From fbe9654480d0d7b50afad2ce249b5874701da1d9 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 5 Nov 2023 20:03:22 +0000
Subject: Throw error if effect field is not handled

---
 .../typechecker/MissingEffectHandlerFieldError.java     | 17 +++++++++++++++++
 .../org/shedlang/compiler/typechecker/TypeChecker.java  |  8 +++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 src/main/java/org/shedlang/compiler/typechecker/MissingEffectHandlerFieldError.java

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/typechecker/MissingEffectHandlerFieldError.java b/src/main/java/org/shedlang/compiler/typechecker/MissingEffectHandlerFieldError.java
new file mode 100644
index 00000000..468ca23d
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/MissingEffectHandlerFieldError.java
@@ -0,0 +1,17 @@
+package org.shedlang.compiler.typechecker;
+
+import org.shedlang.compiler.errors.SourceError;
+import org.shedlang.compiler.sources.Source;
+
+public class MissingEffectHandlerFieldError extends SourceError {
+    private final String fieldName;
+
+    public MissingEffectHandlerFieldError(String fieldName, Source source) {
+        super("Missing effect handler field: " + fieldName, source);
+        this.fieldName = fieldName;
+    }
+
+    public String fieldName() {
+        return fieldName;
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index db81d7cc..44842599 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -1602,7 +1602,7 @@ public class TypeChecker {
     ) {
         var typedHandledEffect = typeCheckEffect(untyped.handledEffect(), context);
 
-        if (!(typedHandledEffect.value() instanceof UserDefinedEffect)) {
+        if (!(typedHandledEffect.value() instanceof UserDefinedEffect handledEffect)) {
             throw new NotUserDefinedEffectError(
                 typedHandledEffect.value(),
                 untyped.handledEffect().source()
@@ -1623,6 +1623,12 @@ public class TypeChecker {
 
         context = context.exit();
 
+        var effectInfo = context.userDefinedEffectInfo(handledEffect, typedHandledEffect.source());
+        // TODO: Don't create unnecessary list
+        for (var field : effectInfo.fields().stream().toList()) {
+            throw new MissingEffectHandlerFieldError(field.getKey(), untyped.source());
+        }
+
         return context.toResult(new TypedTryNode(
             typedBody,
             typedHandledEffect,
-- 
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