refactor(@angular-devkit/build-optimizer): minor type cleanup

Author: clydin

packages/angular_devkit/build_optimizer/src/transforms/wrap-enums.ts

@@ -17,8 +17,7 @@ function isBlockLike(node: ts.Node): node is ts.BlockLike {
 
 export function getWrapEnumsTransformer(): ts.TransformerFactory<ts.SourceFile> {
   return (context: ts.TransformationContext): ts.Transformer<ts.SourceFile> => {
-    const transformer: ts.Transformer<ts.SourceFile> = (sf: ts.SourceFile) => {
-
+    const transformer: ts.Transformer<ts.SourceFile> = sf => {
       const result = visitBlockStatements(sf.statements, context);
 
       return ts.updateSourceFileNode(sf, ts.setTextRange(result, sf.statements));
@@ -45,15 +44,13 @@ function visitBlockStatements(
       result = ts.setTextRange(result, node.statements);
       switch (node.kind) {
         case ts.SyntaxKind.Block:
-          return ts.updateBlock(node as ts.Block, result);
+          return ts.updateBlock(node, result);
         case ts.SyntaxKind.ModuleBlock:
-          return ts.updateModuleBlock(node as ts.ModuleBlock, result);
+          return ts.updateModuleBlock(node, result);
         case ts.SyntaxKind.CaseClause:
-          const clause = node as ts.CaseClause;
-
-          return ts.updateCaseClause(clause, clause.expression, result);
+          return ts.updateCaseClause(node, node.expression, result);
         case ts.SyntaxKind.DefaultClause:
-          return ts.updateDefaultClause(node as ts.DefaultClause, result);
+          return ts.updateDefaultClause(node, result);
         default:
           return node;
       }