Partially fix null unboxing in lambdas

When unboxing a null to a value class in Scala, the default value of the
value class should be returned, before this commit an NPE was thrown instead.
Like in scala/scala-java8-compat@d7e0125,
we fix this by using BoxesRunTime, bun we don't use it for boxing
since it's unnecessary.

After this commit, we still throw NPE when unboxing nulls in
unspecialized lambdas called in generic contexts (see if3_unspecialized
in the added test). This is addressed by the next commits in this PR.

Author: smarter

library/src/scala/compat/java8/JFunction0.java

@@ -13,27 +13,27 @@ public interface JFunction0<R> extends scala.Function0<R> {
         apply();
     }
     default byte apply$mcB$sp() {
-        return (Byte) apply();
+        return scala.runtime.BoxesRunTime.unboxToByte(apply());
     }
     default short apply$mcS$sp() {
-        return (Short) apply();
+        return scala.runtime.BoxesRunTime.unboxToShort(apply());
     }
     default int apply$mcI$sp() {
-        return (Integer) apply();
+        return scala.runtime.BoxesRunTime.unboxToInt(apply());
     }
     default long apply$mcJ$sp() {
-        return (Long) apply();
+        return scala.runtime.BoxesRunTime.unboxToLong(apply());
     }
     default char apply$mcC$sp() {
-        return (Character) apply();
+        return scala.runtime.BoxesRunTime.unboxToChar(apply());
     }
     default float apply$mcF$sp() {
-        return (Float) apply();
+        return scala.runtime.BoxesRunTime.unboxToFloat(apply());
     }
     default double apply$mcD$sp() {
-        return (Double) apply();
+        return scala.runtime.BoxesRunTime.unboxToDouble(apply());
     }
     default boolean apply$mcZ$sp() {
-        return (Boolean) apply();
+        return scala.runtime.BoxesRunTime.unboxToBoolean(apply());
     }
 }

library/src/scala/compat/java8/JFunction1$mcDD$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcDD$sp extends JFunction1 {
     abstract double apply$mcDD$sp(double v1);
 
-    default Object apply(Object t) { return (Double) apply$mcDD$sp((Double) t); }
+    default Object apply(Object t) { return (Double) apply$mcDD$sp(scala.runtime.BoxesRunTime.unboxToDouble(t)); }
 }

library/src/scala/compat/java8/JFunction1$mcDF$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcDF$sp extends JFunction1 {
     abstract double apply$mcDF$sp(float v1);
 
-    default Object apply(Object t) { return (Double) apply$mcDF$sp((Float) t); }
+    default Object apply(Object t) { return (Double) apply$mcDF$sp(scala.runtime.BoxesRunTime.unboxToFloat(t)); }
 }

library/src/scala/compat/java8/JFunction1$mcDI$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcDI$sp extends JFunction1 {
     abstract double apply$mcDI$sp(int v1);
 
-    default Object apply(Object t) { return (Double) apply$mcDI$sp((Integer) t); }
+    default Object apply(Object t) { return (Double) apply$mcDI$sp(scala.runtime.BoxesRunTime.unboxToInt(t)); }
 }

library/src/scala/compat/java8/JFunction1$mcDJ$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcDJ$sp extends JFunction1 {
     abstract double apply$mcDJ$sp(long v1);
 
-    default Object apply(Object t) { return (Double) apply$mcDJ$sp((Long) t); }
+    default Object apply(Object t) { return (Double) apply$mcDJ$sp(scala.runtime.BoxesRunTime.unboxToLong(t)); }
 }

library/src/scala/compat/java8/JFunction1$mcFD$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcFD$sp extends JFunction1 {
     abstract float apply$mcFD$sp(double v1);
 
-    default Object apply(Object t) { return (Float) apply$mcFD$sp((Double) t); }
+    default Object apply(Object t) { return (Float) apply$mcFD$sp(scala.runtime.BoxesRunTime.unboxToDouble(t)); }
 }

library/src/scala/compat/java8/JFunction1$mcFF$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcFF$sp extends JFunction1 {
     abstract float apply$mcFF$sp(float v1);
 
-    default Object apply(Object t) { return (Float) apply$mcFF$sp((Float) t); }
+    default Object apply(Object t) { return (Float) apply$mcFF$sp(scala.runtime.BoxesRunTime.unboxToFloat(t)); }
 }

library/src/scala/compat/java8/JFunction1$mcFI$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcFI$sp extends JFunction1 {
     abstract float apply$mcFI$sp(int v1);
 
-    default Object apply(Object t) { return (Float) apply$mcFI$sp((Integer) t); }
+    default Object apply(Object t) { return (Float) apply$mcFI$sp(scala.runtime.BoxesRunTime.unboxToInt(t)); }
 }

library/src/scala/compat/java8/JFunction1$mcFJ$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcFJ$sp extends JFunction1 {
     abstract float apply$mcFJ$sp(long v1);
 
-    default Object apply(Object t) { return (Float) apply$mcFJ$sp((Long) t); }
+    default Object apply(Object t) { return (Float) apply$mcFJ$sp(scala.runtime.BoxesRunTime.unboxToLong(t)); }
 }

library/src/scala/compat/java8/JFunction1$mcID$sp.java

@@ -9,5 +9,5 @@
 public interface JFunction1$mcID$sp extends JFunction1 {
     abstract int apply$mcID$sp(double v1);
 
-    default Object apply(Object t) { return (Integer) apply$mcID$sp((Double) t); }
+    default Object apply(Object t) { return (Integer) apply$mcID$sp(scala.runtime.BoxesRunTime.unboxToDouble(t)); }
 }