From a3ca2db48aff772b0ff4e317c22681332eda0293 Mon Sep 17 00:00:00 2001
From: Scott Olson <scott@solson.me>
Date: Mon, 28 Dec 2015 22:24:05 -0600
Subject: [PATCH] Add support for references.

---
 src/interpreter.rs | 28 +++++++++++++++++++---------
 test/basic.rs      | 28 ++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/src/interpreter.rs b/src/interpreter.rs
index f5a60770f7fd..e290a8d0c731 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -14,6 +14,7 @@ enum Value {
     Uninit,
     Bool(bool),
     Int(i64), // FIXME(tsion): Should be bit-width aware.
+    Pointer(Pointer),
     Adt { variant: usize, data_ptr: Pointer },
     Func(def_id::DefId),
 }
@@ -247,18 +248,23 @@ impl<'a, 'tcx> Interpreter<'a, 'tcx> {
 
                     mir::ProjectionElem::Downcast(_, variant) => {
                         let adt_val = self.read_pointer(base_ptr);
-
-                        match adt_val {
-                            Value::Adt { variant: actual_variant, data_ptr } => {
-                                debug_assert_eq!(variant, actual_variant);
-                                data_ptr
-                            }
-
-                            _ => panic!("Downcast attempted on non-Adt: {:?}", adt_val),
+                        if let Value::Adt { variant: actual_variant, data_ptr } = adt_val {
+                            debug_assert_eq!(variant, actual_variant);
+                            data_ptr
+                        } else {
+                            panic!("Downcast attempted on non-ADT: {:?}", adt_val)
+                        }
+                    }
+
+                    mir::ProjectionElem::Deref => {
+                        let ptr_val = self.read_pointer(base_ptr);
+                        if let Value::Pointer(ptr) = ptr_val {
+                            ptr
+                        } else {
+                            panic!("Deref attempted on non-pointer: {:?}", ptr_val)
                         }
                     }
 
-                    mir::ProjectionElem::Deref => unimplemented!(),
                     mir::ProjectionElem::Index(ref _operand) => unimplemented!(),
                     mir::ProjectionElem::ConstantIndex { .. } => unimplemented!(),
                 }
@@ -313,6 +319,10 @@ impl<'a, 'tcx> Interpreter<'a, 'tcx> {
                 }
             }
 
+            mir::Rvalue::Ref(_region, _kind, ref lvalue) => {
+                Value::Pointer(self.eval_lvalue(lvalue))
+            }
+
             mir::Rvalue::Aggregate(mir::AggregateKind::Adt(ref adt_def, variant, _substs),
                                    ref operands) => {
                 let max_fields = adt_def.variants
diff --git a/test/basic.rs b/test/basic.rs
index a4d0b4eb8b2d..923abb1b80ea 100644
--- a/test/basic.rs
+++ b/test/basic.rs
@@ -94,6 +94,34 @@ fn match_int() -> i32 {
     }
 }
 
+#[miri_run(expected = "Int(1)")]
+fn one_line_ref() -> i32 {
+    *&1
+}
+
+#[miri_run(expected = "Int(1)")]
+fn basic_ref() -> i32 {
+    let x = &1;
+    *x
+}
+
+#[miri_run(expected = "Int(3)")]
+fn basic_ref_mut() -> i32 {
+    let x = &mut 1;
+    *x += 2;
+    *x
+}
+
+#[miri_run(expected = "Int(3)")]
+fn basic_ref_mut_var() -> i32 {
+    let mut a = 1;
+    {
+        let x = &mut a;
+        *x += 2;
+    }
+    a
+}
+
 // #[miri_run(expected = "Int(4)")]
 // fn match_int_range() -> i32 {
 //     let n = 42;