improve causality reporting for unresolved elements

Author: dougxc

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/phases/SharedGraphBuilderPhase.java

@@ -284,6 +284,7 @@ protected Object loadReferenceTypeLock() {
 
         @Override
         protected void maybeEagerlyResolve(int cpi, int bytecode) {
+            lastUnresolvedElementException = null;
             try {
                 super.maybeEagerlyResolve(cpi, bytecode);
             } catch (UnresolvedElementException e) {
@@ -294,12 +295,19 @@ protected void maybeEagerlyResolve(int cpi, int bytecode) {
                      * ConstantPool.lookupType() which should return an UnresolvedJavaType which we
                      * know how to deal with.
                      */
+                    lastUnresolvedElementException = e;
                 } else {
                     throw e;
                 }
             }
         }
 
+        /**
+         * The type resolution error, if any, encountered in the last call to
+         * {@link #maybeEagerlyResolve}.
+         */
+        UnresolvedElementException lastUnresolvedElementException;
+
         @Override
         protected JavaType maybeEagerlyResolve(JavaType type, ResolvedJavaType accessingClass) {
             try {
@@ -594,7 +602,7 @@ private static Class<?>[] signatureToClasses(JavaMethod method) {
         }
 
         private void reportUnresolvedElement(String elementKind, String elementAsString) {
-            reportUnresolvedElement(elementKind, elementAsString, null);
+            reportUnresolvedElement(elementKind, elementAsString, lastUnresolvedElementException);
         }
 
         private void reportUnresolvedElement(String elementKind, String elementAsString, Throwable cause) {