script.model.ScriptInterpreter: emit what cannot be casted to what

after a single evaluation of the cast.  Before this change
internalEvaluate(castedExpression.getTarget(), context, indicator)
was invoked twice.  When on the first execution an error occured, the
second execution was needed to create an error message, stating what
cannot be casted to what.  However at the time internalEvaluate was
called for a second time, internal states have changed, so there might
be no more errors with casting, thus producing incorrect error message.

Except the line
  "Could not cast (" + result.class + ")" + result + " to " + typeName
the implementation is the same as in XbaseInterpreter.java.

Author: dilyanpalauzov

bundles/org.openhab.core.model.script/src/org/openhab/core/model/script/interpreter/ScriptInterpreter.xtend

@@ -25,6 +25,7 @@ import org.openhab.core.model.script.scoping.StateAndCommandProvider
 import org.openhab.core.model.script.script.QuantityLiteral
 import org.eclipse.xtext.common.types.JvmField
 import org.eclipse.xtext.common.types.JvmIdentifiableElement
+import org.eclipse.xtext.common.types.JvmPrimitiveType
 import org.eclipse.xtext.naming.QualifiedName
 import org.eclipse.xtext.util.CancelIndicator
 import org.eclipse.xtext.xbase.XAbstractFeatureCall
@@ -33,9 +34,12 @@ import org.eclipse.xtext.xbase.XExpression
 import org.eclipse.xtext.xbase.XFeatureCall
 import org.eclipse.xtext.xbase.XMemberFeatureCall
 import org.eclipse.xtext.xbase.interpreter.IEvaluationContext
+import org.eclipse.xtext.xbase.interpreter.impl.EvaluationException
 import org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter
 import org.eclipse.xtext.xbase.jvmmodel.IJvmModelAssociations
 import org.eclipse.xtext.xbase.typesystem.IBatchTypeResolver
+import org.eclipse.xtext.xbase.typesystem.references.StandardTypeReferenceOwner
+import org.eclipse.xtext.xbase.typesystem.util.CommonTypeComputationServices;
 
 /**
  * The script interpreter handles specific script components, which are not known
@@ -60,6 +64,9 @@ class ScriptInterpreter extends XbaseInterpreter {
     @Inject
     extension IJvmModelAssociations
 
+    @Inject
+    CommonTypeComputationServices services
+
     override protected _invokeFeature(JvmField jvmField, XAbstractFeatureCall featureCall, Object receiver,
         IEvaluationContext context, CancelIndicator indicator) {
 
@@ -152,21 +159,43 @@ class ScriptInterpreter extends XbaseInterpreter {
         return QuantityType.valueOf(literal.value + " " + literal.unit.value);
     }
 
-    override Object _doEvaluate(XCastedExpression castedExpression, IEvaluationContext context,
+    /**
+     * This is the same implementation as in XbaseInterpreter.java with the
+     * {@code "Could not cast (" + result.class + ")" + result + " to " + typeName }
+     * line being the only difference.  There is no other way to create an error message,
+     * stating what cannot be casted to what. See
+     * <a href="https://github.com/eclipse-xtext/xtext/issues/3595">github.com/eclipse-xtext/xtext/issues/3595</a>.
+     */
+    override protected _doEvaluate(XCastedExpression castedExpression, IEvaluationContext context,
         CancelIndicator indicator) {
-        try {
-            return super._doEvaluate(castedExpression, context, indicator)
-        } catch (RuntimeException e) {
-            if (e.cause instanceof ClassCastException) {
-                val Object result = internalEvaluate(castedExpression.getTarget(), context, indicator);
-                throw new ScriptExecutionException(new ScriptError(
-                    "Could not cast " + result + " to " + castedExpression.getType().getType().getQualifiedName(),
-                    castedExpression));
-                } else {
-                    throw e;
-                }
+        var result = internalEvaluate(castedExpression.target, context, indicator)
+        val owner = new StandardTypeReferenceOwner(services, castedExpression)
+        val targetType = owner.toLightweightTypeReference(castedExpression.type)
+        result = wrapOrUnwrapArray(result, targetType)
+        result = coerceArgumentType(result, castedExpression.type)
+        val castType = castedExpression.type.type
+        if (castType instanceof JvmPrimitiveType) {
+            if (result === null) {
+                throwNullPointerException(castedExpression, "Cannot cast null to primitive " + castType.identifier)
             }
+            return castToPrimitiveType(result, services.primitives.primitiveKind(castType))
         }
+        val typeName = castType.qualifiedName
+        var Class<?> expectedType = null
+        try {
+            expectedType = getJavaType(castType)
+        } catch (ClassNotFoundException e) {
+            throw new EvaluationException(new NoClassDefFoundError(typeName))
+        }
+        try {
+            expectedType.cast(result)
+        } catch (ClassCastException e) {
+            throw new EvaluationException(new ClassCastException(
+                "Could not cast (" + result.class + ")" + result + " to " + typeName
+                ))
+        }
+        return result
+    }
 
     }