Enforce restrictions on referenced properties

Author: HT154

src/main/kotlin/org/pkl/lsp/PklRefModule.kt

@@ -1,21 +1,36 @@
+/*
+ * Copyright © 2026 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 package org.pkl.lsp
 
 import org.pkl.lsp.ast.PklClass
 import org.pkl.lsp.ast.PklModule
 import org.pkl.lsp.type.Type
 
-class PklRefModule(project: Project): Component(project) {
-    val module: PklModule?
-        get() = project.stdlib.ref?.getModule()?.get()
+class PklRefModule(project: Project) : Component(project) {
+  val module: PklModule?
+    get() = project.stdlib.ref?.getModule()?.get()
 
-    val types: Map<String, Type> = buildMap {
-        for (member in module?.members ?: emptyList()) {
-            if (member is PklClass) {
-                put(member.name, Type.Class.create(member))
-            }
-        }
+  val types: Map<String, Type> = buildMap {
+    for (member in module?.members ?: emptyList()) {
+      if (member is PklClass) {
+        put(member.name, Type.Class.create(member))
+      }
     }
+  }
 
-    // Will be `null` for versions < 0.32
-    val referenceType: Type.Reference? by lazy { types["Reference"] as? Type.Reference }
+  // Will be `null` for versions < 0.32
+  val referenceType: Type.Reference? by lazy { types["Reference"] as? Type.Reference }
 }

src/main/kotlin/org/pkl/lsp/analyzers/TypeAnalyzer.kt

@@ -46,7 +46,10 @@ class TypeAnalyzer(project: Project) : Analyzer(project) {
           unaliased is Type.Reference &&
             type.containsConstrainedType(project.pklBaseModule, node.containingFile.pklProject)
         ) {
-          holder.addError(node, ErrorMessages.create("invalidReferenceTypeWithConstraint"))
+          diagnosticsHolder.addError(
+            node,
+            ErrorMessages.create("invalidReferenceTypeWithConstraint"),
+          )
         }
 
         false

src/main/kotlin/org/pkl/lsp/ast/ModuleOrClass.kt

@@ -50,7 +50,7 @@ class PklModuleImpl(override val ctx: Node, override val virtualFile: VirtualFil
     header?.moduleExtendsAmendsClause?.moduleUri
   }
 
-  private val lock = Object()
+  private val lock = Any()
 
   // This is cached at the VirtualFile level
   override fun supermodule(context: PklProject?): PklModule? =

src/main/kotlin/org/pkl/lsp/type/Types.kt

@@ -560,6 +560,28 @@ sealed class Type(val constraints: List<ConstraintExpr> = listOf()) {
     override fun withTypeArguments(arguments: List<Type>): Class =
       Reference(ctx, arguments, constraints)
 
+    // enforce restrictions! cannot reference:
+    // - external or local properties
+    // - properties of Listing or Mapping
+    // - Dynamic.default
+    // - properties of any external class
+    // - any Module.output
+    private fun isViable(
+      prop: PklClassProperty,
+      type: Type,
+      base: PklBaseModule,
+      context: PklProject?,
+    ): Boolean =
+      !(prop.isExternal ||
+        prop.isLocal ||
+        (type as? Class)?.let {
+          it == base.listingType ||
+            it == base.mappingType ||
+            (it == base.dynamicType && prop.name == "default") ||
+            it.ctx.isExternal
+        } ?: false ||
+        (type.isSubtypeOf(base.moduleType, base, context) && prop.name == "output"))
+
     override fun visitMembers(
       isProperty: Boolean,
       allowClasses: Boolean,
@@ -583,9 +605,9 @@ sealed class Type(val constraints: List<ConstraintExpr> = listOf()) {
           var isUnknown = false
           val candidates = mutableSetOf<PklType>()
 
-          walkCandidates(referent, base, context) { _, properties ->
+          walkCandidates(referent, base, context) { type, properties ->
             for (prop in properties) {
-              if (!(prop.isExternal || prop.isLocal) && prop.name == visitor.exactName) {
+              if (isViable(prop, type, base, context) && prop.name == visitor.exactName) {
                 val propType = prop.type ?: PklFakeUnknownTypeImpl(ctx.project)
                 if (propType is PklUnknownType) {
                   isUnknown = true
@@ -608,9 +630,9 @@ sealed class Type(val constraints: List<ConstraintExpr> = listOf()) {
         }
         else -> {
           val propertyCandidates = mutableMapOf<String, MutableSet<PklType>>()
-          walkCandidates(referent, base, context) { _, properties ->
+          walkCandidates(referent, base, context) { type, properties ->
             for (prop in properties) {
-              if (!(prop.isExternal || prop.isLocal)) {
+              if (isViable(prop, type, base, context)) {
                 propertyCandidates
                   .getOrPut(prop.name) { mutableSetOf() }
                   .add(prop.type ?: PklFakeUnknownTypeImpl(ctx.project))

src/test/files/DiagnosticsSnippetTests/outputs/typecheck/nullabilityMismatch.txt

@@ -4,15 +4,15 @@
    ...foo
       ^^^
 | Warning: Nullability mismatch.
-| Required: Collection|Map|Dynamic|Listing|Mapping|IntSeq|Bytes
+| Required: Collection | Map | Dynamic | Listing | Mapping | IntSeq | Bytes
 | Actual: Listing<String>?
  }
 
  quz {
    for (elem in foo) {
                 ^^^
 | Warning: Nullability mismatch.
-| Required: Collection|Map|Dynamic|Listing|Mapping|IntSeq|Bytes
+| Required: Collection | Map | Dynamic | Listing | Mapping | IntSeq | Bytes
 | Actual: Listing<String>?
      "hi \(elem)"
    }

src/test/files/DiagnosticsSnippetTests/outputs/typecheck/spreadSyntax.txt

@@ -10,15 +10,15 @@
    ...bar
       ^^^
 | Warning: Nullability mismatch.
-| Required: Collection|Map|Dynamic|Listing|Mapping|IntSeq|Bytes
+| Required: Collection | Map | Dynamic | Listing | Mapping | IntSeq | Bytes
 | Actual: Mapping?
  }
 
  prop3 {
    ...myNum
       ^^^^^
 | Error: Type mismatch.
-| Required: Collection|Map|Dynamic|Listing|Mapping|IntSeq|Bytes
+| Required: Collection | Map | Dynamic | Listing | Mapping | IntSeq | Bytes
 | Actual: Int
  }
 
@@ -30,6 +30,6 @@
    ...Bytes(1, 2, 3)
       ^^^^^^^^^^^^^^
 | Error: Type mismatch.
-| Required: Collection<String>|Listing<String>|Dynamic
+| Required: Collection<String> | Listing<String> | Dynamic
 | Actual: Bytes
  }

src/test/files/DiagnosticsSnippetTests/outputs/typecheck/unions.txt

@@ -1,7 +1,7 @@
  foo: Int|String = true
                    ^^^^
 | Error: Type mismatch.
-| Required: Int|String
+| Required: Int | String
 | Actual: Boolean
 
  bar: Int = null