You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: place_encoding.rs
    path of file: ./repos/prusti-dev/prusti-viper/src/encoder/mir_encoder
    
    the code of the file until where you have to start completion: // Â© 2019-2020, ETH Zurich
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

use std::fmt::Display;

use prusti_rustc_interface::middle::ty;
use vir_crate::polymorphic as vir;

use crate::encoder::errors::{EncodingError, EncodingResult};

/// Result of encoding a place
#[derive(Debug, PartialEq, Eq, Hash, Clone)]
pub enum PlaceEncoding<'tcx> {
    /// Just an expression, the most common case.
    Expr(vir::Expr),
    /// Field access expression
    FieldAccess {
        base: Box<PlaceEncoding<'tcx>>,
        field: vir::Field,
    },
    /// Array access expression
    ArrayAccess {
        base: Box<PlaceEncoding<'tcx>>,
        index: vir::Expr,
        encoded_elem_ty: vir::Type,
        rust_array_ty: ty::Ty<'tcx>,
    },
    /// Variant (i.e. enum access)
    Variant {
        base: Box<PlaceEncoding<'tcx>>,
        field: vir::Field,
    },
    /// Slice indexing projection
    SliceAccess {
        base: Box<PlaceEncoding<'tcx>>,
        index: vir::Expr,
        encoded_elem_ty: vir::Type,
        rust_slice_ty: ty::Ty<'tcx>,
    },
}

/// Return type of PlaceEncoding::into_array_base
pub enum ExprOrArrayBase {
    Expr(vir::Expr),
    ArrayBase(vir::Expr),
    #[allow(dead_code)]
    SliceBase(vir::Expr),
}

impl<'tcx> PlaceEncoding<'tcx> {
    pub fn t
    
    pub fn into_array_base(self) -> ExprOrArrayBase {
        match self {
            PlaceEncoding::Expr(e) => ExprOrArrayBase::Expr(e),
            PlaceEncoding::FieldAccess { base, field } => match base.into_array_base() {
                ExprOrArrayBase::Expr(e) => ExprOrArrayBase::Expr(e.field(field)),
                base @ ExprOrArrayBase::ArrayBase(_) => base,
                base @ ExprOrArrayBase::SliceBase(_) => base,
            },
            PlaceEncoding::Variant { base, field } => match base.into_array_base() {
                ExprOrArrayBase::Expr(e) => {
                    ExprOrArrayBase::Expr(vir::Expr::Variant(vir::Variant {
                        base: Box::new(e),
                        variant_index: field,
                        position: vir::Position::default(),
                    }))
                }
                base @ ExprOrArrayBase::ArrayBase(_) => base,
                base @ ExprOrArrayBase::SliceBase(_) => base,
            },
            PlaceEncoding::ArrayAccess { base, .. } => {
                // need to check base's into_expr_or_array_base, maybe we're not the outermost
                // array
                match base.into_array_base() {
                    ExprOrArrayBase::Expr(e) => ExprOrArrayBase::ArrayBase(e),
                    base @ ExprOrArrayBase::ArrayBase(_) => base,
                    base @ ExprOrArrayBase::SliceBase(_) => base,
                }
            }
            PlaceEncoding::SliceAccess { base, .. } => match base.into_array_base() {
                ExprOrArrayBase::Expr(e) => ExprOrArrayBase::SliceBase(e),
                base @ ExprOrArrayBase::ArrayBase(_) => base,
                base @ ExprOrArrayBase::SliceBase(_) => base,
            },
        }
    }