If compile-on-save is enabled in a maven project, the project can still be build with no compile errors using the "build" option in the contextual menu /f11 (maven install).

I created a simple test - a new maven application project with one java class in it. Compile-on-save is enabled by default.

I compile the project now, with no problems.
Now i make an error in the file - for example writing this:

public void test(); //method declaration with missing method body

and hit f11(build), the problem is that I don't get any error.

Not until i either do a clean and build, or deactivates compile-on-save and then compiles i will get the error i should get.

This means that i must rely on the projects tree to find any classes with errors in them (if i for example add a method to an interface and dont get the method implemented in all impl-classes), where i use to be able to just compile and see any errors.