::ty::Ty;
+use rustc_middle::ty::{Instance, Ty};
 use rustc_span::{Span, Symbol};
 
 #[derive(Diagnostic)]
 #[diag(monomorphize_recursion_limit)]
-pub(crate) struct RecursionLimit {
+pub(crate) struct RecursionLimit<'tcx> {
     #[primary_span]
     pub span: Span,
-    pub shrunk: String,
+    pub instance: Instance<'tcx>,
     #[note]
     pub def_span: Span,
     pub def_path_str: String,
-    #[note(monomorphize_written_to_path)]
-    pub was_written: bool,
-    pub path: PathBuf,
 }
 
 #[derive(Diagnostic)]
@@ -53,10 +48,18 @@ pub(crate) struct CouldntDumpMonoStats {
 
 #[derive(Diagnostic)]
 #[diag(monomorphize_encountered_error_while_instantiating)]
-pub(crate) struct EncounteredErrorWhileInstantiating {
+pub(crate) struct EncounteredErrorWhileInstantiating<'tcx> {
+    #[primary_span]
+    pub span: Span,
+    pub kind: &'static str,
+    pub instance: Instance<'tcx>,
+}
+
+#[derive(Diagnostic)]
+#[diag(monomorphize_encountered_error_while_instantiating_global_asm)]
+pub(crate) struct EncounteredErrorWhileInstantiatingGlobalAsm {
     #[primary_span]
     pub span: Span,
-    pub formatted_item: String,
 }
 
 #[derive(Diagnostic)]

tests/ui/async-await/async-closures/post-mono-higher-ranked-hang-2.stderr

@@ -1,4 +1,4 @@
-error: reached the recursion limit while instantiating `recur::<{async closure@$DIR/post-mono-higher-ranked-hang-2.rs:13:24: 13:32}>`
+error: reached the recursion limit while instantiating `recur<{async closure@$DIR/post-mono-higher-ranked-hang-2.rs:13:24: 13:32}>`
   --> $DIR/post-mono-higher-ranked-hang-2.rs:13:17
    |
 LL |           let _ = recur(&async || {