harec

commit 9823d8cae6542d9ff805c089395ba19511537f10
parent 7a9448df40e2927eb8ae01b408d5eac57ab1aa15
Author: Eyal Sawady <ecs@d2evs.net>
Date:   Fri,  3 Sep 2021 10:35:07 +0000

type_is_assignable: implement struct subtyping

Signed-off-by: Eyal Sawady <ecs@d2evs.net>

Diffstat:
M
src/types.c
 | 
16
++++++++++++++++
M
tests/05-implicit-casts.ha
 | 
24
++++++++++++++++++++++++

2 files changed, 40 insertions(+), 0 deletions(-)
diff --git a/src/types.c b/src/types.c
@@ -527,6 +527,19 @@ tagged_subset_compat(const struct type *to, const struct type *from)
 	return !from_tu;
 }
 
+static bool
+struct_subtype(const struct type *to, const struct type *from) {
+	if (from->storage != STORAGE_STRUCT) {
+		return false;
+	}
+	for (struct struct_field *f = from->struct_union.fields; f;
+			f = f->next) {
+		if (f->offset == 0) {
+			return f->type == to;
+		}
+	}
+	return false;
+}
 bool
 type_is_assignable(const struct type *to, const struct type *from)
 {
@@ -580,6 +593,9 @@ type_is_assignable(const struct type *to, const struct type *from)
 		case STORAGE_POINTER:
 			from_secondary = type_dealias(from->pointer.referent);
 			from_secondary = strip_flags(from_secondary, &_from_secondary);
+			if (struct_subtype(to->pointer.referent, from_secondary)) {
+				return true;
+			}
 			switch (to_secondary->storage) {
 			case STORAGE_VOID:
 				break;
diff --git a/tests/05-implicit-casts.ha b/tests/05-implicit-casts.ha
@@ -1,5 +1,24 @@
 use rt;
 
+type subtype = struct {
+	foo: int,
+};
+
+type super1 = struct {
+	foo: subtype,
+	bar: int,
+};
+
+type super2 = struct {
+	subtype,
+	bar: int,
+};
+
+type super3 = struct {
+	struct { foo: int },
+	bar: int,
+};
+
 fn rules() void = {
 	// Fixed precision ints
 	let _i64: i64 = 0i64;
@@ -62,6 +81,11 @@ fn rules() void = {
 	nptr = &i;
 	let vptr: nullable *void = nptr;
 
+	// Struct subtyping
+	let sptr: *subtype = &super1 { ... };
+	let sptr: *subtype = &super2 { ... };
+	let sptr: *struct { foo: int } = &super3 { ... };
+
 	// Invalid pointer conversions
 	assert(rt::compile(
 		"fn test() void = { let x: nullable *int = null; let y: *int = x; };"