85 lines
3.2 KiB
Rust
85 lines
3.2 KiB
Rust
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use rustc_middle::ty::{self, TyCtxt};
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use rustc_target::abi::VariantIdx;
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/// Tries to destructure constants of type Array or Adt into the constants
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/// of its fields.
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pub(crate) fn destructure_const<'tcx>(
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tcx: TyCtxt<'tcx>,
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const_: ty::Const<'tcx>,
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) -> ty::DestructuredConst<'tcx> {
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if let ty::ConstKind::Value(valtree) = const_.kind() {
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let branches = match valtree {
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ty::ValTree::Branch(b) => b,
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_ => bug!("cannot destructure constant {:?}", const_),
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};
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let (fields, variant) = match const_.ty().kind() {
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ty::Array(inner_ty, _) | ty::Slice(inner_ty) => {
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// construct the consts for the elements of the array/slice
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let field_consts = branches
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.iter()
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.map(|b| {
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tcx.mk_const(ty::ConstS { kind: ty::ConstKind::Value(*b), ty: *inner_ty })
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})
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.collect::<Vec<_>>();
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debug!(?field_consts);
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(field_consts, None)
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}
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ty::Adt(def, _) if def.variants().is_empty() => bug!("unreachable"),
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ty::Adt(def, substs) => {
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let variant_idx = if def.is_enum() {
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VariantIdx::from_u32(branches[0].unwrap_leaf().try_to_u32().unwrap())
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} else {
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VariantIdx::from_u32(0)
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};
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let fields = &def.variant(variant_idx).fields;
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let mut field_consts = Vec::with_capacity(fields.len());
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// Note: First element inValTree corresponds to variant of enum
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let mut valtree_idx = if def.is_enum() { 1 } else { 0 };
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for field in fields {
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let field_ty = field.ty(tcx, substs);
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let field_valtree = branches[valtree_idx]; // first element of branches is variant
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let field_const = tcx.mk_const(ty::ConstS {
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kind: ty::ConstKind::Value(field_valtree),
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ty: field_ty,
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});
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field_consts.push(field_const);
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valtree_idx += 1;
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}
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debug!(?field_consts);
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(field_consts, Some(variant_idx))
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}
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ty::Tuple(elem_tys) => {
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let fields = elem_tys
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.iter()
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.enumerate()
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.map(|(i, elem_ty)| {
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let elem_valtree = branches[i];
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tcx.mk_const(ty::ConstS {
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kind: ty::ConstKind::Value(elem_valtree),
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ty: elem_ty,
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})
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})
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.collect::<Vec<_>>();
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(fields, None)
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}
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_ => bug!("cannot destructure constant {:?}", const_),
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};
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let fields = tcx.arena.alloc_from_iter(fields.into_iter());
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ty::DestructuredConst { variant, fields }
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} else {
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bug!("cannot destructure constant {:?}", const_)
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}
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}
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pub fn provide(providers: &mut ty::query::Providers) {
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*providers =
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ty::query::Providers { destructure_const, ..*providers };
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}
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