migrate checkDelete to new property checking

Author: HerringtonDarkholme

src/compiler/checker.ts

@@ -5777,7 +5777,7 @@ namespace ts {
                     getIndexInfoOfType(objectType, IndexKind.String) ||
                     undefined;
                 if (indexInfo) {
-                    if (accessExpression && isAssignmentTarget(accessExpression) && indexInfo.isReadonly) {
+                    if (accessExpression && indexInfo.isReadonly && (isAssignmentTarget(accessExpression) || isDeleteTarget(accessExpression))) {
                         error(accessExpression, Diagnostics.Index_signature_in_type_0_only_permits_reading, typeToString(objectType));
                         return unknownType;
                     }
@@ -13550,9 +13550,16 @@ namespace ts {
 
         function checkDeleteExpression(node: DeleteExpression): Type {
             checkExpression(node.expression);
-            checkReferenceExpression(node.expression,
-                Diagnostics.The_operand_of_a_delete_operator_must_be_a_property_reference,
-                Diagnostics.The_operand_of_a_delete_operator_cannot_be_a_read_only_property);
+            const expr = skipParentheses(node.expression);
+            if (expr.kind !== SyntaxKind.PropertyAccessExpression && expr.kind !== SyntaxKind.ElementAccessExpression) {
+                error(expr, Diagnostics.The_operand_of_a_delete_operator_must_be_a_property_reference);
+                return booleanType;
+            }
+            const links = getNodeLinks(expr);
+            const symbol = getExportSymbolOfValueSymbolIfExported(links.resolvedSymbol);
+            if (symbol && isReadonlySymbol(symbol)) {
+                error(expr, Diagnostics.The_operand_of_a_delete_operator_cannot_be_a_read_only_property);
+            }
             return booleanType;
         }
 

src/compiler/types.ts

@@ -2651,7 +2651,6 @@ namespace ts {
         resolvedType?: Type;              // Cached type of type node
         resolvedSignature?: Signature;    // Cached signature of signature node or call expression
         resolvedSymbol?: Symbol;          // Cached name resolution result
-        resolvedIndexInfo?: IndexInfo;    // Cached indexing info resolution result
         enumMemberValue?: number;         // Constant value of enum member
         isVisible?: boolean;              // Is this node visible
         hasReportedStatementInAmbientContext?: boolean;  // Cache boolean if we report statements in ambient context

src/compiler/utilities.ts

@@ -1,4 +1,4 @@
-/// <reference path="sys.ts" />
+/// <reference path="sys.ts" />
 
 /* @internal */
 namespace ts {
@@ -1666,6 +1666,18 @@ namespace ts {
         return getAssignmentTargetKind(node) !== AssignmentKind.None;
     }
 
+    // a node is delete target iff. it is PropertyAccessExpression/ElementAccessExpression with parentheses skipped
+    export function isDeleteTarget(node: Node): boolean {
+        if (node.kind !== SyntaxKind.PropertyAccessExpression && node.kind !== SyntaxKind.ElementAccessExpression) {
+            return false;
+        }
+        node = node.parent;
+        while (node && node.kind === SyntaxKind.ParenthesizedExpression) {
+            node = node.parent;
+        }
+        return node && node.kind === SyntaxKind.DeleteExpression;
+    }
+
     export function isNodeDescendantOf(node: Node, ancestor: Node): boolean {
         while (node) {
             if (node === ancestor) return true;