checker: add error for `type StructAlias = Struct struct Struct { field StructAlias }`

vlib/v/ast/table.v

@@ -610,7 +610,7 @@ pub fn (t &Table) find_type_idx(name string) int {
 }
 
 [inline]
-pub fn (t &Table) find_type(name string) ?&TypeSymbol {
+pub fn (t &Table) find_sym(name string) ?&TypeSymbol {
 	idx := t.type_idxs[name]
 	if idx > 0 {
 		return t.type_symbols[idx]
@@ -618,6 +618,15 @@ pub fn (t &Table) find_type(name string) ?&TypeSymbol {
 	return none
 }
 
+[inline]
+pub fn (t &Table) find_sym_and_type_idx(name string) (&TypeSymbol, int) {
+	idx := t.type_idxs[name]
+	if idx > 0 {
+		return t.type_symbols[idx], idx
+	}
+	return ast.invalid_type_symbol, idx
+}
+
 pub const invalid_type_symbol = &TypeSymbol{
 	idx: -1
 	parent_idx: -1

vlib/v/checker/checker.v

@@ -2224,7 +2224,7 @@ fn (mut c Checker) import_stmt(node ast.Import) {
 	for sym in node.syms {
 		name := '${node.mod}.$sym.name'
 		if sym.name[0].is_capital() {
-			if type_sym := c.table.find_type(name) {
+			if type_sym := c.table.find_sym(name) {
 				if type_sym.kind != .placeholder {
 					if !type_sym.is_public {
 						c.error('module `$node.mod` type `$sym.name` is private', sym.pos)

vlib/v/checker/struct.v

@@ -8,7 +8,7 @@ pub fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 	if node.language == .v && !c.is_builtin_mod {
 		c.check_valid_pascal_case(node.name, 'struct name', node.pos)
 	}
-	mut struct_sym := c.table.find_type(node.name) or { ast.invalid_type_symbol }
+	mut struct_sym, struct_typ_idx := c.table.find_sym_and_type_idx(node.name)
 	mut has_generic_types := false
 	if mut struct_sym.info is ast.Struct {
 		for embed in node.embeds {
@@ -48,6 +48,14 @@ pub fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 					c.error('field name `$field.name` duplicate', field.pos)
 				}
 			}
+			if field.typ != 0 {
+				if !field.typ.is_ptr() {
+					if c.table.unaliased_type(field.typ) == struct_typ_idx {
+						c.error('Field `$field.name` is part of `$node.name`, they can not both have the same type',
+							field.type_pos)
+					}
+				}
+			}
 			if sym.kind == .struct_ {
 				info := sym.info as ast.Struct
 				if info.is_heap && !field.typ.is_ptr() {

vlib/v/checker/tests/field_can_not_be_from_the_same_type_as_containing_struct.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/field_can_not_be_from_the_same_type_as_containing_struct.vv:5:9: error: Field `field` is part of `Bar`, they can not both have the same type
+    3 | struct Bar {
+    4 |     pfield &Foo = 0
+    5 |     field  Foo  = Bar{}
+      |            ~~~
+    6 | }
+    7 |

vlib/v/checker/tests/field_can_not_be_from_the_same_type_as_containing_struct.vv

@@ -0,0 +1,11 @@
+type Foo = Bar
+
+struct Bar {
+	pfield &Foo = 0
+	field  Foo  = Bar{}
+}
+
+fn main() {
+	bar := Bar{}
+	println(bar)
+}

vlib/v/gen/js/js.v

@@ -175,7 +175,7 @@ pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) string {
 	g.enter_namespace('main')
 	// generate JS methods for interface methods
 	for iface_name, iface_types in g.table.iface_types {
-		iface := g.table.find_type(iface_name) or { panic('unreachable: interface must exist') }
+		iface := g.table.find_sym(iface_name) or { panic('unreachable: interface must exist') }
 		for ty in iface_types {
 			sym := g.table.sym(ty)
 			for method in iface.methods {

vlib/v/markused/markused.v

@@ -249,7 +249,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 	if pref.is_test {
 		all_fn_root_names << 'main.cb_assertion_ok'
 		all_fn_root_names << 'main.cb_assertion_failed'
-		if benched_tests_sym := table.find_type('main.BenchedTests') {
+		if benched_tests_sym := table.find_sym('main.BenchedTests') {
 			bts_type := benched_tests_sym.methods[0].params[0].typ
 			all_fn_root_names << '${bts_type}.testing_step_start'
 			all_fn_root_names << '${bts_type}.testing_step_end'