fix(gnolang): prescriptively reject *ast.(IndexListExpr, GoStmt) as u…

…nrecognized for Gno

The *ast.IndexListExpr is used for generics but in assignment operations
it is illegal to use. This change returns a proper error and matches
Go's output.
Also *ast.GoStmt is for spawning Go routines but those are forbidden
in Gno, hence reject them prescriptively instead of just spewing
out the raw ast type.

Fixes #3731
Updates #3751

gnovm/pkg/gnolang/go2gno.go

@@ -478,6 +478,13 @@ func Go2Gno(fs *token.FileSet, gon ast.Node) (n Node) {
 		}
 	case *ast.EmptyStmt:
 		return &EmptyStmt{}
+	case *ast.IndexListExpr:
+		if len(gon.Indices) > 1 {
+			panicWithPos("invalid operation: more than one index")
+		}
+		panicWithPos("invalid operation: indexList is not permitted in Gno")
+	case *ast.GoStmt:
+		panicWithPos("goroutines are not permitted")
 	default:
 		panicWithPos("unknown Go type %v: %s\n",
 			reflect.TypeOf(gon),

gnovm/tests/files/parse_err1.gno

@@ -0,0 +1,16 @@
+// https://github.com/gnolang/gno/issues/3731
+
+package main
+
+type node struct {
+	r []int
+}
+
+func (n *node) foo(targ, wndex int) {
+	_ = n.r[targ, wndex]
+}
+
+func main() {}
+
+// Error:
+// files/parse_err1.gno:10:6: invalid operation: more than one index

gnovm/tests/files/parse_err2.gno

@@ -0,0 +1,16 @@
+// https://github.com/gnolang/gno/issues/3751
+
+package math
+
+import "testing"
+
+func Add(a, b int) int {
+    return a + b
+}
+
+func TestAdd(t *testing.T) {
+    go Add(1, 1)
+}
+
+// Error:
+// files/parse_err2.gno:12:5: goroutines are not permitted