Fix "Polymorphic parameter declared in return type doesn't compile #464" by giving a conversion error (code wasn't handling polymorphic result types as intended)

src/check_expr.cpp

@@ -5731,9 +5731,13 @@ Entity **populate_proc_parameter_list(CheckerContext *c, Type *proc_type, isize
 		}
 	} else {
 		// NOTE(bill): Create 'lhs' list in order to ignore parameters which are polymorphic
-		lhs_count = pt->params->Tuple.variables.count;
+		if (pt->params == nullptr)  {
+			lhs_count = 0;
+		} else {
+			lhs_count = pt->params->Tuple.variables.count;
+		}
 		lhs = gb_alloc_array(heap_allocator(), Entity *, lhs_count);
-		for_array(i, pt->params->Tuple.variables) {
+		for (isize i = 0; i < lhs_count; i++) {
 			Entity *e = pt->params->Tuple.variables[i];
 			if (!is_type_polymorphic(e->type)) {
 				lhs[i] = e;

src/check_type.cpp

@@ -2507,6 +2507,16 @@ bool check_procedure_type(CheckerContext *ctx, Type *type, Ast *proc_type_node,
 			break;
 		}
 	}
+	for (isize i = 0; i < result_count; i++) {
+		Entity *e = results->Tuple.variables[i];
+		if (e->kind != Entity_Variable) {
+			is_polymorphic = true;
+			break;
+		} else if (is_type_polymorphic(e->type)) {
+			is_polymorphic = true;
+			break;
+		}
+	}
 	type->Proc.is_polymorphic = is_polymorphic;
 
 	return success;