ast, checker, cgen: fix interface method with struct embed (#12783)

vlib/v/ast/table.v

@@ -412,6 +412,18 @@ pub fn (t &Table) find_method_from_embeds(sym &TypeSymbol, method_name string) ?
 	return none
 }
 
+// find_method_with_embeds searches for a given method, also looking through embedded fields
+pub fn (t &Table) find_method_with_embeds(sym &TypeSymbol, method_name string) ?Fn {
+	if func := t.find_method(sym, method_name) {
+		return func
+	} else {
+		// look for embedded field
+		first_err := err
+		func, _ := t.find_method_from_embeds(sym, method_name) or { return first_err }
+		return func
+	}
+}
+
 fn (t &Table) register_aggregate_field(mut sym TypeSymbol, name string) ?StructField {
 	if sym.kind != .aggregate {
 		t.panic('Unexpected type symbol: $sym.kind')

vlib/v/checker/checker.v

@@ -3232,7 +3232,7 @@ fn (mut c Checker) type_implements(typ ast.Type, interface_type ast.Type, pos to
 	if utyp != ast.voidptr_type {
 		// Verify methods
 		for imethod in imethods {
-			method := typ_sym.find_method(imethod.name) or {
+			method := c.table.find_method_with_embeds(typ_sym, imethod.name) or {
 				typ_sym.find_method_with_generic_parent(imethod.name) or {
 					c.error("`$styp` doesn't implement method `$imethod.name` of interface `$inter_sym.name`",
 						pos)

vlib/v/gen/c/cgen.v

@@ -7310,6 +7310,12 @@ static inline $interface_name I_${cctype}_to_Interface_${interface_name}($cctype
 				}
 				else {}
 			}
+			if st_sym.info is ast.Struct {
+				for embed in st_sym.info.embeds {
+					embed_sym := g.table.get_type_symbol(embed)
+					methods << embed_sym.methods
+				}
+			}
 			for method in methods {
 				mut name := method.name
 				if inter_info.parent_type.has_flag(.generic) {
@@ -7345,7 +7351,7 @@ static inline $interface_name I_${cctype}_to_Interface_${interface_name}($cctype
 					// hack to mutate typ
 					params[0] = ast.Param{
 						...params[0]
-						typ: params[0].typ.set_nr_muls(1)
+						typ: st.set_nr_muls(1)
 					}
 					fargs, _, _ := g.fn_args(params, voidptr(0))
 					methods_wrapper.write_string(g.out.cut_last(g.out.len - params_start_pos))
@@ -7354,7 +7360,21 @@ static inline $interface_name I_${cctype}_to_Interface_${interface_name}($cctype
 					if method.return_type != ast.void_type {
 						methods_wrapper.write_string('return ')
 					}
-					methods_wrapper.writeln('${method_call}(*${fargs.join(', ')});')
+					_, embed_types := g.table.find_method_from_embeds(st_sym, method.name) or {
+						ast.Fn{}, []ast.Type{}
+					}
+					if embed_types.len > 0 {
+						embed_sym := g.table.get_type_symbol(embed_types.last())
+						method_name := '${embed_sym.cname}_$method.name'
+						methods_wrapper.write_string('${method_name}(${fargs[0]}')
+						for embed in embed_types {
+							esym := g.table.get_type_symbol(embed)
+							methods_wrapper.write_string('->$esym.embed_name()')
+						}
+						methods_wrapper.writeln('${fargs[1..].join(', ')});')
+					} else {
+						methods_wrapper.writeln('${method_call}(*${fargs.join(', ')});')
+					}
 					methods_wrapper.writeln('}')
 					// .speak = Cat_speak_Interface_Animal_method_wrapper
 					method_call += iwpostfix

vlib/v/tests/interface_method_with_struct_embed_test.v

@@ -0,0 +1,35 @@
+struct Foo {
+	x int
+}
+
+fn (f Foo) get() int {
+	return f.x
+}
+
+struct Bar {
+	Foo
+}
+
+interface Getter {
+	get() int
+}
+
+fn test_interface_method_with_struct_embed() {
+	mut getter := []Getter{}
+
+	foo := Foo{22}
+	getter << foo
+
+	bar := Bar{Foo{11}}
+	getter << bar
+
+	assert getter.len == 2
+
+	println(foo)
+	println(getter[0])
+	assert getter[0].get() == 22
+
+	println(bar)
+	println(getter[1])
+	assert getter[1].get() == 11
+}