typechecker: Choose broader value type when typechecking a dictionary

selfhost/typechecker.jakt

@@ -10685,6 +10685,15 @@ struct Typechecker {
             }
         }
 
+        if value_hint.has_value() {
+            value_type_id = .choose_broader_type_id(
+                original_type_id: value_type_id
+                potential_type_id: value_hint!
+                generic_inferences: &mut .generic_inferences
+                span
+            )
+        }
+
         if key_hint.has_value() {
             key_type_id = .choose_broader_type_id(
                 original_type_id: key_type_id

tests/typechecker/function_base_class_dictionary_argument_derived_given2.jakt

@@ -0,0 +1,14 @@
+/// Expect:
+/// - output: "PASS\n"
+
+class Base {}
+
+class Derived : Base {}
+
+fn func(anon a: [i64:Base]) { 
+    println("PASS")
+}
+
+fn main() {
+    func([2:Derived()])
+}