Remove incorrect getReason call and improve shouldNotReachHere message

Author: tkrodriguez

substratevm/src/com.oracle.graal.pointsto/src/com/oracle/graal/pointsto/ObjectScanner.java

@@ -114,8 +114,11 @@ protected final void scanField(AnalysisField field, JavaConstant receiver, Objec
             JavaConstant fieldValue = bb.getConstantReflectionProvider().readFieldValue(field, receiver);
 
             if (fieldValue == null) {
+                StringBuilder backtrace = new StringBuilder();
+                buildObjectBacktrace(reason, backtrace);
                 throw AnalysisError.shouldNotReachHere("Could not find field " + field.format("%H.%n") +
-                                (receiver == null ? "" : " on " + bb.getSnippetReflectionProvider().asObject(Object.class, receiver).getClass()));
+                                (receiver == null ? "" : " on " + bb.getSnippetReflectionProvider().asObject(Object.class, receiver).getClass()) +
+                                System.lineSeparator() + backtrace.toString());
             }
 
             if (fieldValue.getJavaKind() == JavaKind.Object && bb.getHostVM().isRelocatedPointer(bb.getSnippetReflectionProvider().asObject(Object.class, fieldValue))) {
@@ -229,6 +232,11 @@ public final void scanConstant(JavaConstant value, Object reason) {
 
     private void unsupportedFeature(String key, String message, Object entry) {
         StringBuilder objectBacktrace = new StringBuilder();
+        AnalysisMethod method = buildObjectBacktrace(entry, objectBacktrace);
+        bb.getUnsupportedFeatures().addMessage(key, method, message, objectBacktrace.toString());
+    }
+
+    private AnalysisMethod buildObjectBacktrace(Object entry, StringBuilder objectBacktrace) {
         Object cur = entry;
         AnalysisMethod method = null;
 
@@ -246,8 +254,7 @@ private void unsupportedFeature(String key, String message, Object entry) {
         } else {
             objectBacktrace.append("\t[unknown] ").append(cur.toString());
         }
-
-        bb.getUnsupportedFeatures().addMessage(key, method, message, objectBacktrace.toString());
+        return method;
     }
 
     /**
@@ -268,7 +275,7 @@ assert checkCorrectClassloaders(entry, valueObj) : "Invalid classloader " + valu
             for (AnalysisField field : type.getInstanceFields(true)) {
                 if (field.getJavaKind() == JavaKind.Object && field.isAccessed()) {
                     assert !Modifier.isStatic(field.getModifiers());
-                    scanField(field, entry.constant, entry.getReason());
+                    scanField(field, entry.constant, entry);
                 }
             }
         } else if (type.isArray() && bb.getProviders().getWordTypes().asKind(type.getComponentType()) == JavaKind.Object) {