checker: ensure that the variant SubType exists (#14053)

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

vlib/v/checker/checker.v

@@ -4197,6 +4197,12 @@ fn (mut c Checker) ensure_type_exists(typ ast.Type, pos token.Pos) ? {
 			c.ensure_type_exists(info.key_type, pos) ?
 			c.ensure_type_exists(info.value_type, pos) ?
 		}
+		.sum_type {
+			info := sym.info as ast.SumType
+			for concrete_typ in info.concrete_types {
+				c.ensure_type_exists(concrete_typ, pos) ?
+			}
+		}
 		else {}
 	}
 }

vlib/v/checker/tests/undefined_type_on_sumtype.out

@@ -0,0 +1,13 @@
+vlib/v/checker/tests/undefined_type_on_sumtype.vv:1:17: error: unknown type `Token`.
+Did you mean `Ok<[]Token>`?
+    1 | type ParseRes = Result<[]Token, ParseErr>
+      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~
+    2 | 
+    3 | // Token type is unknown
+vlib/v/checker/tests/undefined_type_on_sumtype.vv:30:4: error: unused variable: `rx`
+   28 |     match r {
+   29 |         Some<ParseRes> {
+   30 |             rx := r.value
+      |             ~~
+   31 |         }
+   32 |         None<ParseRes> {}

vlib/v/checker/tests/undefined_type_on_sumtype.vv

@@ -0,0 +1,34 @@
+type ParseRes = Result<[]Token, ParseErr>
+
+// Token type is unknown
+//struct Token {}
+
+struct ParseErr {}
+
+type Opt<T> = None<T> | Some<T>
+
+struct None<T> {}
+
+struct Some<T> {
+	value T
+}
+
+type Result<T, U> = Err<U> | Ok<T>
+
+struct Ok<T> {
+	value T
+}
+
+struct Err<U> {
+	value U
+}
+
+fn test_report() {
+	r := Opt<ParseRes>(None<ParseRes>{})
+	match r {
+		Some<ParseRes> {
+			rx := r.value
+		}
+		None<ParseRes> {}
+	}
+}

vlib/v/gen/c/testdata/check_combination_of_alias_and_sumtype.vv

@@ -1,5 +1,7 @@
 type ParseRes = Result<[]Token, ParseErr>
 
+struct Token {}
+
 struct ParseErr {}
 
 type Opt<T> = None<T> | Some<T>