diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 01706664d84..c477cfd022c 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -2008,8 +2008,7 @@ class BodyBuilder<Arguments> extends ScopeListener<JumpTarget>
       push(deprecated_buildCompileTimeError(
           "Not a constant expression.", operator.charOffset));
     } else {
-      push(new ShadowAsExpression(expression, type)
-        ..fileOffset = offsetForToken(operator));
+      push(forest.asExpression(expression, type, operator));
     }
   }
 
diff --git a/pkg/front_end/lib/src/fasta/kernel/fangorn.dart b/pkg/front_end/lib/src/fasta/kernel/fangorn.dart
index 566ee452756..8a34d1d9254 100644
--- a/pkg/front_end/lib/src/fasta/kernel/fangorn.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/fangorn.dart
@@ -28,6 +28,7 @@ import '../scanner.dart' show Token;
 import 'kernel_shadow_ast.dart'
     show
         ShadowArguments,
+        ShadowAsExpression,
         ShadowBoolLiteral,
         ShadowCheckLibraryIsLoaded,
         ShadowDoubleLiteral,
@@ -154,6 +155,12 @@ class Fangorn extends Forest<Expression, Statement, Token, Arguments> {
     return new ShadowCheckLibraryIsLoaded(dependency);
   }
 
+  @override
+  Expression asExpression(Expression expression, covariant type, Token token) {
+    return new ShadowAsExpression(expression, type)
+      ..fileOffset = offsetForToken(token);
+  }
+
   @override
   bool isErroneousNode(TreeNode node) {
     if (node is ExpressionStatement) {
diff --git a/pkg/front_end/lib/src/fasta/kernel/forest.dart b/pkg/front_end/lib/src/fasta/kernel/forest.dart
index c9a526ccb70..8b7327fce42 100644
--- a/pkg/front_end/lib/src/fasta/kernel/forest.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/forest.dart
@@ -54,6 +54,9 @@ abstract class Forest<Expression, Statement, Location, Arguments> {
 
   Expression checkLibraryIsLoaded(covariant dependency);
 
+  Expression asExpression(
+      Expression expression, covariant type, Location location);
+
   bool isErroneousNode(covariant node);
 
   // TODO(ahe): Remove this method when all users are moved here.