LibSQL: Gracefully react to unimplemented valid SQL

Fixes a crash that was caused by a syntax error which is difficult to
catch by the parser: usually identifiers are accepted in column lists,
but they are not in a list of column values to be inserted in an INSERT.

Fixed this by putting in a heuristic check; we probably need a better
way to do this.

Included tests for this case.

Also introduced a new SQL Error code, `NotYetImplemented`, and return
that instead of crashing when encountering unimplemented SQL.

1 files changed, 4 insertions, 0 deletions

diff --git a/Userland/Libraries/LibSQL/AST/Expression.cpp b/Userland/Libraries/LibSQL/AST/Expression.cpp
index d4030b3532..ce4c972e0c 100644
--- a/Userland/Libraries/LibSQL/AST/Expression.cpp
+++ b/Userland/Libraries/LibSQL/AST/Expression.cpp
@@ -169,6 +169,10 @@ Value UnaryOperatorExpression::evaluate(ExecutionContext& context) const
 
 Value ColumnNameExpression::evaluate(ExecutionContext& context) const
 {
+    if (!context.current_row) {
+        context.result->set_error(SQLErrorCode::SyntaxError, column_name());
+        return Value::null();
+    }
     auto& descriptor = *context.current_row->descriptor();
     VERIFY(context.current_row->size() == descriptor.size());
     Optional<size_t> index_in_row;