Update the entry point to return property symbol of destructuring assignment

Author: sheetalkamat

src/compiler/checker.ts

@@ -83,7 +83,7 @@ namespace ts {
  getShorthandAssignmentValueSymbol,
  getExportSpecifierLocalTargetSymbol,
  getTypeAtLocation: getTypeOfNode,
- getTypeOfArrayLiteralOrObjectLiteralDestructuringAssignment,
+ getPropertySymbolOfDestructuringAssignment,
  typeToString,
  getSymbolDisplayBuilder,
  symbolToString,
@@ -16568,6 +16568,7 @@ namespace ts {
  // [ a ] from 
  // [a] = [ some array ...]
  function getTypeOfArrayLiteralOrObjectLiteralDestructuringAssignment(expr: Expression): Type {
+ Debug.assert(expr.kind === SyntaxKind.ObjectLiteralExpression || expr.kind === SyntaxKind.ArrayLiteralExpression);
  // If this is from "for of"
  // for ( { a } of elems) {
  // }
@@ -16596,6 +16597,18 @@ namespace ts {
  indexOf((<ArrayLiteralExpression>expr.parent).elements, expr), elementType || unknownType);
  }
 
+ // Gets the property symbol corresponding to the property in destructuring assignment
+ // 'property1' from 
+ // for ( { property1: a } of elems) {
+ // }
+ // 'property1' at location 'a' from: 
+ // [a] = [ property1, property2 ]
+ function getPropertySymbolOfDestructuringAssignment(location: Identifier) {
+ // Get the type of the object or array literal and then look for property of given name in the type
+ const typeOfObjectLiteral = getTypeOfArrayLiteralOrObjectLiteralDestructuringAssignment(<Expression>location.parent.parent);
+ return typeOfObjectLiteral && getPropertyOfType(typeOfObjectLiteral, location.text);
+ }
+
  function getTypeOfExpression(expr: Expression): Type {
  if (isRightSideOfQualifiedNameOrPropertyAccess(expr)) {
  expr = <Expression>expr.parent;

src/compiler/types.ts

@@ -1735,7 +1735,7 @@ namespace ts {
  getSymbolsOfParameterPropertyDeclaration(parameter: ParameterDeclaration, parameterName: string): Symbol[];
  getShorthandAssignmentValueSymbol(location: Node): Symbol;
  getExportSpecifierLocalTargetSymbol(location: ExportSpecifier): Symbol;
- getTypeOfArrayLiteralOrObjectLiteralDestructuringAssignment(expression: Expression): Type;
+ getPropertySymbolOfDestructuringAssignment(location: Identifier): Symbol;
  getTypeAtLocation(node: Node): Type;
  typeToString(type: Type, enclosingDeclaration?: Node, flags?: TypeFormatFlags): string;
  symbolToString(symbol: Symbol, enclosingDeclaration?: Node, meaning?: SymbolFlags): string;

src/services/services.ts

@@ -5651,14 +5651,8 @@ namespace ts {
  }
 
  function getPropertySymbolOfDestructuringAssignment(location: Node) {
- if (isArrayLiteralOrObjectLiteralDestructuringPattern(location.parent.parent)) {
- // Do work to determine if this is a property symbol corresponding to the search symbol
- const typeOfObjectLiteral = typeChecker.getTypeOfArrayLiteralOrObjectLiteralDestructuringAssignment(<Expression>location.parent.parent);
- if (typeOfObjectLiteral) {
- return typeChecker.getPropertyOfType(typeOfObjectLiteral, (<Identifier>location).text);
- }
- }
- return undefined;
+ return isArrayLiteralOrObjectLiteralDestructuringPattern(location.parent.parent) &&
+ typeChecker.getPropertySymbolOfDestructuringAssignment(<Identifier>location);
  }
 
  function isObjectBindingPatternElementWithoutPropertyName(symbol: Symbol) {