From ca8c23e448bef1ce350ff8cf0e2cb787ffb48d96 Mon Sep 17 00:00:00 2001
From: Folkert <folkert@folkertdev.nl>
Date: Wed, 3 Mar 2021 20:05:02 +0100
Subject: [PATCH] fix up zig code

---
 compiler/builtins/bitcode/src/list.zig | 48 ++++++++++++++++++++++----
 compiler/gen/src/llvm/build.rs         |  4 +--
 2 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/compiler/builtins/bitcode/src/list.zig b/compiler/builtins/bitcode/src/list.zig
index cdcd659208..5b8847c92d 100644
--- a/compiler/builtins/bitcode/src/list.zig
+++ b/compiler/builtins/bitcode/src/list.zig
@@ -95,6 +95,7 @@ pub const RocList = extern struct {
             const dest_ptr = first_slot;
 
             @memcpy(dest_ptr, source_ptr, old_length * element_width);
+            @memset(dest_ptr + old_length * element_width, 0, delta_length * element_width);
         }
 
         // NOTE the newly added elements are left uninitialized
@@ -246,19 +247,35 @@ pub fn listWalk(list: RocList, stepper: Opaque, stepper_caller: Caller2, accum:
         return;
     }
 
-    @memcpy(output orelse unreachable, accum orelse unreachable, accum_width);
+    if (list.isEmpty()) {
+        @memcpy(output orelse unreachable, accum orelse unreachable, accum_width);
+        return;
+    }
+
+    const alloc: [*]u8 = @ptrCast([*]u8, std.heap.c_allocator.alloc(u8, accum_width) catch unreachable);
+    var b1 = output orelse unreachable;
+    var b2 = alloc;
+
+    @memcpy(b2, accum orelse unreachable, accum_width);
 
     if (list.bytes) |source_ptr| {
         var i: usize = 0;
         const size = list.len();
         while (i < size) : (i += 1) {
             const element = source_ptr + i * element_width;
-            stepper_caller(stepper, element, output, output);
-        }
+            stepper_caller(stepper, element, b2, b1);
 
-        const data_bytes = list.len() * element_width;
-        utils.decref(std.heap.c_allocator, alignment, list.bytes, data_bytes);
+            const temp = b1;
+            b2 = b1;
+            b1 = temp;
+        }
     }
+
+    @memcpy(output orelse unreachable, b2, accum_width);
+    std.heap.c_allocator.free(alloc[0..accum_width]);
+
+    const data_bytes = list.len() * element_width;
+    utils.decref(std.heap.c_allocator, alignment, list.bytes, data_bytes);
 }
 
 pub fn listWalkBackwards(list: RocList, stepper: Opaque, stepper_caller: Caller2, accum: Opaque, alignment: usize, element_width: usize, accum_width: usize, output: Opaque) callconv(.C) void {
@@ -266,7 +283,16 @@ pub fn listWalkBackwards(list: RocList, stepper: Opaque, stepper_caller: Caller2
         return;
     }
 
-    @memcpy(output orelse unreachable, accum orelse unreachable, accum_width);
+    if (list.isEmpty()) {
+        @memcpy(output orelse unreachable, accum orelse unreachable, accum_width);
+        return;
+    }
+
+    const alloc: [*]u8 = @ptrCast([*]u8, std.heap.c_allocator.alloc(u8, accum_width) catch unreachable);
+    var b1 = output orelse unreachable;
+    var b2 = alloc;
+
+    @memcpy(b2, accum orelse unreachable, accum_width);
 
     if (list.bytes) |source_ptr| {
         const size = list.len();
@@ -275,11 +301,21 @@ pub fn listWalkBackwards(list: RocList, stepper: Opaque, stepper_caller: Caller2
             i -= 1;
             const element = source_ptr + i * element_width;
             stepper_caller(stepper, element, output, output);
+
+            const temp = b1;
+            b2 = b1;
+            b1 = temp;
         }
 
         const data_bytes = list.len() * element_width;
         utils.decref(std.heap.c_allocator, alignment, list.bytes, data_bytes);
     }
+
+    @memcpy(output orelse unreachable, b2, accum_width);
+    std.heap.c_allocator.free(alloc[0..accum_width]);
+
+    const data_bytes = list.len() * element_width;
+    utils.decref(std.heap.c_allocator, alignment, list.bytes, data_bytes);
 }
 
 // List.contains : List k, k -> Bool
diff --git a/compiler/gen/src/llvm/build.rs b/compiler/gen/src/llvm/build.rs
index 506dec1253..923fc7147f 100644
--- a/compiler/gen/src/llvm/build.rs
+++ b/compiler/gen/src/llvm/build.rs
@@ -1104,7 +1104,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             let tag_field_layouts = &fields[*tag_id as usize];
 
             for (field_symbol, tag_field_layout) in arguments.iter().zip(tag_field_layouts.iter()) {
-                let (val, val_layout) = load_symbol_and_layout(scope, field_symbol);
+                let (val, _val_layout) = load_symbol_and_layout(scope, field_symbol);
 
                 // Zero-sized fields have no runtime representation.
                 // The layout of the struct expects them to be dropped!
@@ -1127,7 +1127,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                         field_vals.push(ptr);
                     } else {
                         // this check fails for recursive tag unions, but can be helpful while debugging
-                        debug_assert_eq!(tag_field_layout, val_layout);
+                        // debug_assert_eq!(tag_field_layout, val_layout);
 
                         field_vals.push(val);
                     }