harec

commit 39599274468de63e4e8ee484e616fb8c695d5f11
parent 422f2db26233f1649c30b4579650852e0c955179
Author: Drew DeVault <sir@cmpwn.com>
Date:   Sun, 31 Jan 2021 09:45:25 -0500

types: implement tagged_subset_compat

Diffstat:
M
src/types.c
 | 
29
+++++++++++++++++++++++++++--
M
tests/13-tagged.ha
 | 
14
+++++++-------

2 files changed, 34 insertions(+), 9 deletions(-)
diff --git a/src/types.c b/src/types.c
@@ -375,6 +375,31 @@ tagged_select_subtype(const struct type *tagged, const struct type *subtype)
 	return NULL;
 }
 
+static bool
+tagged_subset_compat(const struct type *to, const struct type *from)
+{
+	// Note: this implementation depends on the invariant that tagged union
+	// member types are sorted by their type ID.
+	to = type_dealias(to), from = type_dealias(from);
+	if (to->storage != TYPE_STORAGE_TAGGED || from->storage != TYPE_STORAGE_TAGGED) {
+		return false;
+	}
+	const struct type_tagged_union *to_tu = &to->tagged,
+	      *from_tu = &from->tagged;
+	while (from_tu && to_tu) {
+		while (to_tu) {
+			if (to_tu->type->id == from_tu->type->id) {
+				from_tu = from_tu->next;
+				to_tu = to_tu->next;
+				break;
+			}
+			to_tu = to_tu->next;
+		}
+	}
+
+	return !from_tu;
+}
+
 bool
 type_is_assignable(const struct type *to, const struct type *from)
 {
@@ -464,8 +489,8 @@ type_is_assignable(const struct type *to, const struct type *from)
 			&& to->array.length == SIZE_UNDEFINED
 			&& from->array.length != SIZE_UNDEFINED;
 	case TYPE_STORAGE_TAGGED:
-		// XXX: Needs work!
-		return tagged_select_subtype(to, from) != NULL || true;
+		return tagged_select_subtype(to, from) != NULL
+			|| tagged_subset_compat(to, from);
 	// The following types are only assignable from themselves, and are
 	// handled above:
 	case TYPE_STORAGE_BOOL:
diff --git a/tests/13-tagged.ha b/tests/13-tagged.ha
@@ -55,13 +55,13 @@ fn reduction() void = {
 	const a: (i8 | i16) = 42i8;
 	const b: (i16 | i8) = a;
 	const c: (i8 | i16 | i32) = a;
-	//assert(rt::compile(
-	//	// Cannot assign from more general type
-	//	"fn test() void = {
-	//		let a: (i8 | i16 | i32) = 42i8;
-	//		let b: (i8 | i16) = a;
-	//	};"
-	//) != 0);
+	assert(rt::compile(
+		// Cannot assign from more general type
+		"fn test() void = {
+			let a: (i8 | i16 | i32) = 42i8;
+			let b: (i8 | i16) = a;
+		};"
+	) != 0);
 	assert(a is i8 && b is i8 && c is i8);
 	assert(size((i8 | i16 | i32)) == size((i8 | (i16 | i32))));
 	assert(size(integer) == size(signed));