Check for number of binding elements in parameter patterns.

DanielRosenwasser · DanielRosenwasser · commit 0f871b9812f2 · 2015-06-22T16:44:13.000-07:00
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
@@ -3142,12 +3142,17 @@ var __param = (this && this.__param) || function (paramIndex, decorator) {
                             return;
                         }
 
-                        if (isBindingPattern(parameter.name)) {
-                            writeLine();
-                            write("var ");
-                            emitDestructuring(parameter, /*isAssignmentExpressionStatement*/ false, tempParameters[tempIndex]);
-                            write(";");
-                            tempIndex++;
+                        let paramName = parameter.name;
+                        if (isBindingPattern(paramName)) {
+                            // In cases where a binding patternm is simply '[]' or '{}',
+                            // we don't want to emit anything.
+                            if (paramName.elements.length > 0) {
+                                writeLine();
+                                write("var ");
+                                emitDestructuring(parameter, /*isAssignmentExpressionStatement*/ false, tempParameters[tempIndex]);
+                                write(";");
+                                tempIndex++;
+                            }
                         }
                         else if (parameter.initializer) {
                             writeLine();
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
@@ -1067,7 +1067,7 @@ namespace ts {
         return SyntaxKind.FirstTemplateToken <= kind && kind <= SyntaxKind.LastTemplateToken;
     }
 
-    export function isBindingPattern(node: Node) {
+    export function isBindingPattern(node: Node): node is BindingPattern {
         return !!node && (node.kind === SyntaxKind.ArrayBindingPattern || node.kind === SyntaxKind.ObjectBindingPattern);
     }
 

Original file line number	Diff line number	Diff line change
`@@ -1067,7 +1067,7 @@ namespace ts {`
`1067`	`1067`	`return SyntaxKind.FirstTemplateToken <= kind && kind <= SyntaxKind.LastTemplateToken;`
`1068`	`1068`	`}`
`1069`	`1069`
`1070`		`- export function isBindingPattern(node: Node) {`
	`1070`	`+ export function isBindingPattern(node: Node): node is BindingPattern {`
`1071`	`1071`	`return !!node && (node.kind === SyntaxKind.ArrayBindingPattern \|\| node.kind === SyntaxKind.ObjectBindingPattern);`
`1072`	`1072`	`}`
`1073`	`1073`