diff --git a/packages/angular_devkit/build_optimizer/src/helpers/ast-utils.ts b/packages/angular_devkit/build_optimizer/src/helpers/ast-utils.ts
index 131dfbf8d4..8c34506d32 100644
--- a/packages/angular_devkit/build_optimizer/src/helpers/ast-utils.ts
+++ b/packages/angular_devkit/build_optimizer/src/helpers/ast-utils.ts
@@ -7,6 +7,8 @@
  */
 import * as ts from 'typescript';
 
+const pureFunctionComment = '@__PURE__';
+
 // Find all nodes from the AST in the subtree of node of SyntaxKind kind.
 export function collectDeepNodes<T extends ts.Node>(node: ts.Node, kind: ts.SyntaxKind): T[] {
   const nodes: T[] = [];
@@ -20,3 +22,22 @@ export function collectDeepNodes<T extends ts.Node>(node: ts.Node, kind: ts.Synt
 
   return nodes;
 }
+
+export function addPureComment<T extends ts.Node>(node: T): T {
+  return ts.addSyntheticLeadingComment(
+    node,
+    ts.SyntaxKind.MultiLineCommentTrivia,
+    pureFunctionComment,
+    false,
+  );
+}
+
+export function hasPureComment(node: ts.Node): boolean {
+  if (!node) {
+    return false;
+  }
+
+  const leadingComment = ts.getSyntheticLeadingComments(node);
+
+  return !!leadingComment && leadingComment.some(comment => comment.text === pureFunctionComment);
+}
diff --git a/packages/angular_devkit/build_optimizer/src/transforms/class-fold.ts b/packages/angular_devkit/build_optimizer/src/transforms/class-fold.ts
index ecc49220ab..206a1b4ab4 100644
--- a/packages/angular_devkit/build_optimizer/src/transforms/class-fold.ts
+++ b/packages/angular_devkit/build_optimizer/src/transforms/class-fold.ts
@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
+import { addPureComment } from '../helpers/ast-utils';
 
 interface ClassData {
   name: string;
@@ -81,18 +82,12 @@ export function getFoldFileTransformer(program: ts.Program): ts.TransformerFacto
           const classStatement = clazz.declaration as ts.ClassDeclaration;
           const innerReturn = ts.createReturn(ts.createIdentifier(clazz.name));
 
-          const iife = ts.createImmediatelyInvokedFunctionExpression([
-            classStatement,
-            ...clazz.statements.map(st => st.expressionStatement),
-            innerReturn,
-          ]);
-
-          const pureIife = ts.addSyntheticLeadingComment(
-            iife,
-            ts.SyntaxKind.MultiLineCommentTrivia,
-            '@__PURE__',
-            false,
-          );
+          const pureIife = addPureComment(
+            ts.createImmediatelyInvokedFunctionExpression([
+              classStatement,
+              ...clazz.statements.map(st => st.expressionStatement),
+              innerReturn,
+            ]));
 
           // Move the original class modifiers to the var statement.
           const newNode = ts.createVariableStatement(
diff --git a/packages/angular_devkit/build_optimizer/src/transforms/prefix-classes.ts b/packages/angular_devkit/build_optimizer/src/transforms/prefix-classes.ts
index cc8797d775..0ade653c54 100644
--- a/packages/angular_devkit/build_optimizer/src/transforms/prefix-classes.ts
+++ b/packages/angular_devkit/build_optimizer/src/transforms/prefix-classes.ts
@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
+import { addPureComment } from '../helpers/ast-utils';
 
 /**
  * @deprecated From 0.9.0
@@ -42,9 +43,6 @@ const extendsHelperName = '__extends';
 export function getPrefixClassesTransformer(): ts.TransformerFactory<ts.SourceFile> {
   return (context: ts.TransformationContext): ts.Transformer<ts.SourceFile> => {
     const transformer: ts.Transformer<ts.SourceFile> = (sf: ts.SourceFile) => {
-
-      const pureFunctionComment = '@__PURE__';
-
       const visitor: ts.Visitor = (node: ts.Node): ts.VisitResult<ts.Node> => {
 
         // Add pure comment to downleveled classes.
@@ -63,12 +61,7 @@ export function getPrefixClassesTransformer(): ts.TransformerFactory<ts.SourceFi
                   varDecl,
                   varDecl.name,
                   varDecl.type,
-                  ts.addSyntheticLeadingComment(
-                    varInitializer,
-                    ts.SyntaxKind.MultiLineCommentTrivia,
-                    pureFunctionComment,
-                    false,
-                  ),
+                  addPureComment(varInitializer),
                 ),
               ],
             ),
diff --git a/packages/angular_devkit/build_optimizer/src/transforms/prefix-functions.ts b/packages/angular_devkit/build_optimizer/src/transforms/prefix-functions.ts
index 99d6227b65..05ac4f0bac 100644
--- a/packages/angular_devkit/build_optimizer/src/transforms/prefix-functions.ts
+++ b/packages/angular_devkit/build_optimizer/src/transforms/prefix-functions.ts
@@ -6,9 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-
-
-const pureFunctionComment = '@__PURE__';
+import { addPureComment, hasPureComment } from '../helpers/ast-utils';
 
 export function getPrefixFunctionsTransformer(): ts.TransformerFactory<ts.SourceFile> {
   return (context: ts.TransformationContext): ts.Transformer<ts.SourceFile> => {
@@ -19,8 +17,7 @@ export function getPrefixFunctionsTransformer(): ts.TransformerFactory<ts.Source
       const visitor: ts.Visitor = (node: ts.Node): ts.Node => {
         // Add pure function comment to top level functions.
         if (topLevelFunctions.has(node)) {
-          const newNode = ts.addSyntheticLeadingComment(
-            node, ts.SyntaxKind.MultiLineCommentTrivia, pureFunctionComment, false);
+          const newNode = addPureComment(node);
 
           // Replace node with modified one.
           return ts.visitEachChild(newNode, visitor, context);
@@ -96,12 +93,3 @@ export function findTopLevelFunctions(parentNode: ts.Node): Set<ts.Node> {
 
   return topLevelFunctions;
 }
-
-function hasPureComment(node: ts.Node) {
-  if (!node) {
-    return false;
-  }
-  const leadingComment = ts.getSyntheticLeadingComments(node);
-
-  return leadingComment && leadingComment.some((comment) => comment.text === pureFunctionComment);
-}
diff --git a/packages/angular_devkit/build_optimizer/src/transforms/wrap-enums.ts b/packages/angular_devkit/build_optimizer/src/transforms/wrap-enums.ts
index 394c122ffb..8b2341cdd0 100644
--- a/packages/angular_devkit/build_optimizer/src/transforms/wrap-enums.ts
+++ b/packages/angular_devkit/build_optimizer/src/transforms/wrap-enums.ts
@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
+import { addPureComment } from '../helpers/ast-utils';
 
 function isBlockLike(node: ts.Node): node is ts.BlockLike {
   return node.kind === ts.SyntaxKind.Block
@@ -384,17 +385,6 @@ function findEnumNameStatements(
   return enumStatements;
 }
 
-function addPureComment<T extends ts.Node>(node: T): T {
-  const pureFunctionComment = '@__PURE__';
-
-  return ts.addSyntheticLeadingComment(
-    node,
-    ts.SyntaxKind.MultiLineCommentTrivia,
-    pureFunctionComment,
-    false,
-  );
-}
-
 function updateHostNode(
   hostNode: ts.VariableStatement,
   expression: ts.Expression,