xai-org/x-algorithm · error · SemanticCheckFailure

Function '%s' does not exist

Error message

Function '%s' does not exist

What it means

Thrown during AST construction when a function name referenced in a BotMaker expression has no corresponding CompilerUnit registered in the CompilerBuilder. It is a semantic-check failure meaning the name resolution of the function failed at compile time, before any runtime evaluation.

Source

Thrown at botmaker/src/java/com/twitter/botmaker/compiler/CompilerBuilder.java:249

          return Type.OBJECT;
        } else {
          throw new SemanticCheckFailure(
              String.format("Input Feature %s does not exist", fullFeatureName));
        }
      }

      @Override
      protected boolean containsFunction(String name) {
        return compilerUnits.containsKey(name);
      }

      @Override
      protected ASTNode createFunctionASTNode(
          CompilerContext<E> context,
          String funcName,
          ImmutableList<ASTNode> children) throws SemanticCheckFailure {
        if (!compilerUnits.containsKey(funcName)) {
          throw new SemanticCheckFailure(String.format("Function '%s' does not exist", funcName));
        }

        CompilerUnit compilerUnit = compilerUnits.get(funcName);
        if (compilerUnit.fingerprint() != Fingerprint.EMPTY) {
          context.trackUsage(compilerUnit);
        }

        return compilerUnit.createASTNode(children);
      }
    };
  }
}

View on GitHub (pinned to 24c60942c5)

Solutions

1. Check the exact function name in the expression string for typos and casing
2. Ensure the CompilerUnit that defines the function is registered/loaded into the CompilerBuilder before compiling
3. If the function was renamed in a newer version, update the expression to the new name
4. Add a pre-check that the function exists in the known function set before compiling

Example fix

// before
ASTNode n = compiler.createASTNodeTree(ctx, Parser.createParseTree("mispelledFunction(x)"));
// after
ASTNode n = compiler.createASTNodeTree(ctx, Parser.createParseTree("correctFunctionName(x)"));

Set<String> known = compilerUnits.keySet(); // or expose from builder
if (!known.contains(funcName)) throw new IllegalArgumentException("Unknown function: " + funcName);

catch (SemanticCheckFailure e) { if (e.getMessage().contains("does not exist")) { /* report unknown function */ } throw e; }

When it happens

Trigger: Calling compiler.createASTNodeTree on a tree containing a function application whose head symbol is not present in the compilerUnits map (e.g. a typo'd function name, a function defined in another unit that was never imported/registered, or a builtin that was removed).

Common situations: Renaming or deleting a library function without updating expressions; forgetting to include a dependency compiler unit when composing the builder; typos in DSL strings; version upgrades where functions were renamed.

Related errors

• Function '%s' does not exist
• unrecognized function name:
• variable %s not defined
• The mock for function %s is not defined.
• Contains expects input of String, Map, Set or Collection typ

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/7fdbfacaf9800724. Report an issue: GitHub.