Eclipse's automated code clean-up tool did most of the heavy lifting
here: it specifically has a clean-up option for converting functional
interfaces to lambdas. I merely had to revert the automated changes
for a single enumeration class for which it produced invalid results,
and for a few test inputs that apparently aren't set up to be compiled
with Java 8.
Previously FilterIterator was very permissive regarding the type
relationships between the original iterator, the filtered iterator,
and the predicate used to prune the former down to the latter. Now we
enforce those relationships more strictly, including proper use of
covariant ("<? extends T>") and contravariant ("<? super T>")
polymorphic type parameters where appropriate.
This lets us get rid of seven suppressed warnings about generic types
and/or unchecked conversions. It also moves us toward being able to
use modern Java features like lambdas and streams more easily.
Each of these required careful consideration of what the original
developer *intended* as distinguished from what the developer's code
actually *does*. I believe I got each one right, and WALA's
regression tests agree. A second opinion by a core WALA developer
would be welcome, though.
We already have plenty of examples of Serializable classes with this
field, and the vast majority of those fields have generated IDs rather
than "1L". From this I infer that using proper serialVersionUID
fields is considered appropriate WALA coding style.
In general, my approach was to try to eliminate each unused parameter
using Eclipse's "Change Method Signature" refactoring. That did not
always succeed: a parameter may be unused in some base class method,
but then be used in subclass's override of that method. In cases
where refactoring to eliminate a parameter failed, I instead annotated
the parameter with '@SuppressWarnings("unused")' to silence the
warning.
Note: this group of changes creates a significant risk of
incompatibility for third-party WALA code. Some removed parameters
change externally-visible APIs. Furthermore, these changes do not
necessarily lead to Java compilation errors. For example, suppose
third-party code subclasses a WALA class or interface, overrides a
method, but does not annotate that method as @Override. Removing a
parameter means that the third-party method no longer overrides. This
can quietly change code behavior without compile-time errors or
warnings. This is exactly why one should use @Override wherever
possible, but we cannot guarantee that third-party WALA users have
done that.
Unnecessary "throws" declarations tend to cascade. If foo() calls
bar() and bar() falsely declares that it might throw IOException, that
often leads a programmer to declare that foo() might throw IOException
as well. Fixing the bar() throws declaration then reveals that we can
fix the foo() throws declaration too. By the time we reach a fixed
point with cleaning these up, we have removed roughly 320 unnecessary
throws declarations.
In a few cases, this cleanup even lets us remove entire "try
... catch" statements where the only thing being caught was an
exception that we now statically know cannot be thrown. Nice!
In Eclipse project configurations, upgrade any future such shenanigans
from warnings to errors. Now that we've fixed this, we don't want it
coming back again.
There is a potential drawback to this change. Conceivably some public
WALA API entry point might have declared that it could throw some
exception merely to reserve the *option* of throwing that exception in
third-party code that subclasses and overrides the API entry point in
question. I have no idea whether this is a significant concern in
practice, though.
I have *not* upgraded this problem to be treated as an error in the
future. Unfortunately Eclipse uses a single configuration setting for
both unnecessary semicolons and also for empty control-flow statements
like `while (p) ;`. I'm not convinced that it's worth rewriting all
instances of the latter into `while (p) { }`. So this is just going
to stay as a warning for now.
In "com.ibm.wala.cast.test", the "cbuild.sh" script is gone entirely.
Instead, "pom.xml" directs Maven to run "make" directly. We still
have a "Makefile.configuration" file in this project, but this file is
now independent of where WALA is being built and of where Java is
installed.
In "com.ibm.wala.cast", a small "cbuild.sh" remains, to do some
special processing involving Visual Studio variables under Windows.
When not building under Windows, "cbuild.sh" now simply runs "make".
It may well be possible to hoist the special Windows stuff up into
this subproject's "pom.xml", or to change that "pom.xml" to run
"cbuild.sh" only when on Windows, and to run "make" directly
otherwise. I don't know "pom.xml" stuff very well, though. We still
have a "Makefile.configuration" file in this project, but this file is
now independent of where WALA is being built and of where Java is
installed.
The changes I've made in both "Makefile.configuration" files use GNU
make extensions. I assume that's safe because "Makefile.definitions"
already relies on GNU make.