Use information of operand value to determine type for java locals

This PR uses the already existing information of the operand's value type to determine the type for java locals. Previously, most of the stack variables were of "unknown" type
.
Fixes soot-oss#635

sootup.java.bytecode/src/main/java/sootup/java/bytecode/frontend/Operand.java

@@ -21,9 +21,7 @@
  * <http://www.gnu.org/licenses/lgpl-2.1.html>.
  * #L%
  */
-import java.util.stream.Collectors;
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
+
 import org.objectweb.asm.tree.AbstractInsnNode;
 import sootup.core.jimple.Jimple;
 import sootup.core.jimple.basic.Immediate;
@@ -35,6 +33,10 @@
 import sootup.core.jimple.common.stmt.Stmt;
 import sootup.core.jimple.visitor.ReplaceUseStmtVisitor;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.stream.Collectors;
+
 /**
  * Stack operand.
  *
@@ -67,7 +69,7 @@ class Operand {
 
   Local getOrAssignValueToStackLocal() {
     if (stackLocal == null) {
-      changeStackLocal(methodSource.newStackLocal());
+      changeStackLocal(methodSource.newStackLocal().withType(value.getType()));
     }
 
     return stackLocal;