checker: fix checker generic alias type (fix #23474) (#23475)

vlib/v/checker/struct.v

@@ -165,11 +165,8 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 				continue
 			}
 			field_is_generic := field.typ.has_flag(.generic)
-			if !c.ensure_generic_type_specify_type_names(field.typ, field.type_pos, c.table.final_sym(field.typ).kind in [
-				.array,
-				.array_fixed,
-				.map,
-			], field_is_generic) {
+			if c.table.type_kind(field.typ) != .alias
+				&& !c.ensure_generic_type_specify_type_names(field.typ, field.type_pos, c.table.final_sym(field.typ).kind in [.array, .array_fixed, .map], field_is_generic) {
 				continue
 			}
 			if field_is_generic {

vlib/v/tests/generics/generic_alias_map_type_test.v

@@ -0,0 +1,69 @@
+module main
+
+import arrays
+
+pub struct Tree {
+pub:
+	//	Type of structural node, `value` should be empty
+	type string
+	// Content of data node, `type` should be empty
+	value string
+pub mut:
+	//	Child nodes
+	kids []&Tree
+}
+
+@[params]
+struct TreeCloneParams {
+	kids []&Tree
+}
+
+// Makes new derived node with different kids id defined.
+pub fn (tree Tree) clone(p TreeCloneParams) &Tree {
+	return &Tree{
+		type:  tree.type
+		value: tree.value
+		kids:  p.kids
+	}
+}
+
+// Collection of hask tools for processing tree.
+pub type TreeBelt = map[string]fn (input &Tree, belt TreeBelt) []&Tree
+
+// Hask tool for processing node.
+pub type TreeHack = fn (input &Tree, belt TreeBelt) []&Tree
+
+pub type TreeContext = map[string]string
+
+@[params]
+struct TreeHackParams {
+	belt    TreeBelt
+	context ?TreeContext
+}
+
+// Transform tree through context with transformers
+pub fn (tree Tree) hack(p TreeHackParams) []&Tree {
+	return arrays.concat(arrays.flatten(tree.kids.map(it.hack_self(p))))
+}
+
+pub fn (tree Tree) hack_self(p TreeHackParams) []&Tree {
+	mut handle := fn [tree] (input &Tree, belt TreeBelt) []&Tree {
+		return [
+			input.clone(kids: input.hack(belt: belt)),
+		]
+	}
+
+	if action := p.belt[tree.type] {
+		handle = action
+	}
+
+	return handle(tree, p.belt)
+}
+
+fn test_main() {
+	t := Tree{}
+	r := t.hack_self(belt: TreeBelt(map[string]fn (&Tree, TreeBelt) []&Tree{}))
+	assert r[0].type == ''
+	assert r[0].value == ''
+	assert r[0].kids.len == 0
+}