Handle no fields in SqlGenerator

1 files changed, 11 insertions, 2 deletions

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/sql/SqlGenerator.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/sql/SqlGenerator.java
index 456ffd8..4a23fa1 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/sql/SqlGenerator.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/sql/SqlGenerator.java
@@ -5,6 +5,7 @@ import org.zwobble.hobgoblin.compiler.ast.typed.RelationTable;
 import org.zwobble.hobgoblin.compiler.ast.typed.TypedQueryDefinitionNode;
 import org.zwobble.hobgoblin.compiler.ast.typed.TypedTableDefinitionNode;
 import org.zwobble.hobgoblin.compiler.builtins.NativeTypes;
+import org.zwobble.hobgoblin.compiler.errors.InternalError;
 import org.zwobble.hobgoblin.compiler.output.lang.sql.ast.*;
 import org.zwobble.hobgoblin.compiler.typechecker.TypesInfo;
 import org.zwobble.hobgoblin.compiler.types.SimpleStructType;
@@ -66,8 +67,16 @@ public class SqlGenerator {
                 var table = relationTable.table();
                 var schemaInfo = typesInfo.databaseSchemaInfo(table.databaseSchema());
                 var tableInfo = schemaInfo.tables().get(table.name());
-                // TODO: handle singleton struct.
-                var fields = typesInfo.fieldsOf(tableInfo.rowType()).orElseThrow();
+
+                var fields = typesInfo.fieldsOf(tableInfo.rowType())
+                    .orElse(List.of());
+
+                // The type-checker should have verified that the row type has
+                // fields, so don't try to handle gracefully here.
+                if (fields.isEmpty()) {
+                    throw new InternalError("row type has no fields");
+                }
+
                 var columns = fields.stream()
                     .map(field -> {
                         var columnName = generateColumnName(field.name());