fix

vlib/v/ast/table.v

@@ -1945,7 +1945,9 @@ pub fn (mut t Table) unwrap_generic_type_ex(typ Type, generic_names []string, co
 			return new_type(idx).derive_add_muls(typ).clear_flag(.generic)
 		}
 		Struct, Interface, SumType {
-			if !ts.info.is_generic {
+			// alias to generic type needs to be rechecked
+			// e.g. type Vec4 = vec.Vec4[f64]
+			if !ts.info.is_generic && !(generic_names.len > 0 && recheck_concrete_types) {
 				return typ
 			}
 			mut t_generic_names := generic_names.clone()
@@ -2054,7 +2056,7 @@ pub fn (mut t Table) unwrap_generic_type_ex(typ Type, generic_names []string, co
 					}
 				}
 				if final_concrete_types.len > 0 {
-					for method in ts.methods {
+					for method in ts.get_methods() {
 						for i in 1 .. method.params.len {
 							if method.params[i].typ.has_flag(.generic)
 								&& method.params[i].typ != method.params[0].typ {

vlib/v/checker/checker.v

@@ -599,6 +599,12 @@ fn (mut c Checker) alias_type_decl(node ast.AliasTypeDecl) {
 						}
 					}
 				}
+
+				// Recheck generic type with its supplied concrete type
+				if parent_typ_sym.info.generic_types.len > 0 {
+					c.table.unwrap_generic_type_ex(node.parent_type, parent_typ_sym.info.generic_types.map(c.table.type_to_str(it)),
+						parent_typ_sym.info.concrete_types, true)
+				}
 			}
 		}
 		.array {

vlib/v/tests/aliases/alias_generic_struct_test.v

@@ -0,0 +1,25 @@
+module main
+
+import math.vec
+
+type Vec4 = vec.Vec4[f32]
+type Vec4x = vec.Vec4[f32]
+
+fn test_main() {
+	mut v := Vec4{0, 0, 0, 1}
+	v.one()
+	assert v.x == 1
+	assert v.y == 1
+	assert v.z == 1
+	assert v.w == 1
+	v.from(vec.Vec4[f32]{2, 2, 2, 2})
+	assert v.x == 2
+	assert v.y == 2
+	assert v.z == 2
+	assert v.w == 2
+	v.from(Vec4x{3, 3, 3, 3})
+	assert v.x == 3
+	assert v.y == 3
+	assert v.z == 3
+	assert v.w == 3
+}