From 399aef569ddedcb58dcb394b394d55f20c78ee83 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 2 Aug 2026 13:23:34 +0100
Subject: Don't panic on unrecognised sum variant tag

---
 .../rusttransient0/RustTransient0Generator.java    | 32 ++++++++++++----------
 1 file changed, 18 insertions(+), 14 deletions(-)

(limited to 'src/main/java/org')

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/rusttransient0/RustTransient0Generator.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/rusttransient0/RustTransient0Generator.java
index fed710f..b70752e 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/rusttransient0/RustTransient0Generator.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/rusttransient0/RustTransient0Generator.java
@@ -379,19 +379,7 @@ public class RustTransient0Generator implements Generator {
 
         decodeMatchArms.add(new RustMatchArm(
             new RustWildcardPattern(),
-            new RustTryPropagationExpression(new RustCallExpression(
-                RustTypes.RESULT_ERR,
-                List.of(
-                    new RustCallExpression(
-                        RustTypes.IO_ERROR.addSegment(RustPathSegment.of("new")),
-                        List.of(
-                            RustTypes.IO_ERROR_KIND_INVALID_DATA,
-                            // TODO: include variant tag
-                            new RustStringLiteral("unrecognised variant tag for " + enumDefinition.type().describe())
-                        )
-                    )
-                )
-            ))
+            new RustTryPropagationExpression(generateUnrecognisedVariantResult(enumDefinition.type()))
         ));
 
         return generateDecodeFunction(
@@ -512,7 +500,7 @@ public class RustTransient0Generator implements Generator {
 
         decodeMatchArms.add(new RustMatchArm(
             new RustWildcardPattern(),
-            generateTodo()
+            new RustTryPropagationExpression(generateUnrecognisedVariantResult(sumDefinition.type()))
         ));
 
         return generateDecodeFunction(
@@ -1104,6 +1092,22 @@ public class RustTransient0Generator implements Generator {
         );
     }
 
+    private static RustCallExpression generateUnrecognisedVariantResult(Type type) {
+        return new RustCallExpression(
+            RustTypes.RESULT_ERR,
+            List.of(
+                new RustCallExpression(
+                    RustTypes.IO_ERROR.addSegment(RustPathSegment.of("new")),
+                    List.of(
+                        RustTypes.IO_ERROR_KIND_INVALID_DATA,
+                        // TODO: include variant tag
+                        new RustStringLiteral("unrecognised variant tag for " + type.describe())
+                    )
+                )
+            )
+        );
+    }
+
     private RustExpression tryIntoOrInvalidData(RustExpression value) {
         return new RustTryPropagationExpression(mapErrToInvalidData(
             methodCall(
-- 
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