Auto merge of #103917 - oli-obk:layout_math, r=RalfJung,lcnr

Various cleanups around scalar layout restrictions

Pulled out of #103724

compiler/rustc_abi/src/layout.rs

@@ -382,28 +382,26 @@ pub trait LayoutCalculator {
  let (start, end) = scalar_valid_range;
  match st.abi {
  Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => {
- // the asserts ensure that we are not using the
- // `#[rustc_layout_scalar_valid_range(n)]`
- // attribute to widen the range of anything as that would probably
- // result in UB somewhere
- // FIXME(eddyb) the asserts are probably not needed,
- // as larger validity ranges would result in missed
+ // Enlarging validity ranges would result in missed
  // optimizations, *not* wrongly assuming the inner
- // value is valid. e.g. unions enlarge validity ranges,
+ // value is valid. e.g. unions already enlarge validity ranges,
  // because the values may be uninitialized.
+ //
+ // Because of that we only check that the start and end
+ // of the range is representable with this scalar type.
+
+ let max_value = scalar.size(dl).unsigned_int_max();
  if let Bound::Included(start) = start {
  // FIXME(eddyb) this might be incorrect - it doesn't
  // account for wrap-around (end < start) ranges.
- let valid_range = scalar.valid_range_mut();
- assert!(valid_range.start <= start);
- valid_range.start = start;
+ assert!(start <= max_value, "{start} > {max_value}");
+ scalar.valid_range_mut().start = start;
  }
  if let Bound::Included(end) = end {
  // FIXME(eddyb) this might be incorrect - it doesn't
  // account for wrap-around (end < start) ranges.
- let valid_range = scalar.valid_range_mut();
- assert!(valid_range.end >= end);
- valid_range.end = end;
+ assert!(end <= max_value, "{end} > {max_value}");
+ scalar.valid_range_mut().end = end;
  }
 
  // Update `largest_niche` if we have introduced a larger niche.

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -785,18 +785,10 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
  }
  }
  Abi::ScalarPair(a_layout, b_layout) => {
- // There is no `rustc_layout_scalar_valid_range_start` for pairs, so
- // we would validate these things as we descend into the fields,
- // but that can miss bugs in layout computation. Layout computation
- // is subtle due to enums having ScalarPair layout, where one field
- // is the discriminant.
- if cfg!(debug_assertions)
- && !a_layout.is_uninit_valid()
- && !b_layout.is_uninit_valid()
- {
- // We can only proceed if *both* scalars need to be initialized.
- // FIXME: find a way to also check ScalarPair when one side can be uninit but
- // the other must be init.
+ // We can only proceed if *both* scalars need to be initialized.
+ // FIXME: find a way to also check ScalarPair when one side can be uninit but
+ // the other must be init.
+ if !a_layout.is_uninit_valid() && !b_layout.is_uninit_valid() {
  let (a, b) =
  self.read_immediate(op, "initiailized scalar value")?.to_scalar_pair();
  self.visit_scalar(a, a_layout)?;

compiler/rustc_const_eval/src/transform/validate.rs

@@ -81,6 +81,7 @@ struct TypeChecker<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
+ #[track_caller]
  fn fail(&self, location: Location, msg: impl AsRef<str>) {
  let span = self.body.source_info(location).span;
  // We use `delay_span_bug` as we might see broken MIR when other errors have already
@@ -226,12 +227,12 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
  let check_equal = |this: &Self, location, f_ty| {
  if !this.mir_assign_valid_types(ty, f_ty) {
  this.fail(
- location,
- format!(
- "Field projection `{:?}.{:?}` specified type `{:?}`, but actual type is `{:?}`",
- parent, f, ty, f_ty
+ location,
+ format!(
+ "Field projection `{:?}.{:?}` specified type `{:?}`, but actual type is `{:?}`",
+ parent, f, ty, f_ty
+ )
  )
- )
  }
  };
 

compiler/rustc_lint/src/builtin.rs

@@ -52,7 +52,7 @@ use rustc_span::edition::Edition;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, InnerSpan, Span};
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{Abi, VariantIdx};
 use rustc_trait_selection::traits::{self, misc::can_type_implement_copy};
 
 use crate::nonstandard_style::{method_context, MethodLateContext};
@@ -2413,8 +2413,34 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
  }
 
  /// Information about why a type cannot be initialized this way.
- /// Contains an error message and optionally a span to point at.
- type InitError = (String, Option<Span>);
+ struct InitError {
+ message: String,
+ /// Spans from struct fields and similar that can be obtained from just the type.
+ span: Option<Span>,
+ /// Used to report a trace through adts.
+ nested: Option<Box<InitError>>,
+ }
+ impl InitError {
+ fn spanned(self, span: Span) -> InitError {
+ Self { span: Some(span), ..self }
+ }
+
+ fn nested(self, nested: impl Into<Option<InitError>>) -> InitError {
+ assert!(self.nested.is_none());
+ Self { nested: nested.into().map(Box::new), ..self }
+ }
+ }
+
+ impl<'a> From<&'a str> for InitError {
+ fn from(s: &'a str) -> Self {
+ s.to_owned().into()
+ }
+ }
+ impl From<String> for InitError {
+ fn from(message: String) -> Self {
+ Self { message, span: None, nested: None }
+ }
+ }
 
  /// Test if this constant is all-0.
  fn is_zero(expr: &hir::Expr<'_>) -> bool {
@@ -2470,25 +2496,54 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
 
  fn variant_find_init_error<'tcx>(
  cx: &LateContext<'tcx>,
+ ty: Ty<'tcx>,
  variant: &VariantDef,
  substs: ty::SubstsRef<'tcx>,
  descr: &str,
  init: InitKind,
  ) -> Option<InitError> {
- variant.fields.iter().find_map(|field| {
- ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(|(mut msg, span)| {
- if span.is_none() {
- // Point to this field, should be helpful for figuring
-  // out where the source of the error is.
- let span = cx.tcx.def_span(field.did);
- write!(&mut msg, " (in this {descr})").unwrap();
- (msg, Some(span))
+ let mut field_err = variant.fields.iter().find_map(|field| {
+ ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(|mut err| {
+ if !field.did.is_local() {
+ err
+ } else if err.span.is_none() {
+ err.span = Some(cx.tcx.def_span(field.did));
+ write!(&mut err.message, " (in this {descr})").unwrap();
+ err
  } else {
- // Just forward.
- (msg, span)
+ InitError::from(format!("in this {descr}"))
+ .spanned(cx.tcx.def_span(field.did))
+ .nested(err)
  }
  })
- })
+ });
+
+ // Check if this ADT has a constrained layout (like `NonNull` and friends).
+ if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty)) {
+ if let Abi::Scalar(scalar) | Abi::ScalarPair(scalar, _) = &layout.abi {
+ let range = scalar.valid_range(cx);
+ let msg = if !range.contains(0) {
+ "must be non-null"
+ } else if init == InitKind::Uninit && !scalar.is_always_valid(cx) {
+ // Prefer reporting on the fields over the entire struct for uninit,
+ // as the information bubbles out and it may be unclear why the type can't
+ // be null from just its outside signature.
+
+ "must be initialized inside its custom valid range"
+ } else {
+ return field_err;
+ };
+ if let Some(field_err) = &mut field_err {
+ // Most of the time, if the field error is the same as the struct error,
+ // the struct error only happens because of the field error.
+ if field_err.message.contains(msg) {
+ field_err.message = format!("because {}", field_err.message);
+ }
+ }
+ return Some(InitError::from(format!("`{ty}` {msg}")).nested(field_err));
+ }
+ }
+ field_err
  }
 
  /// Return `Some` only if we are sure this type does *not*
@@ -2501,63 +2556,36 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
  use rustc_type_ir::sty::TyKind::*;
  match ty.kind() {
  // Primitive types that don't like 0 as a value.
- Ref(..) => Some(("references must be non-null".to_string(), None)),
- Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
- FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
- Never => Some(("the `!` type has no valid value".to_string(), None)),
+ Ref(..) => Some("references must be non-null".into()),
+ Adt(..) if ty.is_box() => Some("`Box` must be non-null".into()),
+ FnPtr(..) => Some("function pointers must be non-null".into()),
+ Never => Some("the `!` type has no valid value".into()),
  RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
  // raw ptr to dyn Trait
  {
- Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
+ Some("the vtable of a wide raw pointer must be non-null".into())
  }
  // Primitive types with other constraints.
  Bool if init == InitKind::Uninit => {
- Some(("booleans must be either `true` or `false`".to_string(), None))
+ Some("booleans must be either `true` or `false`".into())
  }
  Char if init == InitKind::Uninit => {
- Some(("characters must be a valid Unicode codepoint".to_string(), None))
+ Some("characters must be a valid Unicode codepoint".into())
  }
  Int(_) | Uint(_) if init == InitKind::Uninit => {
- Some(("integers must not be uninitialized".to_string(), None))
- }
- Float(_) if init == InitKind::Uninit => {
- Some(("floats must not be uninitialized".to_string(), None))
+ Some("integers must be initialized".into())
  }
+ Float(_) if init == InitKind::Uninit => Some("floats must be initialized".into()),
  RawPtr(_) if init == InitKind::Uninit => {
- Some(("raw pointers must not be uninitialized".to_string(), None))
+ Some("raw pointers must be initialized".into())
  }
  // Recurse and checks for some compound types. (but not unions)
  Adt(adt_def, substs) if !adt_def.is_union() => {
- // First check if this ADT has a layout attribute (like `NonNull` and friends).
- use std::ops::Bound;
- match cx.tcx.layout_scalar_valid_range(adt_def.did()) {
- // We exploit here that `layout_scalar_valid_range` will never
- // return `Bound::Excluded`. (And we have tests checking that we
- // handle the attribute correctly.)
- // We don't add a span since users cannot declare such types anyway.
- (Bound::Included(lo), Bound::Included(hi)) if 0 < lo && lo < hi => {
- return Some((format!("`{}` must be non-null", ty), None));
- }
- (Bound::Included(lo), Bound::Unbounded) if 0 < lo => {
- return Some((format!("`{}` must be non-null", ty), None));
- }
- (Bound::Included(_), _) | (_, Bound::Included(_))
- if init == InitKind::Uninit =>
- {
- return Some((
- format!(
- "`{}` must be initialized inside its custom valid range",
- ty,
- ),
- None,
- ));
- }
- _ => {}
- }
  // Handle structs.
  if adt_def.is_struct() {
  return variant_find_init_error(
  cx,
+ ty,
  adt_def.non_enum_variant(),
  substs,
  "struct field",
@@ -2581,13 +2609,14 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
  Some((variant, definitely_inhabited))
  });
  let Some(first_variant) = potential_variants.next() else {
- return Some(("enums with no inhabited variants have no valid value".to_string(), Some(span)));
+ return Some(InitError::from("enums with no inhabited variants have no valid value").spanned(span));
  };
  // So we have at least one potentially inhabited variant. Might we have two?
  let Some(second_variant) = potential_variants.next() else {
  // There is only one potentially inhabited variant. So we can recursively check that variant!
  return variant_find_init_error(
  cx,
+ ty,
  &first_variant.0,
  substs,
  "field of the only potentially inhabited enum variant",
@@ -2605,10 +2634,9 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
  .filter(|(_variant, definitely_inhabited)| *definitely_inhabited)
  .count();
  if definitely_inhabited > 1 {
- return Some((
- "enums with multiple inhabited variants have to be initialized to a variant".to_string(),
- Some(span),
- ));
+ return Some(InitError::from(
+ "enums with multiple inhabited variants have to be initialized to a variant",
+ ).spanned(span));
  }
  }
  // We couldn't find anything wrong here.
@@ -2637,8 +2665,7 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
  // using zeroed or uninitialized memory.
  // We are extremely conservative with what we warn about.
  let conjured_ty = cx.typeck_results().expr_ty(expr);
- if let Some((msg, span)) =
- with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
+ if let Some(mut err) = with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
  {
  // FIXME(davidtwco): make translatable
  cx.struct_span_lint(
@@ -2664,10 +2691,17 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
  "help: use `MaybeUninit<T>` instead, \
  and only call `assume_init` after initialization is done",
  );
- if let Some(span) = span {
- lint.span_note(span, &msg);
- } else {
- lint.note(&msg);
+ loop {
+ if let Some(span) = err.span {
+ lint.span_note(span, &err.message);
+ } else {
+ lint.note(&err.message);
+ }
+ if let Some(e) = err.nested {
+ err = *e;
+ } else {
+ break;
+ }
  }
  lint
  },

compiler/rustc_middle/src/ty/consts/int.rs

@@ -245,6 +245,18 @@ impl ScalarInt {
  self.to_bits(size)
  }
 
+ // Tries to convert the `ScalarInt` to `bool`. Fails if the `size` of the `ScalarInt`
+ // in not equal to `Size { raw: 1 }` or if the value is not 0 or 1 and returns the `size`
+ // value of the `ScalarInt` in that case.
+ #[inline]
+ pub fn try_to_bool(self) -> Result<bool, Size> {
+ match self.try_to_u8()? {
+ 0 => Ok(false),
+ 1 => Ok(true),
+ _ => Err(self.size()),
+ }
+ }
+
  // Tries to convert the `ScalarInt` to `u8`. Fails if the `size` of the `ScalarInt`
  // in not equal to `Size { raw: 1 }` and returns the `size` value of the `ScalarInt` in
  // that case.

compiler/rustc_span/src/def_id.rs

@@ -34,7 +34,7 @@ impl CrateNum {
 
 impl fmt::Display for CrateNum {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Display::fmt(&self.private, f)
+ fmt::Display::fmt(&self.as_u32(), f)
  }
 }
 

compiler/rustc_span/src/hygiene.rs

@@ -76,7 +76,7 @@ pub struct ExpnId {
 impl fmt::Debug for ExpnId {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  // Generate crate_::{{expn_}}.
- write!(f, "{:?}::{{{{expn{}}}}}", self.krate, self.local_id.private)
+ write!(f, "{:?}::{{{{expn{}}}}}", self.krate, self.local_id.as_u32())
  }
 }