From 756d73b3ca9a64a8d0d6e3b7d0dd29b6cac853be Mon Sep 17 00:00:00 2001
From: Scott Olson <scott@solson.me>
Date: Thu, 30 Jun 2016 21:30:03 -0600
Subject: [PATCH] Remove filling drop to prep for elaborated drops.

---
 src/interpreter/mod.rs        |  3 ---
 src/interpreter/terminator.rs | 36 +++++++----------------------------
 src/lib.rs                    |  1 -
 src/memory.rs                 |  6 +-----
 4 files changed, 8 insertions(+), 38 deletions(-)

diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index d17640bb675..dd352cc2410 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -820,9 +820,6 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
     fn move_(&mut self, src: Pointer, dest: Pointer, ty: Ty<'tcx>) -> EvalResult<'tcx, ()> {
         let size = self.type_size(ty);
         self.memory.copy(src, dest, size)?;
-        if self.type_needs_drop(ty) {
-            self.memory.drop_fill(src, size)?;
-        }
         Ok(())
     }
 
diff --git a/src/interpreter/terminator.rs b/src/interpreter/terminator.rs
index 536d9b678ab..a9bb1fa5317 100644
--- a/src/interpreter/terminator.rs
+++ b/src/interpreter/terminator.rs
@@ -6,7 +6,7 @@ use rustc::ty::layout::Layout;
 use rustc::ty::subst::{self, Substs};
 use rustc::ty::{self, Ty, TyCtxt, BareFnTy};
 use std::rc::Rc;
-use std::{iter, mem};
+use std::iter;
 use syntax::{ast, attr};
 use syntax::codemap::{DUMMY_SP, Span};
 
@@ -303,11 +303,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                 self.memory.write_uint(dest, discr_val, 8)?;
             }
 
-            "forget" => {
-                let arg_ty = *substs.types.get(subst::FnSpace, 0);
-                let arg_size = self.type_size(arg_ty);
-                self.memory.drop_fill(args_ptrs[0], arg_size)?;
-            }
+            "forget" => {}
 
             "init" => self.memory.write_repeat(dest, 0, dest_layout.size(&self.tcx.data_layout).bytes() as usize)?,
 
@@ -549,35 +545,17 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         // TODO(solson): Call user-defined Drop::drop impls.
 
         match ty.sty {
-            ty::TyBox(contents_ty) => {
-                match self.memory.read_ptr(ptr) {
-                    Ok(contents_ptr) => {
-                        self.drop(contents_ptr, contents_ty)?;
-                        trace!("-deallocating box");
-                        self.memory.deallocate(contents_ptr)?;
-                    }
-                    Err(EvalError::ReadBytesAsPointer) => {
-                        let size = self.memory.pointer_size();
-                        let possible_drop_fill = self.memory.read_bytes(ptr, size)?;
-                        if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
-                            return Ok(());
-                        } else {
-                            return Err(EvalError::ReadBytesAsPointer);
-                        }
-                    }
-                    Err(e) => return Err(e),
-                }
+            ty::TyBox(_contents_ty) => {
+                let contents_ptr = self.memory.read_ptr(ptr)?;
+                // self.drop(contents_ptr, contents_ty)?;
+                trace!("-deallocating box");
+                self.memory.deallocate(contents_ptr)?;
             }
 
             // TODO(solson): Implement drop for other relevant types (e.g. aggregates).
             _ => {}
         }
 
-        // Filling drop.
-        // FIXME(solson): Trait objects (with no static size) probably get filled, too.
-        let size = self.type_size(ty);
-        self.memory.drop_fill(ptr, size)?;
-
         Ok(())
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index 93dfe4e2201..83a1aeec68b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,7 +2,6 @@
     btree_range,
     collections,
     collections_bound,
-    filling_drop,
     question_mark,
     rustc_private,
     pub_restricted,
diff --git a/src/memory.rs b/src/memory.rs
index e3e4279049a..64c105a4e7f 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -1,7 +1,7 @@
 use byteorder::{ReadBytesExt, WriteBytesExt, LittleEndian, BigEndian, self};
 use std::collections::Bound::{Included, Excluded};
 use std::collections::{btree_map, BTreeMap, HashMap, HashSet, VecDeque};
-use std::{fmt, iter, mem, ptr};
+use std::{fmt, iter, ptr};
 
 use rustc::hir::def_id::DefId;
 use rustc::ty::BareFnTy;
@@ -340,10 +340,6 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
         Ok(())
     }
 
-    pub fn drop_fill(&mut self, ptr: Pointer, size: usize) -> EvalResult<'tcx, ()> {
-        self.write_repeat(ptr, mem::POST_DROP_U8, size)
-    }
-
     pub fn read_ptr(&self, ptr: Pointer) -> EvalResult<'tcx, Pointer> {
         let size = self.pointer_size();
         self.check_defined(ptr, size)?;