From c7244afea1bd6254f9417b47a2afaaeee15eee1a Mon Sep 17 00:00:00 2001
From: Scott Olson <scott@solson.me>
Date: Thu, 19 Nov 2015 16:49:13 -0600
Subject: [PATCH] Implement SwitchInt (for some match expressions).

---
 src/interpreter.rs | 16 ++++++++++++----
 test/basic.rs      | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/src/interpreter.rs b/src/interpreter.rs
index 596f539060fc..6f2f604d84ec 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -6,7 +6,7 @@ use syntax::attr::AttrMetaMethods;
 
 use std::iter;
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq)]
 enum Value {
     Uninit,
     Bool(bool),
@@ -120,11 +120,19 @@ impl<'a, 'tcx> Interpreter<'a, 'tcx> {
                     }
                 }
 
-                _ => unimplemented!(),
+                SwitchInt { ref discr, switch_ty: _, ref values, ref targets } => {
+                    let discr_val = &self.value_stack[self.eval_lvalue(discr)];
+
+                    let index = values.iter().position(|v| *discr_val == self.eval_constant(v))
+                        .expect("discriminant matched no values");
+
+                    block = targets[index];
+                }
+
                 // Diverge => unimplemented!(),
                 // Panic { target } => unimplemented!(),
                 // Switch { ref discr, adt_def, ref targets } => unimplemented!(),
-                // SwitchInt { ref discr, switch_ty, ref values, ref targets } => unimplemented!(),
+                _ => unimplemented!(),
             }
         }
 
@@ -220,7 +228,7 @@ impl<'a, 'tcx> Interpreter<'a, 'tcx> {
             Uint(_u) => unimplemented!(),
             Str(ref _s) => unimplemented!(),
             ByteStr(ref _bs) => unimplemented!(),
-            Bool(_b) => unimplemented!(),
+            Bool(b) => Value::Bool(b),
             Struct(_node_id) => unimplemented!(),
             Tuple(_node_id) => unimplemented!(),
             Function(_def_id) => unimplemented!(),
diff --git a/test/basic.rs b/test/basic.rs
index 99a3fb39ad2c..bd60733b3d07 100644
--- a/test/basic.rs
+++ b/test/basic.rs
@@ -73,4 +73,38 @@ fn factorial_recursive() -> i32 {
     fact(10)
 }
 
+#[miri_run(expected = "Int(1)")]
+fn match_bool() -> i32 {
+    let b = true;
+    match b {
+        true => 1,
+        false => 0,
+    }
+}
+
+#[miri_run(expected = "Int(20)")]
+fn match_int() -> i32 {
+    let n = 2;
+    match n {
+        0 => 0,
+        1 => 10,
+        2 => 20,
+        3 => 30,
+        _ => 100,
+    }
+}
+
+// #[miri_run(expected = "Int(4)")]
+// fn match_int_range() -> i32 {
+//     let n = 42;
+//     match n {
+//         0...9 => 0,
+//         10...19 => 1,
+//         20...29 => 2,
+//         30...39 => 3,
+//         40...49 => 4,
+//         _ => 5,
+//     }
+// }
+
 fn main() {}