Revert "Add check for delete expression must be optional"

This reverts commit 76937c3.

Author: Kingwl

src/compiler/checker.ts

@@ -27564,27 +27564,14 @@ namespace ts {
             if (expr.kind === SyntaxKind.PropertyAccessExpression && isPrivateIdentifier((expr as PropertyAccessExpression).name)) {
                 error(expr, Diagnostics.The_operand_of_a_delete_operator_cannot_be_a_private_identifier);
             }
-
             const links = getNodeLinks(expr);
             const symbol = getExportSymbolOfValueSymbolIfExported(links.resolvedSymbol);
-            if (symbol) {
-                if (isReadonlySymbol(symbol)) {
-                    error(expr, Diagnostics.The_operand_of_a_delete_operator_cannot_be_a_read_only_property);
-                }
-
-                checkDeleteExpressionMustBeOptional(expr, getTypeOfSymbol(symbol));
+            if (symbol && isReadonlySymbol(symbol)) {
+                error(expr, Diagnostics.The_operand_of_a_delete_operator_cannot_be_a_read_only_property);
             }
-
             return booleanType;
         }
 
-        function checkDeleteExpressionMustBeOptional(expr: AccessExpression, type: Type) {
-            const AnyOrUnknownOrNeverFlags = TypeFlags.AnyOrUnknown | TypeFlags.Never;
-            if (strictNullChecks && !(type.flags & AnyOrUnknownOrNeverFlags) && !(getFalsyFlags(type) & TypeFlags.Undefined)) {
-                error(expr, Diagnostics.The_operand_of_a_delete_operator_must_be_optional);
-            }
-        }
-
         function checkTypeOfExpression(node: TypeOfExpression): Type {
             checkExpression(node.expression);
             return typeofType;

src/compiler/diagnosticMessages.json

@@ -2963,10 +2963,6 @@
         "category": "Error",
         "code": 2789
     },
-    "The operand of a 'delete' operator must be optional.": {
-        "category": "Error",
-        "code": 2790
-    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/controlFlowDeleteOperator.errors.txt

@@ -1,8 +1,7 @@
-tests/cases/conformance/controlFlow/controlFlowDeleteOperator.ts(10,12): error TS2790: The operand of a 'delete' operator must be optional.
 tests/cases/conformance/controlFlow/controlFlowDeleteOperator.ts(14,12): error TS2703: The operand of a 'delete' operator must be a property reference.
 
 
-==== tests/cases/conformance/controlFlow/controlFlowDeleteOperator.ts (2 errors) ====
+==== tests/cases/conformance/controlFlow/controlFlowDeleteOperator.ts (1 errors) ====
     function f() {
         let x: { a?: number | string, b: number | string } = { b: 1 };
         x.a;
@@ -13,8 +12,6 @@ tests/cases/conformance/controlFlow/controlFlowDeleteOperator.ts(14,12): error T
         x.b;
         delete x.a;
         delete x.b;
-               ~~~
-!!! error TS2790: The operand of a 'delete' operator must be optional.
         x.a;
         x.b;
         x;