Fix iterators in Java API (#3000)

Fixes #2989. SWIG 3 seems to have an issue properly resolving
`T::const_iterator::value_type` if that type itself is a `typedef`.
This is for example the case in the `UnsatCore` class, which `typedef`s
`const_iterator` to `std::vector<Expr>::const_iterator`. As a
workaround, this commit changes the `JavaIteratorAdapter` class to take
two template parameters, one of which is the `value_type`. The commit
also adds a compile-time assertion that `T::const_iterator::value_type`
can be converted to `value_type` to avoid nasty surprises. A nice
side-effect of this solution is that explicit `typemap`s are not
necessary anymore, so they are removed. Additionally, the commit adds a
`toString()` method for the Java API of `UnsatCore` and adds examples
that show and test the iteration over the unsat core and the statistics.
Iterating over `Statistics` now returns instances of `Statistic` instead
of `Object[]`, which is a bit cleaner and requires less glue code.

1 files changed, 17 insertions, 14 deletions

diff --git a/src/proof/unsat_core.i b/src/proof/unsat_core.i
index cee78da06..d3fd615ce 100644
--- a/src/proof/unsat_core.i
+++ b/src/proof/unsat_core.i
@@ -21,8 +21,16 @@
 %ignore CVC4::UnsatCore::begin() const;
 %ignore CVC4::UnsatCore::end() const;
 %extend CVC4::UnsatCore {
-  CVC4::JavaIteratorAdapter<CVC4::UnsatCore> iterator() {
-    return CVC4::JavaIteratorAdapter<CVC4::UnsatCore>(*$self);
+  CVC4::JavaIteratorAdapter<CVC4::UnsatCore, CVC4::Expr> iterator()
+  {
+    return CVC4::JavaIteratorAdapter<CVC4::UnsatCore, CVC4::Expr>(*$self);
+  }
+
+  std::string toString()
+  {
+    std::stringstream ss;
+    ss << (*$self);
+    return ss.str();
   }
 }
 
@@ -30,10 +38,10 @@
 %typemap(javainterfaces) CVC4::UnsatCore "java.lang.Iterable<edu.nyu.acsys.CVC4.Expr>";
 
 // the JavaIteratorAdapter should not be public, and implements Iterator
-%typemap(javaclassmodifiers) CVC4::JavaIteratorAdapter<CVC4::UnsatCore> "class";
-%typemap(javainterfaces) CVC4::JavaIteratorAdapter<CVC4::UnsatCore> "java.util.Iterator<edu.nyu.acsys.CVC4.Expr>";
+%typemap(javaclassmodifiers) CVC4::JavaIteratorAdapter<CVC4::UnsatCore, CVC4::Expr> "class";
+%typemap(javainterfaces) CVC4::JavaIteratorAdapter<CVC4::UnsatCore, CVC4::Expr> "java.util.Iterator<edu.nyu.acsys.CVC4.Expr>";
 // add some functions to the Java side (do it here because there's no way to do these in C++)
-%typemap(javacode) CVC4::JavaIteratorAdapter<CVC4::UnsatCore> "
+%typemap(javacode) CVC4::JavaIteratorAdapter<CVC4::UnsatCore, CVC4::Expr> "
   public void remove() {
     throw new java.lang.UnsupportedOperationException();
   }
@@ -47,13 +55,7 @@
   }
 "
 // getNext() just allows C++ iterator access from Java-side next(), make it private
-%javamethodmodifiers CVC4::JavaIteratorAdapter<CVC4::UnsatCore>::getNext() "private";
-
-// map the types appropriately
-%typemap(jni) CVC4::UnsatCore::const_iterator::value_type "jobject";
-%typemap(jtype) CVC4::UnsatCore::const_iterator::value_type "edu.nyu.acsys.CVC4.Expr";
-%typemap(jstype) CVC4::UnsatCore::const_iterator::value_type "edu.nyu.acsys.CVC4.Expr";
-%typemap(javaout) CVC4::UnsatCore::const_iterator::value_type { return $jnicall; }
+%javamethodmodifiers CVC4::JavaIteratorAdapter<CVC4::UnsatCore, CVC4::Expr>::getNext() "private";
 
 #endif /* SWIGJAVA */
 
@@ -61,9 +63,10 @@
 
 #ifdef SWIGJAVA
 
+%include <std_vector.i>
+
 %include "bindings/java_iterator_adapter.h"
-%include "bindings/java_stream_adapters.h"
 
-%template(JavaIteratorAdapter_UnsatCore) CVC4::JavaIteratorAdapter<CVC4::UnsatCore>;
+%template(JavaIteratorAdapter_UnsatCore) CVC4::JavaIteratorAdapter<CVC4::UnsatCore, CVC4::Expr>;
 
 #endif /* SWIGJAVA */