diff --git a/.idea/formula-evaluator.iml b/.idea/formula-evaluator.iml
index b25edf75..d12b25e0 100644
--- a/.idea/formula-evaluator.iml
+++ b/.idea/formula-evaluator.iml
@@ -5,7 +5,7 @@
       <configuration>
         <option name="connectionName" value="Expression" />
         <option name="connectionType" value="SFDX" />
-        <option name="defaultSourceRootUrl" value="file://$MODULE_DIR$/force-app" />
+        <option name="defaultSourceRootUrl" value="file://$MODULE_DIR$/src-pull" />
         <option name="moduleContents">
           <ModuleContents>
             <option name="contentSelectionType" value="LOCAL_FILES" />
diff --git a/README.md b/README.md
index 0b90c1f1..863b6f91 100644
--- a/README.md
+++ b/README.md
@@ -2199,12 +2199,11 @@ The source code includes a `Visitor` implementation
 whose sole purpose is to do this, `AstPrinter`. When enabled, it will
 print the AST to the logs.
 
-You can enable it by passing an `expression.Evaluator.Config` option to the `run` 
+You can enable it by passing an `expression.Configuration` option to the `run` 
 method with the `printAst` option enabled :
 
 ```apex
-expression.Evaluator.Config config = new expression.Evaluator.Config();
-config.printAst = true;
+expression.Configuration config = new expression.Configuration().printAst();
 Object value = expression.Evaluator.run('AND(true, false, 1=1)', config);
 // Outputs to the logs:
 // (AND true false (= 1 1))
diff --git a/expression-components/main/ui/controllers/FormulaEvaluatorUiController.cls b/expression-components/main/ui/controllers/FormulaEvaluatorUiController.cls
index 10b7ec49..2482c44a 100644
--- a/expression-components/main/ui/controllers/FormulaEvaluatorUiController.cls
+++ b/expression-components/main/ui/controllers/FormulaEvaluatorUiController.cls
@@ -14,8 +14,7 @@ public with sharing class FormulaEvaluatorUiController {
     @AuraEnabled(Cacheable=true)
     public static Object evaluate(String recordId, String formula, Boolean respectSharing) {
         try {
-            Evaluator.Config config = new Evaluator.Config();
-            config.sharing = respectSharing ? Evaluator.SharingMode.WITH : Evaluator.SharingMode.WITHOUT;
+            Configuration config = new Configuration().respectSharing(respectSharing);
             if (String.isBlank(recordId)) {
                 return Evaluator.run(formula, config);
             } else {
diff --git a/expression-src/main/api/Configuration.cls b/expression-src/main/api/Configuration.cls
new file mode 100644
index 00000000..27692469
--- /dev/null
+++ b/expression-src/main/api/Configuration.cls
@@ -0,0 +1,43 @@
+global with sharing class Configuration {
+    public static Configuration.SharingMode evaluationSharingMode;
+
+    global enum SharingMode {
+        WITH,
+        WITHOUT
+    }
+
+    global SharingMode sharing = SharingMode.WITH;
+    global Boolean printAst = false;
+    public Boolean withDiagnostics = false;
+
+    global Configuration respectSharing(Boolean respect) {
+        sharing = respect ? SharingMode.WITH : SharingMode.WITHOUT;
+        return this;
+    }
+
+    global Configuration printAst() {
+        printAst = true;
+        return this;
+    }
+
+    global Configuration withDiagnostics() {
+        withDiagnostics = true;
+        return this;
+    }
+
+    public void subscribe(EvaluatorEventNotifier notifier) {
+        // Always subscribe to the event that sets the sharing mode
+        // at the beginning of the evaluation regardless of configuration.
+        notifier.subscribe(OnEvaluationStartEvent.class, new EvaluationSharingModeSetter());
+
+        if (this.printAst) {
+            notifier.subscribe(OnAfterParseEvent.class, new AstPrinter());
+        }
+
+        if (this.withDiagnostics) {
+            EvaluationDiagnosticsListener diagnosticsListener = new EvaluationDiagnosticsListener();
+            notifier.subscribe(OnEvaluationStartEvent.class, diagnosticsListener);
+            notifier.subscribe(OnEvaluationEndEvent.class, diagnosticsListener);
+        }
+    }
+}
\ No newline at end of file
diff --git a/expression-src/main/src/helpers/AstPrinter.cls-meta.xml b/expression-src/main/api/Configuration.cls-meta.xml
similarity index 100%
rename from expression-src/main/src/helpers/AstPrinter.cls-meta.xml
rename to expression-src/main/api/Configuration.cls-meta.xml
diff --git a/expression-src/main/api/Evaluator.cls b/expression-src/main/api/Evaluator.cls
index c383595b..b74bfc83 100644
--- a/expression-src/main/api/Evaluator.cls
+++ b/expression-src/main/api/Evaluator.cls
@@ -1,16 +1,14 @@
 /**
  * @description Evaluates a formula and returns the result.
  */
-global with sharing class Evaluator {
-    public static SharingMode evaluationSharingMode;
-
+global with sharing abstract class Evaluator {
     /**
      * @description Evaluates a formula and returns the result.
      * @param formula The formula to evaluate.
      * @return The result of the formula.
      */
     global static Object run(String formula) {
-        return run(formula, new Config());
+        return run(formula, new Configuration());
     }
 
     /**
@@ -20,7 +18,7 @@ global with sharing class Evaluator {
      *        the evaluation.
      * @return The result of the formula.
      */
-    global static Object run(String formula, Config config) {
+    global static Object run(String formula, Configuration config) {
         return run(formula, (SObject) null, config);
     }
 
@@ -33,7 +31,7 @@ global with sharing class Evaluator {
      * @return The result of the formula.
      */
     global static Object run(String formula, SObject context) {
-        return run(formula, context, new Config());
+        return run(formula, context, new Configuration());
     }
 
     /**
@@ -46,9 +44,8 @@ global with sharing class Evaluator {
      *        the evaluation.
      * @return The result of the formula.
      */
-    global static Object run(String formula, SObject context, Config config) {
-        Expr pipedExpression = parseExpression(formula, config);
-        return interpretWithContext(context, pipedExpression, config);
+    global static Object run(String formula, SObject context, Configuration config) {
+        return EvaluatorResolver.forRecord(context).evaluate(formula, config).result;
     }
 
     /**
@@ -60,7 +57,7 @@ global with sharing class Evaluator {
      * @return The result of the formula.
      */
     global static Object run(String formula, Id recordId) {
-        return run(formula, recordId, new Config());
+        return run(formula, recordId, new Configuration());
     }
 
     /**
@@ -73,58 +70,7 @@ global with sharing class Evaluator {
      *        the evaluation.
      * @return The result of the formula.
      */
-    global static Object run(String formula, Id recordId, Config config) {
-        Expr pipedExpression = parseExpression(formula, config);
-        SObject record = getRecord(recordId, pipedExpression);
-        return interpretWithContext(record, pipedExpression, config);
-    }
-
-    private static Expr parseExpression(String formula, Config config) {
-        evaluationSharingMode = config.sharing;
-        Scanner scanner = new Scanner(formula);
-        List<Token> tokens = scanner.scanTokens();
-
-        Parser parser = new Parser(tokens);
-        Expr expression = parser.parse();
-
-        if (config.printAst) {
-            AstPrinter printer = new AstPrinter();
-            printer.printAst(expression);
-        }
-
-        PipeResolver pipeInterpreter = new PipeResolver();
-        Expr pipedExpression = pipeInterpreter.resolve(expression);
-        return pipedExpression;
-    }
-
-    private static SObject getRecord(Id recordId, Expr pipedExpression) {
-        ContextResolver ctxInterpreter = new ContextResolver(recordId);
-        return ctxInterpreter.build(pipedExpression);
-    }
-
-    private static Object interpretWithContext(SObject record, Expr pipedExpression, Config config) {
-        Environment env = new Environment(record);
-        IInterpreter interpreter = getInterpreter(env, config);
-        return interpreter.interpret(pipedExpression);
-    }
-
-    global enum SharingMode {
-        WITH,
-        WITHOUT
-    }
-
-    global class Config {
-        global SharingMode sharing = SharingMode.WITH;
-        global Boolean printAst = false;
-        public Boolean withDiagnostics = false;
-    }
-
-    private static IInterpreter getInterpreter(Environment env, Config config) {
-        IInterpreter mainInterpreter = new Interpreter(env);
-        if (config.withDiagnostics) {
-            return new DiagnosticsDecorator(mainInterpreter);
-        } else {
-            return mainInterpreter;
-        }
+    global static Object run(String formula, Id recordId, Configuration config) {
+        return EvaluatorResolver.forId(recordId).evaluate(formula, config).result;
     }
 }
diff --git a/expression-src/main/editor/controllers/PlaygroundController.cls b/expression-src/main/editor/controllers/PlaygroundController.cls
index 207152d9..ad3f8d4e 100644
--- a/expression-src/main/editor/controllers/PlaygroundController.cls
+++ b/expression-src/main/editor/controllers/PlaygroundController.cls
@@ -33,16 +33,30 @@ public with sharing class PlaygroundController {
         return toReturn;
     }
 
+    // Record Id is of type String because we could receive an empty String
+    // from the front-end, so we can't use Id as the type in that case.
     @AuraEnabled
-    public static Result validate(String expr, Id recordId) {
+    public static Result validate(String expr, String recordId) {
         Result toReturn = new Result();
-        Evaluator.Config config = new Evaluator.Config();
-        config.withDiagnostics = true;
+        Configuration config = new Configuration().withDiagnostics().printAst();
         try {
+            EvaluationResult evalResult;
             if (String.isNotBlank(recordId)) {
-                toReturn.result = Evaluator.run(expr, recordId, config);
+                evalResult = EvaluatorResolver.forId(recordId).evaluate(expr, config);
             } else {
-                toReturn.result = Evaluator.run(expr, config);
+                evalResult = EvaluatorResolver.withoutContext().evaluate(expr, config);
+            }
+
+            toReturn.result = evalResult.result;
+
+            if (evalResult.additionalData.containsKey('diagnostics')) {
+                EvaluationDiagnosticsListener.DiagnosticsResult diagnosticsResult =
+                    (EvaluationDiagnosticsListener.DiagnosticsResult)evalResult.additionalData.get('diagnostics');
+                toReturn.diagnostics = new Diagnostics(diagnosticsResult);
+            }
+
+            if (evalResult.additionalData.containsKey('ast')) {
+                toReturn.ast = evalResult.additionalData.get('ast');
             }
         } catch (Exceptions.PositionAwareException e) {
             EvaluationError error = new EvaluationError();
@@ -60,8 +74,6 @@ public with sharing class PlaygroundController {
             toReturn.error = error;
         }
 
-        toReturn.diagnostics = new Diagnostics(DiagnosticsDecorator.result);
-
         return toReturn;
     }
 
@@ -74,6 +86,9 @@ public with sharing class PlaygroundController {
 
         @AuraEnabled
         public Diagnostics diagnostics;
+
+        @AuraEnabled
+        public Object ast;
     }
 
     public class Diagnostics {
@@ -89,7 +104,7 @@ public with sharing class PlaygroundController {
         @AuraEnabled
         public Integer queryRows;
 
-        public Diagnostics(DiagnosticsDecorator.DiagnosticsResult result) {
+        public Diagnostics(EvaluationDiagnosticsListener.DiagnosticsResult result) {
             this.cpuTime = result?.cpuTime;
             this.dmlStatements = result?.dmlStatements;
             this.queries = result?.queries;
diff --git a/expression-src/main/editor/lwc/playground/playground.html b/expression-src/main/editor/lwc/playground/playground.html
index 5b68615a..e84c8a35 100644
--- a/expression-src/main/editor/lwc/playground/playground.html
+++ b/expression-src/main/editor/lwc/playground/playground.html
@@ -40,13 +40,19 @@
                                 </lightning-tab>
                                 <lightning-tab label="Diagnostics">
                                     <ul>
-                                        <li><strong>CPU Time:</strong> {diagnostics.cpuTime}<span
-                                            if:true={diagnostics.cpuTime}>ms</span></li>
+                                        <li><strong>CPU Time (ms):</strong> {diagnostics.cpuTime}<span
+                                            if:true={diagnostics.cpuTime}></span></li>
                                         <li><strong>DML Statements:</strong> {diagnostics.dmlStatements}</li>
                                         <li><strong>Queries:</strong> {diagnostics.queries}</li>
                                         <li><strong>Query Rows:</strong> {diagnostics.queryRows}</li>
                                     </ul>
                                 </lightning-tab>
+                                <lightning-tab label="AST">
+                                    <pre class={resultColor}>
+                                        <lightning-formatted-rich-text
+                                                value={ast}></lightning-formatted-rich-text>
+                                    </pre>
+                                </lightning-tab>
                             </lightning-tabset>
                         </div>
                     </div>
diff --git a/expression-src/main/editor/lwc/playground/playground.js b/expression-src/main/editor/lwc/playground/playground.js
index b0e01800..b5632abd 100644
--- a/expression-src/main/editor/lwc/playground/playground.js
+++ b/expression-src/main/editor/lwc/playground/playground.js
@@ -7,7 +7,13 @@ export default class Monaco extends LightningElement {
   recordId;
   iframeUrl = `${monaco}/main.html`;
   result = {};
-  diagnostics = {};
+  diagnostics = {
+    cpuTime: "Unavailable",
+    dmlStatements: "Unavailable",
+    queries: "Unavailable",
+    queryRows: "Unavailable",
+  };
+  ast = "";
 
   async iframeLoaded() {
     const functionKeywords = await getFunctions();
@@ -40,7 +46,22 @@ export default class Monaco extends LightningElement {
       }
     }
 
-    this.diagnostics = result.diagnostics;
+    this._setDiagnostics(result);
+    this.ast = result.ast ?
+      this._syntaxHighlight(JSON.stringify(result.ast, null, 4)) :
+      "";
+  }
+
+  _setDiagnostics(result) {
+    this.diagnostics = Object.keys(result.diagnostics).reduce((acc, key) => {
+      acc[key] = result.diagnostics[key] ?? "Unavailable";
+      return acc;
+    }, {
+      cpuTime: "Unavailable",
+      dmlStatements: "Unavailable",
+      queries: "Unavailable",
+      queryRows: "Unavailable",
+    });
   }
 
   handleInputChange(event) {
diff --git a/expression-src/main/src/helpers/QRunner.cls b/expression-src/main/src/helpers/QRunner.cls
index d011c325..2ad1638a 100644
--- a/expression-src/main/src/helpers/QRunner.cls
+++ b/expression-src/main/src/helpers/QRunner.cls
@@ -7,7 +7,7 @@ public inherited sharing abstract class QRunner {
             return mockRunner;
         }
 
-        if (Evaluator.evaluationSharingMode == Evaluator.SharingMode.WITH) {
+        if (Configuration.evaluationSharingMode == Configuration.SharingMode.WITH) {
             return new WithSharingRunner();
         } else {
             return new WithoutSharingRunner();
diff --git a/expression-src/main/src/interpreter/DiagnosticsDecorator.cls b/expression-src/main/src/interpreter/DiagnosticsDecorator.cls
deleted file mode 100644
index cac81b23..00000000
--- a/expression-src/main/src/interpreter/DiagnosticsDecorator.cls
+++ /dev/null
@@ -1,46 +0,0 @@
-public with sharing class DiagnosticsDecorator implements IInterpreter {
-    private final IInterpreter decorated;
-
-    public static DiagnosticsResult result { get; private set; }
-
-    public class DiagnosticsResult {
-        public final Integer cpuTime;
-        public final Integer dmlStatements;
-        public final Integer queries;
-        public final Integer queryRows;
-
-        public DiagnosticsResult(Integer cpuTime, Integer dmlStatements, Integer queries, Integer queryRows) {
-            this.cpuTime = cpuTime;
-            this.dmlStatements = dmlStatements;
-            this.queries = queries;
-            this.queryRows = queryRows;
-        }
-    }
-
-    public DiagnosticsDecorator(IInterpreter decorated) {
-        this.decorated = decorated;
-    }
-
-    public Object interpret(Expr expr) {
-        Integer startCpuTime = Limits.getCpuTime();
-        Integer startDmlStatements = Limits.getDmlStatements();
-        Integer startQueries = Limits.getQueries();
-        Integer startQueryRows = Limits.getQueryRows();
-
-        Object toReturn = this.decorated.interpret(expr);
-
-        Integer endCpuTime = Limits.getCpuTime();
-        Integer endDmlStatements = Limits.getDmlStatements();
-        Integer endQueries = Limits.getQueries();
-        Integer endQueryRows = Limits.getQueryRows();
-
-        result = new DiagnosticsResult(
-            endCpuTime - startCpuTime,
-            endDmlStatements - startDmlStatements,
-            endQueries - startQueries,
-            endQueryRows - startQueryRows
-        );
-
-        return toReturn;
-    }
-}
diff --git a/expression-src/main/src/interpreter/IInterpreter.cls b/expression-src/main/src/interpreter/IInterpreter.cls
deleted file mode 100644
index 2749f41a..00000000
--- a/expression-src/main/src/interpreter/IInterpreter.cls
+++ /dev/null
@@ -1,3 +0,0 @@
-public interface IInterpreter {
-    Object interpret(Expr expr);
-}
diff --git a/expression-src/main/src/interpreter/Interpreter.cls b/expression-src/main/src/interpreter/Interpreter.cls
index 869dbf65..a3ae8446 100644
--- a/expression-src/main/src/interpreter/Interpreter.cls
+++ b/expression-src/main/src/interpreter/Interpreter.cls
@@ -1,4 +1,4 @@
-public with sharing class Interpreter implements IInterpreter, Visitor {
+public with sharing class Interpreter implements Visitor {
     private final Environment env;
 
     private Boolean inListLiteral = false;
diff --git a/expression-src/main/src/interpreter/std-lib/CollectionFunctions.cls b/expression-src/main/src/interpreter/std-lib/CollectionFunctions.cls
index ba8cc9b8..8e220b7e 100644
--- a/expression-src/main/src/interpreter/std-lib/CollectionFunctions.cls
+++ b/expression-src/main/src/interpreter/std-lib/CollectionFunctions.cls
@@ -78,7 +78,7 @@ public with sharing class CollectionFunctions {
         }
 
         public override Arity getArity() {
-            return Arity.atLeast(1);
+            return Arity.atLeast(0);
         }
     }
 
diff --git a/expression-src/main/src/interpreter/tests/DiagnosticsDecoratorTest.cls b/expression-src/main/src/interpreter/tests/DiagnosticsDecoratorTest.cls
deleted file mode 100644
index ab3da420..00000000
--- a/expression-src/main/src/interpreter/tests/DiagnosticsDecoratorTest.cls
+++ /dev/null
@@ -1,17 +0,0 @@
-@IsTest
-private class DiagnosticsDecoratorTest {
-    @IsTest
-    static void populatesDiagnosticsWhenRun() {
-        String expression = '1 + 2';
-        Evaluator.Config configWithDiagnostics = new Evaluator.Config();
-        configWithDiagnostics.withDiagnostics = true;
-
-        Object result = Evaluator.run(expression, configWithDiagnostics);
-
-        Assert.areEqual(3, result);
-        Assert.isNotNull(DiagnosticsDecorator.result.cpuTime);
-        Assert.isNotNull(DiagnosticsDecorator.result.dmlStatements);
-        Assert.isNotNull(DiagnosticsDecorator.result.queries);
-        Assert.isNotNull(DiagnosticsDecorator.result.queryRows);
-    }
-}
diff --git a/expression-src/main/src/resolver/EvaluationResult.cls b/expression-src/main/src/resolver/EvaluationResult.cls
new file mode 100644
index 00000000..799869e1
--- /dev/null
+++ b/expression-src/main/src/resolver/EvaluationResult.cls
@@ -0,0 +1,10 @@
+public with sharing class EvaluationResult {
+    public Object result { get; private set; }
+
+    public Map<String, Object> additionalData { get; private set; }
+
+    public EvaluationResult(Object result, Map<String, Object> additionalData) {
+        this.result = result;
+        this.additionalData = additionalData;
+    }
+}
\ No newline at end of file
diff --git a/expression-src/main/src/interpreter/DiagnosticsDecorator.cls-meta.xml b/expression-src/main/src/resolver/EvaluationResult.cls-meta.xml
similarity index 100%
rename from expression-src/main/src/interpreter/DiagnosticsDecorator.cls-meta.xml
rename to expression-src/main/src/resolver/EvaluationResult.cls-meta.xml
diff --git a/expression-src/main/src/resolver/EvaluatorEventListener.cls b/expression-src/main/src/resolver/EvaluatorEventListener.cls
new file mode 100644
index 00000000..b8830f30
--- /dev/null
+++ b/expression-src/main/src/resolver/EvaluatorEventListener.cls
@@ -0,0 +1,3 @@
+public interface EvaluatorEventListener {
+    Map<String, Object> handle(EvaluatorEvent event);
+}
\ No newline at end of file
diff --git a/expression-src/main/src/interpreter/IInterpreter.cls-meta.xml b/expression-src/main/src/resolver/EvaluatorEventListener.cls-meta.xml
similarity index 100%
rename from expression-src/main/src/interpreter/IInterpreter.cls-meta.xml
rename to expression-src/main/src/resolver/EvaluatorEventListener.cls-meta.xml
diff --git a/expression-src/main/src/resolver/EvaluatorEventNotifier.cls b/expression-src/main/src/resolver/EvaluatorEventNotifier.cls
new file mode 100644
index 00000000..c4bac91e
--- /dev/null
+++ b/expression-src/main/src/resolver/EvaluatorEventNotifier.cls
@@ -0,0 +1,33 @@
+public with sharing class EvaluatorEventNotifier {
+    final Map<Type, List<EvaluatorEventListener>> listeners =
+        new Map<Type, List<EvaluatorEventListener>>();
+
+    // Holds any data received from the event handler.
+    final Map<String, Object> listenerData;
+
+    public EvaluatorEventNotifier(Map<String, Object> listenerData) {
+        this.listenerData = listenerData;
+    }
+
+    public void subscribe(Type eventType, EvaluatorEventListener listener) {
+        List<EvaluatorEventListener> users = listeners.get(eventType);
+        if (users == null) {
+            users = new List<EvaluatorEventListener>();
+            listeners.put(eventType, users);
+        }
+        users.add(listener);
+    }
+
+    public void notify(EvaluatorEvent event) {
+        Type eventType = event.getType();
+        List<EvaluatorEventListener> users = listeners.get(eventType);
+        if (users != null) {
+            for (EvaluatorEventListener listener : users) {
+                Map<String, Object> handlerResult = listener.handle(event);
+                if (handlerResult != null) {
+                    listenerData.putAll(handlerResult);
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/expression-src/main/src/interpreter/tests/DiagnosticsDecoratorTest.cls-meta.xml b/expression-src/main/src/resolver/EvaluatorEventNotifier.cls-meta.xml
similarity index 100%
rename from expression-src/main/src/interpreter/tests/DiagnosticsDecoratorTest.cls-meta.xml
rename to expression-src/main/src/resolver/EvaluatorEventNotifier.cls-meta.xml
diff --git a/expression-src/main/src/resolver/EvaluatorResolver.cls b/expression-src/main/src/resolver/EvaluatorResolver.cls
new file mode 100644
index 00000000..1adc38ce
--- /dev/null
+++ b/expression-src/main/src/resolver/EvaluatorResolver.cls
@@ -0,0 +1,86 @@
+public with sharing abstract class EvaluatorResolver {
+    private final Map<String, Object> additionalResultData = new Map<String, Object>();
+    private final EvaluatorEventNotifier eventNotifier;
+
+    private EvaluatorResolver() {
+        this.eventNotifier = new EvaluatorEventNotifier(additionalResultData);
+    }
+
+    public static EvaluatorResolver forId(Id recordId) {
+        return new ContextResolverEvaluator(recordId);
+    }
+
+    public static EvaluatorResolver forRecord(SObject record) {
+        return new BaseEvaluator(record);
+    }
+
+    public static EvaluatorResolver withoutContext() {
+        return new BaseEvaluator(null);
+    }
+
+    public EvaluationResult evaluate(String input, Configuration config) {
+        config.subscribe(this.eventNotifier);
+
+        eventNotifier.notify(new OnEvaluationStartEvent(config));
+
+        List<Token> tokens = this.scan(input);
+        Expr parsedExpression = this.parse(tokens);
+
+        eventNotifier.notify(new OnAfterParseEvent(parsedExpression));
+
+        Expr pipedExpression = this.desugarPipe(parsedExpression);
+        Environment anEnvironment = this.prepareEnvironment(pipedExpression);
+        Object result = interpret(anEnvironment, pipedExpression);
+
+        eventNotifier.notify(new OnEvaluationEndEvent());
+
+        return new EvaluationResult(result, additionalResultData);
+    }
+
+    private List<Token> scan(String expression) {
+        Scanner scanner = new Scanner(expression);
+        return scanner.scanTokens();
+    }
+
+    private Expr parse(List<Token> tokens) {
+        Parser parser = new Parser(tokens);
+        return parser.parse();
+    }
+
+    private Expr desugarPipe(Expr rawExpression) {
+        PipeResolver pipeInterpreter = new PipeResolver();
+        Expr pipedExpression = pipeInterpreter.resolve(rawExpression);
+        return pipedExpression;
+    }
+
+    protected abstract Environment prepareEnvironment(Expr pipedExpression);
+
+    private Object interpret(Environment anEnvironment, Expr pipedExpression) {
+        Interpreter theInterpreter = new Interpreter(anEnvironment);
+        return theInterpreter.interpret(pipedExpression);
+    }
+
+    private class ContextResolverEvaluator extends EvaluatorResolver {
+        private final Id recordId;
+
+        public ContextResolverEvaluator(Id recordId) {
+            this.recordId = recordId;
+        }
+        public override Environment prepareEnvironment(Expr pipedExpression) {
+            ContextResolver ctxInterpreter = new ContextResolver(recordId);
+            SObject record = ctxInterpreter.build(pipedExpression);
+            return new Environment(record);
+        }
+    }
+
+    private class BaseEvaluator extends EvaluatorResolver {
+        private final SObject record;
+
+        public BaseEvaluator(SObject record) {
+            this.record = record;
+        }
+        public override Environment prepareEnvironment(Expr pipedExpression) {
+            return new Environment(record);
+        }
+    }
+}
\ No newline at end of file
diff --git a/expression-src/main/src/resolver/EvaluatorResolver.cls-meta.xml b/expression-src/main/src/resolver/EvaluatorResolver.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/EvaluatorResolver.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/expression-src/main/src/resolver/events/EvaluatorEvent.cls b/expression-src/main/src/resolver/events/EvaluatorEvent.cls
new file mode 100644
index 00000000..cdd13e68
--- /dev/null
+++ b/expression-src/main/src/resolver/events/EvaluatorEvent.cls
@@ -0,0 +1,3 @@
+public interface EvaluatorEvent {
+    Type getType();
+}
\ No newline at end of file
diff --git a/expression-src/main/src/resolver/events/EvaluatorEvent.cls-meta.xml b/expression-src/main/src/resolver/events/EvaluatorEvent.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/events/EvaluatorEvent.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/expression-src/main/src/resolver/events/OnAfterParseEvent.cls b/expression-src/main/src/resolver/events/OnAfterParseEvent.cls
new file mode 100644
index 00000000..97246f0c
--- /dev/null
+++ b/expression-src/main/src/resolver/events/OnAfterParseEvent.cls
@@ -0,0 +1,11 @@
+public with sharing class OnAfterParseEvent implements EvaluatorEvent {
+    public final Expr expression;
+
+    public OnAfterParseEvent(Expr expression) {
+        this.expression = expression;
+    }
+
+    public Type getType() {
+        return OnAfterParseEvent.class;
+    }
+}
\ No newline at end of file
diff --git a/expression-src/main/src/resolver/events/OnAfterParseEvent.cls-meta.xml b/expression-src/main/src/resolver/events/OnAfterParseEvent.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/events/OnAfterParseEvent.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/expression-src/main/src/resolver/events/OnEvaluationEndEvent.cls b/expression-src/main/src/resolver/events/OnEvaluationEndEvent.cls
new file mode 100644
index 00000000..8792fde9
--- /dev/null
+++ b/expression-src/main/src/resolver/events/OnEvaluationEndEvent.cls
@@ -0,0 +1,5 @@
+public with sharing class OnEvaluationEndEvent implements EvaluatorEvent {
+    public Type getType() {
+        return OnEvaluationEndEvent.class;
+    }
+}
\ No newline at end of file
diff --git a/expression-src/main/src/resolver/events/OnEvaluationEndEvent.cls-meta.xml b/expression-src/main/src/resolver/events/OnEvaluationEndEvent.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/events/OnEvaluationEndEvent.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/expression-src/main/src/resolver/events/OnEvaluationStartEvent.cls b/expression-src/main/src/resolver/events/OnEvaluationStartEvent.cls
new file mode 100644
index 00000000..11d6d02d
--- /dev/null
+++ b/expression-src/main/src/resolver/events/OnEvaluationStartEvent.cls
@@ -0,0 +1,11 @@
+public with sharing class OnEvaluationStartEvent implements EvaluatorEvent {
+    public final Configuration config;
+
+    public OnEvaluationStartEvent(Configuration config) {
+        this.config = config;
+    }
+
+    public Type getType() {
+        return OnEvaluationStartEvent.class;
+    }
+}
\ No newline at end of file
diff --git a/expression-src/main/src/resolver/events/OnEvaluationStartEvent.cls-meta.xml b/expression-src/main/src/resolver/events/OnEvaluationStartEvent.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/events/OnEvaluationStartEvent.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/expression-src/main/src/helpers/AstPrinter.cls b/expression-src/main/src/resolver/listeners/AstPrinter.cls
similarity index 93%
rename from expression-src/main/src/helpers/AstPrinter.cls
rename to expression-src/main/src/resolver/listeners/AstPrinter.cls
index 839648a5..941050dc 100644
--- a/expression-src/main/src/helpers/AstPrinter.cls
+++ b/expression-src/main/src/resolver/listeners/AstPrinter.cls
@@ -1,7 +1,11 @@
-public with sharing class AstPrinter implements Visitor {
-    public void printAst(Expr expr) {
-        Object toPrint = expr.accept(this);
+public with sharing class AstPrinter implements Visitor, EvaluatorEventListener {
+    public Map<String, Object> handle(EvaluatorEvent event) {
+        OnAfterParseEvent parseEvent = (OnAfterParseEvent)event;
+        Object toPrint = parseEvent.expression.accept(this);
         System.debug(JSON.serializePretty(toPrint));
+        return new Map<String, Object> {
+            'ast' => toPrint
+        };
     }
 
     public Object visit(Expr.Binary binary) {
diff --git a/expression-src/main/src/resolver/listeners/AstPrinter.cls-meta.xml b/expression-src/main/src/resolver/listeners/AstPrinter.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/listeners/AstPrinter.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/expression-src/main/src/resolver/listeners/EvaluationDiagnosticsListener.cls b/expression-src/main/src/resolver/listeners/EvaluationDiagnosticsListener.cls
new file mode 100644
index 00000000..ed38daf3
--- /dev/null
+++ b/expression-src/main/src/resolver/listeners/EvaluationDiagnosticsListener.cls
@@ -0,0 +1,54 @@
+public with sharing class EvaluationDiagnosticsListener implements EvaluatorEventListener {
+    Integer startCpuTime;
+    Integer startDmlStatements;
+    Integer startQueries;
+    Integer startQueryRows;
+
+    public class DiagnosticsResult {
+        public final Integer cpuTime;
+        public final Integer dmlStatements;
+        public final Integer queries;
+        public final Integer queryRows;
+
+        public DiagnosticsResult(Integer cpuTime, Integer dmlStatements, Integer queries, Integer queryRows) {
+            this.cpuTime = cpuTime;
+            this.dmlStatements = dmlStatements;
+            this.queries = queries;
+            this.queryRows = queryRows;
+        }
+    }
+
+    public Map<String, Object> handle(EvaluatorEvent event) {
+        if (event.getType() == OnEvaluationStartEvent.class) {
+            this.onEvaluationStart();
+        } else if (event.getType() == OnEvaluationEndEvent.class) {
+            return this.onEvaluationEnd();
+        }
+        return null;
+    }
+
+    private void onEvaluationStart() {
+        startCpuTime = Limits.getCpuTime();
+        startDmlStatements = Limits.getDmlStatements();
+        startQueries = Limits.getQueries();
+        startQueryRows = Limits.getQueryRows();
+    }
+
+    private Map<String, Object> onEvaluationEnd() {
+        Integer endCpuTime = Limits.getCpuTime();
+        Integer endDmlStatements = Limits.getDmlStatements();
+        Integer endQueries = Limits.getQueries();
+        Integer endQueryRows = Limits.getQueryRows();
+
+        DiagnosticsResult result = new DiagnosticsResult(
+            endCpuTime - startCpuTime,
+            endDmlStatements - startDmlStatements,
+            endQueries - startQueries,
+            endQueryRows - startQueryRows
+        );
+
+        return new Map<String, Object> {
+            'diagnostics' => result
+        };
+    }
+}
diff --git a/expression-src/main/src/resolver/listeners/EvaluationDiagnosticsListener.cls-meta.xml b/expression-src/main/src/resolver/listeners/EvaluationDiagnosticsListener.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/listeners/EvaluationDiagnosticsListener.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/expression-src/main/src/resolver/listeners/EvaluationSharingModeSetter.cls b/expression-src/main/src/resolver/listeners/EvaluationSharingModeSetter.cls
new file mode 100644
index 00000000..8b1ad0d3
--- /dev/null
+++ b/expression-src/main/src/resolver/listeners/EvaluationSharingModeSetter.cls
@@ -0,0 +1,7 @@
+public with sharing class EvaluationSharingModeSetter implements EvaluatorEventListener {
+    public Map<String, Object> handle(EvaluatorEvent event) {
+        OnEvaluationStartEvent startEvent = (OnEvaluationStartEvent)event;
+        Configuration.evaluationSharingMode = startEvent.config.sharing;
+        return null;
+    }
+}
\ No newline at end of file
diff --git a/expression-src/main/src/resolver/listeners/EvaluationSharingModeSetter.cls-meta.xml b/expression-src/main/src/resolver/listeners/EvaluationSharingModeSetter.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/listeners/EvaluationSharingModeSetter.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/expression-src/main/src/resolver/listeners/tests/EvaluationDiagnosticsListenerTest.cls b/expression-src/main/src/resolver/listeners/tests/EvaluationDiagnosticsListenerTest.cls
new file mode 100644
index 00000000..8f8a48c4
--- /dev/null
+++ b/expression-src/main/src/resolver/listeners/tests/EvaluationDiagnosticsListenerTest.cls
@@ -0,0 +1,18 @@
+@IsTest
+private class EvaluationDiagnosticsListenerTest {
+    @IsTest
+    static void populatesDiagnosticsWhenRun() {
+        String expression = '1 + 2';
+        Configuration configWithDiagnostics = new Configuration().withDiagnostics();
+        EvaluationResult result = EvaluatorResolver.withoutContext().evaluate(expression, configWithDiagnostics);
+
+        Assert.isNotNull(result.additionalData.get('diagnostics'));
+
+        EvaluationDiagnosticsListener.DiagnosticsResult diagnostics =
+            (EvaluationDiagnosticsListener.DiagnosticsResult) result.additionalData.get('diagnostics');
+        Assert.isNotNull(diagnostics.cpuTime);
+        Assert.isNotNull(diagnostics.dmlStatements);
+        Assert.isNotNull(diagnostics.queries);
+        Assert.isNotNull(diagnostics.queryRows);
+    }
+}
diff --git a/expression-src/main/src/resolver/listeners/tests/EvaluationDiagnosticsListenerTest.cls-meta.xml b/expression-src/main/src/resolver/listeners/tests/EvaluationDiagnosticsListenerTest.cls-meta.xml
new file mode 100644
index 00000000..7a518297
--- /dev/null
+++ b/expression-src/main/src/resolver/listeners/tests/EvaluationDiagnosticsListenerTest.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>58.0</apiVersion>
+    <status>Active</status>
+</ApexClass>
diff --git a/unpackaged/examples/expression-conf/main/default/pricing/SalesOrderLinePricingService.cls b/unpackaged/examples/expression-conf/main/default/pricing/SalesOrderLinePricingService.cls
index f962a151..97740dc8 100644
--- a/unpackaged/examples/expression-conf/main/default/pricing/SalesOrderLinePricingService.cls
+++ b/unpackaged/examples/expression-conf/main/default/pricing/SalesOrderLinePricingService.cls
@@ -14,8 +14,7 @@ public with sharing class SalesOrderLinePricingService {
 
         System.debug('salesOrderLine: ' + salesOrderLine);
 
-        Evaluator.Config config = new Evaluator.Config();
-        config.sharing = Evaluator.SharingMode.WITHOUT;
+        Configuration config = new Configuration().respectSharing(false);
         // Surcharges
         for (PriceComponent surcharge : components.getSurcharges()) {
             Boolean shouldInclude = (Boolean)Evaluator.run(surcharge.expression, config);