address review

Cargo.lock

@@ -358,7 +358,6 @@ dependencies = [
  "libgit2-sys",
  "log",
  "memchr",
- "num_cpus",
  "opener",
  "openssl",
  "os_info",

compiler/rustc_const_eval/src/const_eval/error.rs

@@ -140,6 +140,7 @@ pub fn report_as_lint(
     ///
     /// If `lint_root.is_some()` report it as a lint, else report it as a hard error.
     /// (Except that for some errors, we ignore all that -- see `must_error` below.)
+    #[instrument(skip(self, tcx, decorate, lint_root), level = "debug")]
     fn struct_generic(
         &self,
         tcx: TyCtxtAt<'tcx>,
@@ -190,6 +191,7 @@ fn struct_generic(
             decorate(err);
         };
 
+        debug!("self.error: {:?}", self.error);
         // Special handling for certain errors
         match &self.error {
             // Don't emit a new diagnostic for these errors

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -24,12 +24,6 @@
 pub use machine::*;
 pub(crate) use valtrees::{const_to_valtree_inner, valtree_to_const_value};
 
-pub(crate) enum ValTreeCreationError {
-    NonSupportedType,
-    Other,
-}
-pub(crate) type ValTreeCreationResult<'tcx> = Result<ty::ValTree<'tcx>, ValTreeCreationError>;
-
 pub(crate) fn const_caller_location(
     tcx: TyCtxt<'_>,
     (file, line, col): (Symbol, u32, u32),
@@ -44,6 +38,16 @@ pub(crate) fn const_caller_location(
     ConstValue::Scalar(Scalar::from_maybe_pointer(loc_place.ptr, &tcx))
 }
 
+// We forbid type-level constants that contain more than `VALTREE_MAX_NODES` nodes.
+const VALTREE_MAX_NODES: usize = 100000;
+
+pub(crate) enum ValTreeCreationError {
+    NodesOverflow,
+    NonSupportedType,
+    Other,
+}
+pub(crate) type ValTreeCreationResult<'tcx> = Result<ty::ValTree<'tcx>, ValTreeCreationError>;
+
 /// Evaluates a constant and turns it into a type-level constant value.
 pub(crate) fn eval_to_valtree<'tcx>(
     tcx: TyCtxt<'tcx>,
@@ -62,11 +66,28 @@ pub(crate) fn eval_to_valtree<'tcx>(
     let place = ecx.raw_const_to_mplace(const_alloc).unwrap();
     debug!(?place);
 
-    let valtree_result = const_to_valtree_inner(&ecx, &place);
+    let mut num_nodes = 0;
+    let valtree_result = const_to_valtree_inner(&ecx, &place, &mut num_nodes);
 
     match valtree_result {
         Ok(valtree) => Ok(Some(valtree)),
-        Err(_) => Ok(None),
+        Err(err) => {
+            let did = cid.instance.def_id();
+            let s = cid.display(tcx);
+            match err {
+                ValTreeCreationError::NodesOverflow => {
+                    let msg = format!("maximum number of nodes exceeded in constant {}", &s);
+                    let mut diag = match tcx.hir().span_if_local(did) {
+                        Some(span) => tcx.sess.struct_span_err(span, &msg),
+                        None => tcx.sess.struct_err(&msg),
+                    };
+                    diag.emit();
+
+                    Ok(None)
+                }
+                ValTreeCreationError::NonSupportedType | ValTreeCreationError::Other => Ok(None),
+            }
+        }
     }
 }
 
@@ -75,7 +96,7 @@ pub(crate) fn eval_to_valtree<'tcx>(
 pub(crate) fn try_destructure_const<'tcx>(
     tcx: TyCtxt<'tcx>,
     const_: ty::Const<'tcx>,
-) -> Option<mir::DestructuredConst<'tcx>> {
+) -> Option<ty::DestructuredConst<'tcx>> {
     if let ty::ConstKind::Value(valtree) = const_.val() {
         let branches = match valtree {
             ty::ValTree::Branch(b) => b,
@@ -141,7 +162,7 @@ pub(crate) fn try_destructure_const<'tcx>(
 
         let fields = tcx.arena.alloc_from_iter(fields.into_iter());
 
-        Some(mir::DestructuredConst { variant, fields })
+        Some(ty::DestructuredConst { variant, fields })
     } else {
         None
     }

compiler/rustc_const_eval/src/const_eval/valtrees.rs

 use super::eval_queries::{mk_eval_cx, op_to_const};
 use super::machine::CompileTimeEvalContext;
-use super::{ValTreeCreationError, ValTreeCreationResult};
+use super::{ValTreeCreationError, ValTreeCreationResult, VALTREE_MAX_NODES};
 use crate::interpret::{
     intern_const_alloc_recursive, ConstValue, ImmTy, Immediate, InternKind, MemPlaceMeta,
     MemoryKind, PlaceTy, Scalar, ScalarMaybeUninit,
@@ -16,6 +16,7 @@ fn branches<'tcx>(
     place: &MPlaceTy<'tcx>,
     n: usize,
     variant: Option<VariantIdx>,
+    num_nodes: &mut usize,
 ) -> ValTreeCreationResult<'tcx> {
     let place = match variant {
         Some(variant) => ecx.mplace_downcast(&place, variant).unwrap(),
@@ -27,7 +28,7 @@ fn branches<'tcx>(
     let mut fields = Vec::with_capacity(n);
     for i in 0..n {
         let field = ecx.mplace_field(&place, i).unwrap();
-        let valtree = const_to_valtree_inner(ecx, &field)?;
+        let valtree = const_to_valtree_inner(ecx, &field, num_nodes)?;
         fields.push(Some(valtree));
     }
 
@@ -39,6 +40,11 @@ fn branches<'tcx>(
         .collect::<Option<Vec<_>>>()
         .expect("should have already checked for errors in ValTree creation");
 
+    // Have to account for ZSTs here
+    if branches.len() == 0 {
+        *num_nodes += 1;
+    }
+
     Ok(ty::ValTree::Branch(ecx.tcx.arena.alloc_from_iter(branches)))
 }
 
@@ -46,6 +52,7 @@ fn branches<'tcx>(
 fn slice_branches<'tcx>(
     ecx: &CompileTimeEvalContext<'tcx, 'tcx>,
     place: &MPlaceTy<'tcx>,
+    num_nodes: &mut usize,
 ) -> ValTreeCreationResult<'tcx> {
     let n = place
         .len(&ecx.tcx.tcx)
@@ -54,7 +61,7 @@ fn slice_branches<'tcx>(
     let mut elems = Vec::with_capacity(n as usize);
     for i in 0..n {
         let place_elem = ecx.mplace_index(place, i).unwrap();
-        let valtree = const_to_valtree_inner(ecx, &place_elem)?;
+        let valtree = const_to_valtree_inner(ecx, &place_elem, num_nodes)?;
         elems.push(valtree);
     }
 
@@ -65,12 +72,18 @@ fn slice_branches<'tcx>(
 pub(crate) fn const_to_valtree_inner<'tcx>(
     ecx: &CompileTimeEvalContext<'tcx, 'tcx>,
     place: &MPlaceTy<'tcx>,
+    num_nodes: &mut usize,
 ) -> ValTreeCreationResult<'tcx> {
     let ty = place.layout.ty;
     debug!("ty kind: {:?}", ty.kind());
 
+    if *num_nodes >= VALTREE_MAX_NODES {
+        return Err(ValTreeCreationError::NodesOverflow);
+    }
+
     match ty.kind() {
         ty::FnDef(..) => {
+            *num_nodes += 1;
             Ok(ty::ValTree::zst())
         }
         ty::Bool | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Char => {
@@ -78,6 +91,7 @@ pub(crate) fn const_to_valtree_inner<'tcx>(
                 return Err(ValTreeCreationError::Other);
             };
             let val = val.to_scalar().unwrap();
+            *num_nodes += 1;
 
             Ok(ty::ValTree::Leaf(val.assert_int()))
         }
@@ -94,11 +108,11 @@ pub(crate) fn const_to_valtree_inner<'tcx>(
             };
             debug!(?derefd_place);
 
-            const_to_valtree_inner(ecx, &derefd_place)
+            const_to_valtree_inner(ecx, &derefd_place, num_nodes)
         }
 
         ty::Str | ty::Slice(_) | ty::Array(_, _) => {
-            slice_branches(ecx, place)
+            slice_branches(ecx, place, num_nodes)
         }
         // Trait objects are not allowed in type level constants, as we have no concept for
         // resolving their backing type, even if we can do that at const eval time. We may
@@ -107,7 +121,7 @@ pub(crate) fn const_to_valtree_inner<'tcx>(
         ty::Dynamic(..) => Err(ValTreeCreationError::NonSupportedType),
 
         ty::Tuple(elem_tys) => {
-            branches(ecx, place, elem_tys.len(), None)
+            branches(ecx, place, elem_tys.len(), None, num_nodes)
         }
 
         ty::Adt(def, _) => {
@@ -120,7 +134,7 @@ pub(crate) fn const_to_valtree_inner<'tcx>(
             let Ok((_, variant)) = ecx.read_discriminant(&place.into()) else {
                 return Err(ValTreeCreationError::Other);
             };
-            branches(ecx, place, def.variant(variant).fields.len(), def.is_enum().then_some(variant))
+            branches(ecx, place, def.variant(variant).fields.len(), def.is_enum().then_some(variant), num_nodes)
         }
 
         ty::Never

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

@@ -194,7 +194,7 @@ fn eval_to_allocation(
 impl<'tcx> TyCtxt<'tcx> {
     /// Destructure a type-level constant ADT or array into its variant index and its field values.
     /// Panics if the destructuring fails, use `try_destructure_const` for fallible version.
-    pub fn destructure_const(self, const_: ty::Const<'tcx>) -> mir::DestructuredConst<'tcx> {
+    pub fn destructure_const(self, const_: ty::Const<'tcx>) -> ty::DestructuredConst<'tcx> {
         self.try_destructure_const(const_).unwrap()
     }
 

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

@@ -78,7 +78,6 @@ pub fn try_to_scalar_int(&self) -> Option<ScalarInt> {
         Some(self.try_to_scalar()?.assert_int())
     }
 
-    #[inline(always)]
     pub fn try_to_bits(&self, size: Size) -> Option<u128> {
         self.try_to_scalar_int()?.to_bits(size).ok()
     }

compiler/rustc_middle/src/query/mod.rs

@@ -967,26 +967,26 @@
     query eval_to_valtree(
         key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>
     ) -> EvalToValTreeResult<'tcx> {
-        desc { "evaluate type-level constant" }
+        desc { "evaluating type-level constant" }
     }
 
     /// Converts a type level constant value into `ConstValue`
     query valtree_to_const_val(key: (Ty<'tcx>, ty::ValTree<'tcx>)) -> ConstValue<'tcx> {
-        desc { "convert type-level constant value to mir constant value"}
+        desc { "converting type-level constant value to mir constant value"}
     }
 
     /// Destructure a constant ADT or array into its variant index and its
     /// field values or return `None` if constant is invalid.
     ///
     /// Use infallible `TyCtxt::destructure_const` when you know that constant is valid.
-    query try_destructure_const(key: ty::Const<'tcx>) -> Option<mir::DestructuredConst<'tcx>> {
-        desc { "destructure type level constant"}
+    query try_destructure_const(key: ty::Const<'tcx>) -> Option<ty::DestructuredConst<'tcx>> {
+        desc { "destructuring type level constant"}
     }
 
     /// Tries to destructure an `mir::ConstantKind` ADT or array into its variant index
     /// and its field values.
     query try_destructure_mir_constant(key: ty::ParamEnvAnd<'tcx, mir::ConstantKind<'tcx>>) -> Option<mir::DestructuredMirConstant<'tcx>> {
-        desc { "destructure mir constant"}
+        desc { "destructuring mir constant"}
         remap_env_constness
     }
 
@@ -995,7 +995,7 @@
     query deref_mir_constant(
         key: ty::ParamEnvAnd<'tcx, mir::ConstantKind<'tcx>>
     ) -> mir::ConstantKind<'tcx> {
-        desc { "deref constant" }
+        desc { "dereferencing mir constant" }
         remap_env_constness
     }
 

compiler/rustc_middle/src/ty/mod.rs

@@ -42,8 +42,8 @@
 use rustc_session::cstore::CrateStoreDyn;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
-use rustc_target::abi::Align;
 pub use subst::*;
+use rustc_target::abi::{Align, VariantIdx};
 pub use vtable::*;
 
 use std::fmt::Debug;
@@ -2453,3 +2453,10 @@ pub struct FoundRelationships {
     /// _>::AssocType = ?T`
     pub output: bool,
 }
+
+/// The constituent parts of a type level constant of kind ADT or array.
+#[derive(Copy, Clone, Debug, HashStable)]
+pub struct DestructuredConst<'tcx> {
+    pub variant: Option<VariantIdx>,
+    pub fields: &'tcx [ty::Const<'tcx>],
+}

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

@@ -98,6 +98,7 @@ fn path_generic_args(
 
     // Defaults (should not be overridden):
 
+    #[instrument(skip(self), level = "debug")]
     fn default_print_def_path(
         self,
         def_id: DefId,

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

@@ -1460,9 +1460,7 @@ fn pretty_print_const_valtree(
                 return Ok(self);
             }
             // Aggregates, printed as array/tuple/struct/variant construction syntax.
-            (ty::ValTree::Branch(_), ty::Array(..) | ty::Tuple(..) | ty::Adt(..))
-                if !ty.has_param_types_or_consts() =>
-            {
+            (ty::ValTree::Branch(_), ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) => {
                 let Some(contents) = self.tcx().try_destructure_const(
                     ty::Const::from_value(self.tcx(), valtree, ty)
                 ) else {

compiler/rustc_mir_build/src/build/mod.rs

 use crate::build;
+pub(crate) use crate::build::expr::as_constant::lit_to_mir_constant;
 use crate::build::expr::as_place::PlaceBuilder;
 use crate::build::scope::DropKind;
 use crate::thir::constant::parse_float_into_scalar;
 use crate::thir::pattern::pat_from_hir;
-use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
@@ -14,9 +14,7 @@
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
 use rustc_middle::middle::region;
-use rustc_middle::mir::interpret::{
-    Allocation, ConstValue, LitToConstError, LitToConstInput, Scalar,
-};
+use rustc_middle::mir::interpret::ConstValue;
 use rustc_middle::mir::*;
 use rustc_middle::thir::{BindingMode, Expr, ExprId, LintLevel, LocalVarId, PatKind, Thir};
 use rustc_middle::ty::subst::Subst;
@@ -24,7 +22,6 @@
 use rustc_span::symbol::sym;
 use rustc_span::Span;
 use rustc_span::Symbol;
-use rustc_target::abi::Size;
 use rustc_target::spec::abi::Abi;
 
 use super::lints;
@@ -1096,57 +1093,6 @@ fn parse_float_into_constval<'tcx>(
     parse_float_into_scalar(num, float_ty, neg).map(ConstValue::Scalar)
 }
 
-#[instrument(skip(tcx, lit_input))]
-pub(crate) fn lit_to_mir_constant<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    lit_input: LitToConstInput<'tcx>,
-) -> Result<ConstantKind<'tcx>, LitToConstError> {
-    let LitToConstInput { lit, ty, neg } = lit_input;
-    let trunc = |n| {
-        let param_ty = ty::ParamEnv::reveal_all().and(ty);
-        let width = tcx.layout_of(param_ty).map_err(|_| LitToConstError::Reported)?.size;
-        trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
-        let result = width.truncate(n);
-        trace!("trunc result: {}", result);
-        Ok(ConstValue::Scalar(Scalar::from_uint(result, width)))
-    };
-
-    let value = match (lit, &ty.kind()) {
-        (ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
-            let s = s.as_str();
-            let allocation = Allocation::from_bytes_byte_aligned_immutable(s.as_bytes());
-            let allocation = tcx.intern_const_alloc(allocation);
-            ConstValue::Slice { data: allocation, start: 0, end: s.len() }
-        }
-        (ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _))
-            if matches!(inner_ty.kind(), ty::Slice(_)) =>
-        {
-            let allocation = Allocation::from_bytes_byte_aligned_immutable(data as &[u8]);
-            let allocation = tcx.intern_const_alloc(allocation);
-            ConstValue::Slice { data: allocation, start: 0, end: data.len() }
-        }
-        (ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _)) if inner_ty.is_array() => {
-            let id = tcx.allocate_bytes(data);
-            ConstValue::Scalar(Scalar::from_pointer(id.into(), &tcx))
-        }
-        (ast::LitKind::Byte(n), ty::Uint(ty::UintTy::U8)) => {
-            ConstValue::Scalar(Scalar::from_uint(*n, Size::from_bytes(1)))
-        }
-        (ast::LitKind::Int(n, _), ty::Uint(_)) | (ast::LitKind::Int(n, _), ty::Int(_)) => {
-            trunc(if neg { (*n as i128).overflowing_neg().0 as u128 } else { *n })?
-        }
-        (ast::LitKind::Float(n, _), ty::Float(fty)) => {
-            parse_float_into_constval(*n, *fty, neg).ok_or(LitToConstError::Reported)?
-        }
-        (ast::LitKind::Bool(b), ty::Bool) => ConstValue::Scalar(Scalar::from_bool(*b)),
-        (ast::LitKind::Char(c), ty::Char) => ConstValue::Scalar(Scalar::from_char(*c)),
-        (ast::LitKind::Err(_), _) => return Err(LitToConstError::Reported),
-        _ => return Err(LitToConstError::TypeError),
-    };
-
-    Ok(ConstantKind::Val(value, ty))
-}
-
 ///////////////////////////////////////////////////////////////////////////
 // Builder methods are broken up into modules, depending on what kind
 // of thing is being lowered. Note that they use the `unpack` macro

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

@@ -503,7 +503,7 @@ fn recur(
                 // deref pattern.
                 _ => {
                     if !pointee_ty.is_sized(tcx.at(span), param_env) {
-                        // `tcx.deref_mirconstant()` below will ICE with an unsized type
+                        // `tcx.deref_mir_constant()` below will ICE with an unsized type
                         // (except slices, which are handled in a separate arm above).
                         let msg = format!("cannot use unsized non-slice type `{}` in constant patterns", pointee_ty);
                         if self.include_lint_checks {

src/test/incremental/issue-54242.rs

@@ -14,7 +14,7 @@ impl Tr for str {
     type Arr = [u8; 8];
     #[cfg(cfail)]
     type Arr = [u8; Self::C];
-    //[cfail]~^ ERROR cycle detected when evaluate type-level constant
+    //[cfail]~^ ERROR cycle detected when evaluating type-level constant
 }
 
 fn main() {}

src/test/ui/consts/const-size_of-cycle.stderr

-error[E0391]: cycle detected when evaluate type-level constant
+error[E0391]: cycle detected when evaluating type-level constant
   --> $DIR/const-size_of-cycle.rs:4:17
    |
 LL |     bytes: [u8; std::mem::size_of::<Foo>()]
@@ -17,7 +17,7 @@ LL |     bytes: [u8; std::mem::size_of::<Foo>()]
    = note: ...which requires computing layout of `Foo`...
    = note: ...which requires computing layout of `[u8; _]`...
    = note: ...which requires normalizing `[u8; _]`...
-   = note: ...which again requires evaluate type-level constant, completing the cycle
+   = note: ...which again requires evaluating type-level constant, completing the cycle
 note: cycle used when checking that `Foo` is well-formed
   --> $DIR/const-size_of-cycle.rs:3:1
    |

src/test/ui/consts/issue-44415.rs

@@ -4,7 +4,7 @@
 
 struct Foo {
     bytes: [u8; unsafe { intrinsics::size_of::<Foo>() }],
-    //~^ ERROR cycle detected when evaluate type-level constant
+    //~^ ERROR cycle detected when evaluating type-level constant
     x: usize,
 }
 

src/test/ui/consts/issue-44415.stderr

-error[E0391]: cycle detected when evaluate type-level constant
+error[E0391]: cycle detected when evaluating type-level constant
   --> $DIR/issue-44415.rs:6:17
    |
 LL |     bytes: [u8; unsafe { intrinsics::size_of::<Foo>() }],
@@ -17,7 +17,7 @@ LL |     bytes: [u8; unsafe { intrinsics::size_of::<Foo>() }],
    = note: ...which requires computing layout of `Foo`...
    = note: ...which requires computing layout of `[u8; _]`...
    = note: ...which requires normalizing `[u8; _]`...
-   = note: ...which again requires evaluate type-level constant, completing the cycle
+   = note: ...which again requires evaluating type-level constant, completing the cycle
 note: cycle used when checking that `Foo` is well-formed
   --> $DIR/issue-44415.rs:5:1
    |