llgo/ssa: checkExpr to auto convert funcPtr into closure

cl/_testrt/intgen/in.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"github.com/goplus/llgo/internal/runtime/c"
+)
+
+func genInts(n int, gen func() c.Int) []c.Int {
+	a := make([]c.Int, n)
+	for i := range a {
+		a[i] = gen()
+	}
+	return a
+}
+
+func main() {
+	a := genInts(5, c.Rand)
+	for _, v := range a {
+		c.Printf(c.Str("%d\n"), v)
+	}
+}