Support object property name completions in lambda body syntax

src/Bicep.Core/TypeSystem/DeclaredTypeManager.cs

@@ -1790,6 +1790,14 @@ AccessExpressionSyntax access when access.BaseExpression is ForSyntax
                     var type = TypeHelper.MakeRequiredPropertiesOptional(enclosingObjectType);
 
                     return TryCreateAssignment(type, syntax);
+
+                case TypedLambdaSyntax lambda when binder.IsEqualOrDescendent(syntax, lambda.Body):
+                    if (GetTypedLambdaType(lambda).Reference is not LambdaType lambdaType)
+                    {
+                        return null;
+                    }
+
+                    return TryCreateAssignment(lambdaType.ReturnType, syntax);
             }
 
             return null;

src/Bicep.LangServer.IntegrationTests/CompletionTests.cs

@@ -5204,5 +5204,35 @@ public async Task String_literal_union_with_object_value_should_not_cause_stack_
             var completions = await mainFile.RequestCompletion(cursor);
             completions.Should().BeEmpty();
         }
+
+        [TestMethod]
+        // https://github.com/azure/bicep/issues/14429
+        public async Task Lambda_output_type_completions_are_offered()
+        {
+            var serverHelper = new ServerRequestHelper(TestContext, DefaultServer);
+
+            var (text, cursor) = ParserHelper.GetFileWithSingleCursor("""
+type fooType = {
+  bar: 'bar'
+}
+
+func fooFunc() fooType => {
+  |
+}
+""");
+            var mainFile = await serverHelper.OpenFile(text);
+
+            var newFile = await mainFile.RequestAndApplyCompletion(cursor, "bar");
+
+            newFile.Should().HaveSourceText("""
+type fooType = {
+  bar: 'bar'
+}
+
+func fooFunc() fooType => {
+  bar:|
+}
+""");
+        }
     }
 }

src/Bicep.LangServer.IntegrationTests/Helpers/ServerRequestHelper.cs

@@ -148,6 +148,14 @@ public BicepFile ApplyCompletion(CompletionItem completion, params string[] tabS
             return SourceFileFactory.CreateBicepFile(bicepFile.Uri, replaced);
         }
 
+        public async Task<BicepFile> RequestAndApplyCompletion(int cursor, string label)
+        {
+            var completionList = await RequestCompletion(cursor);
+            var completion = completionList.Should().ContainSingle(x => x.Label == label).Subject;
+
+            return ApplyCompletion(completion);
+        }
+
         public BicepFile ApplyWorkspaceEdit(WorkspaceEdit? edit)
         {
             // not yet supported by this logic