take alignment into account when calculating stack size

cli/src/repl/eval.rs

@@ -247,7 +247,7 @@ fn jit_to_ast_help<'a>(
                                                     *(ptr.add(offset as usize) as *const i16) as i64
                                                 }
                                                 Builtin::Int64 => {
-                                                    // used by non-recursive tag unions at the
+                                                    // used by non-recursive unions at the
                                                     // moment, remove if that is no longer the case
                                                     *(ptr.add(offset as usize) as *const i64) as i64
                                                 }

compiler/mono/src/layout.rs

@@ -636,6 +636,19 @@ impl<'a> Layout<'a> {
     }
 
     pub fn stack_size(&self, pointer_size: u32) -> u32 {
+        let width = self.stack_size_without_alignment(pointer_size);
+        let alignment = self.alignment_bytes(pointer_size);
+
+        if alignment == 0 {
+            width
+        } else if width % alignment > 0 {
+            width + alignment - (width % alignment)
+        } else {
+            width
+        }
+    }
+
+    fn stack_size_without_alignment(&self, pointer_size: u32) -> u32 {
         use Layout::*;
 
         match self {

compiler/test_gen/src/gen_primitives.rs

@@ -2529,3 +2529,25 @@ fn pattern_match_unit_tag() {
         i64
     );
 }
+
+#[test]
+fn mirror_llvm_alignment_padding() {
+    // see https://github.com/rtfeldman/roc/issues/1569
+    assert_evals_to!(
+        indoc!(
+            r#"
+                app "test" provides [ main ] to "./platform"
+
+                main : Str
+                main =
+                    p1 = {name : "test1", test: 1 == 1 }
+
+                    List.map [p1, p1 ] (\{ test } -> if test  then "pass" else "fail")
+                       |> Str.joinWith "\n"
+
+            "#
+        ),
+        RocStr::from_slice(b"pass\npass"),
+        RocStr
+    );
+}