fix(gnovm): fix issue with locally re-definition (gnolang#3014)

closes: gnolang#3013
<!-- please provide a detailed description of the changes made in this
pull request. -->

<details><summary>Contributors' checklist...</summary>

- [ ] Added new tests, or not needed, or not feasible
- [ ] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [ ] Updated the official documentation or not needed
- [ ] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [ ] Added references to related issues and PRs
- [ ] Provided any useful hints for running manual tests
</details>

---------

Co-authored-by: Morgan Bazalgette <[email protected]>

gnovm/pkg/gnolang/preprocess.go

@@ -157,24 +157,19 @@ func initStaticBlocks(store Store, ctx BlockNode, bn BlockNode) {
 			switch n := n.(type) {
 			case *AssignStmt:
 				if n.Op == DEFINE {
-					var defined bool
 					for _, lx := range n.Lhs {
 						nx := lx.(*NameExpr)
 						ln := nx.Name
 						if ln == blankIdentifier {
 							continue
 						}
 						if !isLocallyDefined2(last, ln) {
-							// if loop extern, will change to
+							// if loop extern, will promote to
 							// NameExprTypeHeapDefine later.
 							nx.Type = NameExprTypeDefine
 							last.Predefine(false, ln)
-							defined = true
 						}
 					}
-					if !defined {
-						panic(fmt.Sprintf("nothing defined in assignment %s", n.String()))
-					}
 				}
 			case *ImportDecl:
 				nx := &n.NameExpr

gnovm/tests/files/redefine.gno

@@ -0,0 +1,15 @@
+package main
+
+var ss = []int{1, 2, 3}
+
+func main() {
+	for _, s := range ss {
+		s := s
+		println(s)
+	}
+}
+
+// Output:
+// 1
+// 2
+// 3

gnovm/tests/files/redefine2.gno

@@ -0,0 +1,25 @@
+package main
+
+var testTable = []struct {
+	name string
+}{
+	{
+		"one",
+	},
+	{
+		"two",
+	},
+}
+
+func main() {
+
+	for _, testCase := range testTable {
+		testCase := testCase
+
+		println(testCase.name)
+	}
+}
+
+// Output:
+// one
+// two

gnovm/tests/files/redefine3.gno

@@ -0,0 +1,13 @@
+package main
+
+func main() {
+	for i := 0; i < 3; i++ {
+		i := i
+		println(i)
+	}
+}
+
+// Output:
+// 0
+// 1
+// 2

gnovm/tests/files/redefine4.gno

@@ -0,0 +1,15 @@
+package main
+
+func main() {
+	a := 1
+	b := 3
+	println(a, b) // prints 1 3
+
+	// Re-declaration of 'a' is allowed because 'c' is a new variable
+	a, c := 2, 5
+	println(a, c) // prints 2 5
+}
+
+// Output:
+// 1 3
+// 2 5

gnovm/tests/files/redefine5.gno

@@ -0,0 +1,18 @@
+package main
+
+func main() {
+	a := 1
+	println(a) // prints 1
+
+	if true {
+		a := 2     // valid: new scope inside the if statement
+		println(a) // prints 2
+	}
+
+	println(a) // prints 1: outer variable is unchanged
+}
+
+// Output:
+// 1
+// 2
+// 1

gnovm/tests/files/redefine6.gno

@@ -0,0 +1,9 @@
+package main
+
+func main() {
+	a, b := 1, 2
+	a, b := 3, 4
+}
+
+// Error:
+// files/redefine6.gno:5:2: no new variables on left side of :=