From d7842c79e3b1ea16db0a8a78b3654ea14bfbf6f0 Mon Sep 17 00:00:00 2001
From: Noah <33094578+coolreader18@users.noreply.github.com>
Date: Fri, 24 Apr 2020 15:14:58 -0500
Subject: [PATCH 1/2] Disable the unpack optimization

---
 compiler/src/peephole.rs               |  2 +-
 compiler/src/peephole/optimizations.rs | 47 +++++++++++++-------------
 2 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/compiler/src/peephole.rs b/compiler/src/peephole.rs
index 67a4b9efe0..aaec0470c7 100644
--- a/compiler/src/peephole.rs
+++ b/compiler/src/peephole.rs
@@ -92,7 +92,7 @@ impl<O: OutputStream> PeepholeOptimizer<O> {
     }
 
     fn optimize(&mut self) {
-        apply_optimizations!(self, operator, unpack);
+        apply_optimizations!(self, operator /* , unpack */);
     }
 }
 
diff --git a/compiler/src/peephole/optimizations.rs b/compiler/src/peephole/optimizations.rs
index 28bac862c9..461baa7cc2 100644
--- a/compiler/src/peephole/optimizations.rs
+++ b/compiler/src/peephole/optimizations.rs
@@ -73,26 +73,27 @@ pub fn operator(buf: &mut impl OptimizationBuffer) {
     }
 }
 
-pub fn unpack(buf: &mut impl OptimizationBuffer) {
-    let (instruction, meta) = buf.pop();
-    if let Instruction::UnpackSequence { size } = instruction {
-        let (arg, arg_meta) = buf.pop();
-        match arg {
-            Instruction::BuildTuple {
-                size: tup_size,
-                unpack,
-            } if !unpack && tup_size == size => {
-                buf.emit(
-                    Instruction::Reverse { amount: size },
-                    vec![arg_meta, meta].into(),
-                );
-            }
-            arg => {
-                buf.emit(arg, arg_meta);
-                buf.emit(instruction, meta);
-            }
-        }
-    } else {
-        buf.emit(instruction, meta)
-    }
-}
+// TODO: make a version of this that doesn't miscompile `a, b = (1, 2) if True else (3, 4)`
+// pub fn unpack(buf: &mut impl OptimizationBuffer) {
+//     let (instruction, meta) = buf.pop();
+//     if let Instruction::UnpackSequence { size } = instruction {
+//         let (arg, arg_meta) = buf.pop();
+//         match arg {
+//             Instruction::BuildTuple {
+//                 size: tup_size,
+//                 unpack,
+//             } if !unpack && tup_size == size => {
+//                 buf.emit(
+//                     Instruction::Reverse { amount: size },
+//                     vec![arg_meta, meta].into(),
+//                 );
+//             }
+//             arg => {
+//                 buf.emit(arg, arg_meta);
+//                 buf.emit(instruction, meta);
+//             }
+//         }
+//     } else {
+//         buf.emit(instruction, meta)
+//     }
+// }

From c50ab85bbb971328be75f0418ea80af7dd19bbb9 Mon Sep 17 00:00:00 2001
From: Noah <33094578+coolreader18@users.noreply.github.com>
Date: Sat, 25 Apr 2020 02:15:14 -0500
Subject: [PATCH 2/2] Add test for unpack regression

---
 tests/snippets/if_expressions.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/snippets/if_expressions.py b/tests/snippets/if_expressions.py
index 143cb64580..ac5f492730 100644
--- a/tests/snippets/if_expressions.py
+++ b/tests/snippets/if_expressions.py
@@ -24,3 +24,7 @@ def func2():
     return 20
 
 assert ret(func1() or func2()) == 20
+
+a, b = (1, 2) if True else (3, 4)
+assert a == 1
+assert b == 2