From 15cce94576557de13db6d855f8ac47a2a2b652be Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 17 Sep 2023 17:40:57 +0100
Subject: Check expression is tuple

---
 .../java/org/shedlang/compiler/typechecker/TypeChecker.java |  9 ++++++++-
 .../org/shedlang/compiler/typechecker/typesets/TypeSet.java |  2 +-
 .../compiler/typechecker/typesets/TypeSetTuple.java         | 13 +++++++++++++
 .../shedlang/compiler/typechecker/typesets/TypeSets.java    |  1 +
 4 files changed, 23 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTuple.java

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index eafa9f47..435de6de 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -865,7 +865,14 @@ public class TypeChecker {
             }
 
             case UntypedTargetNode.Tuple targetTuple -> {
-                var tupleType = (TupleType) expressionType;
+                if (!(expressionType instanceof TupleType tupleType)) {
+                    throw new UnexpectedTypeError(
+                        TypeSets.TUPLE,
+                        expressionType,
+                        // TODO: should the source be the target or the expression?
+                        targetTuple.source()
+                    );
+                }
 
                 var typedTargetElements = new ArrayList<TypedTargetNode>();
 
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java
index 01899978..5a0350f4 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java
@@ -1,5 +1,5 @@
 package org.shedlang.compiler.typechecker.typesets;
 
-public sealed interface TypeSet permits TypeSetFunction, TypeSetType, TypeSetTypeLevelValue {
+public sealed interface TypeSet permits TypeSetFunction, TypeSetTuple, TypeSetType, TypeSetTypeLevelValue {
     String describe();
 }
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTuple.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTuple.java
new file mode 100644
index 00000000..dc8773b5
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetTuple.java
@@ -0,0 +1,13 @@
+package org.shedlang.compiler.typechecker.typesets;
+
+public final class TypeSetTuple implements TypeSet {
+    static final TypeSetTuple INSTANCE = new TypeSetTuple();
+
+    private TypeSetTuple() {
+    }
+
+    @Override
+    public String describe() {
+        return "tuple";
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
index 3dd47cae..6b6d2d69 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
@@ -9,6 +9,7 @@ public class TypeSets {
     public static final TypeSetEffect EFFECT = TypeSetEffect.INSTANCE;
     public static final TypeSet FUNCTION = TypeSetFunction.INSTANCE;
     public static final TypeSetMetaType META_TYPE = TypeSetMetaType.INSTANCE;
+    public static final TypeSetTuple TUPLE = TypeSetTuple.INSTANCE;
 
     public static TypeSet type(Type type) {
         return new TypeSetType(type);
-- 
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