Merge pull request #2692 from rtfeldman/walk-return-tag

`List.walk` return tag

compiler/gen_llvm/src/llvm/build.rs

@@ -2581,6 +2581,7 @@ pub fn build_exp_stmt<'a, 'ctx, 'env>(
                         let align_bytes = layout.alignment_bytes(env.target_info);
 
                         if align_bytes > 0 {
+                            debug_assert!(value.is_pointer_value(), "{:?}\n{:?}", value, layout);
                             let value_ptr = value.into_pointer_value();
 
                             // We can only do this if the function itself writes data into this

compiler/gen_llvm/src/llvm/build_list.rs

@@ -43,7 +43,7 @@ fn pass_element_as_opaque<'a, 'ctx, 'env>(
     env.builder.build_bitcast(
         element_ptr,
         env.context.i8_type().ptr_type(AddressSpace::Generic),
-        "to_opaque",
+        "pass_element_as_opaque",
     )
 }
 
@@ -75,7 +75,7 @@ pub fn pass_as_opaque<'a, 'ctx, 'env>(
     env.builder.build_bitcast(
         ptr,
         env.context.i8_type().ptr_type(AddressSpace::Generic),
-        "to_opaque",
+        "pass_as_opaque",
     )
 }
 
@@ -407,10 +407,19 @@ pub fn list_walk_generic<'a, 'ctx, 'env>(
         ListWalk::WalkBackwardsUntil => todo!(),
     };
 
-    let default_ptr = builder.build_alloca(default.get_type(), "default_ptr");
-    env.builder.build_store(default_ptr, default);
+    let default_ptr = if default_layout.is_passed_by_reference() {
+        debug_assert!(default.is_pointer_value());
+        default.into_pointer_value()
+    } else {
+        let default_ptr = builder.build_alloca(default.get_type(), "default_ptr");
+        env.builder.build_store(default_ptr, default);
+        default_ptr
+    };
 
-    let result_ptr = env.builder.build_alloca(default.get_type(), "result");
+    let result_ptr = {
+        let basic_type = basic_type_from_layout(env, default_layout);
+        env.builder.build_alloca(basic_type, "result")
+    };
 
     match variant {
         ListWalk::Walk | ListWalk::WalkBackwards => {
@@ -467,7 +476,11 @@ pub fn list_walk_generic<'a, 'ctx, 'env>(
         }
     }
 
-    env.builder.build_load(result_ptr, "load_result")
+    if default_layout.is_passed_by_reference() {
+        result_ptr.into()
+    } else {
+        env.builder.build_load(result_ptr, "load_result")
+    }
 }
 
 /// List.range : Int a, Int a -> List (Int a)

compiler/test_gen/src/gen_list.rs

@@ -798,6 +798,34 @@ fn list_walk_until_sum() {
     );
 }
 
+#[test]
+#[cfg(any(feature = "gen-llvm"))]
+fn list_walk_imlements_position() {
+    assert_evals_to!(
+        r#"
+        Option a : [ Some a, None ]
+
+        find : List a, a -> Option Nat
+        find = \list, needle ->
+            findHelp list needle
+                |> .v
+
+        findHelp = \list, needle ->
+            List.walkUntil list { n: 0, v: None } \{ n, v }, element ->
+                if element == needle then
+                    Stop { n, v: Some n }
+                else
+                    Continue { n: n + 1, v }
+
+        when find [ 1, 2, 3 ] 3 is
+            None -> 0
+            Some v -> v
+        "#,
+        2,
+        i64
+    );
+}
+
 #[test]
 #[cfg(any(feature = "gen-llvm"))]
 fn list_walk_until_even_prefix_sum() {