veb: fix generic field access from alias (fix #25215) (#25246)

vlib/v/gen/c/cgen.v

@@ -4479,7 +4479,7 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 	}
 	// struct embedding
 	mut has_embed := false
-	if sym.info in [ast.Struct, ast.Aggregate] {
+	if sym.info in [ast.Alias, ast.Struct, ast.Aggregate] {
 		if node.generic_from_embed_types.len > 0 && sym.info is ast.Struct {
 			if sym.info.embeds.len > 0 {
 				mut is_find := false

vlib/veb/tests/veb_aliased_app_and_context_test.v

@@ -0,0 +1,53 @@
+import os
+import veb
+import time
+import net.http
+
+const app_port = 29123
+const exit_after = 10 * time.second
+
+pub struct Context {
+	veb.Context
+}
+
+pub struct App {
+	veb.Middleware[Context]
+	veb.Controller
+	veb.StaticHandler
+	started chan bool
+}
+
+pub fn (mut app App) before_accept_loop() {
+	app.started <- true
+}
+
+type AliasApp = App
+type AliasContext = Context
+
+fn testsuite_begin() {
+	os.chdir(os.dir(@FILE))!
+	spawn fn () {
+		time.sleep(exit_after)
+		assert true == false, 'timeout reached!'
+		exit(1)
+	}()
+}
+
+fn test_aliased_app_compiles_and_starts() {
+	mut app := &AliasApp{}
+	spawn veb.run_at[AliasApp, AliasContext](mut app,
+		port:               app_port
+		timeout_in_seconds: 2
+		family:             .ip
+	)
+	eprintln('waiting for app to start ...')
+	_ := <-app.started
+	eprintln('>>> app was started')
+}
+
+fn test_static_root() {
+	x := http.get('http://127.0.0.1:${app_port}/')!
+	eprintln('>>>> http request was sent and received')
+	assert x.status() == .not_found
+	assert x.body == '404 Not Found'
+}