From a0f1c1ffefc08aea85a08068d0b5e7e5d6777d87 Mon Sep 17 00:00:00 2001
From: ChAoS_UnItY <minecraft.kyle.train@gmail.com>
Date: Sun, 5 Jun 2022 10:05:48 +0800
Subject: [PATCH] cgen: fix array type as interface (fix #14677) (#14681)

---
 vlib/v/gen/c/cgen.v                          | 16 +++++++++++-----
 vlib/v/gen/c/testdata/array_as_interface.out |  2 ++
 vlib/v/gen/c/testdata/array_as_interface.vv  |  8 ++++++++
 vlib/v/tests/array_as_interface_test.v       | 19 +++++++++++++++++++
 4 files changed, 40 insertions(+), 5 deletions(-)
 create mode 100644 vlib/v/gen/c/testdata/array_as_interface.out
 create mode 100644 vlib/v/gen/c/testdata/array_as_interface.vv
 create mode 100644 vlib/v/tests/array_as_interface_test.v

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index b284ba72b6..ae0a6cb85e 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -5654,17 +5654,23 @@ fn (mut g Gen) interface_table() string {
 					field_styp := g.typ(field.typ)
 					if _ := st_sym.find_field(field.name) {
 						cast_struct.writeln('\t\t.$cname = ($field_styp*)((char*)x + __offsetof_ptr(x, $cctype, $cname)),')
+					} else if st_sym.kind == .array
+						&& field.name in ['element_size', 'data', 'offset', 'len', 'cap', 'flags'] {
+						// Manaully checking, we already knows array contains above fields
+						cast_struct.writeln('\t\t.$cname = ($field_styp*)((char*)x + __offsetof_ptr(x, $cctype, $cname)),')
 					} else {
 						// the field is embedded in another struct
 						cast_struct.write_string('\t\t.$cname = ($field_styp*)((char*)x')
 						if st == ast.voidptr_type {
 							cast_struct.write_string('/*.... ast.voidptr_type */')
 						} else {
-							for embed_type in st_sym.struct_info().embeds {
-								embed_sym := g.table.sym(embed_type)
-								if _ := embed_sym.find_field(field.name) {
-									cast_struct.write_string(' + __offsetof_ptr(x, $cctype, $embed_sym.embed_name()) + __offsetof_ptr(x, $embed_sym.cname, $cname)')
-									break
+							if st_sym.kind == .struct_ {
+								for embed_type in st_sym.struct_info().embeds {
+									embed_sym := g.table.sym(embed_type)
+									if _ := embed_sym.find_field(field.name) {
+										cast_struct.write_string(' + __offsetof_ptr(x, $cctype, $embed_sym.embed_name()) + __offsetof_ptr(x, $embed_sym.cname, $cname)')
+										break
+									}
 								}
 							}
 						}
diff --git a/vlib/v/gen/c/testdata/array_as_interface.out b/vlib/v/gen/c/testdata/array_as_interface.out
new file mode 100644
index 0000000000..68bd7b8b18
--- /dev/null
+++ b/vlib/v/gen/c/testdata/array_as_interface.out
@@ -0,0 +1,2 @@
+4
+1
\ No newline at end of file
diff --git a/vlib/v/gen/c/testdata/array_as_interface.vv b/vlib/v/gen/c/testdata/array_as_interface.vv
new file mode 100644
index 0000000000..e10bb802f4
--- /dev/null
+++ b/vlib/v/gen/c/testdata/array_as_interface.vv
@@ -0,0 +1,8 @@
+interface Source {
+    len int
+}
+
+fn main() {
+    println(Source('test').len)
+    println(Source([`a`]).len) 
+}
\ No newline at end of file
diff --git a/vlib/v/tests/array_as_interface_test.v b/vlib/v/tests/array_as_interface_test.v
new file mode 100644
index 0000000000..ba4d041711
--- /dev/null
+++ b/vlib/v/tests/array_as_interface_test.v
@@ -0,0 +1,19 @@
+interface Source {
+	element_size int
+	data voidptr
+	offset int
+	len int
+	cap int
+	flags ArrayFlags
+}
+
+fn test_array_as_interface() {
+	arr := []rune{len: 1}
+	src := Source(arr)
+	assert arr.element_size == src.element_size
+	assert arr.data == src.data
+	assert arr.offset == src.offset
+	assert arr.len == src.len
+	assert arr.cap == src.cap
+	assert arr.flags == src.flags
+}