Currently javac appears to try to parse the transitive closure of all referenced source files, which can impact performance and causes errors if any files are missing. This also happens with -implicit:none

For example:

===
>more *.java
::::::::::::::
A.java
::::::::::::::

public class A {
    public void foo(B b) {
        // empty
    }
}
::::::::::::::
B.java
::::::::::::::

public class B {
    public int bar() {
        return new C().hashCode();
    }
}
>/java/re/j2se/1.7.0/latest/binaries/solaris-i586/bin/javac -implicit:none A.java
./B.java:4: cannot find symbol
symbol : class C
location: class B
        return new C().hashCode();
                   ^
1 error
===

C.java is not required to determine that A.java is a valid Java source file and to compile it, so C.java being unavailable should not cause an error.