NPE in Type.UndetVar.debugString()

[B. Blaser]

Hi,

When working on [1], I saw that "Type.UndetVar.debugString()"
sometimes throws a NPE when called from within "UndetVar", for example
in "addBound()" as here under, which is annoying...

Could someone eventually push the following harmless fix to the amber
and jdk10 repositories?

This might be really helpful when debugging...

Thanks,
Bernard

[1] http://mail.openjdk.java.net/pipermail/amber-dev/2017-September/002061.html

diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Type.java
b/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Type.java
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Type.java
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Type.java
@@ -1974,7 +1974,7 @@
             }
             for (InferenceBound bound: InferenceBound.values()) {
                 List<Type> aboundList = bounds.get(bound);
-                if (aboundList.size() > 0) {
+                if (aboundList != null && aboundList.size() > 0) {
                     result += bound + " = " + aboundList + '\n';
                 }
             }
@@ -2112,6 +2112,7 @@
                 bounds.put(ib, prevBounds.prepend(bound2));
                 notifyBoundChange(ib, bound2, false);
             }
+//System.err.println("debug: " + debugString());
         }
         //where
             TypeMapping<Void> toTypeVarMap = new
StructuralTypeMapping<Void>() {