Allow destructuring in ambient context

Author: Yui T

src/compiler/checker.ts

@@ -12005,9 +12005,6 @@ module ts {
         function checkGrammarVariableDeclaration(node: VariableDeclaration) {
             if (node.parent.parent.kind !== SyntaxKind.ForInStatement && node.parent.parent.kind !== SyntaxKind.ForOfStatement) {
                 if (isInAmbientContext(node)) {
-                    if (isBindingPattern(node.name)) {
-                        return grammarErrorOnNode(node, Diagnostics.Destructuring_declarations_are_not_allowed_in_ambient_contexts);
-                    }
                     if (node.initializer) {
                         // Error on equals token which immediate precedes the initializer
                         let equalsTokenLength = "=".length;

tests/baselines/reference/declarationInAmbientContext.errors.txt

@@ -0,0 +1,9 @@
+=== tests/cases/conformance/es6/destructuring/declarationInAmbientContext.ts ===
+declare var [a, b];  // Error, destructuring declaration not allowed in ambient context
+>a : any
+>b : any
+
+declare var {c, d};  // Error, destructuring declaration not allowed in ambient context
+>c : any
+>d : any
+