fix isParameterDeclaration changes

Author: gabritto

src/compiler/utilities.ts

@@ -3346,7 +3346,7 @@ namespace ts {
         return node.escapedText === "push" || node.escapedText === "unshift";
     }
 
-    export function isParameterDeclaration(node: VariableLikeDeclaration): node is ParameterDeclaration {
+    export function isParameterDeclaration(node: VariableLikeDeclaration): boolean {
         const root = getRootDeclaration(node);
         return root.kind === SyntaxKind.Parameter;
     }

src/services/completions.ts

@@ -981,7 +981,7 @@ namespace ts.Completions {
         }
 
         function addSnippetsWorker(node: Node, parent: Node | undefined) {
-            if (isVariableLike(node) && isParameterDeclaration(node)) {
+            if (isVariableLike(node) && node.kind === SyntaxKind.Parameter) {
                 // Placeholder
                 setSnippetElement(node.name, { kind: SnippetKind.Placeholder, order });
                 order += 1;