> The VBE will not compile VBA code that isn't in a module that's not loaded in the execution path of a given entry point. For example if you had Module1 with invalid code, and a macro in Sheet1 and nothing in Sheet1 is referring to anything in Module1, the Sheet1 macro can still compile and run even though the project as a whole won't.
You can manually verify whether your project compiles using the "Compile (ProjectName)" command from the Debug menu... or, there's a setting in Rubberduck to re