Improve error message thrown for "cannot instantiate" (#1916)

If the parent comes from an implicit node (e.g. read super entry node),
Pkl will currently bury its source section when rendering the error
message.

pkl-core/src/main/java/org/pkl/core/ast/expression/generator/GeneratorObjectLiteralNode.java

@@ -98,7 +98,7 @@ public abstract class GeneratorObjectLiteralNode extends ObjectLiteralNode {
 
   @Specialization(guards = "checkObjectCannotHaveParameters()")
   protected VmTyped evalTyped(VirtualFrame frame, VmTyped parent) {
-    VmUtils.checkIsInstantiable(parent.getVmClass(), getParentNode());
+    VmUtils.checkIsInstantiable(parent.getVmClass(), getParentNode(), this);
     var data = executeChildren(frame, parent, 0);
     if (data.hasNoMembers()) {
       return parent;
@@ -207,7 +207,7 @@ public abstract class GeneratorObjectLiteralNode extends ObjectLiteralNode {
 
   @Specialization(guards = {"isTypedObjectClass(parent)", "checkObjectCannotHaveParameters()"})
   protected VmTyped evalTypedObjectClass(VirtualFrame frame, VmClass parent) {
-    VmUtils.checkIsInstantiable(parent, getParentNode());
+    VmUtils.checkIsInstantiable(parent, getParentNode(), this);
     var data = executeChildren(frame, parent, 0);
     if (data.hasNoMembers()) {
       return parent.getPrototype();
@@ -225,7 +225,9 @@ public abstract class GeneratorObjectLiteralNode extends ObjectLiteralNode {
       value = getNullDefaultValue(vmNull);
     }
     VmUtils.checkIsInstantiable(
-        value instanceof VmClass vmClass ? vmClass : VmUtils.getClass(value), getParentNode());
+        value instanceof VmClass vmClass ? vmClass : VmUtils.getClass(value),
+        getParentNode(),
+        this);
 
     throw exceptionBuilder().unreachableCode().build();
   }

pkl-core/src/main/java/org/pkl/core/ast/expression/literal/EmptyObjectLiteralNode.java

@@ -52,7 +52,7 @@ public abstract class EmptyObjectLiteralNode extends ExpressionNode {
       return VmDynamic.empty();
     }
 
-    VmUtils.checkIsInstantiable(parent, getParentNode());
+    VmUtils.checkIsInstantiable(parent, getParentNode(), this);
     return parent.getPrototype();
   }
 
@@ -70,7 +70,7 @@ public abstract class EmptyObjectLiteralNode extends ExpressionNode {
   @TruffleBoundary
   protected void fallback(Object parent) {
     assert !(parent instanceof VmClass);
-    VmUtils.checkIsInstantiable(VmUtils.getClass(parent), getParentNode());
+    VmUtils.checkIsInstantiable(VmUtils.getClass(parent), getParentNode(), this);
     throw exceptionBuilder().unreachableCode().build();
   }
 

pkl-core/src/main/java/org/pkl/core/ast/expression/literal/SpecializedObjectLiteralNode.java

@@ -72,7 +72,7 @@ public abstract class SpecializedObjectLiteralNode extends ObjectLiteralNode {
   @Idempotent
   protected boolean checkIsValidTypedAmendment(Object parent) {
     var parentClass = parent instanceof VmClass vmClass ? vmClass : VmUtils.getClass(parent);
-    VmUtils.checkIsInstantiable(parentClass, getParentNode());
+    VmUtils.checkIsInstantiable(parentClass, getParentNode(), this);
 
     for (var member : EconomicMaps.getValues(members)) {
       if (member.isLocal()) continue;
@@ -290,7 +290,7 @@ public abstract class SpecializedObjectLiteralNode extends ObjectLiteralNode {
       Object parent, @Nullable ObjectMember firstElemOrEntry, boolean isElementsOnly) {
     var parentIsClass = parent instanceof VmClass;
     var parentClass = parentIsClass ? (VmClass) parent : VmUtils.getClass(parent);
-    VmUtils.checkIsInstantiable(parentClass, getParentNode());
+    VmUtils.checkIsInstantiable(parentClass, getParentNode(), this);
 
     var property = findFirstNonDefaultProperty(members);
     if (property != null

pkl-core/src/main/java/org/pkl/core/ast/expression/member/AbstractInferParentNode.java

@@ -59,7 +59,7 @@ public abstract class AbstractInferParentNode extends ExpressionNode {
     // try to produce a more specific error message than "cannotInstantiateType"
     var clazz = typeNode.getType().getVmClass();
     if (clazz != null) {
-      VmUtils.checkIsInstantiable(clazz, typeNode);
+      VmUtils.checkIsInstantiable(clazz, typeNode, this);
     }
 
     throw exceptionBuilder()

pkl-core/src/main/java/org/pkl/core/runtime/VmUtils.java

@@ -903,7 +903,7 @@ public final class VmUtils {
     return resolvedNodes;
   }
 
-  public static void checkIsInstantiable(VmClass parentClass, @Nullable Node parentNode) {
+  public static void checkIsInstantiable(VmClass parentClass, Node parentNode, Node callerNode) {
     if (parentClass.isInstantiable()) return;
 
     CompilerDirectives.transferToInterpreter();
@@ -911,14 +911,15 @@ public final class VmUtils {
     if (parentClass.isAbstract()) {
       throw new VmExceptionBuilder()
           .evalError("cannotInstantiateAbstractClass", parentClass)
-          .withOptionalLocation(parentNode)
+          .withOptionalLocation(
+              parentNode.getSourceSection().isAvailable() ? parentNode : callerNode)
           .build();
     }
 
     assert parentClass.isExternal();
     throw new VmExceptionBuilder()
         .evalError("cannotInstantiateExternalClass", parentClass)
-        .withOptionalLocation(parentNode)
+        .withOptionalLocation(parentNode.getSourceSection().isAvailable() ? parentNode : callerNode)
         .build();
   }
 

pkl-core/src/main/java/org/pkl/core/stdlib/base/DynamicNodes.java

@@ -108,7 +108,7 @@ public final class DynamicNodes {
         throw exceptionBuilder().evalError("notASubclassOfTyped", clazz).build();
       }
 
-      VmUtils.checkIsInstantiable(clazz, this);
+      VmUtils.checkIsInstantiable(clazz, this, this);
 
       var result =
           new VmTyped(

pkl-core/src/main/java/org/pkl/core/stdlib/base/MapNodes.java

@@ -255,7 +255,7 @@ public final class MapNodes {
         throw exceptionBuilder().evalError("notASubclassOfTyped", clazz).build();
       }
 
-      VmUtils.checkIsInstantiable(clazz, null);
+      VmUtils.checkIsInstantiable(clazz, this, this);
 
       var result =
           new VmTyped(

pkl-core/src/test/files/LanguageSnippetTests/input/errors/cannotInstantiateExternalClass.pkl

@@ -0,0 +1,13 @@
+class Holder {
+  name: String
+}
+
+base: Holder = new {
+  name = "base"
+}
+
+result: Holder = (base) {
+  name {
+    "foo"
+  }
+}

pkl-core/src/test/files/LanguageSnippetTests/output/errors/cannotInstantiateExternalClass.err

@@ -0,0 +1,19 @@
+–– Pkl Error ––
+Cannot instantiate, or amend an instance of, external class `String`.
+
+xx | name {
+     ^^^^^^
+at cannotInstantiateExternalClass#result.name (file:///$snippetsDir/input/errors/cannotInstantiateExternalClass.pkl)
+
+To create an instance of an external class, use its literal syntax or constructor method.
+Examples:
+* `123` uses literal syntax to create an instance of class `Int`.
+* `Pair(1, 2)` uses the `Pair()` constructor method to create an instance of class `Pair`.
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)