evaluator: introduce and expose scope tracking

evaluator/src/main/kotlin/gay/pizza/pork/evaluator/CompilationUnitContext.kt

@@ -9,10 +9,11 @@ import gay.pizza.pork.frontend.ImportLocator
 class CompilationUnitContext(
   val compilationUnit: CompilationUnit,
   val evaluator: Evaluator,
-  rootScope: Scope
+  rootScope: Scope,
+  name: String = "unknown"
 ) {
-  val internalScope = rootScope.fork()
-  val externalScope = rootScope.fork()
+  val internalScope = rootScope.fork("internal $name")
+  val externalScope = rootScope.fork("external $name")
 
   private var initialized = false
 

evaluator/src/main/kotlin/gay/pizza/pork/evaluator/Evaluator.kt

@@ -14,7 +14,7 @@ class Evaluator(val world: World, val scope: Scope) {
     val unit = world.load(locator)
     val identity = world.stableIdentity(locator)
     val context = contexts.computeIfAbsent(identity) {
-      CompilationUnitContext(unit, this, scope)
+      CompilationUnitContext(unit, this, scope, name = "${locator.form} ${locator.path}")
     }
     context.initIfNeeded()
     return context

evaluator/src/main/kotlin/gay/pizza/pork/evaluator/Scope.kt

@@ -1,6 +1,10 @@
 package gay.pizza.pork.evaluator
 
-class Scope(val parent: Scope? = null, inherits: List<Scope> = emptyList()) {
+class Scope(
+  val parent: Scope? = null,
+  inherits: List<Scope> = emptyList(),
+  val name: String? = null
+) {
   private val inherited = inherits.toMutableList()
   private val variables = mutableMapOf<String, Any>()
 
@@ -41,8 +45,8 @@ class Scope(val parent: Scope? = null, inherits: List<Scope> = emptyList()) {
     return value
   }
 
-  fun fork(): Scope =
-    Scope(this)
+  fun fork(name: String? = null): Scope =
+    Scope(this, name = name)
 
   internal fun inherit(scope: Scope) {
     inherited.add(scope)
@@ -55,5 +59,26 @@ class Scope(val parent: Scope? = null, inherits: List<Scope> = emptyList()) {
     return parent
   }
 
+  fun crawlScopePath(
+    path: List<String> = mutableListOf(name ?: "unknown"),
+    block: (String, List<String>) -> Unit
+  ) {
+    for (key in variables.keys) {
+      block(key, path)
+    }
+
+    for (inherit in inherited) {
+      val mutablePath = path.toMutableList()
+      mutablePath.add("inherit ${inherit.name ?: "unknown"}")
+      inherit.crawlScopePath(mutablePath, block)
+    }
+
+    if (parent != null) {
+      val mutablePath = path.toMutableList()
+      mutablePath.add("parent ${parent.name ?: "unknown"}")
+      parent.crawlScopePath(mutablePath, block)
+    }
+  }
+
   private object NotFound
 }