Merge pull request #6462 from roc-lang/list-prepend-bug

List prepend bug

crates/compiler/gen_dev/src/generic64/mod.rs

@@ -3299,7 +3299,7 @@ impl<
         let elem_layout = arg_layouts[1];
 
         // List alignment argument (u32).
-        self.load_layout_alignment(*ret_layout, Symbol::DEV_TMP);
+        self.load_layout_alignment(elem_layout, Symbol::DEV_TMP);
 
         // Have to pass the input element by pointer, so put it on the stack and load it's address.
         self.storage_manager

crates/compiler/gen_wasm/src/wasm32_sized.rs

@@ -75,19 +75,36 @@ impl Wasm32Sized for isize {
     const ALIGN_OF_WASM: usize = 4;
 }
 
+const fn next_multiple_of(lhs: usize, rhs: usize) -> usize {
+    if lhs == 0 {
+        return lhs;
+    }
+
+    match lhs % rhs {
+        0 => lhs,
+        r => lhs + (rhs - r),
+    }
+}
+
 impl<T: Wasm32Sized, U: Wasm32Sized> Wasm32Sized for (T, U) {
-    const SIZE_OF_WASM: usize = T::SIZE_OF_WASM + U::SIZE_OF_WASM;
+    const SIZE_OF_WASM: usize =
+        next_multiple_of(T::SIZE_OF_WASM + U::SIZE_OF_WASM, Self::ALIGN_OF_WASM);
     const ALIGN_OF_WASM: usize = max(&[T::ALIGN_OF_WASM, U::ALIGN_OF_WASM]);
 }
 
 impl<T: Wasm32Sized, U: Wasm32Sized, V: Wasm32Sized> Wasm32Sized for (T, U, V) {
-    const SIZE_OF_WASM: usize = T::SIZE_OF_WASM + U::SIZE_OF_WASM + V::SIZE_OF_WASM;
+    const SIZE_OF_WASM: usize = next_multiple_of(
+        T::SIZE_OF_WASM + U::SIZE_OF_WASM + V::SIZE_OF_WASM,
+        Self::ALIGN_OF_WASM,
+    );
     const ALIGN_OF_WASM: usize = max(&[T::ALIGN_OF_WASM, U::ALIGN_OF_WASM, V::ALIGN_OF_WASM]);
 }
 
 impl<T: Wasm32Sized, U: Wasm32Sized, V: Wasm32Sized, W: Wasm32Sized> Wasm32Sized for (T, U, V, W) {
-    const SIZE_OF_WASM: usize =
+    const SIZE_OF_WASM: usize = next_multiple_of(
-        T::SIZE_OF_WASM + U::SIZE_OF_WASM + V::SIZE_OF_WASM + W::SIZE_OF_WASM;
+        T::SIZE_OF_WASM + U::SIZE_OF_WASM + V::SIZE_OF_WASM + W::SIZE_OF_WASM,
+        Self::ALIGN_OF_WASM,
+    );
     const ALIGN_OF_WASM: usize = max(&[
         T::ALIGN_OF_WASM,
         U::ALIGN_OF_WASM,

crates/compiler/test_gen/src/gen_list.rs

@@ -910,6 +910,25 @@ fn list_prepend_big_list() {
     );
 }
 
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
+fn list_prepend_record() {
+    assert_evals_to!(
+        indoc!(
+            r"
+            payment1 : { amount: Dec, date: [RD I32] }
+            payment1 = { amount: 1dec, date: (RD 1000) }
+            payment2 : { amount: Dec, date: [RD I32] }
+            payment2 = { amount: 2dec, date: (RD 1001) }
+
+            List.prepend [payment2] payment1
+            "
+        ),
+        RocList::from_slice(&[(RocDec::from(1), 1000i32), (RocDec::from(2), 1001i32),]),
+        RocList<(RocDec, i32)>
+    );
+}
+
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn list_walk_backwards_empty_all_inline() {

crates/compiler/test_gen/src/helpers/from_wasm32_memory.rs

@@ -91,15 +91,11 @@ impl<T: FromWasm32Memory + Clone> FromWasm32Memory for RocList<T> {
         let capacity =
             <u32 as FromWasm32Memory>::decode(memory, offset + 4 * Builtin::WRAPPER_CAPACITY);
 
-        let mut items = Vec::with_capacity(length as usize);
+        let step = <T as Wasm32Sized>::SIZE_OF_WASM;
 
-        for i in 0..length {
+        let items: Vec<_> = (0..length)
-            let item = <T as FromWasm32Memory>::decode(
+            .map(|i| <T as FromWasm32Memory>::decode(memory, elements + i * step as u32))
-                memory,
+            .collect();
-                elements + i * <T as Wasm32Sized>::SIZE_OF_WASM as u32,
-            );
-            items.push(item);
-        }
 
         let mut list = RocList::with_capacity(capacity as usize);
         list.extend_from_slice(&items);