[GitHub] [calcite] yanlin-Lynn commented on a change in pull request #1507: [CALCITE-3414] Unify Expression's type cast and conversion as a robust one

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yanlin-Lynn commented on a change in pull request #1507: [CALCITE-3414] Unify Expression's type cast and conversion as a robust one
URL: https://github.com/apache/calcite/pull/1507#discussion_r335791504
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/adapter/enumerable/RexToLixTranslator.java
 ##########
 @@ -1143,14 +1156,20 @@ public static Expression convert(Expression operand, Type fromType,
                 "toString",
                 operand));
       } else {
-        // E.g. from "BigDecimal" to "String"
-        // Generate "x == null ? null : x.toString()"
-        return Expressions.condition(
-            Expressions.equal(operand, RexImpTable.NULL_EXPR),
-            RexImpTable.NULL_EXPR,
-            Expressions.call(
-                operand,
-                "toString"));
+        Expression result;
+        try {
+          // Try to call "toString()" method
+          // E.g. from "Integer" to "String"
+          // Generate "x == null ? null : x.toString()"
+          result = Expressions.condition(
+              Expressions.equal(operand, RexImpTable.NULL_EXPR),
+              RexImpTable.NULL_EXPR,
+              Expressions.call(operand, "toString"));
+        } catch (Exception e) {
+          // No "toString()" method, fall through to (String)x
 
 Review comment:
   can this every happen for no `toString` method?

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