v: add support for T.unaliased_typ (#22546)

vlib/v/ast/ast.v

@@ -279,6 +279,7 @@ pub enum GenericKindField {
 	unknown
 	name
 	typ
+	unaliased_typ
 }
 
 // `foo.bar`

vlib/v/checker/checker.v

@@ -1513,6 +1513,9 @@ fn (mut c Checker) selector_expr(mut node ast.SelectorExpr) ast.Type {
 			.name {
 				return ast.string_type
 			}
+			.unaliased_typ {
+				return ast.int_type
+			}
 			.typ {
 				return ast.int_type
 			}

vlib/v/gen/c/cgen.v

@@ -3880,6 +3880,10 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 				g.write(int(g.unwrap_generic(node.name_type)).str())
 				return
 			}
+			.unaliased_typ {
+				g.write(int(g.table.unaliased_type(g.unwrap_generic(node.name_type))).str())
+				return
+			}
 			.unknown {
 				// ast.TypeOf of `typeof(string).idx` etc
 				if node.field_name == 'name' {

vlib/v/gen/c/comptime.v

@@ -473,6 +473,8 @@ fn (mut g Gen) get_expr_type(cond ast.Expr) ast.Type {
 		ast.SelectorExpr {
 			if cond.gkind_field == .typ {
 				return g.unwrap_generic(cond.name_type)
+			} else if cond.gkind_field == .unaliased_typ {
+				return g.table.unaliased_type(g.unwrap_generic(cond.name_type))
 			} else {
 				name := '${cond.expr}.${cond.field_name}'
 				if name in g.comptime.type_map {

vlib/v/gen/js/js.v

@@ -3250,12 +3250,18 @@ fn (mut g JsGen) gen_selector_expr(it ast.SelectorExpr) {
 			}
 			.typ {
 				g.write('new int(')
-
 				g.write('${int(g.unwrap_generic(it.name_type))}')
 				g.write(')')
 				g.write(')')
 				return
 			}
+			.unaliased_typ {
+				g.write('new int(')
+				g.write('${int(g.table.unaliased_type(g.unwrap_generic(it.name_type)))}')
+				g.write(')')
+				g.write(')')
+				return
+			}
 			.unknown {
 				if node.field_name == 'name' {
 					g.type_name(it.name_type)

vlib/v/parser/parser.v

@@ -2936,6 +2936,7 @@ fn (mut p Parser) name_expr() ast.Expr {
 			fkind := match field {
 				'name' { ast.GenericKindField.name }
 				'typ' { ast.GenericKindField.typ }
+				'unaliased_typ' { ast.GenericKindField.unaliased_typ }
 				else { ast.GenericKindField.unknown }
 			}
 			pos.extend(p.tok.pos())

vlib/v/tests/comptime/comptime_generic_unaliased_typ_test.v

@@ -0,0 +1,35 @@
+struct Struct {
+	a int
+}
+
+type StructAlias = Struct
+
+fn test_main() {
+	mut a := StructAlias(Struct{})
+	assert alias_first(a) == 'alias'
+	assert struct_first(a) == 'struct'
+}
+
+fn alias_first[T](val T) string {
+	$if T is $alias {
+		return 'alias'
+	} $else $if T is $struct {
+		return 'struct'
+	} $else {
+		return 'else'
+	}
+}
+
+fn struct_first[T](val T) string {
+	$if T is $struct {
+		return 'struct'
+	} $else $if T is $alias {
+		$if T.unaliased_typ is $struct {
+			return 'struct'
+		} $else {
+			return 'alias'
+		}
+	} $else {
+		return 'else'
+	}
+}