fix: detect gaps in bindKeywordArguments and add test for round(base=1)

Agent-Logs-Url: https://github.com/Ultimaker/CuraFormulaeEngine/sessions/bb29b144-a878-4363-8aec-f3d1835aad79

Co-authored-by: casperlamboo <6638028+casperlamboo@users.noreply.github.com>

Author: Copilot

src/ast/fn_application_expr.cpp

@@ -63,6 +63,18 @@ std::optional<std::vector<eval::Value>> bindKeywordArguments(
         }
         bound.push_back(slot.value());
     }
+
+    // If any slot beyond the bound range has a value there is a gap (a required
+    // earlier argument is missing while a later one was supplied via keyword).
+    // Return nullopt so the caller can report InvalidNumberOfArguments.
+    for (size_t i = bound.size(); i < slots.size(); ++i)
+    {
+        if (slots[i].has_value())
+        {
+            return std::nullopt;
+        }
+    }
+
     return bound;
 }
 

tests/parser.cpp

@@ -2113,6 +2113,21 @@ TEST_CASE("fn unknown keyword arg", "[parser, fn, keyword]")
     REQUIRE(eval.error() == CuraFormulaeEngine::eval::Error::InvalidNumberOfArguments);
 }
 
+TEST_CASE("fn keyword arg with gap in positional args", "[parser, fn, keyword]")
+{
+    // round(base=1) omits the required first argument 'x'; bindKeywordArguments
+    // should detect the gap and return InvalidNumberOfArguments instead of
+    // invoking RoundFunction with 0 args (which would cause out-of-bounds UB).
+    auto input = "round(base=1)"sv;
+
+    const auto message = CuraFormulaeEngine::parser::parse(input);
+    REQUIRE(message.has_value());
+    const auto &ast = message.value();
+    const auto eval = ast.evaluate(&CuraFormulaeEngine::env::std_env);
+    REQUIRE_FALSE(eval.has_value());
+    REQUIRE(eval.error() == CuraFormulaeEngine::eval::Error::InvalidNumberOfArguments);
+}
+
 TEST_CASE("fn any trailing comma", "[parser, fn]")
 {
     auto input = "any([True], )"sv;