Restore reference change

Author: rbuckton

src/compiler/binder.ts

@@ -837,9 +837,8 @@ namespace ts {
  function isNarrowableReference(expr: Expression): boolean {
  return expr.kind === SyntaxKind.Identifier || expr.kind === SyntaxKind.ThisKeyword || expr.kind === SyntaxKind.SuperKeyword ||
  (isPropertyAccessExpression(expr) || isNonNullExpression(expr) || isParenthesizedExpression(expr)) && isNarrowableReference(expr.expression) ||
- isElementAccessExpression(expr) && isStringOrNumericLiteralLike(expr.argumentExpression) && isNarrowableReference(expr.expression);
- // ||
- // isAssignmentExpression(expr) && isNarrowableReference(expr.left);
+ isElementAccessExpression(expr) && isStringOrNumericLiteralLike(expr.argumentExpression) && isNarrowableReference(expr.expression) ||
+ isAssignmentExpression(expr) && isNarrowableReference(expr.left);
  }
 
  function containsNarrowableReference(expr: Expression): boolean {

src/compiler/checker.ts

@@ -20131,11 +20131,11 @@ namespace ts {
  case SyntaxKind.ParenthesizedExpression:
  case SyntaxKind.NonNullExpression:
  return isMatchingReference(source, (target as NonNullExpression | ParenthesizedExpression).expression);
- // case SyntaxKind.BinaryExpression:
- //  if (isAssignmentExpression(target)) {
- //  return isMatchingReference(source, target.left);
- //  }
- //  break;
+ case SyntaxKind.BinaryExpression:
+ if (isAssignmentExpression(target)) {
+ return isMatchingReference(source, target.left);
+ }
+ break;
  }
  switch (source.kind) {
  case SyntaxKind.Identifier: