Cherry-pick PR microsoft#53665 into release-5.0

Component commits:
8adc6ca Fix crash when private id in array assignment

Author: jakebailey

src/compiler/transformers/classFields.ts

@@ -2977,11 +2977,11 @@ export function transformClassFields(context: TransformationContext): (x: Source
     }
 
     function visitArrayAssignmentElement(node: Expression): Expression {
-        Debug.assertNode(node, isArrayBindingOrAssignmentElement);
-        if (isSpreadElement(node)) return visitAssignmentRestElement(node);
-        if (!isOmittedExpression(node)) return visitAssignmentElement(node);
+        if (isArrayBindingOrAssignmentElement(node)) {
+            if (isSpreadElement(node)) return visitAssignmentRestElement(node);
+            if (!isOmittedExpression(node)) return visitAssignmentElement(node);
+        }
         return visitEachChild(node, visitor, context);
-
     }
 
     function visitAssignmentProperty(node: PropertyAssignment) {

tests/baselines/reference/parserPrivateIdentifierInArrayAssignment.errors.txt

@@ -0,0 +1,11 @@
+tests/cases/compiler/parserPrivateIdentifierInArrayAssignment.ts(1,2): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
+tests/cases/compiler/parserPrivateIdentifierInArrayAssignment.ts(1,8): error TS1109: Expression expected.
+
+
+==== tests/cases/compiler/parserPrivateIdentifierInArrayAssignment.ts (2 errors) ====
+    [#abc]=
+     ~~~~
+!!! error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
+           
+!!! error TS1109: Expression expected.
+    

tests/baselines/reference/parserPrivateIdentifierInArrayAssignment.js

@@ -0,0 +1,6 @@
+//// [parserPrivateIdentifierInArrayAssignment.ts]
+[#abc]=
+
+
+//// [parserPrivateIdentifierInArrayAssignment.js]
+#abc = [0];

tests/baselines/reference/parserPrivateIdentifierInArrayAssignment.symbols

@@ -0,0 +1,4 @@
+=== tests/cases/compiler/parserPrivateIdentifierInArrayAssignment.ts ===
+
+[#abc]=
+

tests/baselines/reference/parserPrivateIdentifierInArrayAssignment.types

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/parserPrivateIdentifierInArrayAssignment.ts ===
+[#abc]=
+>[#abc]= : any
+>[#abc] : [any]
+
+> : any
+

tests/cases/compiler/parserPrivateIdentifierInArrayAssignment.ts

@@ -0,0 +1 @@
+[#abc]=