From 88b9a1010b974c435e3a4c3360049da801caeb60 Mon Sep 17 00:00:00 2001
From: Tristan Menzel <tristanmenzel@gmail.com>
Date: Tue, 15 Oct 2024 18:43:24 -0700
Subject: [PATCH] feat: Error when attemping to mutate an immutable tuple type

---
 src/awst_build/eb/index.ts                    |  6 +++++-
 tests/expected-output/mutating-tuples.algo.ts | 16 ++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 tests/expected-output/mutating-tuples.algo.ts

diff --git a/src/awst_build/eb/index.ts b/src/awst_build/eb/index.ts
index 14e77339..ff65eead 100644
--- a/src/awst_build/eb/index.ts
+++ b/src/awst_build/eb/index.ts
@@ -1,6 +1,7 @@
 import { awst } from '../../awst'
 import { nodeFactory } from '../../awst/node-factory'
 import type { Expression } from '../../awst/nodes'
+import { TupleItemExpression } from '../../awst/nodes'
 import type { SourceLocation } from '../../awst/source-location'
 import { CodeError, NotSupported } from '../../errors'
 import { logger } from '../../logger'
@@ -236,6 +237,9 @@ export function requireLValue(expr: awst.Expression): awst.LValue {
     awst.AppAccountStateExpression,
     awst.BoxValueExpression,
   ]
+  if (expr instanceof TupleItemExpression) {
+    throw new CodeError('Expression is not a valid assignment target - object is immutable', { sourceLocation: expr.sourceLocation })
+  }
   if (!lValueNodes.some((l) => expr instanceof l)) {
     throw new CodeError(`Expression is not a valid assignment target`, {
       sourceLocation: expr.sourceLocation,
@@ -243,7 +247,7 @@ export function requireLValue(expr: awst.Expression): awst.LValue {
   }
   if (expr instanceof awst.IndexExpression || expr instanceof awst.FieldExpression) {
     if (expr.base.wtype.immutable) {
-      throw new CodeError(`${expr.wtype} is not a valid assignment target as it is immutable`, {
+      throw new CodeError(`Expression is not a valid assignment target - object is immutable`, {
         sourceLocation: expr.sourceLocation,
       })
     }
diff --git a/tests/expected-output/mutating-tuples.algo.ts b/tests/expected-output/mutating-tuples.algo.ts
new file mode 100644
index 00000000..138c6a31
--- /dev/null
+++ b/tests/expected-output/mutating-tuples.algo.ts
@@ -0,0 +1,16 @@
+import type { uint64 } from '@algorandfoundation/algorand-typescript'
+
+function test(a: uint64) {
+  const t1: [uint64, uint64, uint64] = [a, a, a]
+  let t2 = { a, b: a, c: a }
+
+  a *= 2
+
+  // @expect-error Expression is not a valid assignment target - object is immutable
+  t1[0] = a
+
+  // @expect-error Expression is not a valid assignment target - object is immutable
+  t2.a = a
+
+  t2 = { ...t2, a }
+}