Previously in Matlab Stateflow 7.1 all variables and functions had to be included before they can be referred to in the state diagram or else it would throw an error when you tried to parse the diagram.
But now in 7.7 it doesn't catch those kinds of errors. Its still compiling the diagram because it catches other syntactic errors.
Am I missing an option somewhere? Can this be turned on?
The release notes to Stateflow 7.2 say:
Parsing a Stateflow Chart Without Simulation No Longer Detects Unresolved Symbol Errors
To detect unresolved symbol errors in a chart, you must start simulation or update the model diagram. When you parse a chart without simulation or diagram updates, the Stateflow parser does not have access to all the information needed to check for unresolved symbols, such as exported graphical functions from other charts and enumerated data types. Therefore, the parser now skips unresolved symbol detection to avoid generating false error messages. However, if you start simulation or update the model diagram, you invoke the model compilation process, which has full access to the information needed, and unresolved symbols are flagged.
For more information, see Parsing Stateflow Charts and Resolving Symbols in the Stateflow and Stateflow Coder User's Guide.
So it looks like that you need to "start the simulation, update the model diagram, or invoke the model compilation process" to get the flags.