From a67d677caa6052c3cf13d37b88adf98f50885fcb Mon Sep 17 00:00:00 2001
From: Omar Sy <syomar.pro@gmail.com>
Date: Mon, 4 Nov 2024 23:40:52 +0100
Subject: [PATCH] fix(gnovm): improve error message for nil assignment in
 variable declaration

---
 gnovm/pkg/gnolang/type_check.go |  2 +-
 gnovm/tests/files/assign29.gno  | 10 ++++++++++
 gnovm/tests/files/var31.gno     |  8 ++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 gnovm/tests/files/assign29.gno
 create mode 100644 gnovm/tests/files/var31.gno

diff --git a/gnovm/pkg/gnolang/type_check.go b/gnovm/pkg/gnolang/type_check.go
index f86c44e7921..8b1d1eb1e3d 100644
--- a/gnovm/pkg/gnolang/type_check.go
+++ b/gnovm/pkg/gnolang/type_check.go
@@ -289,7 +289,7 @@ func checkAssignableTo(xt, dt Type, autoNative bool) error {
 	// case0
 	if xt == nil { // see test/files/types/eql_0f18
 		if !maybeNil(dt) {
-			panic(fmt.Sprintf("invalid operation, nil can not be compared to %v", dt))
+			panic(fmt.Sprintf("cannot use nil as %v value in variable declaration", dt))
 		}
 		return nil
 	} else if dt == nil { // _ = xxx, assign8.gno, 0f31. else cases?
diff --git a/gnovm/tests/files/assign29.gno b/gnovm/tests/files/assign29.gno
new file mode 100644
index 00000000000..1856e85e49f
--- /dev/null
+++ b/gnovm/tests/files/assign29.gno
@@ -0,0 +1,10 @@
+package main
+
+func main() {
+	a := 1
+	a = nil
+	println(a)
+}
+
+// Error:
+// main/files/assign29.gno:5:2: cannot use nil as int value in variable declaration
diff --git a/gnovm/tests/files/var31.gno b/gnovm/tests/files/var31.gno
new file mode 100644
index 00000000000..d5571f148ca
--- /dev/null
+++ b/gnovm/tests/files/var31.gno
@@ -0,0 +1,8 @@
+package main
+
+func main() {
+	var i int = nil
+}
+
+// Error:
+// main/files/var31.gno:4:6: cannot use nil as int value in variable declaration