Always parse an argument for an ElementAccessExpression (#23683)

src/compiler/diagnosticMessages.json

@@ -23,6 +23,10 @@
         "category": "Error",
         "code": 1010
     },
+    "An element access expression should take an argument.": {
+        "category": "Error",
+        "code": 1011
+    },
     "Unexpected token.": {
         "category": "Error",
         "code": 1012

src/compiler/parser.ts

@@ -1240,7 +1240,7 @@ namespace ts {
             if (reportAtCurrentPosition) {
                 parseErrorAtPosition(scanner.getStartPos(), 0, diagnosticMessage, arg0);
             }
-            else {
+            else if (diagnosticMessage) {
                 parseErrorAtCurrentToken(diagnosticMessage, arg0);
             }
 
@@ -4348,14 +4348,15 @@ namespace ts {
                     const indexedAccess = <ElementAccessExpression>createNode(SyntaxKind.ElementAccessExpression, expression.pos);
                     indexedAccess.expression = expression;
 
-                    // It's not uncommon for a user to write: "new Type[]".
-                    // Check for that common pattern and report a better error message.
-                    if (token() !== SyntaxKind.CloseBracketToken) {
-                        indexedAccess.argumentExpression = allowInAnd(parseExpression);
-                        if (indexedAccess.argumentExpression.kind === SyntaxKind.StringLiteral || indexedAccess.argumentExpression.kind === SyntaxKind.NumericLiteral) {
-                            const literal = <LiteralExpression>indexedAccess.argumentExpression;
-                            literal.text = internIdentifier(literal.text);
+                    if (token() === SyntaxKind.CloseBracketToken) {
+                        indexedAccess.argumentExpression = createMissingNode(SyntaxKind.Identifier, /*reportAtCurrentPosition*/ true, Diagnostics.An_element_access_expression_should_take_an_argument);
+                    }
+                    else {
+                        const argument = allowInAnd(parseExpression);
+                        if (isStringOrNumericLiteral(argument)) {
+                            argument.text = internIdentifier(argument.text);
                         }
+                        indexedAccess.argumentExpression = argument;
                     }
 
                     parseExpected(SyntaxKind.CloseBracketToken);

src/compiler/types.ts

@@ -1685,7 +1685,7 @@ namespace ts {
     export interface ElementAccessExpression extends MemberExpression {
         kind: SyntaxKind.ElementAccessExpression;
         expression: LeftHandSideExpression;
-        argumentExpression?: Expression;
+        argumentExpression: Expression;
     }
 
     export interface SuperElementAccessExpression extends ElementAccessExpression {