perf: eagerly convert literals to consts, this avoids creating loads on unevaluated consts

which requires a lot of unnecessary work to evaluate them further down the line.

src/librustc/dep_graph/dep_node.rs

@@ -52,7 +52,7 @@
 use crate::hir::map::DefPathHash;
 use crate::ich::{Fingerprint, StableHashingContext};
 use crate::mir;
-use crate::mir::interpret::GlobalId;
+use crate::mir::interpret::{GlobalId, LitToConstInput};
 use crate::traits;
 use crate::traits::query::{
     CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal,

src/librustc/mir/interpret/mod.rs

@@ -119,7 +119,7 @@
 use crate::ty::codec::TyDecoder;
 use crate::ty::layout::{self, Size};
 use crate::ty::subst::GenericArgKind;
-use crate::ty::{self, Instance, TyCtxt};
+use crate::ty::{self, Instance, Ty, TyCtxt};
 use byteorder::{BigEndian, LittleEndian, ReadBytesExt, WriteBytesExt};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{HashMapExt, Lock};
@@ -131,6 +131,7 @@
 use std::io;
 use std::num::NonZeroU32;
 use std::sync::atomic::{AtomicU32, Ordering};
+use syntax::ast::LitKind;
 
 /// Uniquely identifies one of the following:
 /// - A constant
@@ -147,6 +148,24 @@ pub struct GlobalId<'tcx> {
     pub promoted: Option<mir::Promoted>,
 }
 
+/// Input argument for `tcx.lit_to_const`
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, HashStable)]
+pub struct LitToConstInput<'tcx> {
+    /// The absolute value of the resultant constant
+    pub lit: &'tcx LitKind,
+    /// The type of the constant
+    pub ty: Ty<'tcx>,
+    /// If the constant is negative
+    pub neg: bool,
+}
+
+/// Error type for `tcx.lit_to_const`
+#[derive(Copy, Clone, Debug, Eq, PartialEq, HashStable)]
+pub enum LitToConstError {
+    UnparseableFloat,
+    Reported,
+}
+
 #[derive(Copy, Clone, Eq, Hash, Ord, PartialEq, PartialOrd, Debug)]
 pub struct AllocId(pub u64);
 

src/librustc/query/mod.rs

 use crate::dep_graph::{DepKind, DepNode, RecoverKey, SerializedDepNodeIndex};
 use crate::mir;
-use crate::mir::interpret::GlobalId;
+use crate::mir::interpret::{GlobalId, LitToConstInput};
 use crate::traits;
 use crate::traits::query::{
     CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal,
@@ -518,6 +518,13 @@ fn describe_as_module(def_id: DefId, tcx: TyCtxt<'_>) -> String {
             no_force
             desc { "get a &core::panic::Location referring to a span" }
         }
+
+        query lit_to_const(
+            key: LitToConstInput<'tcx>
+        ) -> Result<&'tcx ty::Const<'tcx>, LitToConstError> {
+            no_force
+            desc { "converting literal to const" }
+        }
     }
 
     TypeChecking {

src/librustc/ty/query/keys.rs

@@ -52,6 +52,16 @@ fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
     }
 }
 
+impl<'tcx> Key for mir::interpret::LitToConstInput<'tcx> {
+    fn query_crate(&self) -> CrateNum {
+        LOCAL_CRATE
+    }
+
+    fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
+        DUMMY_SP
+    }
+}
+
 impl Key for CrateNum {
     fn query_crate(&self) -> CrateNum {
         *self

src/librustc/ty/query/mod.rs

@@ -15,6 +15,7 @@
 use crate::mir;
 use crate::mir::interpret::GlobalId;
 use crate::mir::interpret::{ConstEvalRawResult, ConstEvalResult};
+use crate::mir::interpret::{LitToConstError, LitToConstInput};
 use crate::mir::mono::CodegenUnit;
 use crate::session::config::{EntryFnType, OptLevel, OutputFilenames, SymbolManglingVersion};
 use crate::session::CrateDisambiguator;

src/librustc_mir/lib.rs

@@ -62,5 +62,5 @@ pub fn provide(providers: &mut Providers<'_>) {
     providers.destructure_const = |tcx, param_env_and_value| {
         let (param_env, value) = param_env_and_value.into_parts();
         const_eval::destructure_const(tcx, param_env, value)
-    }
+    };
 }

src/librustc_mir_build/hair/constant.rs

-use rustc::mir::interpret::{ConstValue, Scalar};
-use rustc::ty::{self, layout::Size, ParamEnv, Ty, TyCtxt};
+use rustc::mir::interpret::{
+    truncate, Allocation, ConstValue, LitToConstError, LitToConstInput, Scalar,
+};
+use rustc::ty::{self, layout::Size, ParamEnv, TyCtxt};
 use rustc_span::symbol::Symbol;
 use syntax::ast;
 
-#[derive(PartialEq)]
-crate enum LitToConstError {
-    UnparseableFloat,
-    Reported,
-}
-
 crate fn lit_to_const<'tcx>(
-    lit: &'tcx ast::LitKind,
     tcx: TyCtxt<'tcx>,
-    ty: Ty<'tcx>,
-    neg: bool,
+    lit_input: LitToConstInput<'tcx>,
 ) -> Result<&'tcx ty::Const<'tcx>, LitToConstError> {
-    use syntax::ast::*;
+    let LitToConstInput { lit, ty, neg } = lit_input;
 
     let trunc = |n| {
         let param_ty = ParamEnv::reveal_all().and(ty);
@@ -26,35 +20,50 @@
         Ok(ConstValue::Scalar(Scalar::from_uint(result, width)))
     };
 
-    use rustc::mir::interpret::*;
     let lit = match *lit {
-        LitKind::Str(ref s, _) => {
+        ast::LitKind::Str(ref s, _) => {
             let s = s.as_str();
             let allocation = Allocation::from_byte_aligned_bytes(s.as_bytes());
             let allocation = tcx.intern_const_alloc(allocation);
             ConstValue::Slice { data: allocation, start: 0, end: s.len() }
         }
-        LitKind::ByteStr(ref data) => {
-            let id = tcx.allocate_bytes(data);
-            ConstValue::Scalar(Scalar::Ptr(id.into()))
+        ast::LitKind::ByteStr(ref data) => {
+            if let ty::Ref(_, ref_ty, _) = ty.kind {
+                match ref_ty.kind {
+                    ty::Slice(_) => {
+                        let allocation = Allocation::from_byte_aligned_bytes(data as &Vec<u8>);
+                        let allocation = tcx.intern_const_alloc(allocation);
+                        ConstValue::Slice { data: allocation, start: 0, end: data.len() }
+                    }
+                    ty::Array(_, _) => {
+                        let id = tcx.allocate_bytes(data);
+                        ConstValue::Scalar(Scalar::Ptr(id.into()))
+                    }
+                    _ => {
+                        bug!("bytestring should have type of either &[u8] or &[u8; _], not {}", ty)
+                    }
+                }
+            } else {
+                bug!("bytestring should have type of either &[u8] or &[u8; _], not {}", ty)
+            }
         }
-        LitKind::Byte(n) => ConstValue::Scalar(Scalar::from_uint(n, Size::from_bytes(1))),
-        LitKind::Int(n, _) if neg => {
+        ast::LitKind::Byte(n) => ConstValue::Scalar(Scalar::from_uint(n, Size::from_bytes(1))),
+        ast::LitKind::Int(n, _) if neg => {
             let n = n as i128;
             let n = n.overflowing_neg().0;
             trunc(n as u128)?
         }
-        LitKind::Int(n, _) => trunc(n)?,
-        LitKind::Float(n, _) => {
+        ast::LitKind::Int(n, _) => trunc(n)?,
+        ast::LitKind::Float(n, _) => {
             let fty = match ty.kind {
                 ty::Float(fty) => fty,
                 _ => bug!(),
             };
             parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)?
         }
-        LitKind::Bool(b) => ConstValue::Scalar(Scalar::from_bool(b)),
-        LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)),
-        LitKind::Err(_) => unreachable!(),
+        ast::LitKind::Bool(b) => ConstValue::Scalar(Scalar::from_bool(b)),
+        ast::LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)),
+        ast::LitKind::Err(_) => return Err(LitToConstError::Reported),
     };
     Ok(tcx.mk_const(ty::Const { val: ty::ConstKind::Value(lit), ty }))
 }

src/librustc_mir_build/hair/cx/mod.rs

@@ -5,9 +5,9 @@
 use crate::hair::util::UserAnnotatedTyHelpers;
 use crate::hair::*;
 
-use crate::hair::constant::{lit_to_const, LitToConstError};
 use rustc::infer::InferCtxt;
 use rustc::middle::region;
+use rustc::mir::interpret::{LitToConstError, LitToConstInput};
 use rustc::ty::layout::VariantIdx;
 use rustc::ty::subst::Subst;
 use rustc::ty::subst::{GenericArg, InternalSubsts};
@@ -136,7 +136,7 @@ impl<'a, 'tcx> Cx<'a, 'tcx> {
     ) -> &'tcx ty::Const<'tcx> {
         trace!("const_eval_literal: {:#?}, {:?}, {:?}, {:?}", lit, ty, sp, neg);
 
-        match lit_to_const(lit, self.tcx, ty, neg) {
+        match self.tcx.at(sp).lit_to_const(LitToConstInput { lit, ty, neg }) {
             Ok(c) => c,
             Err(LitToConstError::UnparseableFloat) => {
                 // FIXME(#31407) this is only necessary because float parsing is buggy

src/librustc_mir_build/hair/mod.rs

@@ -16,7 +16,7 @@
 use rustc_hir::def_id::DefId;
 use rustc_span::Span;
 
-mod constant;
+crate mod constant;
 crate mod cx;
 
 crate mod pattern;

src/librustc_mir_build/hair/pattern/mod.rs

@@ -6,10 +6,11 @@
 
 pub(crate) use self::check_match::check_match;
 
-use crate::hair::constant::*;
 use crate::hair::util::UserAnnotatedTyHelpers;
 
-use rustc::mir::interpret::{get_slice_bytes, sign_extend, ConstValue, ErrorHandled};
+use rustc::mir::interpret::{
+    get_slice_bytes, sign_extend, ConstValue, ErrorHandled, LitToConstError, LitToConstInput,
+};
 use rustc::mir::UserTypeProjection;
 use rustc::mir::{BorrowKind, Field, Mutability};
 use rustc::ty::layout::VariantIdx;
@@ -822,35 +823,30 @@ fn lower_path(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) ->
     /// which would overflow if we tried to evaluate `128_i8` and then negate
     /// afterwards.
     fn lower_lit(&mut self, expr: &'tcx hir::Expr<'tcx>) -> PatKind<'tcx> {
-        match expr.kind {
-            hir::ExprKind::Lit(ref lit) => {
-                let ty = self.tables.expr_ty(expr);
-                match lit_to_const(&lit.node, self.tcx, ty, false) {
-                    Ok(val) => *self.const_to_pat(val, expr.hir_id, lit.span).kind,
-                    Err(LitToConstError::UnparseableFloat) => {
-                        self.errors.push(PatternError::FloatBug);
-                        PatKind::Wild
-                    }
-                    Err(LitToConstError::Reported) => PatKind::Wild,
+        if let hir::ExprKind::Path(ref qpath) = expr.kind {
+            *self.lower_path(qpath, expr.hir_id, expr.span).kind
+        } else {
+            let (lit, neg) = match expr.kind {
+                hir::ExprKind::Lit(ref lit) => (lit, false),
+                hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => {
+                    let lit = match expr.kind {
+                        hir::ExprKind::Lit(ref lit) => lit,
+                        _ => span_bug!(expr.span, "not a literal: {:?}", expr),
+                    };
+                    (lit, true)
                 }
-            }
-            hir::ExprKind::Path(ref qpath) => *self.lower_path(qpath, expr.hir_id, expr.span).kind,
-            hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => {
-                let ty = self.tables.expr_ty(expr);
-                let lit = match expr.kind {
-                    hir::ExprKind::Lit(ref lit) => lit,
-                    _ => span_bug!(expr.span, "not a literal: {:?}", expr),
-                };
-                match lit_to_const(&lit.node, self.tcx, ty, true) {
-                    Ok(val) => *self.const_to_pat(val, expr.hir_id, lit.span).kind,
-                    Err(LitToConstError::UnparseableFloat) => {
-                        self.errors.push(PatternError::FloatBug);
-                        PatKind::Wild
-                    }
-                    Err(LitToConstError::Reported) => PatKind::Wild,
+                _ => span_bug!(expr.span, "not a literal: {:?}", expr),
+            };
+
+            let lit_input = LitToConstInput { lit: &lit.node, ty: self.tables.expr_ty(expr), neg };
+            match self.tcx.at(expr.span).lit_to_const(lit_input) {
+                Ok(val) => *self.const_to_pat(val, expr.hir_id, lit.span).kind,
+                Err(LitToConstError::UnparseableFloat) => {
+                    self.errors.push(PatternError::FloatBug);
+                    PatKind::Wild
                 }
+                Err(LitToConstError::Reported) => PatKind::Wild,
             }
-            _ => span_bug!(expr.span, "not a literal: {:?}", expr),
         }
     }
 }

src/librustc_mir_build/lib.rs

@@ -22,5 +22,6 @@
 
 pub fn provide(providers: &mut Providers<'_>) {
     providers.check_match = hair::pattern::check_match;
+    providers.lit_to_const = hair::constant::lit_to_const;
     providers.mir_built = build::mir_built;
 }

src/librustc_typeck/astconv.rs

+// ignore-tidy-filelength FIXME(#67418) Split up this file
 //! Conversion from AST representation of types to the `ty.rs` representation.
 //! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an
 //! instance of `AstConv`.
@@ -37,6 +38,7 @@
 use std::iter;
 use std::slice;
 
+use rustc::mir::interpret::LitToConstInput;
 use rustc_error_codes::*;
 
 #[derive(Debug)]
@@ -2699,17 +2701,28 @@ pub fn ast_const_to_const(
         let tcx = self.tcx();
         let def_id = tcx.hir().local_def_id(ast_const.hir_id);
 
-        let mut const_ = ty::Const {
-            val: ty::ConstKind::Unevaluated(
-                def_id,
-                InternalSubsts::identity_for_item(tcx, def_id),
-                None,
-            ),
-            ty,
+        let expr = &tcx.hir().body(ast_const.body).value;
+
+        let lit_input = match expr.kind {
+            hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
+            hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => match expr.kind {
+                hir::ExprKind::Lit(ref lit) => {
+                    Some(LitToConstInput { lit: &lit.node, ty, neg: true })
+                }
+                _ => None,
+            },
+            _ => None,
         };
 
-        let expr = &tcx.hir().body(ast_const.body).value;
-        if let Some(def_id) = self.const_param_def_id(expr) {
+        if let Some(lit_input) = lit_input {
+            // If an error occurred, ignore that it's a literal and leave reporting the error up to
+            // mir
+            if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) {
+                return c;
+            }
+        }
+
+        let kind = if let Some(def_id) = self.const_param_def_id(expr) {
             // Find the name and index of the const parameter by indexing the generics of the
             // parent item and construct a `ParamConst`.
             let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
@@ -2718,10 +2731,11 @@ pub fn ast_const_to_const(
             let generics = tcx.generics_of(item_def_id);
             let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id)];
             let name = tcx.hir().name(hir_id);
-            const_.val = ty::ConstKind::Param(ty::ParamConst::new(index, name));
-        }
-
-        tcx.mk_const(const_)
+            ty::ConstKind::Param(ty::ParamConst::new(index, name))
+        } else {
+            ty::ConstKind::Unevaluated(def_id, InternalSubsts::identity_for_item(tcx, def_id), None)
+        };
+        tcx.mk_const(ty::Const { val: kind, ty })
     }
 
     pub fn impl_trait_ty_to_ty(

src/libsyntax/ast.rs

@@ -1441,8 +1441,17 @@ pub struct MacroDef {
     pub legacy: bool,
 }
 
-// Clippy uses Hash and PartialEq
-#[derive(Clone, RustcEncodable, RustcDecodable, Debug, Copy, Hash, PartialEq, HashStable_Generic)]
+#[derive(
+    Clone,
+    RustcEncodable,
+    RustcDecodable,
+    Debug,
+    Copy,
+    Hash,
+    Eq,
+    PartialEq,
+    HashStable_Generic
+)]
 pub enum StrStyle {
     /// A regular string, like `"foo"`.
     Cooked,
@@ -1491,9 +1500,18 @@ impl StrLit {
     }
 }
 
-// Clippy uses Hash and PartialEq
 /// Type of the integer literal based on provided suffix.
-#[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug, Hash, PartialEq, HashStable_Generic)]
+#[derive(
+    Clone,
+    Copy,
+    RustcEncodable,
+    RustcDecodable,
+    Debug,
+    Hash,
+    Eq,
+    PartialEq,
+    HashStable_Generic
+)]
 pub enum LitIntType {
     /// e.g. `42_i32`.
     Signed(IntTy),
@@ -1504,7 +1522,17 @@ pub enum LitIntType {
 }
 
 /// Type of the float literal based on provided suffix.
-#[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug, Hash, PartialEq, HashStable_Generic)]
+#[derive(
+    Clone,
+    Copy,
+    RustcEncodable,
+    RustcDecodable,
+    Debug,
+    Hash,
+    Eq,
+    PartialEq,
+    HashStable_Generic
+)]
 pub enum LitFloatType {
     /// A float literal with a suffix (`1f32` or `1E10f32`).
     Suffixed(FloatTy),
@@ -1515,8 +1543,7 @@ pub enum LitFloatType {
 /// Literal kind.
 ///
 /// E.g., `"foo"`, `42`, `12.34`, or `bool`.
-// Clippy uses Hash and PartialEq
-#[derive(Clone, RustcEncodable, RustcDecodable, Debug, Hash, PartialEq, HashStable_Generic)]
+#[derive(Clone, RustcEncodable, RustcDecodable, Debug, Hash, Eq, PartialEq, HashStable_Generic)]
 pub enum LitKind {
     /// A string literal (`"foo"`).
     Str(Symbol, StrStyle),

src/test/ui/consts/const-eval/ub-nonnull.stderr

@@ -13,7 +13,7 @@ LL | / const OUT_OF_BOUNDS_PTR: NonNull<u8> = { unsafe {
 LL | |     let ptr: &[u8; 256] = mem::transmute(&0u8); // &0 gets promoted so it does not dangle
 LL | |     // Use address-of-element for pointer arithmetic. This could wrap around to NULL!
 LL | |     let out_of_bounds_ptr = &ptr[255];
-   | |                             ^^^^^^^^^ Memory access failed: pointer must be in-bounds at offset 256, but is outside bounds of allocation 9 which has size 1
+   | |                             ^^^^^^^^^ Memory access failed: pointer must be in-bounds at offset 256, but is outside bounds of allocation 8 which has size 1
 LL | |     mem::transmute(out_of_bounds_ptr)
 LL | | } };
    | |____-

src/test/ui/did_you_mean/bad-assoc-ty.stderr

@@ -59,7 +59,7 @@ error[E0223]: ambiguous associated type
   --> $DIR/bad-assoc-ty.rs:1:10
    |
 LL | type A = [u8; 4]::AssocTy;
-   |          ^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<[u8; _] as Trait>::AssocTy`
+   |          ^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<[u8; 4] as Trait>::AssocTy`
 
 error[E0223]: ambiguous associated type
   --> $DIR/bad-assoc-ty.rs:5:10

src/test/ui/symbol-names/impl1.legacy.stderr

@@ -46,25 +46,25 @@ error: def-path(bar::<impl foo::Foo>::baz)
 LL |         #[rustc_def_path]
    |         ^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_ZN209_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$C$$u20$...$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method17hf07584432cd4d8beE)
+error: symbol-name(_ZN209_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$C$$u20$...$RP$$u2b$impl1..AutoTrait$u3b$$u20$3$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method17h62e540f14f879d56E)
   --> $DIR/impl1.rs:62:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method::hf07584432cd4d8be)
+error: demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; 3] as impl1::main::{{closure}}::Bar>::method::h62e540f14f879d56)
   --> $DIR/impl1.rs:62:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method)
+error: demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; 3] as impl1::main::{{closure}}::Bar>::method)
   --> $DIR/impl1.rs:62:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
+error: def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; 3] as main::{{closure}}#1::Bar>::method)
   --> $DIR/impl1.rs:69:13
    |
 LL |             #[rustc_def_path]

src/test/ui/symbol-names/impl1.rs

@@ -60,15 +60,15 @@ fn method(&self) {}
         // Test type mangling, by putting them in an `impl` header.
         impl Bar for [&'_ (dyn Foo<Assoc = extern fn(&u8, ...)> + AutoTrait); 3] {
             #[rustc_symbol_name]
-            //[legacy]~^ ERROR symbol-name(_ZN209_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$C$$u20$...$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method
-            //[legacy]~| ERROR demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method
-            //[legacy]~| ERROR demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method)
+            //[legacy]~^ ERROR symbol-name(_ZN209_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$C$$u20$...$RP$$u2b$impl1..AutoTrait$u3b$$u20$3$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method
+            //[legacy]~| ERROR demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; 3] as impl1::main::{{closure}}::Bar>::method
+            //[legacy]~| ERROR demangling-alt(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; 3] as impl1::main::{{closure}}::Bar>::method)
              //[v0]~^^^^ ERROR symbol-name(_RNvXNCNvCs4fqI2P2rA04_5impl14mains_0ARDNtB6_3Foop5AssocFG_KCRL0_hvEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
                 //[v0]~| ERROR demangling(<[&dyn impl1[317d481089b8c8fe]::Foo<Assoc = for<'a> extern "C" fn(&'a u8, ...)> + impl1[317d481089b8c8fe]::AutoTrait; 3: usize] as impl1[317d481089b8c8fe]::main::{closure#1}::Bar>::method)
                 //[v0]~| ERROR demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a> extern "C" fn(&'a u8, ...)> + impl1::AutoTrait; 3] as impl1::main::{closure#1}::Bar>::method)
             #[rustc_def_path]
-            //[legacy]~^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
-               //[v0]~^^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
+            //[legacy]~^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; 3] as main::{{closure}}#1::Bar>::method)
+               //[v0]~^^ ERROR def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; 3] as main::{{closure}}#1::Bar>::method)
             fn method(&self) {}
         }
     };

src/test/ui/symbol-names/impl1.v0.stderr

@@ -64,7 +64,7 @@ error: demangling-alt(<[&dyn impl1::Foo<Assoc = for<'a> extern "C" fn(&'a u8, ..
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; _] as main::{{closure}}#1::Bar>::method)
+error: def-path(<[&dyn Foo<Assoc = for<'r> extern "C" fn(&'r u8, ...)> + AutoTrait; 3] as main::{{closure}}#1::Bar>::method)
   --> $DIR/impl1.rs:69:13
    |
 LL |             #[rustc_def_path]