fix

vlib/v/checker/tests/missing_concrete_type_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/missing_concrete_type_err.vv:4:6: error: missing concrete type on generic type
+    2 | 
+    3 | fn main() {
+    4 |     bar[Foo]()
+      |         ~~~
+    5 | }
+    6 |

vlib/v/checker/tests/missing_concrete_type_err.vv

@@ -0,0 +1,9 @@
+struct Foo[T] {}
+
+fn main() {
+	bar[Foo]()
+}
+
+fn bar[T]() {
+
+}

vlib/v/parser/parse_type.v

@@ -537,6 +537,11 @@ fn (mut p Parser) parse_type() ast.Type {
 			return 0
 		}
 		sym := p.table.sym(typ)
+		if sym.info is ast.Struct {
+			if !typ.has_flag(.generic) && sym.info.generic_types.len > 0 {
+				p.error_with_pos('missing concrete type on generic type', option_pos.extend(p.prev_tok.pos()))
+			}
+		}
 		if is_option && sym.info is ast.SumType && sym.info.is_anon {
 			p.error_with_pos('an inline sum type cannot be an Option', option_pos.extend(p.prev_tok.pos()))
 		}