Rollup merge of #98429 - b-naber:use-correct-substs-discriminant-cast, r=lcnr
Use correct substs in enum discriminant cast Fixes https://github.com/rust-lang/rust/issues/97634 r? ```@lcnr```
This commit is contained in:
Matthias Krüger
GitHub
commit
ea07b969ea
@ -1,3 +1,4 @@
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use crate::thir::cx::region::Scope;
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use crate::thir::cx::Cx;
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use crate::thir::util::UserAnnotatedTyHelpers;
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use rustc_data_structures::stack::ensure_sufficient_stack;
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@ -158,6 +159,98 @@ fn apply_adjustment(
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Expr { temp_lifetime, ty: adjustment.target, span, kind }
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}
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/// Lowers a cast expression.
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///
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/// Dealing with user type annotations is left to the caller.
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fn mirror_expr_cast(
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&mut self,
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source: &'tcx hir::Expr<'tcx>,
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temp_lifetime: Option<Scope>,
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span: Span,
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) -> ExprKind<'tcx> {
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let tcx = self.tcx;
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// Check to see if this cast is a "coercion cast", where the cast is actually done
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// using a coercion (or is a no-op).
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if self.typeck_results().is_coercion_cast(source.hir_id) {
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// Convert the lexpr to a vexpr.
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ExprKind::Use { source: self.mirror_expr(source) }
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} else if self.typeck_results().expr_ty(source).is_region_ptr() {
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// Special cased so that we can type check that the element
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// type of the source matches the pointed to type of the
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// destination.
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ExprKind::Pointer {
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source: self.mirror_expr(source),
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cast: PointerCast::ArrayToPointer,
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}
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} else {
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// check whether this is casting an enum variant discriminant
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// to prevent cycles, we refer to the discriminant initializer
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// which is always an integer and thus doesn't need to know the
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// enum's layout (or its tag type) to compute it during const eval
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// Example:
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// enum Foo {
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// A,
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// B = A as isize + 4,
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// }
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// The correct solution would be to add symbolic computations to miri,
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// so we wouldn't have to compute and store the actual value
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let hir::ExprKind::Path(ref qpath) = source.kind else {
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return ExprKind::Cast { source: self.mirror_expr(source)};
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};
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let res = self.typeck_results().qpath_res(qpath, source.hir_id);
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let ty = self.typeck_results().node_type(source.hir_id);
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let ty::Adt(adt_def, substs) = ty.kind() else {
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return ExprKind::Cast { source: self.mirror_expr(source)};
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};
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let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Const), variant_ctor_id) = res else {
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return ExprKind::Cast { source: self.mirror_expr(source)};
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};
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let idx = adt_def.variant_index_with_ctor_id(variant_ctor_id);
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let (discr_did, discr_offset) = adt_def.discriminant_def_for_variant(idx);
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use rustc_middle::ty::util::IntTypeExt;
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let ty = adt_def.repr().discr_type();
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let discr_ty = ty.to_ty(tcx);
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let param_env_ty = self.param_env.and(discr_ty);
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let size = tcx
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.layout_of(param_env_ty)
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.unwrap_or_else(|e| {
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panic!("could not compute layout for {:?}: {:?}", param_env_ty, e)
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})
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.size;
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let lit = ScalarInt::try_from_uint(discr_offset as u128, size).unwrap();
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let kind = ExprKind::NonHirLiteral { lit, user_ty: None };
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let offset = self.thir.exprs.push(Expr { temp_lifetime, ty: discr_ty, span, kind });
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let source = match discr_did {
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// in case we are offsetting from a computed discriminant
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// and not the beginning of discriminants (which is always `0`)
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Some(did) => {
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let kind = ExprKind::NamedConst { def_id: did, substs, user_ty: None };
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let lhs =
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self.thir.exprs.push(Expr { temp_lifetime, ty: discr_ty, span, kind });
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let bin = ExprKind::Binary { op: BinOp::Add, lhs, rhs: offset };
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self.thir.exprs.push(Expr {
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temp_lifetime,
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ty: discr_ty,
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span: span,
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kind: bin,
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})
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}
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None => offset,
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};
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ExprKind::Cast { source }
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}
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}
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fn make_mirror_unadjusted(&mut self, expr: &'tcx hir::Expr<'tcx>) -> Expr<'tcx> {
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let tcx = self.tcx;
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let expr_ty = self.typeck_results().expr_ty(expr);
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@ -604,98 +697,7 @@ fn make_mirror_unadjusted(&mut self, expr: &'tcx hir::Expr<'tcx>) -> Expr<'tcx>
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expr, cast_ty.hir_id, user_ty,
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);
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// Check to see if this cast is a "coercion cast", where the cast is actually done
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// using a coercion (or is a no-op).
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let cast = if self.typeck_results().is_coercion_cast(source.hir_id) {
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// Convert the lexpr to a vexpr.
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ExprKind::Use { source: self.mirror_expr(source) }
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} else if self.typeck_results().expr_ty(source).is_region_ptr() {
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// Special cased so that we can type check that the element
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// type of the source matches the pointed to type of the
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// destination.
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ExprKind::Pointer {
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source: self.mirror_expr(source),
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cast: PointerCast::ArrayToPointer,
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}
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} else {
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// check whether this is casting an enum variant discriminant
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// to prevent cycles, we refer to the discriminant initializer
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// which is always an integer and thus doesn't need to know the
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// enum's layout (or its tag type) to compute it during const eval
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// Example:
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// enum Foo {
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// A,
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// B = A as isize + 4,
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// }
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// The correct solution would be to add symbolic computations to miri,
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// so we wouldn't have to compute and store the actual value
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let var = if let hir::ExprKind::Path(ref qpath) = source.kind {
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let res = self.typeck_results().qpath_res(qpath, source.hir_id);
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self.typeck_results().node_type(source.hir_id).ty_adt_def().and_then(
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|adt_def| match res {
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Res::Def(
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DefKind::Ctor(CtorOf::Variant, CtorKind::Const),
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variant_ctor_id,
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) => {
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let idx = adt_def.variant_index_with_ctor_id(variant_ctor_id);
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let (d, o) = adt_def.discriminant_def_for_variant(idx);
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use rustc_middle::ty::util::IntTypeExt;
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let ty = adt_def.repr().discr_type();
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let ty = ty.to_ty(tcx);
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Some((d, o, ty))
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}
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_ => None,
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},
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)
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} else {
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None
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};
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let source = if let Some((did, offset, var_ty)) = var {
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let param_env_ty = self.param_env.and(var_ty);
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let size = tcx
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.layout_of(param_env_ty)
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.unwrap_or_else(|e| {
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panic!("could not compute layout for {:?}: {:?}", param_env_ty, e)
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})
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.size;
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let lit = ScalarInt::try_from_uint(offset as u128, size).unwrap();
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let kind = ExprKind::NonHirLiteral { lit, user_ty: None };
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let offset = self.thir.exprs.push(Expr {
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temp_lifetime,
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ty: var_ty,
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span: expr.span,
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kind,
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});
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match did {
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Some(did) => {
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// in case we are offsetting from a computed discriminant
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// and not the beginning of discriminants (which is always `0`)
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let substs = InternalSubsts::identity_for_item(tcx, did);
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let kind =
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ExprKind::NamedConst { def_id: did, substs, user_ty: None };
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let lhs = self.thir.exprs.push(Expr {
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temp_lifetime,
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ty: var_ty,
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span: expr.span,
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kind,
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});
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let bin = ExprKind::Binary { op: BinOp::Add, lhs, rhs: offset };
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self.thir.exprs.push(Expr {
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temp_lifetime,
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ty: var_ty,
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span: expr.span,
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kind: bin,
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})
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}
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None => offset,
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}
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} else {
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self.mirror_expr(source)
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};
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ExprKind::Cast { source: source }
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};
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let cast = self.mirror_expr_cast(*source, temp_lifetime, expr.span);
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if let Some(user_ty) = user_ty {
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// NOTE: Creating a new Expr and wrapping a Cast inside of it may be
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10
src/test/ui/const-generics/issues/issue-97634.rs
Normal file
10
src/test/ui/const-generics/issues/issue-97634.rs
Normal file
@ -0,0 +1,10 @@
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// build-pass
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pub enum Register<const N: u16> {
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Field0 = 40,
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Field1,
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}
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fn main() {
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let _b = Register::<0>::Field1 as u16;
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}
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