desc { "destructure constant" }
}
+ /// Dereference a constant reference or raw pointer and turn the result into a constant
+ /// again.
+ query deref_const(
+ key: ty::ParamEnvAnd<'tcx, &'tcx ty::Const<'tcx>>
+ ) -> &'tcx ty::Const<'tcx> {
+ desc { "deref constant" }
+ }
+
query const_caller_location(key: (rustc_span::Symbol, u32, u32)) -> ConstValue<'tcx> {
desc { "get a &core::panic::Location referring to a span" }
}
use std::convert::TryFrom;
+use rustc_hir::Mutability;
use rustc_middle::mir;
use rustc_middle::ty::{self, TyCtxt};
use rustc_span::{source_map::DUMMY_SP, symbol::Symbol};
-use crate::interpret::{intern_const_alloc_recursive, ConstValue, InternKind, InterpCx};
+use crate::interpret::{
+ intern_const_alloc_recursive, ConstValue, InternKind, InterpCx, MemPlaceMeta, Scalar,
+};
mod error;
mod eval_queries;
mir::DestructuredConst { variant, fields }
}
+
+pub(crate) fn deref_const<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ param_env: ty::ParamEnv<'tcx>,
+ val: &'tcx ty::Const<'tcx>,
+) -> &'tcx ty::Const<'tcx> {
+ trace!("deref_const: {:?}", val);
+ let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, false);
+ let op = ecx.const_to_op(val, None).unwrap();
+ let mplace = ecx.deref_operand(op).unwrap();
+ if let Scalar::Ptr(ptr) = mplace.ptr {
+ assert_eq!(
+ ecx.memory.get_raw(ptr.alloc_id).unwrap().mutability,
+ Mutability::Not,
+ "deref_const cannot be used with mutable allocations as \
+ that could allow pattern matching to observe mutable statics",
+ );
+ }
+
+ let ty = match mplace.meta {
+ MemPlaceMeta::None => mplace.layout.ty,
+ MemPlaceMeta::Poison => bug!("poison metadata in `deref_const`: {:#?}", mplace),
+ // In case of unsized types, figure out the real type behind.
+ MemPlaceMeta::Meta(scalar) => match mplace.layout.ty.kind {
+ ty::Dynamic(..) => ecx.read_drop_type_from_vtable(scalar).unwrap().1,
+ ty::Str => bug!("there's no sized equivalent of a `str`"),
+ ty::Slice(elem_ty) => tcx.mk_array(elem_ty, scalar.to_machine_usize(&tcx).unwrap()),
+ _ => bug!(
+ "type {} should not have metadata, but had {:?}",
+ mplace.layout.ty,
+ mplace.meta
+ ),
+ },
+ };
+
+ tcx.mk_const(ty::Const { val: ty::ConstKind::Value(op_to_const(&ecx, mplace.into())), ty })
+}