fix: handle out of order type declaration for global var declaration

_test/fun11.go

@@ -0,0 +1,12 @@
+package main
+
+var f F
+
+type F func(int)
+
+func main() {
+	println("ok")
+}
+
+// Output:
+// ok

interp/gta.go

@@ -52,7 +52,7 @@ func (interp *Interpreter) gta(root *node, rpath, pkgID string) ([]*node, error)
 					val = src.rval
 				}
 				if typ.incomplete {
-					// Come back when type is known
+					// Come back when type is known.
 					revisit = append(revisit, n)
 					return false
 				}
@@ -80,6 +80,11 @@ func (interp *Interpreter) gta(root *node, rpath, pkgID string) ([]*node, error)
 				if n.typ, err = nodeType(interp, sc, n.child[l]); err != nil {
 					return false
 				}
+				if n.typ.incomplete {
+					// Come back when type is known.
+					revisit = append(revisit, n)
+					return false
+				}
 			}
 			for _, c := range n.child[:l] {
 				sc.sym[c.ident] = &symbol{index: sc.add(n.typ), kind: varSym, global: true, typ: n.typ}