Add lexical scope and redefining variables in functions (#3015)

* Fix to allow variable shadowing inside functions

* Implement closures

* Fix KCL test code to not reference future tag definition

* Remove tag declarator from function parameters

This is an example where the scoping change revealed a subtle issue
with TagDeclarators.  You cannot bind a new tag using a function
parameter.

The issue is that evaluating a TagDeclarator like $foo binds an
identifier to its corresponding TagIdentifier, but returns the
TagDeclarator.  If you have a TagDeclarator passed in as a parameter
to a function, you can never get its corresponding TagIdentifier.

This seems like a case where TagDeclarator evaluation needs to be
revisited, especially now that we have scoped tags.

* Fix to query return, functions, and tag declarator AST nodes correctly

src/lang/KclSingleton.ts

@@ -14,9 +14,7 @@ import {
   Program,
   ProgramMemory,
   recast,
-  SketchGroup,
   SourceRange,
-  ExtrudeGroup,
 } from 'lang/wasm'
 import { getNodeFromPath } from './queryAst'
 import { codeManager, editorManager, sceneInfra } from 'lib/singletons'
@@ -33,10 +31,7 @@ export class KclManager {
     },
     digest: null,
   }
-  private _programMemory: ProgramMemory = {
-    root: {},
-    return: null,
-  }
+  private _programMemory: ProgramMemory = ProgramMemory.empty()
   private _logs: string[] = []
   private _kclErrors: KCLError[] = []
   private _isExecuting = false
@@ -505,10 +500,7 @@ function defaultSelectionFilter(
   programMemory: ProgramMemory,
   engineCommandManager: EngineCommandManager
 ) {
-  const firstSketchOrExtrudeGroup = Object.values(programMemory.root).find(
-    (node) => node.type === 'ExtrudeGroup' || node.type === 'SketchGroup'
-  ) as SketchGroup | ExtrudeGroup
-  firstSketchOrExtrudeGroup &&
+  programMemory.hasSketchOrExtrudeGroup() &&
     engineCommandManager.sendSceneCommand({
       type: 'modeling_cmd_req',
       cmd_id: uuidv4(),