CSE Machine: Fix display bug when scanning out declarations (#1527)

* Add declaration type to symbol's description

* Revert "CSE Machine: Rename to CS1101S terms (#1514)"

This reverts commit d6553ca.

* Remove some outdated lines

* Modification while running tests

* Remove package-lock.json

The project uses Yarn.

* Remove erroneous dependency changes

* Revert back to Yarn registry in lockfile

* Revert "Revert "CSE Machine: Rename to CS1101S terms (#1514)""

This reverts commit 77d8c4b.

* Pull updated test cases from master branch

* bumping version

---------

Co-authored-by: Richard Dominick <[email protected]>
Co-authored-by: henz <[email protected]>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "js-slang",
-  "version": "1.0.38",
+  "version": "1.0.39",
   "license": "Apache-2.0",
   "description": "Javascript-based implementations of Source, written in Typescript",
   "keywords": [

src/cse-machine/interpreter.ts

@@ -362,7 +362,6 @@ const cmdEvaluators: { [type: string]: CmdEvaluator } = {
     const environment = createBlockEnvironment(context, 'blockEnvironment')
     declareFunctionsAndVariables(context, command, environment)
     pushEnvironment(context, environment)
-
     // Push block body
     control.push(...handleSequence(command.body))
   },

src/cse-machine/utils.ts

@@ -299,13 +299,15 @@ export const createBlockEnvironment = (
  * Variables
  */
 
-const DECLARED_BUT_NOT_YET_ASSIGNED = Symbol('Used to implement block scope')
+const UNASSIGNED_CONST = Symbol('const declaration')
+const UNASSIGNED_LET = Symbol('let declaration')
 
 export function declareIdentifier(
   context: Context,
   name: string,
   node: es.Node,
-  environment: Environment
+  environment: Environment,
+  constant: boolean = false
 ) {
   if (environment.head.hasOwnProperty(name)) {
     const descriptors = Object.getOwnPropertyDescriptors(environment.head)
@@ -315,7 +317,7 @@ export function declareIdentifier(
       new errors.VariableRedeclaration(node, name, descriptors[name].writable)
     )
   }
-  environment.head[name] = DECLARED_BUT_NOT_YET_ASSIGNED
+  environment.head[name] = constant ? UNASSIGNED_CONST : UNASSIGNED_LET
   return environment
 }
 
@@ -325,7 +327,9 @@ function declareVariables(
   environment: Environment
 ) {
   for (const declaration of node.declarations) {
-    declareIdentifier(context, (declaration.id as es.Identifier).name, node, environment)
+    // Retrieve declaration type from node
+    const constant = node.kind === 'const'
+    declareIdentifier(context, (declaration.id as es.Identifier).name, node, environment, constant)
   }
 }
 
@@ -340,7 +344,14 @@ export function declareFunctionsAndVariables(
         declareVariables(context, statement, environment)
         break
       case 'FunctionDeclaration':
-        declareIdentifier(context, (statement.id as es.Identifier).name, statement, environment)
+        // FunctionDeclaration is always of type constant
+        declareIdentifier(
+          context,
+          (statement.id as es.Identifier).name,
+          statement,
+          environment,
+          true
+        )
         break
     }
   }
@@ -377,7 +388,7 @@ export function defineVariable(
 ) {
   const environment = currentEnvironment(context)
 
-  if (environment.head[name] !== DECLARED_BUT_NOT_YET_ASSIGNED) {
+  if (environment.head[name] !== UNASSIGNED_CONST && environment.head[name] !== UNASSIGNED_LET) {
     return handleRuntimeError(context, new errors.VariableRedeclaration(node, name, !constant))
   }
 
@@ -394,7 +405,10 @@ export const getVariable = (context: Context, name: string, node: es.Identifier)
   let environment: Environment | null = currentEnvironment(context)
   while (environment) {
     if (environment.head.hasOwnProperty(name)) {
-      if (environment.head[name] === DECLARED_BUT_NOT_YET_ASSIGNED) {
+      if (
+        environment.head[name] === UNASSIGNED_CONST ||
+        environment.head[name] === UNASSIGNED_LET
+      ) {
         return handleRuntimeError(context, new errors.UnassignedVariable(name, node))
       } else {
         return environment.head[name]
@@ -415,7 +429,10 @@ export const setVariable = (
   let environment: Environment | null = currentEnvironment(context)
   while (environment) {
     if (environment.head.hasOwnProperty(name)) {
-      if (environment.head[name] === DECLARED_BUT_NOT_YET_ASSIGNED) {
+      if (
+        environment.head[name] === UNASSIGNED_CONST ||
+        environment.head[name] === UNASSIGNED_LET
+      ) {
         break
       }
       const descriptors = Object.getOwnPropertyDescriptors(environment.head)